Category Archives: Nematodes

Nematodes are microscopic, eel-like roundworms. The most troublesome species in the garden are those that live and feed within plant roots most of their lives and those that live freely in the soil and feed on plant roots.

Nematodes

Anguina funesta Price, Fisher & Kerr, 1979

California Pest Rating for
Anguina funesta Price, Fisher & Kerr, 1979
Pest Rating: A 

 

PEST RATING PROFILE
Initiating Event:

None.

History & Status:

Background:  Anguina funesta is a plant parasitic nematode that induces formation of galls in developing seeds of annual rye grass (Lolium rigidium), Festuca and Vulpia species.  Commonly known as a seed gall nematode, A. funesta is not only an agricultural pest of economic significance in its own right, but is considered more important because it is a vector of the toxigenic actinomycete bacterium, Rathyibacter toxicus that causes Rathayibacter poisoning most commonly known as annual ryegrass toxicity (ARGT) disease (Murray et al., 2014; Riley & Barbetti, 2008).  This bacterium is also vectored by other Anguina species, namely, A. agrostis, A. tritici, A. australis, and A. paludicola, and is a USDA APHIS Select Agent (Murray et al., 2014).  It is also noteworthy that Anguina funesta and other Anguina species are vectors of the fungus, Dilophospora alopecuri which inhibits gall formation and bacterial colonization thereby providing biological control of both nematode and bacterium.  Rathyibacter toxicus and Dilophospora alopecuri are transported to the plant host by adhering to the external cuticular surface of A. funesta.

The first record of ARGT was in Southern Australia in 1956, and caused considerable crop and animal losses.   Since then, ARGT and A. funesta spread to Western Australia, South Africa in 1981, and Japan in 1997, most likely with the importation of contaminated ryegrass seed and hay from Australia (Meng et al., 2012).  Both nematode and bacterial pathogen now continue to be an economic problem in northern cropping regions of Western Australia.  They generally follow a pattern of increase, impact, and then decline.  The decline appears to be associated with the build-up of Dilophosphora alopecuri and alterations in land management practices that had supported high host densities protected through to seed set (Subbotin & Riley, 2012).

In the USA, Anguina funesta has only been reported from Oregon having been detected in annual ryegrass seed lots in 2010.  Rathayibacter toxicus was not found in Oregon (ODA, 2011; Meng et al., 2012).  To date, the nematode and bacterial species have not been reported from any other US states outside of Oregon.  Anguina funesta has not been detected in California, nor was it found in turf and pasture seed samples analyzed at CDFA in 2012.  During that year, the CDFA Nematology Laboratory did not detect seed gall nematodes in seed samples of perennial ryegrass, tall fescue, and annual bluegrass received from various sources in Oregon, California, and Arizona and maintained in storage at the CDFA Seed Laboratory.

Hosts:  The principal host of A. funesta is annual ryegrass (Lolium rigidum).  It also induces galls in Festuca and Vulpia species.  Only L. rigidum and V. myuros are natural hosts of the nematode pathogen (Subbotin & Riley, 2012).

Symptoms:  Ryegrass plants do not show any visible symptoms of infection until inflorescence appears.  Nematode galls in annual ryegrass are difficult detect in the field as galls are covered by lemma and paleas.  However, once the latter are removed the galls are shrunken, fusiform, smaller than normal seed, and purplish.  On the other hand, the bacterial pathogen, R. toxicus may remain within a nematode gall or ooze out and partly or completely cover a gall with yellow bacterial slime which turns orange once it dries.  Also, while infected plants do not exhibit apparent symptoms, some entire seed heads may be twisted and malformed and covered with yellow slime.  However, the absence of slime (gummosis) does not necessarily indicate that a field is free of the bacterium (Murray et al., 2014; Putnam, 2011).

Disease cycle: Mature seed galls induced in the plant by the nematode contain anhydrobiotic second stage juveniles (J2) which form its survival and dispersal stage.  These juveniles overwinter in seed galls on the soil surface and can survive in dry state for many years.  Under moist conditions, the nematodes rehydrate, become active, and emerge from degrading galls onto the soil surface.  If the soil surface dries out, then the juveniles again become anhydrobiotic until another period of rehydration.   In moist soil surfaces, active juveniles seek and invade host seedlings and feed on the growing point (meristem tissue) of tillers where they accumulate until ovaries initiate development.  Then they invade ovaries of inflorescence and transform developing seed into seed galls.  J2 feed within galls, and develop through two further juveniles stages into adults.  A gall may be infested with a few to 20 male and female nematodes.  Sexual reproduction is necessary for formation of successive generations and occurs within the galls resulting in several hundred eggs per gall.  J2s hatch from the eggs within galls. Freshly-hatched J2s cannot survive desiccation, however, as infested plants mature and senesce, J2s also mature into their anhydrobiotic survival stage.  Galls are harvested and replanted along with healthy seed.  During harvest, galls fall to the ground and remain there until the nematodes regain activity under moist spring conditions, thus completing the cycle.  Toxigenic Rathyibacter toxicus bacteria in soil adhere to the external cuticular surface of Anguina J2s and are carried into the host plant’s inflorescence and nematode galls where thy proliferate and colonize these structures.  As the plant matures, bacteria produce glycolipid toxins known as corynetoxins that when consumed, cause neurological disorders, toxicosis, and fatality in animals.  When galls fall to the ground at harvest, bacteria reenter the soil (Riley & Barbetti, 2008; Subbotin & Riley, 2012).

Spread:  The nematode and bacteria can be spread commonly in galls intermixed with non-cleaned or poorly cleaned grass seed lots.  They can be dispersed by wind and in hay.  Other means of spread include infested soil/gall contaminated machinery, vehicles, humans and animals or run-off water.

Damage Potential:   While Anguina funesta will reduce healthy seed set in host plants, it must be noted that galled florets are likely to be removed with regular seed cleaning procedures.  However, there is the possibility for A. funesta galls to be accidently overlooked during cleaning procedures because they are concealed by lemma and palea coverings.  In which case, the likelihood of introduction to non-infested regions is increased.  The nematode species is considered a “High-Risk” species by USDA and the Society of Nematologists (SON, not dated), mainly due to its ability to vector the toxigenic bacterium which is a USDA APHIS Select Agent.  The threat of introduction, spread and establishment of the bacterium is very high due to the presence of susceptible grasses and the occurrence of Anguina species in the USA including California.  Pasture, rangeland, private and commercial lawns and turf gardens cultivated to annual ryegrass and fescue grasses are potentially susceptible to the nematode and bacterium.  Livestock deaths and production losses to annual ryegrass toxicity (ARGT) disease are caused by corynetoxins produced by R. toxicus and vectored by A. funesta.  Most valuable susceptible livestock include cattle, sheep and horses. Domestic and international trade are likely to be negatively impacted.

Worldwide Distribution:  North America: USA (Oregon); Oceania: Australia;

Official Control: Presently, Anguina funesta is on the ‘Harmful Organism List’ for Lolium spp. and L. temulentus seeds intended for export to Chile, while Anguina spp. is on the ‘Harmful Organism List’ for Australia, Namibia, Nauru, and South Africa (USDA-PCIT, 2017).  The USDA APHIS originally added the Anguina spp.-vectored bacterial pathogen, Rathayibacter toxicus to the Select Agent List in 2008, relisted it in 2012 and continues to date.

California Distribution:  Anguina funesta has not been reported from California.

California Interceptions: None reported.

The risk Anguina funesta would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: If allowed introduction, Anguina funesta is likely to establish a widespread distribution wherever annual ryegrass and fescue grass are able to grow throughout California. The grasses are commonly grown in commercial, private, and agricultural environments within the State.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 3

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: The host range is limited to annual ryegrass (Lolium rigidum) and fescue grasses (Festuca spp. and Vulpia).  Only L. rigidum and V. myuros are natural hosts of the nematode pathogen.

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: The nematode is spread over short and long distances mainly through artificial means. The primary means of spread is through galls intermixed with non-cleaned or poorly cleaned grass seed lots.  They can also be spread by wind and in hay.  Other means of spread include infested soil/gall contaminated machinery, vehicles, humans and animals or run-off water.   The nematodes have high reproductive potential and are capable of surviving in dry state within seeds for many years, thus enhancing spread over long durations.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Anguina funesta infestations resulting in seed galls, could potentially lower crop yield, increase costs of crop production, trigger loss of markets including establishment of quarantines, and change normal cultural practices.  Furthermore, the nematode species is a vector of bacterial pathogen, Rathayibacter toxicus that causes Rathayibacter poisoning or annual ryegrass toxicity (ARGT) disease resulting in death of agricultural livestock.  Therefore, a high rating is given to this category.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C, D, E, F.

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Anguina funesta may significantly affect residential and commercial turf gardens.  Annual ryegrass may also be used in agricultural and other environments as a cover crop to prevent soil erosion, improve soil structure and drainage, suppress weeds, and improve organic content of soil. Infestation of the nematode species could impact these environments and consequently trigger additional official or private treatment programs.  A ‘High’ rating is given to this category.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: D, E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 3

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Anguina funesta:  High (13)

Add up the total score and include it here.

 -Low = 5-8 points

 -Medium = 9-12 points

 –High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Anguina funesta to California = 13.

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included.

Evaluation is ‘Not established in California’.  

Score: 0

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

 Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 13

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the seed gall nematode, Anguina funesta is A.

References:

Alderman S. C. et al. 2003.  Use of a seed scarifier for detection and enumeration of galls of Anguina and Rathayibacter species in Orchard grass seed.  Plant Disease 87:320-323.

Kessell, D.  2010.  Annual ryegrass toxicity – current situation.  Department of Agriculture and Food, Government of Western Australia, Note: 417.

Murray, T. D., I. Agarkova, S. Alderman, J. Allen, R. Bulluck, J. Chitambar, C. Divan, I. Riley, B. Schroeder, A. Sechler, and S. Subbotin. 2014. Recovery Plan for Rathayibacter Poisoning caused by Rathayibacter toxicus (syn. Clavibacter toxicus) National Plant Disease Recovery System, a cooperative project of The American Phytopathological Society and The United States Department of Agriculture, posted at http://www.ars.usda.gov/research/npdrs.  Updated March 2015.

ODA.  2011.  2011 Plant Health Section Annual Report Commodity Inspection Division. State of Oregon Department of Agriculture.

Price, P. C., Fisher, J. M. and Kerr, A.  1979.  On Anguina funesta n. sp. and its association with Corynebacterium sp., in infecting Lolium rigidium.  Nematologica 25:76-85.

Putnam M. L.  2011.  Rathyibacter toxicus, select agent.  Oregon State University Plant Clinic, Corvallis, Oregon (Poster).

Riley, I. T. and Barbetti, M. J.  2008.  Australian anguinids: their agricultural impact and control.  Australasian Plant Pathology 37:289-297.

Riley, I. T. and McKay, A. C.  1990.  Specificity of the adhesion of some plant pathogenic microorganisms to the cuticle of nematodes in the genus Anguina (Nematoda: Anguinidae).  Nematologica 36:90-103.

SON.  (Not dated).  Anguina funesta Pest Information.  Exotic Nematode Plant Pests of Agricultural and Environmental significance to the United States.  The Society of Nematologists. http://nematode.unl.edu/pest55.htm

Subbotin, S. A. et al.  2003.  Evolution of the gall-forming plant parasitic nematodes (Tylenchida: Anguinidae) and their relationships with hosts as inferred from Internal Transcribed Spacer sequences of nuclear ribosomal DNA.  Molecular Phylogenetics and Evolution 30:226-235.

Subbotin, S. A. and I. T. Riley.  Stem and gall forming nematodes. In Practical Plant Nematology.  Eds. Manzanilla-Lopez R., and M. Marban-Mendoza.  Biblioteca Básica de Agricultura, Grupo Mundi-Prensa, Mexico.  521-577 pp.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. May 24, 2017, 11:51:23 am CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health@cdfa.ca.gov

Comment Period: CLOSED

6/5/2017 – 7/20/2017

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: A 

Posted by ls

Nematodes

Heterodera carotae Jones, 1950

California Pest Rating Proposal for
Heterodera carotae Jones, 1950
Pest Rating: B

 

PEST RATING PROFILE
Initiating Event:

None.

History & Status:

Background:  Prior to the discovery of the carrot cyst nematode, “carrot-sickness” was believed to be caused by pathogenic fungi.  However, in 1931, when all cyst-forming nematodes were considered strains of H. schachtii (sugarbeet cyst nematode), Triffit (1931) found that Heterodera females on carrots cultivated in UK, were atypical and smaller than H. schachtii.  This led to possibly the first record of H. carotae (Mathews, 1975).  In 1944, Jones (1950) found field-grown carrots infested with cyst nematodes in Chatteris, Isle of Ely, England.  This discovery resulted in the report of a distinct new species, H. carotae.   Since then, H. carotae has been reported as a pest of carrots in several countries of Europe, and fewer countries in Asia and North America (see: ‘Worldwide Distribution’).

Hosts:  The host range is limited to Daucus spp. including, Daucus carota ssp. sativa (carrot), D. carota ssp. carota, D. pulcherrimus (Jones 1950), and several wild Umbelliferae, such as Torilis leptophylla (bristlefruit hedgeparsley), T. arvensis (spreading hedgeparsley), T. japonica (erect hedgeparsley) (Mugniéry & Bossis, 1988).

Symptoms: There are no specific above ground symptoms in plants that can be attributed to infection by carrot cyst nematode.  General above ground symptoms include stunting with leaves appearing yellowish-red then turning necrotic in the older parts.  In fields, poor and patchy plant growth is apparent in small, circular areas which may extend to the entire field resulting in complete loss of crop.  Infested tap roots are usually smaller than those of non-infested plants with abnormal prolific growth of lateral roots giving a bearded appearance. Also, tap roots may be distorted and deformed with several growing points or digitate root apex (Greco, 1986, 1987; Mathews, 1975).  

Biology:  Eggs produced by Heterodera carotae females are retained in cysts and egg sacs.  The first juvenile stage and first molt occur within the egg, and the infective second stage juveniles emerge during egg hatch.  Hatching from cysts is usually delayed, whereas, juveniles from egg sacs hatch as soon as favorable soil temperature and soil moisture are available.  Eggs from cysts hatch only under the stimulus of root exudates of carrots however, root exudates from other plant species including members of Umbelliferae, do not significantly influence hatching of eggs from cysts.  Age of carrot plant affects hatching, and eggs from cysts less than 2 months old rarely hatch, but juveniles regularly emerge from mature cysts provided environmental conditions are favorable.  Second stage juveniles from egg sacs hatch promptly under favorable soil moisture and soil temperature, and stimulus of exudates from host plants is not necessary since eggs from egg sacs can hatch in water under suitable environment.  While egg hatch may occur at 5°C, the optimum temperature range is 15-20°C and at 25°C hatching is repressed.  Emerged second stage juveniles move through the soil in search of a suitable host which, once found, they penetrate.  Root penetration occurs at 5-30°C, but the nematode does not develop below 10°C.  Heterodera carotae is a sedentary endoparasite.  Once within the root, second stage juveniles establish a typical feeding site and undergo three more molts to develop into white, lemon-shaped females and worm-shaped males.  After mating, the female produces a gelatinous matrix in which 100 or more eggs are laid.  Eggs are also retained within the female’s body which forms a brown cyst, without forming an intermediate ‘yellow stage’.  Females and cysts develop 26 and 36 days after carrot root invasion at 20°C (Greco, 1986, 1987; Baldwin & Mundo-OCampo, 1991).

Damage Potential: Infected carrot roots are small, deformed, and unmarketable.  Yields are reduced, however quantitative losses in yield have not been reported. Severe infections may result incomplete loss of crop.

Spread:  Infected nursery stock, infected plants, soil contaminated with cysts, cysts, nematode-infested irrigation water.

Worldwide Distribution: Asia: Cyprus, India; Africa: South Africa; Europe: Denmark, France, Germany, Hungary, Italy, Ireland, The Netherlands, Portugal, Poland, Russia, Serbia, Slovenia, Slovakia, Sweden, Switzerland, UK; North America: Canada, USA (Michigan)  (Berney & Bird, 1992; Greco, 1986, 1987; Subbotin et al., 2010; Yu et al., 2017).

Official Control:  Heterodera carotae is on the ‘Harmful Organisms Lists’ for Colombia, Ecuador, Honduras, Indonesia, and Timor-Leste (USDA-PCIT, 2017).  Presently, the nematode species has a temporary ‘Q’ rating in California.

California Distribution: Heterodera carotae is not known to be present in California.

California Interceptions: None.

The risk Heterodera carotae would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Heterodera carotae may be able to establish in moderately cool and moist regions of the State wherever carrots are cultivated. Temperature requirements for egg hatch and nematode development are very specific.  Optimum temperature for egg hatch is 15-20°C and is repressed at 25°C.  One life cycle per season has been reported, however, with a longer growing season that would allow repeated crops under cool temperatures, as many as four cycles may occur (Greco, 1986).

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: The host range is limited to Daucus (carrot) and few wild Umbelliferae members.

Evaluate the host range of the pest.

Score: 1

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: One hundred or more eggs are produced in egg sacs and retained within cysts. For long and short distance dispersal the nematode species is mainly dependent on movements of cysts, cyst-infested soils, and infected planting stock.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 2

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Infestations of the carrot cyst nematode could affect carrot production resulting in crop loss and unmarketable carrots. Cysts in soil could be spread by movements of soil and irrigation water requiring changes in normal cultural practices.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C, D

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Infestations of the carrot cyst nematode could significantly affect carrot cultivations in home/urban gardening practices.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Heterodera carotae: Medium (10) 

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is: Not established (0). 

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10.

Uncertainty: 

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for carrot cyst nematode, Heterodera carotae, is B.

References:

Baldwin, J. G., and M. Mundo-Ocampo.  1991.  Heteroderinae, cyst – and non-cyst-forming nematodes.  In Manual of Agricultural Nematology Ed. W. R. Nickle, Marcel Dekker, Inc. Pp. 275-362.

Berney, M. F., and G. W. Bird.  1992.  Distribution of Heterodera carotae and Meloidogyne hapla in Michigan carrot production.  Journal of Nematology 24 (4S), 776-778.

Greco, N.  1986.  The carrot cyst nematode. In F. Lamberti and C.E. Taylor Eds. Cyst nematodes.  New York: Plenum Press. Pp.333-346.

Greco, N.  1987.  Heterodera carotae: Destructive nematode of carrot. Nematology Circular No. 140, Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville, FL, USA.

Jones, F. G. W.  1950.  A new species of root eelworm attacking carrots.  Nature 165: 81.

Mathews, H. J. P. 1975. Heterodera carotae.  CIH descriptions of plant parasitic nematodes set 5, No. 61. St. Albans, UK: Commonwealth Institute of Helminthology.

Mugniéry, D. and M. Bossis.  1988.  Heterodera carotae Jones, 1950. 1. Host range speed of development cycle. Revue de Nématologie 11, 307-314.

Subbotin, S. A., M. Mundo-Ocampo, and J. G. Baldwin.  2010.  Systematics of cyst nematodes (Nematoda” Heteroderinae) D. J. Hunt and R. N. Perry (Series Editor).  Nematology Monographs and Perspectives Volume 8B.  Brill Leiden-Boston. 512 p.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System.  March 24, 2017, 5:49:32 PM CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Yu, Q., E. Ponomareva, D. Van Dyk, M. R. McDonald, F. Sun, M. Madani, et al.  2017.  First report of the carrot cyst nematode (Heterodera carotae Jones) from carrot fields in Ontario, Canada.  Plant Disease DOI: 10.1094/PDIS-01-17-0070-PDN. Last accessed March 9, 2017, from http://apsjournals.apsnet.org/doi/pdf/10.1094/PDIS-01-17-0070-PDN.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health@cdfa.ca.gov

Comment Period: CLOSED

4/3/2017 – 5/18/2017

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: B

Posted by ls

Nematodes

Anguina tritici (Steinbach, 1799), Chitwood, 1935 | Wheat Seed gall nematode

California Pest Rating for
Anguina tritici (Steinbach, 1799), Chitwood, 1935
Wheat Seed gall nematode
Tylenchida: Anguinidae
Pest Rating: A

 

PEST RATING PROFILE
Initiating Event:

A pest risk assessment of Anguina tritici and a re-evaluation of its current pest rating in California is presented here.

History & Status:

Background: Anguina tritici, commonly named the wheat seed gall nematode, was the first plant-parasitic nematodes to be described in literature. The wheat seed gall nematode is an economically important pest of wheat (Triticum sp.) and rye (Secale cereal L.), causing a disease called ‘ear-cockle’ or seed gall, that has destroyed 30-70% of the wheat crop in undeveloped parts of the world (Clark et. al. 1991, Ferris, 2013, Subbotin & Riley, 2012). This nematode was first found in the United States in 1909 and subsequently in numerous states, primarily in wheat but also in rye to a lesser extent (PERAL, 2015). Modern mechanized agricultural seed grading practices that result in separation of clean seed from galls, along with crop rotation, have practically eliminated A. tritici from countries which have adopted these practices, and the nematode has not been found in the United States since 1975 (PERAL, 2015). Furthermore, from 2005 to 2009, CDFA conducted USDA CAPS sponsored statewide surveys for A. tritici and 21 other target nematode species associated with major host plant species, including wheat, barley, and several other agricultural crops and ornamentals in California’s major cropping and nursery production regions.  Anguina tritici was not detected (Chitambar et al., 2008).  However, A. tritici is still a problem in traditional farming systems in west and south Asia where modern mechanized seed grading practices are not widely adapted or efficiently applied (SON, 2003).

Hosts: Emmer (Triticum monococcum), rye (Secale cereale), spelt (T. spelta), and bread wheat (T. aestivum) are the primary hosts. Barley (Hordeum vulgare), oats (Avena sativa), durum wheat (T. durum), and rivet wheat (T. turgidum) are minor hosts (CABI, 2016; EPPO, 2016; Mackesy & Sullivan, 2016).

Symptoms: Anguina tritici infect aboveground plant parts by invading and becoming endoparasitic in the plant tissue (Clark et al., 1991). Slight elevations occur on upper leaf surface with indentations on the lower side. Other symptoms include wrinkling, twisting, curling of the margins towards the midrib, distortion, buckling, swelling and bulging (CABI, 2016). Infected plants become stunted and have shorter and deformed stems and leaves (Subbotin & Riley, 2012). In severe infection, plants do not form ears or form only stunted ears on stunted stems. Generally infested ears are smaller, shorter and thicker than healthy ones, and have abnormally spreading glumes.  Some or all grains are transformed to galls which are light to dark brown to black, hard to the touch and filled with numerous infective juvenile nematodes. (Subbotin & Riley, 2012). The entire above ground plant is distorted to some degree and a disease problem is usually obvious (CABI, 2016). Wheat seeds with low nematode numbers do not show typical symptoms of infection, i.e., seed galls (Lal & Lal, 2006).

Disease Development: Anguina tritici prefers cool conditions in most climates where wheat is grown. The favored micro-habitat for the survival of A. tritici is within seed galls, where all stages are protected from hostile environmental factors. This nematode also survives on the soil surface, either in or out of galls, and in dry seed storage (CABI, 2016). Second stage juveniles (J2s) within drying galls are capable of entering a cryptobiotic state to survive during dry conditions (Bird and Buttrose, 1974). Viable juveniles have been recovered for up to periods as long as 38 years (Ferris, 2013).  In moist soils, galls are softened enough to release infective second stage juveniles.  The juveniles enter young seedlings and move upwards within the plant to the meristem or concentrate in the leaf axis of shoots where they feed ectoparasitically and remain there until inflorescence develops. Juveniles invade the floral tissue and gall formation is stimulated.  Juveniles develop into 40 or more adult males or females with each female laying 30,000 or more eggs and/or juveniles (CABI, 2016; Subbotin & Riley, 2012).  Swarup and Sosa-Moss (1990) reported that a minimum population of 10,000 juveniles/kg soil is needed for the development of ear-cockle disease and the severity of the disease is greatest when nematode galls are place in soil at a depth of 2-6 cm than when placed deeper.

Transmission: The principal means of dispersion is by wheat seed containing infected galls in commerce and by sowing infected galls in fields. Other means of spread include straw from an infected crop, rainfall and flooding, natural migration and cow, sheep, sparrow, pigeon and goldfinch manure. A. tritici is also spread by animal feet, farm implements and machines, and by wind (Leukel, 1957).

Worldwide Distribution: Anguina tritici has been reported in Africa: Egypt and Ethiopia. Asia: Afghanistan, China, India, Iran, Iraq, Israel, Pakistan, Saudi Arabia, South Korea, Syria, Slovenia, and Taiwan. Europe: Austria, Azerbaijan, Bulgaria, Croatia, Cyprus, France, Germany, Greece, Hungary, Ireland, Italy, Lithuania, Netherlands, Poland, Romania, Russia, Serbia, Spain, Sweden, Switzerland, Turkey, Ukraine, and the United Kingdom (UK). Oceania: Australia and New Zealand (CABI, 2017).

Official Control: Anguina tritici is in the ‘Harmful organism Lists’ for  Argentina, Brazil, Chile, Colombia, Ecuador, Egypt, Guatemala, Indonesia, Israel, Madagascar, Namibia, Nepal, New Zealand, Paraguay, Peru, South Africa, Taiwan, Thailand, Timor-Leste, and Uruguay (USDA-PCIT, 2017).

California Distribution:  Anguina tritici is not present in California.

US Distribution: Although formerly present in several states, Anguina tritici was eliminated in 1975 and is not present in the U.S.

California Interceptions: Anguina tritici has never been intercepted in California (CDFA Pest and Damage Reports Database).

While the likelihood of introduction of Anguina tritici into California is minimal largely due to effective ongoing modern seed grading and other practices, the economic damage potential of this pest cannot be undermined. As stated earlier, wheat seeds infested with low populations of the nematode may not show typical symptoms of seed galling and pose the probability of accidental introductions. Therefore, the risk Anguina tritici (Wheat seed gall nematode) would pose to California, consequent to its introduction, is evaluated below:

Consequences of Introduction: 

1) Climate/Host Interaction: Wheat, the main host of Anguina tritici, is primarily grown in Sacramento Valley, San Joaquin Valley, and Central Valley regions, and Imperial County (USDA-NASS Wheat County Estimates 2008). If introduced into California, Anguina tritici is likely to establish wherever wheat is grown within the state. Therefore, it receives a High (3) score in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California:

Score:  3

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Primary hosts of Anguina tritici include wheat, rye, spelt and emmer wheat   Oats, barley, durum wheat and rivet wheat are considered minor hosts.  It receives a Medium (2) score in this category.

Evaluate the host range of the pest:

Score: 2

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Reproduction of Anguina tritici is amphimictic. Mating occurs and female produces up to 2000 eggs per individual over several weeks. These eggs hatch and produce juvenile two stage (J2s), which remain within the galls as the survival stage and perpetuate plant infection as the invasive stage in following years. Dry galls are harvested with developed seeds, and each gall may contain thousands of J2s (Crop Protection Compendium). Anguina tritici produces one generation per year (Ferris, 2013). It is likely to enter California through transport of infested host plants or seed material. Since 2006, the import of Triticum sp. seed and Secale sp. is allowed from certain countries, some of which are known to have tritici (USDA- 2015).  Because of its high reproduction and dispersal potential, Anguina tritici receives a High (3) score in this category.

Evaluate the natural and artificial dispersal potential of the pest:

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Anguina tritici can cause severe crop losses to wheat 70% and rye (35-65%) in underdeveloped and developing countries due to poor agricultural practices, monoculture and use of poor quality seed. While there may be insignificant damage to California grown wheat and rye by this nematode due to modern agricultural production systems, export of CA grown grains to international markets can be severely hampered due to historical records of the presence of this nematode in production areas of the state (SON, 2003). The interaction of this nematode and Rathayibacter tritici in wheat in India results in an oozing bacterial infection of the grain known as ‘Tundu’ disease. The disease is also known as spike blight or yellow ear rot. (Ferris, 2013). Dilohosphora alopecuri in association with Anguina tritici could result in Dilophosphorosis disease of wheat where the spike is covered by black sticky mass. It receives a High (3) score in this category.

Evaluate the economic impact of the pest to California using the criteria below:

Economic Impact: A, B, C, E

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 3

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: Anguina tritici infestation is likely to cause ear-cockle disease in Sacramento/San Joaquin area and central valley. To prevent ear-cockle and spread of this nematode species, growers would require seed cleaning and crop rotation to eliminate the pest. Hot water treatments would be needed to eradicate A. tritici from seed lots and mechanical separation of wheat seeds from nematode galls. (PKB 2016). Additionally, infestations of tritici could significantly impact irrigation and other cultural practices. Therefore, it receives a High (3) score in this category.

Evaluate the environmental impact of the pest on California using the criteria below:

Environmental Impact:  D, E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

Environmental Impact Score:  3

– Low (1) causes none of the above to occur.

– Medium (2) causes 2 of these impacts.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Anguina tritici (Wheat seed gall Nematode): High (14)

Add up the total score and include it here:

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Anguina tritici has never been found in the environment and receives a Not established (0) in this category.

Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included:

Score: 0

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Final Score:

The final score is the consequences of introduction score minus the post entry distribution and survey information score: High (14)

Uncertainty:  

Anguina tritici has never been detected through regulatory pathways in California.  Introduction of the nematode species into California can still occur especially in seeds that pass inspection because they may be infested with low numbers of nematode inoculum and not transformed to typical galls. Inspection of wheat fields for symptomatic plants and commercial seed lots in storage or moved in trade is necessary to further confirm the non-presence status of Anguina triticii in California.

Conclusion and Rating Justification:

Based on all the evidence presented above, Anguina tritici would likely have significant economic and environmental impacts if it were to enter and establish in Wheat growing areas of California. Therefore, an “A” rating is justified and proposed herein.

References:
  1. Bird, A. F., and M. S. Buttrose. 1974. Ultrastructural changes in the nematode Anguina tritici associated with anhydrobiosis. Journal of Ultrastructure Research 48: 177-189.
  2. Clark, R.A., R. P. Esser, and J. H. O’Bannon. 1991. Procedures to detect wheat seed gall nematode in Florida. Nematology Circular No. 186. Florida Dept. of Agric. & Consumer Services, Division of Plant Industry
  3. CABI 2016. Anguina tritici (wheat seed gall nematode) datasheet (full).    http://www.cabi.org/cpc/
  4. Chitambar, J., K. Dong, S. Subbotin, and R. Luna.   California Statewide Nematode Survey Project.  California Plant Pest and Disease Report, 24: 59
  5. 2016. Anguina tritici (ANGUTR). PQR database.  Paris, France:  European and Mediterranean Plant Protection Organization. http://newpqr.eppo.int
  6. Ferris, H. 2013. Nemaplex: The Nematode Plant Expert Information System: A Virtual Encyclopedia on Soil and Plant Nematodes: Anguina tritici. University of California, Davis. December 7, 2016 http://plpnemweb.ucdavis.edu/nemaplex/Taxadata/G006S4.htm
  7. Lal, R., and A. Lal.   Plant parasitic nematode intercepted ffrom seeds, soil clods and packing material under import quarantine.  Journal of New Seeds. *: 49-60.
  8. Leukel, R. W., 1957. Nematode Disease of wheat and rye. USDA Farmers Bulletin, 1607.
  9. Mackesy, D. Z., and M. Sullivan.   CPHST Pest datasheet for Anguina tritici.  USDA-APHISPPQ-CPHST.  download.ceris.purdue.edu/file/3293
  10. 2015. Qualitative pest risk analysis for the wheat gall nematode, Anguina tritici, in U.S. United States Department of Agriculture, Animal and Plant Health Inspection Service, Plant Protection and Quarantine, Center for Plant Health Science and Technology, Plant Epidemiology and Risk Analysis Laboratory.
  11. Pest and Damage Report Database: Plant Health and Pest Prevention Services, California Department of Food and Agriculture. December 5, 2016 http://phpps.cdfa.ca.gov/user/frmLogon2.asp
  12. PKB 2016. Plantwise Technical Fact Sheet: Wheat Seed Gall Nematode. Plantwise Knowledge Bank. http://www.plantwise.org/KnowledgeBank/Datasheet.aspx?dsid=5388
  13. 2003 Exotic Nematode Plant Pests of Agricultural and Environmental Significance to United States, The Society of Nematologists. Anguina tritici
  14. Subbotin, S. A., and I. T. Riley. Stem and gall nematodes.  In Practical Plant Nematology (book) Edited by R. H. Manzanilla-Lopez and N. Marbán-Mendoza.  Biblioteca Basica de Agricultura, p. 521-577.
  15. Swarup, G., and C. Sosa-Moss. Nematode parasites of cereals.  In Plant Parasitic Neamtodes in Subtropical and Tropical Agriculture, edited by M. Luc, R. A. Sikora, and J. Bridge. 109-136.
  16. 2015. Plants for planting manual. Interim edition, updated 12/23/2015. https://www.aphis.usda.gov/import_export/plants/manuals/ports/downloads/plants_for_planting.pdf.
  17. USDA NASS: 2008 California Wheat County Estimates  https://www.nass.usda.gov/Statistics_by_State/California/Publications/County_Estimates/2009/200902whetf.pdf
  18. USDA Phytosanitary Certificate Issuance & Tracking System (PCIT): Phytosanitary Export Database (PExD), December 5, 2016  https://pcit.aphis.usda.gov/PExD/faces/PExDReport.jsp
Responsible Party:

Raj Randhawa, Senior Environmental Scientist; John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: (916) 262-1110 ; plant.health[@]cdfa.ca.gov.

Comment Period: CLOSED

3/3/2017 – 4/17/2017

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: A

Posted by ls

Nematodes

Paratylenchus spp. Micoletzky, 1922

California Pest Rating for
Paratylenchus spp.  Micoletzky, 1922
Pest Rating: C 

 

PEST RATING PROFILE
Initiating Event:

During the 1950-60s, several species of plant parasitic nematodes were given a ‘D’ rating as they were regarded as parasites, predators or organisms of little or no economic importance that did not require State enforced regulatory action.  However, these nematode species were inaccurately assigned a D rating as most, if not all, are plant parasitic and therefore, capable of damaging plant production and causing significant economic losses especially at the county and local residential/grower level.  Furthermore, the detection of plant parasitic nematodes in nursery stock may be an indication of contamination in violation of the State’s standard of pest cleanliness required for nurseries. Paratylenchus spp. were originally rated D.  The risk of infestation and permanent rating of this genus group are re-assessed here.

History & Status:

Background:  Generally, pest risk assessments and assignment of pest ratings are conducted per individual pest species and not per genus group primarily due to differing pest biologies, geographical distributions, host ranges, damage potentials, and risk mitigating requirements. However, an exception to this rule is made here for the genus Paratylenchus largely because of historical practice.  Over the past several decades, the genus, Paratylenchus, was seldom differentiated to species level by CDFA Nematologists mainly due to i) the common occurrence and wide distribution of member species within California, ii) no state enforced regulatory action required subsequent to their detection, and iii) greater demands of time involved in diagnosing high risk and other nematode species considered to be of greater economic importance than those belonging to Paratylenchus.

Members of the genus, Paratylenchus, are commonly known as ‘pin nematodes’.  Species reproduce producing eggs, four juvenile stages (J1, J2, J3, and J4) and adults.  The J1 juvenile stage is produced within the egg and undergoes a molt before the egg taches to release J2.  Males and J4 preadults do not feed. These nematodes inhabit the soil-root region of plants and feed on roots as obligate sedentary ectoparasites. Feeding by adults is limited to epidermal cells and the base of root hairs.  Juveniles may feed far out on the root hairs (Maggenti, 1981).  The nematodes move sluggishly and females become more sluggish after feeding.  The life cycle takes about 23 days for P. bukowinensis (Brzeski, 1976).  The non-feeding preadult of Paratylenchus is the most resistant stage that comprises about 90% of stages found in winter.  They can survive up to four years in the absence of a host.  Apparently, molting to the adult stage occurs in the presence of stimulatory substances emitted by suitable host roots (Mai et al., 1996; Maggenti, 1981).

Taxonomically, Paratylenchus spp. belong to family Paratylenchidae in the order Tylenchida and are characterized by their small body lengths ranging from 0.2 to 0.6 mm.  The genus comprises several species and in California, species diversity is high and yet to be determined.  Morphological identification of some species is difficult and therefore, diagnostics of Paratylenchus spp. can be based on rRNA gene sequences which are reliable genetic markers (Van den Berg et al., 2014).

Hosts: Paratylenchus spp. are associated with the roots of a wide range of herbaceous and woody plants including native plants, ornamentals, and many agricultural crops (Maggenti, 1981).  The host status of associated plants is not always known.  Dropkin (1989) lists host included in the families Cruciferae and Umbelliferae, such as carrot, celeriac, parsley and cabbage.  Other forage and woody plants include clover, grasses, grapes, and fruit trees.

Symptoms:  General plant damage associated with Paratylenchus spp. is minimal except when nematode populations are high in number.  Under favorable conditions, nematode populations can increase to tremendous numbers and in greenhouse experiments damaging levels of 100-125 nematodes per gram of soil have been found (Maggenti, 1981).  In general, infection by large numbers results in overall reduction in top and root growth without obvious symptoms on roots.  Feeding results in brown necrotic regions in some hosts (Mai et al., 1996; Maggenti, 1981).

Damage Potential:  Generally, Paratylenchus spp. are common associates of several plants.  Few Paratylenchus species, such as P. bukowinensis and P. projectus have known economic importance.  However, plant damage caused by high populations of pin nematodes could be more significant in small-area plant productions and/or containerized crops in nursery, greenhouse, residential and local situations than in large acreages and environments such as, pastures, parks, and cultivated fields. Crop damage under field conditions may be difficult to assess as Paratylenchus spp. are often mixed with other genera and/or two or more stunt nematode species occurring together.

Spread:  The main mode of long and short distance spread through artificial means: infested plant roots, movement of nematode-contaminated soil, run-off and irrigation water, cultivation tools, equipment and any human activity that can move soils from infested to non-infested sites.

Worldwide Distribution: Paratylenchus spp. are distributed widely geographically (Mai, 1996).

Official Control:  Currently, Paratylenchus spp. are D rated pests in California (see ‘Initiating Event’).  Paratylenchus spp. are on the ‘Harmful Organism Lists” for Australia and Nauru (USDA-PCIT, 2016).

California Distribution:  Paratylenchus spp. are widely distributed in California.

California Interceptions: For the past several decades, Paratylenchus spp. have been detected in several imported plant and soil shipments intercepted in California.

The risk Paratylenchus spp. would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Paratylenchus are able to establish throughout the State.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 3

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

2) Known Pest Host Range: Paratylenchus are known to be associated with several diverse plant species, however, the host status of associated plants is not always known.

Evaluate the host range of the pest.

Score: 3

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: The main mode of long and short distance spread through artificial means: Infested plant roots, movement of contaminated soil, run-off and irrigation water, cultivation tools, equipment and any human activity that can move soils from infested to non-infested sites.  Increase in reproduction rates depends on the plant species parasitized.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

4) Economic Impact: Generally, Paratylenchus are considered mild and common pathogens of plants.  However, under high population levels in residential, nurseries, greenhouse, and other small-area plantings, where high nematode populations can build up under favorable conditions, Paratylenchus spp. infections could result in lowered crop yield.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

Economic Impact Score: 1

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

5) Environmental Impact: The impact of  Paratylenchus spp. on natural environments is most likely not significant as the species is already widespread without causing apparent detriment to ecological balances and processes, however, heavy infestations of pin nematodes, particularly in potted plants, could affect home/urban gardening.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact.

Environmental Impact Score: 2

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Consequences of Introduction to California for Paratylenchus spp.: Medium (12)

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is High (-3).  Paratylenchus spp. are widespread in several contiguous and non-contiguous climate and host regions throughout the state.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 9

Uncertainty: 

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the pin nematodes, Paratylenchus spp., is C.

References:

Brzeski, M.  1976.  Paratylenchus bukowinensis.  C.I.H. Descriptions of Plant-parasitic Nematodes Set 6, No. 79.

Mai, W. F., P. G. Mullin, H. H. Lyon, and K. Loeffler.  1996.  Plant parasitic nematodes – a pictorial key to genera.  Fifth Edition.  Comstock Publishing Associates a division of Cornell University Press, Ithaca and London.  277 p.

Maggenti, A.  1981.  General nematology.  Springer-Verlag New York Heidelberg Berlin.  372 p.

USDA-PCIT.  2016.  United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp .

Van den Berg, E., L. R. Tiedt, and S. A Subbotin.  2014.  Morphological and molecular characterization of several Paratylenchus Micoletzky, 1922 (Tylenchida: Paratylenchidae) species from South Africa and USA, together with some taxonomic notes.  Nematology 16: 323-358.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health@cdfa.ca.gov

Comment Period: CLOSED

1/11/2017 – 2/25/2017

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment:
Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: C 

Posted by ls

Nematodes

Hemicycliophora arenaria Raski, 1958 | Citrus sheath nematode

California Pest Rating for
Hemicycliophora arenaria Raski, 1958
Citrus sheath nematode
Pest Rating: B

 

PEST RATING PROFILE
Initiating Event:  

None.  The current status and rating of Hemicycliophora arenaria is assessed.

History & Status:

Background:  The citrus sheath nematode, Hemicycliophora arenaria, was first reported in 1957 as an unknown species parasitizing rough lemon seedlings in a grower’s nursery in the Coachella Valley, near Mecca, southern California (Van Gundy, 1957).  The effect on seedling roots was noteworthy due to symptoms of ‘peculiar galling’ produced in infected plants, quite unlike those caused by the root-knot nematode. Soon after, in 1964, the same species was found in a citrus ranch approximately 2 miles from the original site in Riverside County and on citrus land in Imperial County.  All properties were planted with citrus trees from a commercial nursery located near Niland in Imperial County, approximately 40 miles from the original site in Riverside County. This nursery had been planted on virgin desert soil and failed due to lack of moisture, and consequently, was abandoned in 1956.  Surveys were conducted by the CDFA at that time to establish origin and extent of spread of the nematode species.  In 1965, H. arenaria was found in a number of soil samples collected from cheese bush, a California native plant, growing in a virgin desert region about one mile north of the original abandoned nursery.  At about the same time, the nematode species was also found on cheese bush in another native situation near Palm Springs, about 30 miles northwest from the infestation in Mecca.  Additionally, another California native plant, coyote melon, was experimentally shown to be a host of the nematode species (McElroy & Van Gundy, 1967).  In 1971, H. arenaria was found in soil and root samples collected from roadside cheese bush plants near the entrance of a desert state park in San Diego County.   These detections indicated that H. arenaria is indigenous to native plants in low and high elevation deserts of California and had been spread with citrus nursery stock from the abandoned nursery planting near Niland.  The species was assigned an ‘A’ rating because of its limited distribution and demonstrated potential for injury to citrus and vegetables (discussed below), and the infested sites were placed under a county “hold-order” quarantine.  This action restricted the movement of all soil, bare-rooted plants and equipment with soil.  Also, at the time of its discovery the citrus sheath nematode in California was of great concern to other state trading partners thereby making quarantine action necessary.  In 2006, in statewide, USDA APHIS CAPS-sponsored surveys, CDFA once again detected H. arenaria in lemon and grapefruit soils in Imperial County (Chitambar, 2008).

Hemicycliophora arenaria was named and described by Raski (1958).  Since its original discovery, the citrus sheath nematode had only been reported from California until more than 25 years later, when it was also reported from Australia and southern Argentina (Chitambar & Subbotin, 2014; Reay, 1984; Brugni & Chaves, 1994).

Hemicycliophora arenaria is a plant parasitic nematode species whose females feed ectoparasitically on host plant roots and lay their eggs singly in the soil.  Each egg has a gelatinous coating that makes it adhere to soil and roots. The optimum range for reproduction is 30-32.5°C with 32.5°C being the optimum. Within this temperature, the nematode completes a life cycle of 15-18 days.  Males do not feed and are not required for reproduction, which can be parthenogenetic.  Almost no reproduction occurs at 20°C and at 35°C reproduction is greatly reduced.  Furthermore, reproduction is greatest in sandy soils. Reproduction was determined to be greatest on tomato grown in 90% sand, 5% silt, and 5% clay, and at the original detection site in the Coachella Valley, the soil comprised 75% sand, 9% silt and 16% clay (Van Gundy & Rackham, 1961; Maggenti, 1981).  The nematode also requires adequate aeration and maybe killed by reduced aeration caused by prolonged irrigation cycles.  This preference of high temperature and sandy soils explains the very limited distribution of the citrus sheath nematode within desert regions of California, where it was discovered to be endemic on native desert plants namely, cheese bush and coyote melon (McElroy et al. 1966; McElroy & Van Gundy, 1967).  Subsequently, the citrus sheath nematode gained economic importance as a parasite of agricultural crops with the reclamation of southern California deserts (Maggenti, 1981).

Hosts:   Citrus is the main host.  Citrus limonia (Rough lemon), C. aurantifolia (West Indian lime), C. limon (Dorshapo sweet lemon), C. reticulata (Cleopatra mandarin), C. taiwanica (Taiwanica), Severinia buxifolia, Solanum lycopersicum (Rutgers tomato), Vigna sinensis (blackeye bean), Capsicum frutescens var. grossum (pepper), Apium graveolens (celery), Cucurbita moschata (squash) (Van Gundy, 1959; Van Gundy & Rackham, 1961; Van Gundy & McElroy, 1969), Hymenoclea salsola (syn. Ambrosia salsola; cheesebush), Cucurbita palmata (coyote melon), and Vitis vinifera (Tokay grape) (McElroy et al. 1966; McElroy & Van Gundy, 1967). Moura & Almeida (1982) found this species in sugar-cane field. Reay (1984) reports the following hosts from Australia: Auraucaria bidwillii, Acacia euthycarpa, A. gracilifolia, A. continua, A. myrtifolia, A. paradoxa, A. pycnantha, Banksia marginata, B. ornata, Callitris preisii, Eucalyptus anceps, E. baxteri, E. fasciculosa, E. foecunda, E. goniocalyx, E. incrassata, E. maculata, E. obliqua, E. odorata, E. oleosa, E. socialis, E. vitrea, Macrozamia spiralis, cycad, Melaleuca acuminata, M. lanceolata, and M. uncinata, Pteridium esculentum, bracken, Xanthorrhoea quadrangulata, and Austrocedrus chilensis.

Symptoms:  Plants infected by H. arenaria are easily recognized by swellings or galls produced on lateral and terminal roots.  Unlike galls formed along the length of roots parasitized by root-knot nematodes, galls caused by H. arenaria are produced at the tips of lateral and terminal roots.  The nematodes remain tightly attached to freshly dug roots and are visible through a hand lens (McElroy & Van Gundy, 1967).

Damage Potential: Feeding of H. arenaria results in the production of galls at tips of lateral and terminal roots, as well as a reduction in the number of feeder roots and top growth. The growth of rough lemon seedlings in H. arenaria infested soil at 30°C for 5 months was reduced by 36% in comparison to seedlings in non-infested soil.  Dry weight of tomato plants was reduced by 28%, and a 10-20% yield reduction in field-grown tomato and squash occurred at the original locality in Mecca, California. Growth of citrus and tomato was reduced from 12% at 25°C to 37% at 30°C (McElroy & Van Gundy, 1967, 1968; Van Gundy & Rackham, 1961).  Significant damage may affect citrus production under climates suitable for the development of the nematode species.

Transmission:  Infested rootstock, rooted plants, soil, irrigation and run-off water, cultivation tools and equipment that can move infested soil and plant roots to non-infested sites.  

Worldwide Distribution: Oceania: Australia (South Australia, New South Wales, Queensland); North America: USA (California); South America: Argentina, Brazil (Brugni & Chaves, 1994; Reay, 1984; Van Gundy, 1957; McElroy & Van Gundy, 1967; Moura & Almeida, 1982).

Official Control: Hemicycliophora arenaria is on the ‘Harmful Organism Lists’ for Honduras, Republic of Korea, and Taiwan (USDA PCIT, 2016).  Within the USA, Florida has listed H. arenaria as a plant pest of quarantine significance and potentially subject to quarantine action (FDACS, 2016).

California Distribution: Limited desert regions within Imperial, Riverside and San Diego Counties.

California Interceptions: Hemicycliophora arenaria has never been detected in intercepted plant and soil shipments to California.

The risk citrus sheath nematode would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

-Low (1) not likely to establish in California; or likely to establish in very limited areas

-Medium (2) may be able to establish in a larger but limited part of California

– High (3) likely to establish a widespread distribution in California.

Risk is Medium (2).  Hemicycliophora arenaria is naturally endemic to limited hot desert regions within Imperial, Riverside and San Diego Counties.  Within those regions it has been found naturally infesting coyote melon and cheese bush which are indigenous desert plants commonly found in the sandy washes and stream beds in the Coachella and Imperial valleys and provide a reservoir of nematodes for infesting plantings in non-infested soils.  High soil temperatures and coarse soils are needed for the nematode to develop and affect plant growth and production.  Agricultural host plants grown under those climate conditions are likely to establish and further spread the nematode to non-infested regions particularly in reclaimed desert regions of southern California.      

2) Known Pest Host Range: Evaluate the host range of the pest:

-Low (1) has a very limited host range

-Medium (2) has a moderate host range

– High (3) has a wide host range.

Risk is Medium (2).  Hemicycliophora arenaria has a moderate host range which includes citrus as the main host, also tomato and other vegetable plants, and grape (Tokay variety).  California native desert plants, cheese bush and coyote melon are hosts of the nematode species in California.    

3) Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

-Low (1) does not have high reproductive or dispersal potential

-Medium (2) has either high reproductive or dispersal potential

– High (3) has both high reproduction and dispersal potential.

Risk is High (3).  Hemicycliophora arenaria has high reproduction and is dispersed primarily by movement of infested rootstock, plant roots, soil, irrigation and run-off water, cultivation tools and equipment that can move infested soil and plant roots to non-infested sites.  

4) Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A. The pest could lower crop yield

B. The pest could lower crop value (includes increasing crop production costs)

C. The pest could trigger the loss of markets (includes quarantines by other states or countries)

D. The pest could negatively change normal production cultural practices

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses

-Low (1) causes 0 or 1 of these impacts

-Medium (2) causes 2 of these impacts

– High (3) causes 3 or more of these impacts.

Risk is High (3).  Under suitable climates for infestations of the citrus sheath nematode, crop yield and value could be lowered.  Reductions of 36% growth of rough lemon seedlings in H. arenaria infested soil at 30°C has been reported.  Also, reported was 28% reduction in dry weight of tomato plants and 10-20% yield reduction in field-grown tomato and squash. Growth of citrus and tomato was reduced from 12% at 25°C to 37% at 30°C.  The nematode may also spread along the flow of irrigation water in a field, thereby, requiring change in normal irrigation and cultural practices.  The original detection of H. arenaria in California resulted in establishment of quarantines by other states and to date, the citrus sheath nematode is a quarantine regulated pest in Florida. Therefore, a ‘High’ rating is given here for the potential economic impact of H. arenaria.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur

– Medium (2) causes one of the above to occur

– High (3) causes two or more of the above to occur.

Risk is Medium (2).  Under favorable conditions of warm to hot soil temperatures and coarse textured soils, the citrus sheath nematode could significantly impact home and commercial urban plantings and cultural practices.     

Consequences of Introduction to California for Common Name:  Score

Add up the total score and include it here. (Score)

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 12.

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas

Evaluation Low (-1):  Hemicycliophora arenaria is established in limited hot desert regions within Imperial, Riverside and San Diego Counties.

Final Score:

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 11.

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence presented above, the proposed pest rating for the citrus sheath nematode, Hemicycliophora arenaria is B. 

References:

Brugni, N., and E. Chaves.  1994.  Criconemoides from a cypress forest of South Argentina.  Nematologica 40: 467-473.

CABI.  2016.  Hemicycliophora arenaria (sheath nematode).  http://www.cabi.org/cpc/datasheet/46685 .

Chitambar, J. J.  2008.  Status of ten quarantine “A” nematode pests in California.  California Plant Pest and Disease Report 24: 62-75.

Chitambar, J. J. and S. A. Subbotin.  2014.  Systematics of the sheath nematodes of the superfamily Hemicycliophoroidea.  Nematology Monographs and Perspectives, Vol. 10 (Series Editors: D. J. Hunt and R. N. Perry).  The Netherlands, Leiden, Brill, 2014. 732 p.

FDACS.  2016.  Florida summary of plant protection regulations updated June 2016.  Florida Department of Agriculture and Consumer Services Division of Plant Industry.  http://nationalplantboard.org/wp-content/uploads/docs/summaries/florida.pdf .

Maggenti, A. 1981.  General Nematology.  Springer-Verlag New York, Inc. 372 p.

McElroy, F. D., and S. D. Van Gundy.  1967.  The sheath nematode.  The California Citrograph 52, 379-384.

McElroy, F. D., and S. D. Van Gundy.  1968.  Observations on the feeding process of Hemicycliophora arenaria.  Phytopathology 58: 1558-1565.

McElroy, F. D., S. A. Sher, and S. D. Van Gundy.  1966.  The sheath nematode, Hemicycliophora arenaria, a native to California soils.  Plant Disease Reporter 40: 581-583.

Moura, R. M., and A. V. Almeida.  1982.  Preliminary studies on the occurrence of phytonematodes associated with sugarcane in areas of low productivity in Pernambuco State.  Nematologia Brasileira 5: 213-220.

Raski, D. J.  1958.  Four new species of Hemicycliophora de Man, 1921, with further observations on H. brevis Thorne, 1955 (Nematoda: Criconematidae).  Proceedings of the Helminthological Society of Washington 25: 125-131.

Reay, F.  1984.  Plant nematodes from Australia: new records of Hemicycliophoroidea (Nematoda: Tylenchida).  Australasian Plant Pathology 13: 8-11.

USDA PCIT.  2016.  USDA Phytosanitary Certificate Issuance & Tracking System. September 27, 2016.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Van Gundy, S. D.  1957.  The first report of a species of Hemicycliophora attacking citrus roots.  Plant Disease Reporter 41: 1016-1018.

Van Gundy, S. D.  1959.  The life history of Hemicycliophora arenaria Raski (Nematoda: Criconematidae).  Proceedings of the Helminthological Society of Washington 26: 67-72.

Van Gundy, S. D. and R. L. Rackham.  1961.  Studies on the biology and pathogenicity of Hemicycliophora arenaria.  Phytopathology 51: 393-397. 

 Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: (916) 262-1110, plant.health[@]cdfa.ca.gov.

Comment Period:  CLOSED

Oct 25 – Dec 9, 2016

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Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

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Pest Rating: B

Posted by ls

Nematodes

Radopholus similis (Cobb, 1893) Thorne, 1949

1356104-burrowing-nematode-byMichaelMcClure-Univ-of-Ariz-bugwood
California Pest Rating for
Radopholus similis (Cobb, 1893) Thorne, 1949
(Burrowing Nematode)
Pest Rating: A

 

PEST RATING PROFILE
Initiating Event:  

None.  The current status and rating of Radopholus similis is re-evaluated.

 History & Status:

Background:  The burrowing nematode, Radopholus similis, is one of the most economically important plant parasitic nematode in tropical and subtropical regions of the world.  It is widespread in most banana-growing regions where it causes blackhead toppling disease or decline of banana. It is also known to cause declines of avocado, tea, coconut, citrus, and yellows (slow-wilt) disease of black pepper, and attacks several fruit, ornamentals, forest trees, sugarcane, coffee, weeds, vegetables, grasses, and weeds.

Radopholus similis has undergone several name changes over the past several years.  In 1893, Cobb first described the nematode as Tylenchus similis associated with a serious disease of bananas in Fiji.  From 1898 to 1915 the nematode was discovered in sugarcane in Hawaii, banana in Jamaica, and coffee in Java but described under different names which were later regarded as synonyms of T. similis.  In 1949, Thorne established the genus Radopholus for the species originally belonging to Tylenchus, and T. similis became R. similis.  Radopholus similis was known to have two biological races, a banana and citrus race.  In 1984, the citrus race was elevated to species status and became known as R. citrophilus, separate from R. similis (Huettel, 1984).  However, through molecular and morphological analyses, R. citrophilus was determined to be similar to R. similis and is now accepted as synonymous to the latter species (CABI, 2016; Kaplan & Opperman, 1997; Valette et al., 1998). For regulatory purposes, the CDFA has always regarded R. similis (sensu lato) to include both banana and citrus races (Chitambar, 1997).

Radopholus similis is a migratory endoparasite of plant roots.  The nematode develops from egg through four larval stages to adult male and female which reproduce sexually and parthenogenetically.  Radopholus similis completes its life cycle in 25 days at 25-28°C in coconut, 20-25 days at 24-32°C in banana, and 18-20 days at 24-27°C in citrus.  The nematode species is able to complete its entire life cycle within the root cortex, however in adverse conditions, motile, vermiform larvae and adults may emerge from the roots and invade rhizosphere soils (EPPO, not dated; Tarjan & O’Bannon, 1984).  The number of nematodes present in soil and roots varies with soil temperature, texture, moisture, and season.  On citrus, R. similis is found at soil depths of 60-150 cm (DuCharme, 1967), and is more pathogenic to citrus in sandy soils than loam or sandy loam soils (O’Bannon & Tomerlin, 1971).

Hosts:  Radopholus similis has a very wide host range of more than 350 known hosts although the pathogenicity of the nematode is not known for all hosts (Ferris et al., 2003).  Main hosts include, Musa sp. (banana), M. textilis (Manila hemp), Musa x paradisiaca (plantain), Citrus spp. (citrus), Cocos nucifera (coconut), Zingiber officinale (ginger), palm, Persea americana (avocado), Coffea arabica (arabica coffee), C. canephora (robusta coffee), Piper nigrum (black pepper), Lycopersicum esculentum (tomato), Daucas carota (carrot),vegetables, trees, ornamentals, grasses, and weeds (CABI, 2016; Ford et al., 1960; Ferris, et al., 2003).  In California, agricultural crops of economic importance include citrus, strawberry, carrots, and ornamentals.

Symptoms: Above ground symptoms are non-specific and include yellowing, stunting, reduction in number and size of leaves and fruit, delay in flowering, and overall sparse foliage of orchard trees.  Infected trees wilt more readily than healthy trees under adverse environmental conditions (Griffith & Koshy, 1990; Tarjan & O’Bannon, 1984).  Banana plants become uprooted and topple over, especially those burdened with fruit.  Below ground symptoms include, brown to black lesions formed at the site of nematode penetration in citrus roots.  These lesions coalesce to form cankers.  A greater percentage of citrus feeder roots are destroyed below 75 cm than at 25-75 cm.  In banana roots, dark red lesions appear on the outer root portion, penetrating throughout the cortex but not into the stele.  Lesions may coalesce and girdle the root forming black, necrotic lesions which may extend into the corm (Gowen & Quénéhervé, 1990).  Tender roots of coconut seedlings become spongy in texture and small, elongate orange lesions are formed in tender white roots.  Lesions enlarge as rot sets in.  Cracks in lesions may appears as lesions harden. Secondary and tertiary roots rot and slough off quickly on infestation (Griffith & Koshy, 1990).

Damage Potential: In Florida orchards, yield losses of 40-70% for oranges and 50-80% for grapefruit have been reported (DuCharme, 1968).  Reduction in fruit production varies with age of the tree, citrus variety, farming practices and duration of the nematode infestation (CABI, 2016).   Avocado trees show spreading decline symptoms similar to citrus.  Several indoor decorative plants can be severely affected (Ferris, 2003).  Nurseries may suffer significant losses in production.

Transmission: Infested nursery stock, propagative planting materials, bare root stock, corms, rhizomes, suckers, seedlings, rooted and non-rooted cuttings, soil, infested-soil contaminated cultivation tools and containers, irrigation water.

Brief update of detections in California:  The CDFA has been protecting California against the burrowing nematode since the early 1950s when the nematode pathogen was first found to cause spreading decline of citrus in Florida.  In the years that followed, statewide surveys revealed several ornamental nurseries to be infested with Radopholus similis and consequently, the nematode species was eradicated.  In 1956, The Burrowing Nematode Exterior Quarantine (Sec. 3271) was established by CDFA to restrict the entrance of the pathogen from infested regions.  In 1956, surveys of citrus and avocado orchards and ornamental nurseries, were conducted through the cooperative efforts of federal, state, and county agricultural commissioners.   These surveys resulted in no detection of R. similis in CA.  In 1963, the burrowing nematode was detected in Anthurium spp. in a nursery in San Mateo County.  The plants were destroyed and the nematode was eradicated. From 1963-64, additional statewide surveys were conducted for Anthurium spp., citrus, and avocado in orchards, nurseries, and residential properties adjacent to nurseries.  No R. similis was detected.  In 1964, CDFA created the ‘Burrowing Nematode Detection Program in California Nurseries’ which terminated in 1994.  Surveys continued in 1971, 2005-2009, and 2011 all which resulted in no detection of R. similis.  Intercepted plant shipments imported to California under the Burrowing Nematode Exterior Quarantine continue to be examined for the burrowing nematode.  A noteworthy early detection of an established R. similis population occurred in 1996 in a residential property in Huntington Beach. Consequently, the nematode was eradicated from the infested region (Chitambar, 2007). Since then, there have been no further detections of R. similis established in California and the pathogen is not known to be present in California.

Worldwide Distribution: The burrowing nematode is found worldwide in tropical and subtropical regions and occurs wherever bananas are grown.  Worldwide distribution includes Asia: Brunei Darussalam, India, Indonesia, Japan, Lebanon, Malaysia, Oman, Pakistan, Philippines, Singapore, Sri Lanka, Thailand, Yemen; Africa: Benin, Burkino Faso, Burundi, Cameroon, Central African Republic, Congo, Congo Democratic Republic, Côte d’Ivoire, East Africa, Egypt, Ethiopia, Gabon, Gambia, Ghana, Guinea, Guinea-Bissau, Kenya, Madagascar, Malawi, Mauritius, Morocco, Mozambique, Nigeria, Réunion, Rwanda, Senegal, Seychelles, Somalia, South Africa, Sudan, Tanzania, Uganda, Zambia, Zimbabwe; North America: Canada, Mexico, USA; Central America and Caribbean: Barbados, Belize, Costa Rica, Cuba, Dominica, Dominican Republic, El Salvador, French West Indies, Grenada, Guadeloupe, Guatemala, Honduras, Jamaica, Martinique, Panama, Puerto Rico, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Trinidad and Tobago, United States Virgin Islands, Windward Islands; South America: Bolivia, Brazil, Colombia, Ecuador, French Guiana, Guyana, Peru, Suriname, Venezuela; Europe: Belgium, France, Italy, the Netherlands, Slovenia; Oceania: American Samoa, Australia, Cook Islands, Fiji, French Polynesia, Guam, Micronesia, New Caledonia, Niue, Norfolk, Palau, Papua New Guinea, Samoa, Solomon Islands, Tonga (CABI, 2016; EPPO, 2016).

Official Control: Radopholus similis is a quarantine, A-rated nematode pest under CDFA Sec. 3271. Burrowing and Reniform Nematode State Exterior Quarantine. Areas under quarantine include, the states of Alabama, Arkansas, Florida, Georgia, Hawaii, Louisiana, Mississippi, North Carolina, South Carolina, Texas, and the commonwealth of Puerto Rico.

Radopholus similis is listed in the ‘Harmful Organism Lists’ for 32 countries including, Antigua and Barbuda, Argentina, Bangladesh, Bermuda, Chile, China, European Union, French Polynesia, Georgia, Guatemala, Holy See (Vatican City State), Israel, Japan, Jordan, Madagascar, Mexico, Monaco, Morocco, Namibia, Nepal, Norway, Panama, Paraguay, San Marion, Serbia, South Africa, Taiwan, Tunisia, Turkey, United Arab Emirates, Uruguay, and Vietnam.  Radopholus citrophilis (synonym of R. similis) is listed in the ‘Harmful Organism Lists’ for Antigua and Barbuda, Namibia, and South Africa; R. similis citrophilus (synonym of R. similis) is listed for Argentina, Brazil, European Union, French Polynesia, Grenada, Guatemala, Holy See (Vatican City State), Israel, Japan, Jordan, Monaco, Morocco, New Caledonia, San Marino, Serbia, Tunisia, Turkey, and Uruguay; Radopholus spp. is listed for Australia, French Polynesia, and Nauru (USDA PCIT, 2016).

California Distribution: Radopholus similis is not established in California.

California Interceptions: Since 1982 to September 2016, CDFA has made 182 detections of Radopholus similis and 13 detections of Radopholus sp. in incoming quarantine shipments of nursery and household plants at nurseries and border stations in California, of which only 16 detections of R. similis and 0 detections of Radopholus sp. were made during 2000-2016 (CDFA Pest and Damage Records Database).

The risk burrowing nematode would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

-Low (1) not likely to establish in California; or likely to establish in very limited areas

-Medium (2) may be able to establish in a larger but limited part of California

– High (3) likely to establish a widespread distribution in California.

Risk is High (3).  California provides favorable climate and hosts for the establishment, increase, and widespread distribution of the burrowing nematode. The nematode prefers coarse, sandy soils which are present in the Coachella Valley, the Bard Valley near Blythe, the Edison-Arvin citrus district of Kern County, and in streaks throughout the state. Citrus and date palm, good hosts of the nematode, in the Coachella Valley are planted in soils subject to temperatures favorable to the development of the nematode.  Host crops along the coastal areas, when planted in sandy soil, experience soil temperatures that can favor the development of the nematode if even for a few months.  

2) Known Pest Host Range: Evaluate the host range of the pest:

-Low (1) has a very limited host range

-Medium (2) has a moderate host range

– High (3) has a wide host range.

Risk is High (3).  Radopholus similis has a wide host range of over 350 host plants including citrus, strawberry, carrots, date palm, and ornamentals which are major hosts cultivated in California.

3) Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

-Low (1) does not have high reproductive or dispersal potential

-Medium (2) has either high reproductive or dispersal potential

– High (3) has both high reproduction and dispersal potential.

Risk is High (3).  Radopholus similis has both high reproduction and dispersal potential.  It is spread over long and short distances by infected plant roots, soil, planting stock, rooted and non-rooted cuttings, weeds, soil, nematode-contaminated cultivation tools, and containers, planting beds, irrigation and run-off water.

4) Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A. The pest could lower crop yield

B. The pest could lower crop value (includes increasing crop production costs)

C. The pest could trigger the loss of markets (includes quarantines by other states or countries)

D. The pest could negatively change normal production cultural practices

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses

-Low (1) causes 0 or 1 of these impacts

-Medium (2) causes 2 of these impacts

– High (3) causes 3 or more of these impacts.

Risk is High (3).  The establishment of Radopholus similis in California could result in lowered crop yield and value, increased crop production costs, loss of markets, imposition of domestic and international quarantines against California export plant commodities, and alteration of normal cultural practices, including delivery of irrigation water, to inhibit spread of the pathogen to non-infested sites.    Citrus, strawberry, carrots, date palms, and ornamentals are some of the main industries that would be affected.   Additionally, several other crops of lesser production in California are also at risk.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur

– Medium (2) causes one of the above to occur

– High (3) causes two or more of the above to occur.

Risk is High (3).   The establishment of Radopholus similis in California could adversely impact the environment by destroying natural communities, critical habitats, significantly affect residential gardening and cultural practices thereby requiring additional official or private treatment programs. Given its wide host range several, agricultural and environmental communities are at definite risk of being impacted.  These can include habitats of minor and major animal communities.

Consequences of Introduction to California for Common Name:  Score

Add up the total score and include it here. (Score)

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 15 (High).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas

Evaluation:  Radopholus similis is not established in California (0).  In 1996, the nematode species was discovered in a residential area in Huntington Beach, California, however, due to the early detection and isolated nature of the incident, the infestation was successfully eradicated by the CDFA.  Similarly, eradicative actions taken subsequent to the detection of the nematode species in imported nursery and household plant shipments, vigilant screening of plant materials grown in California soils and inspected for plant parasitic nematodes through CDFA’s phytosanitary certification programs, USDA CAPS sponsored statewide surveys conducted by CDFA from 2005-2009 for 22 target nematode species including R. similis, and all published studies to date on plant parasitic nematodes in California have never resulted in the detection of R. similis.

Final Score:

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 15 (High).

Uncertainty:

The damage potential and crop loss information on several hosts of this nematode species are yet to be determined.  Nevertheless, based on the nematode’s biology, diverse host range, and favorable climatic conditions that (historically have) allowed the pest to establish within California (and then be eradicated), more information gained on crop damage and losses can only further confirm the burrowing nematode as a pest of major economic importance within several regions of California.

Conclusion and Rating Justification: 

Based on the evidence presented above, reniform nematode is definitely a pest of high risk to agricultural and environmental communities of California.  The current given “A” pest rating of Radopholus similis is duly justified and is herein, proposed to remain unchanged. 

References:

CABI.  2016.  Radopholus similis (burrowing nematode) datasheet (full). http://www.cabi.org/cpc/datasheet/46685

Chitambar, J. J.  1997.  A brief review of the burrowing nematode, Radopholus similis.  California Plant Pest & Damage Report, California Department of Food and Agriculture, 16: 66-70.

Chitambar, J. J. 2007.  Status of ten quarantine “A” nematode pests in California.  California Plant Pest & Damage Report, California Department of Food and Agriculture, 24: 62-75.

DuCharme, E. P. 1967.  Annual population periodicity of Radopholus similis in Florida citrus groves.  Plant Disease Reporter 51: 1013-1034.

DuCharme, E. P. 1968. Burrowing nematode decline of citrus. A review. In: Smart GC, Perry VG, eds. Tropical Nematology. Gainesville, USA: University of Florida Press, 20-37.

EPPO.  2016.  Radopholus similis (RADOSI).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.

EPPO.  Not dated.  Data sheets on quarantine pests Radopholus citrophilus and Radopholus similis.  Prepared by CABI and EPPO for the EU under Contract 90/399003.  https://www.eppo.int/QUARANTINE/data_sheets/nematodes/RADOSP_ds.pdf

Ferris, H., K. M. Jetter, I. A. Zasada, J. J. Chitambar, R. C. Venette, K. M. Klonsky, and J. Ole Becker.  2003.  Risk Assessment of plant parasitic nematodes. In Exotic Pests and Diseases Biology and Economics for Biosecurity, D. A. Summer Editor. Iowa State Press. 265 p.

Ford, H. W., W. A. Feder, and P. C. Hutchins.  1960.  Citrus varieties, hybrids, species and relatives evaluated for resistance to the burrowing nematode Radopholus similis.  Plant Disease Reporter 44:405.

Gowen, S., and P. Quénéhervé.  1990.  Nematode parasites of bananas, plantains and abaca. In: Luc, M., R. A. Sikora, J. Bridge, eds. Plant Parasitic Nematodes in Subtropical and Tropical Agriculture. Wallingford, UK: CAB International, 431-460.

Griffith, R., P. K. Koshy.  1990.  Nematode parasites of coconut and other palms. In: Luc, M., R. A. Sikora, J. Bridge, eds. Plant Parasitic Nematodes in Subtropical and Tropical Agriculture. Wallingford, UK: CAB International, 363-386.

Huettel, R. N., D. W. Dickson, and D. T. Kaplan.  1984.  Radopholus citrophilus n. sp., a sibling species of Radopholus similis.  Proceedings of the Helminthological Society of Washington 51: 32-35.

Kaplan, D. T., and C. H. Opperman.  1997.  Genome similarity implies that citrus-parasitic burrowing nematodes do not represent a unique species. Journal of Nematology, 29: 430-440.

O’Bannon, J. H., and A. T. Tomerlin.  1970.  Response of citrus seedlings to Radopholus similis in two soils.  Journal of Nematology 3: 255-260.

USDA PCIT.  2016.  USDA Phytosanitary Certificate Issuance & Tracking System. September 27, 2016.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Valette, C., D. Mouonport, M. Nicole, J. L. Sarah, and P. Baujard.  1998.  Scanning electron microscope study of two African populations of Radopholus similis (Nematoda: Pratylenchidae) and proposal of R. citrophilus as a junior synonym of R. similis.  Fundamental and Applied Nematology 21: 139-146.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: (916) 262-1110, plant.health[@]cdfa.ca.gov.

Comment Period:  CLOSED

Oct 5 – Nov 19, 2016

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment: 

Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

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♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: A

Posted by ls

Nematodes

Ditylenchus destructor Thorne, 1945

 potato rot nematode
California Pest Rating for
Ditylenchus destructor Thorne, 1945
Pest Rating: A

 

PEST RATING PROFILE
Initiating Event:

On June 1, 2016, the USDA added Ditylenchus destructor to the ‘List of Pests No Longer Regulated at U.S. Ports of Entry’. Consequently, the risk of introduction and establishment of Ditylenchus destructor in California is evaluated and the current rating is reviewed.

History & Status:

Background:  Ditylenchus destructor was described by Thorne as a valid species in 1945.  However, prior to 1945, it was regarded as a strain or race of Ditylenchus dipsaci – the stem and bulb nematode.  Therefore, much of the earlier literature provides confusing information on the two species especially in relation to potato. Both species are distinctly differentiated from each other morphologically and molecularly.

Ditylenchus destructor, commonly known as the potato rot nematode after its principal host, is a plant parasitic nematode that causes significant loss in crop production mainly of potato, iris, and several other crops.    Ditylenchus destructor is a migratory endoparasite of roots and underground subterranean modified plant parts such as tubers, stolons, bulbs, and rhizomes, and rarely invades above-ground parts, mainly the stem base (EPPO, 2008).  The nematode species is also capable of feeding and reproducing on several fungal species and can destroy the hyphae of cultivated mushroom (Agaricus hortensis).  Nematodes enter potato tubers through lenticels, rapidly multiply and invade the entire tuber within which they continue to develop and increase in numbers.  External lesions subsequently serve as avenues for secondary infections by other pathogens. The nematode species secretes enzymes that digest starch and proteins and cause cell disintegration or rot of the infected plant parts.  Generally significant damage to potatoes can occur at cool temperatures (15-20°C) and high relative humidity (90%) (CABI, 2016).

Ditylenchus destructor has been reported from several countries including limited regions within the USA (see ‘Worldwide Distribution”).

Status of detections in California:  For long, the potato rot nematode has been cited in scientific publications as being present in California.   An up-to-date, brief review of detections of the nematode pathogen in California is presented here.  In California, the first recorded instance of potato tuber rot caused by D. destructor, was in 1968 in an experimental planting of potatoes in infested soil at Muir Beach, Marin County (Ayoub, 1970).  During the late 1950s to mid-1970s, CDFA recorded few detections of D. destructor only in iris bulbs from nurseries in Humboldt, Contra Costa, San Diego, and Santa Cruz Counties, few detections, also in iris bulbs, from residential/dooryard environments in San Diego, San Francisco, and San Luis Obispo Counties, and few detections from commercial environments in Marin and Santa Cruz Counties.  The most recent detection was in 1995 from round-headed garlic (Allium sphaerocephalum) bulbs in a nursery in Santa Cruz County (CDFA Nematology Laboratory Pest and Damage Records).  There have been no other reports of potato rot nematode detections in California’s agricultural and natural environments.  Viglierchio’s (1978) report of D. destructor infesting Ponderosa pine in California has sometimes been cited incorrectly in subsequent publications to infer that the nematode species naturally infests California pines, when in fact, Viglierchio reported only experimental studies conducted in a greenhouse. Early infestations found in nurseries and commercial productions would have been destroyed or significantly minimized through use of nematode-free planting stock and treatments of infected sites. Presently, the 1995 Santa Cruz nursery is no longer in business and non-existent.

It is important to note that with one exception occurring in 1995, over the past 30-40 years, D. destructor has not been detected through CDFA’s nematode surveys and nematode detection programs.  From 2005 to 2009, CDFA conducted USDA CAPS sponsored statewide surveys for 22 target nematode species including D. destructor, associated with 24 major host plant species, including potato, tomato, iris and several other agricultural crops and ornamentals in California’s major cropping and nursery production regions.  Ditylenchus destructor was not detected (Chitambar et al., 2008). Additional surveys, namely, potato cyst nematode surveys and golden nematode trace-forward surveys, and California’s citrus and golf course exotic nematode survey conducted by CDFA during 2006-2011, 2008, and 2012 respectively, and sponsored by USDA APHIS PPQ, failed to detect D. destructor in California’s potato seed and production fields, citrus, and golf course turf soils.  Although, D. destructor was not the target species of those surveys, nematode extraction techniques deployed by the CDFA Nematology Lab would have enabled the possible detection of the potato rot nematode, if present.   Furthermore, outside the afore-mentioned historical records, D. destructor has not been detected in CDFA’s regulatory detection programs involving plants grown in California soils.  Those regulatory programs include phytosanitary certification or California-grown potatoes for export, nursery stock certification of California-grown strawberry, garlic, and fruit trees (CDFA Nematology Laboratory Pest and Damage Records). Also, the in-state presence of the nematode species has not been reported from other sources. Therefore, it can be inferred that the potato rot nematode, D. destructor, is no longer detectable in California’s agricultural production sites.

Hosts:  The known host range of Ditylenchus destructor comprises more than 100 plant species from a wide variety of plants including ornamental plants, agricultural crops, and weeds.  Solanum tuberosum (potato) is the principal host.  Other economically important crops include Iris spp. (iris), Tulipa spp. (tulip), Dahlia spp. (dahlia), Gladiolus spp., (gladiolus), Rheum rhabarbarum (rhubarb), Trifolium spp. (clover), Daucus carota (carrot), and Beta vulgaris (sugarbeet).  Weed hosts include, Cirsium arvense, Mentha arvensis, Argentina (Potentilla) anserina, Rumex acetosella, and Stachys palustris (EPPO, 2008).

Symptoms: Generally, there are no obvious symptoms in above-ground parts of a plant infected with Ditylenchus destructor. Rarely when above ground parts are infected, symptoms may include dwarfing, thickening and branching of the stem and dwarfed, curled and discolored leaves (Sturhan & Brzeski, 1991).  Heavily infested potato tubers may result in weak plants that eventually die. Common symptoms are discoloration and rotting of plant tissue.  Symptom expression may vary with host.

Symptoms in potatoes: Initial symptoms appear in tubers as white spots under the skin.  These spots later enlarge, become woolly in texture, and may have slightly hollow centers.  Similar symptoms develop in dahlia tubers.  Badly infected tubers have slightly sunken areas with cracked and papery skin detached from underlying tissue.  The underlying tissue is discolored grey to dark brown or black bearing a mealy or spongy appearance.  Discoloration is mainly due to secondary invasion of fungi, bacteria and free-living nematodes. In storage, rotting may increase with increasing temperature, without infestation spreading from diseased to healthy tubers (CABI, 2016).

Symptoms on flower bulbs and corms (e.g. tulips, iris): Infestations usually initiate at the base of a bulb and extend upwards to the fleshy scales producing yellow to dark brown lesions.  Rotting may occur due to secondary invaders resulting in destruction of bulbs.

Symptoms on carrots:   Transverse cracks are produced in the skin with white patches in the underlying sub-cortical tissue.  Rotting may occur due to secondary invaders resulting in destruction of carrots.

Survival: Unlike the stem and bulb nematode, Ditylenchus dipsaci, the potato rot nematode does not have a resistant life stage (4th stage juvenile) that allows it to survive anhydrobiotically.  However, D. destructor can survive on fungal hosts in the absence of plant hosts.

Transmission:  The nematode can move only short distances on its own in soil, and is dependent on secondary means for its spread over long distances.  The main means of transmission is with infested subterranean propagative plant parts (tubers, rhizomes, bulbs).  Other means of spread include infested soil, irrigation water, weeds (CABI, 2016).

Damage Potential:  Ditylenchus destructor causes rotting of tubers and other subterranean plant parts resulting in losses in crop growth and yield.  Rotting may increase during storage.

Worldwide Distribution: Asia: Azerbaijan, China, Iran, Japan, Kazakhstan, Republic of Korea, Kyrgyzstan, Pakistan, Saudi Arabia, Tajikistan, Turkey, Uzbekistan; Africa: South Africa; North America: Canada, Mexico, USA; South America: Ecuador, Peru; Europe: Albania, Austria, Belarus, Belgium, Bulgaria, Czech Republic, Estonia, France, Germany, Greece, Hungary, Ireland, Jersey, Latvia, Luxembourg, Moldova, the Netherlands, Norway, Poland, Romania, Russian Federation, Slovakia, Sweden, Switzerland, UK, Ukraine; Oceania: Australia, New Zealand (CABI, 2016; EPPO, 2008, 2016).

Due to unreliable detection records, Ditylenchus destructor is regarded as absent from the following countries and states: Bangladesh, India, Malaysia, Australia, Haiti, Peru, Italy, Spain (mainland), British Columbia (Canada), Arkansas, Indiana, New Jersey, North Carolina, and Virginia.  Its presence is not confirmed in West Virginia (USA) (CABI, 2016).

In the USA, Ditylenchus destructor has been reported from California, Hawaii, Idaho, Oregon, South Carolina, Washington and Wisconsin (CABI, 2016; EPPO, 2016).

Official Control: Ditylenchus destructor is on the ‘Harmful Organism’ lists for 45 countries: Algeria, Argentina, Brazil, Canada, Chile, China, Colombia, Costa Rica, Cuba, Ecuador, Egypt, El Salvador, European Union, French Polynesia, Guatemala, Holy See (Vatican City State), Honduras, Iceland, Indonesia, Israel, Jordan, Madagascar, Mexico, Monaco, Morocco, Namibia, New Caledonia, Nicaragua, Norway, Panama, San Marino, Serbia, South Africa, Sri Lanka, Taiwan, Thailand, Timor-Leste, Tunisia, Turkey, United Arab Emirates, Uruguay, Vietnam (USDA PCIT, 2016).

On June 1, 2016, the USDA added Ditylenchus destructor to the ‘List of Pests No Longer Regulated at U.S. Ports of Entry’, however, the nematode pathogen remains actionable at certain ports of entry in Hawaii, Puerto Rico, or the U.S. territories (USDA, 2016).

Presently, Ditylenchus destructor is a “B’-rated, actionable nematode pathogen in California.

California Distribution: Presently, Ditylenchus destructor is not known to be present in California’s agricultural production sites (see “Status of detections in California”).

California Interceptions:  From 1983 to 2016, Ditylenchus destructor has been detected in seven shipments of Iris spp. bulbs imported to Watsonville, California (CDFA Pest and Damage Records).

This risk potato rot nematode, Ditylenchus destructor would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is Medium (2): Ditylenchus destructor may be able to establish a large but limited distribution primarily within the States potato production acreage under cool and humid/moist climates.  It is also likely to spread in cools regions where economically important hosts are grown and survive adverse climates in weed hosts.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3): The main host is potato.  However, the known host range of Ditylenchus destructor comprises more than 100 plant species from a wide variety of plants including ornamental plants, agricultural crops, and weeds.  Other economically important crops include iris, tulip, dahlia, gladiolus, rhubarb, clover, carrot, and sugarbeet.  Several weed hosts are also included.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3):  Ditylenchus destructor has high reproduction potential.  On its own, the nematode species can move only short distances in soil, and is dependent on secondary means for its spread over long distances.  The main means of transmission is with infested subterranean propagative plant parts (tubers, rhizomes, bulbs).  Other means of spread include infested soil, irrigation water, weeds.  Therefore, it is given a high score for reproduction and dispersal potential.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is High (3):  Ditylenchus destructor causes rotting of tubers and other subterranean plant parts.  Rotting may increase during storage.   Therefore, the nematode species could lower crop yield, increase production costs, trigger the loss of markets, and interfere with transference of irrigation water that may aid in its spread from infested fields.  Infestations of D. destructor could significantly impact nursery ornamental and cultivated mushroom productions.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2):  Infestations of Ditylenchus destructor could significantly impact home/urban gardening and ornamental plantings, and trigger additional private treatment programs to mitigate potential crop loss.

Consequences of Introduction to California for Ditylenchus destructor:

Add up the total score and include it here. (Score)

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 13.

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is ‘Not established’ (0): Presently, Ditylenchus destructor is not detectable or known to be present in California’s agricultural production sites (see “Status of detections in California”).

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 13.

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the potato rot nematode, Ditylenchus destructor, is A.

References:

Ayoub, S. M.  1970.  The first occurrence in California of the potato rot nematode, Ditylenchus destructor, in potato tubers.  California Department of Agriculture, Bureau of Plant Pathology, Sacramento, Special Publication. Number 70-2.

CABI.  2016.  Ditylenchus destructor (potato tuber nematode) datasheet (full) report.  Crop Protection Compendium.  www.cabi.org/cpc/ .

Chitambar, J., K. Dong, S. Subbotin, and R. Luna.  2007.  California Statewide Nematode Survey Project.  California Plant Pest and Disease Report, 24: 59

EPPO.  2008.  Ditylenchus destructor and Ditylenchus dipsaci.  EPPO Bulletin 38: 363-373.

Sturhan, D. and M. W. Brzeski.  1991.  Stem and bulb nematodes, Ditylenchus spp. In W.R. Nickle, ed. Manual of Agricultural Nematology, pp. 423–464. New York, Marcel Decker, Inc. 1064 pp.

Subbotin, S. A., A. M. Deimi, J. Zheng, and V. N. Chizov.  2011.  Length variation and repetitive sequences of internal transcribed spacer of ribosomal RNA gene, diagnostics and relationships of populations of potato rot nematode, Ditylenchus destructor Thorne, 1945 (Tylenchida: Anguinidae).  Nematology, 13: 773-785.

USDA.  2016.  FRSMP: Pests no longer regulated at U. S. ports of entry.  Last modified Aug 1, 2016. https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/frsmp/ct_non-reg-pests.

USDA PCIT.  2016.  USDA Phytosanitary Certificate Issuance & Tracking System.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Viglierchio, D. R.  1978.  Stylet-bearing nemas and growth of Ponderosa pine seedlings.  Forest Science, 24: 222-227.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Period:  CLOSED

Sep 27- Nov 11, 2016

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment: 

Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: A

Posted by ls

 

Nematodes

Scutellonema spp. Cobb, 1913

California Pest Rating for
Scutellonema spp.  Cobb, 1913
Pest Rating: C 

 

PEST RATING PROFILE
Initiating Event:

During the 1950-60s, several species of plant parasitic nematodes were given a ‘D’ rating as they were regarded as parasites, predators or organisms of little or no economic importance that did not require State enforced regulatory action.  However, these nematode species were inaccurately assigned a D rating as most, if not all, are plant parasitic and therefore, capable of damaging plant production and causing significant economic losses especially at the county and local residential/grower level.  Furthermore, the detection of plant parasitic nematodes in nursery stock may be an indication of contamination in violation of the State’s standard of pest cleanliness required for nurseries. Scutellonema spp. were originally rated D.  The risk of infestation and permanent rating of this genus group are re-assessed here.

History & Status:

Background:  Generally, pest risk assessments and assignment of pest ratings are conducted per individual pest species and not per genus group primarily due to differing pest biologies, geographical distributions, host ranges, damage potentials, and risk mitigating requirements. However, an exception to this rule is made here for the genus Scutellonema largely because of historical practice.  Over the past several decades, the genus, Scutellonema, was seldom differentiated to species level by CDFA Nematologists mainly due to i) the common occurrence and wide distribution of member species within California, ii) no state enforced regulatory action required subsequent to their detection, and iii) greater demands of time involved in diagnosing high risk and other nematode species considered to be of greater economic importance than those belonging to Scutellonema.

Members of the genus, Scutellonema, are commonly known as ‘spiral nematodes’.  Apparently, species reproduce mainly by amphimixis (fertilization by female and male) or parthenogenesis where males are rare or absent, producing eggs, three juvenile stages, and adults.  These nematodes usually inhabit the soil-root region of plants and feed primarily as obligate migratory ectoparasites, while some species feed as endoparasites of roots. All motile juvenile and adult stages feed and all species of the genus are considered to be plant parasites.  The life cycle takes about one month.  The nematode may survive in dry soil by anhydrobiosis in a coiled state (CABI, 2016; Mai et al., 1996; Maggenti, 1981).

Hosts: Scutellonema spp. are associated with the roots of a wide range of agricultural crops, fruit trees, ornamentals, nursery stock, forest trees and shrubs, desert shrubs, grasses, and weeds. Agricultural crops include alfalfa, cotton, tobacco, potato, sweet potato, corn, coconut, banana, yams, and several other crops.  The host status of associated plants is not always known.

Symptoms:  General plant damage associated with Scutellonema spp. is commonly exhibited in roots as numerous small, brown necrotic lesion produced as a result of feeding by the nematode.  Internally, isolated root cavities are produced by the nematodes. Above ground symptoms may include leaf stunting and chlorosis, and reduced growth.  On yams, large numbers of Scutellonema (S. bradys) feed as endoparasites and cause extensive dry rot damage.  Shallow lesion caused by the feeding of the nematode become avenues for secondary invaders, namely bacteria, fungi and mites (CABI, 2016; Maggenti, 1981; Van Den Berg, et al., 2013).

Damage Potential:  Generally, Scutellonema spp. are common associates of several plants.  Few Scutellonema species have known economic importance as agricultural pests while other species cause no known or little economic damage to crops (Van Den Berg, et al., 2013).  However, plant damage caused by high populations of spiral nematodes could be more significant in small-area plant productions and/or containerized crops in nursery, residential and local situations than in large acreages and environments such as, pastures, parks, and cultivated fields. Crop damage under field conditions may be difficult to assess as Scutellonema spp. are often mixed with other genera and/or two or more stunt nematode species occurring together.

Spread:  The main mode of long and short distance spread through artificial means: infested plants, including tubers, movement of nematode-contaminated soil, run-off and irrigation water, cultivation tools, equipment and any human activity that can move soils from infested to non-infested sites.

Worldwide Distribution: Scutellonema spp. are widely distributed in tropical and subtropical regions of the world, with the most number of species reported from Africa (Sher, 1964).

Official Control:  Currently, Scutellonema spp. are D rated pests in California (see ‘Initiating Event’).  Scutellonema spp. are on the ‘Harmful Organism Lists” for Chile (USDA-PCIT, 2016).

California Distribution:  Scutellonema spp. are widely distributed in California.

California Interceptions: For the past several decades, Scutellonema spp. have been detected in several imported plant and soil shipments intercepted in California.

The risk Scutellonema spp. would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is High (3) –Scutellonema spp. are able to establish throughout the State.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3) –Scutellonema spp. are known to be associated with several diverse plant species, however, the host status of associated plants is not always known.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The main mode of long and short distance spread through artificial means: Infested plant roots and subterranean storage plant parts (e.g., tubers, bulbs), movement of contaminated soil, run-off and irrigation water, cultivation tools, equipment and any human activity that can move soils from infested to non-infested sites.  Increase in reproduction rates depends on the plant species parasitized.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is Low (1) –Generally, Scutellonema spp. are considered mild and common pathogens of plants.  However, under high population levels in residential, nurseries and other small-area plantings, Scutellonema spp. infections could result in lowered crop yield.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2) – The impact of  Scutellonema spp. on natural environments is most likely not significant as the species is already widespread without causing apparent detriment to ecological balances and processes, however, heavy infestations of spiral nematodes could affect home/urban gardening.

Consequences of Introduction to California for Scutellonema spp.:

Add up the total score and include it here. (Score)

-Low = 5-8 points

  –Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Scutellonema spp. to California = (12).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is High (-3).  Scutellonema spp. are widespread in several contiguous and non-contiguous climate and host regions throughout the state.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 9

Uncertainty: 

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the spiral nematodes, Scutellonema spp., is C.

References:

CABI, 2016.  Scutellonema brachyurus full datasheet. http://www.cabi.org/cpc/datasheet/49316 .

Mai, W. F., P. G. Mullin, H. H. Lyon, and K. Loeffler.  1996.  Plant parasitic nematodes – a pictorial key to genera.  Fifth Edition.  Comstock Publishing Associates a division of Cornell University Press, Ithaca and London.  277 p.

Maggenti, A.  1981.  General nematology.  Springer-Verlag New York Heidelberg Berlin.  372 p.

Sher, S. A.   1964.   Revision of the Hoplolaiminae (Nematoda) III.  Scutellonema Andrássy, 1958.  Nematologica 9: 421-443.

Siddiqi, M. R.  1976.  Commonwealth Institute of Helminthology (C. I. H.) descriptions of plant-parasitic nematodes. Set 6, No. 85.

USDA-PCIT.  2016.  United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp .

Van Den Berg, E., L. R. Tiedt, D. L. Coyne, A. T. Ploeg, J. A. Navas-Cortés, P. A. Roberts, G. W. Yeates, and S. A. Subbotin.  2013.  Morphological and molecular characterization and diagnostics of some species of Scutellonema Andrássy, 1958 (Tylenchida: Hoplolaimidae) with a molecular phylogeny of the genus.  Nematology, 15: 716-745.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health@cdfa.ca.gov

Comment Period:  CLOSED

9/21/2016 – 11/5/2016

Pest Rating: C 

Posted by ls

Nematodes

Meloidogyne enterolobii Yang and Eisenback, 1983.

California Pest Rating Profile for
Meloidogyne enterolobii Yang and Eisenback, 1983.
(A Root knot Nematode)
Pest Rating: A
PEST RATING PROFILE*

*Revised August 22, 2024

Initiating Event:  

None.

History & Status:

Background: Meloidogyne enterolobii is considered one of the most important root-knot nematode species because of its ability to overcome resistance in important crops carrying genes of resistance to the main Meloidogyne spp. thereby causing a substantial reduction in crop yields. Meloidogyne enterolobii was first discovered parasitizing roots of the pacara earpod tree, Enterolobium contortisiliquum in China in 1983 (Yang & Eisenback, 1983). The nematode species was later described from other regions in China, mainly on guava, Psidium guajava. Taxonomically, M. enterolobii is a senior synonym of M. mayaguensis that was originally described from Puerto Rico parasitizing eggplant (Solanum melongena) roots (Xu et al., 2004; Tigano et al., 2010).  Meloidogyne enterolobii belongs to the family Meloidogynidae in the order Tylenchida.

In 2023/2024, CDFA’s Pest Detection Emergency Projects branch and the Merced County Agricultural Commissioner’s Office conducted a multi-county detection survey in commercial sweet potato fields. Samples were taken from fields just prior to harvest, just after harvest, or from nursery blocks in Merced, Kern, and Stanislaus counties. Samples of sweet potato roots and associated rhizosphere soil were sent to CDFA’s Pest Diagnostics Center at Meadowview. Nematode extraction and identification was done by State Nematologists K. Dong and S. Subbotin.

A total of 375 samples were collected. The samples were examined for all plant pathogenic nematodes and the results were as follows: 115 samples were positive for Meloidogyne incognita, the Southern root-knot nematode, and 260 samples were negative for all pathogenic nematodes. There were no detections of Meloidogyne enterolobii (CDFA PDR Database, 2024).

Life Cycle: Meloidogyne enterolobii is a root knot nematode species with a life cycle and feeding behavior similar to other root knot nematode species.  It is a sedentary endoparasite that feeds within host plant roots.  Adult females embedded in host roots produce eggs within a mass either on the surface of, or within roots.  The first stage juvenile develops within the egg and molts to develop into the second stage.  The second-stage juveniles (J2) are the infective stage that hatch from eggs, migrate in rhizosphere soil to host roots, reinfest the roots or are attracted to other nearby host roots which are then penetrated.  Within roots, J2 establish a specialized feeding site or giant plant cells that are formed at the head end of the nematode in response to its feeding.  The second stage juveniles become sedentary while feeding at the specialized site, increase in size and undergo two more molts and non-feeding stages before developing into mature adult females or males and completing the life cycle.  Reproduction is by mitotic parthenogenesis.  Generally, the life cycle for root knot nematodes may take about 30 days at 25-28°C and longer at lower temperatures.

Hosts: Major hosts include Capsicum annuum (pepper), Citrullus lanatus (watermelon), Coffeae arabica (coffee),Glycine max (soybean), Ipomoea batatas (sweet potato), Nicotiana tabacum (tobacco), Psidium guajava (guava),Solanum lycopersicum (tomato), S. melongena (eggplant), Gossypium sp. (cotton), Capsicum annuum (bell pepper), Apium graveolens (celery), Brassica oleracea var. oleracea (cabbage), Phaseolus vulgaris (common bean), (garden beet), (mustard), squash (all types), (sweet basil).  Other minor hosts include Angelonia angustifolia, Aquilaria malaccensis, Brugmansia, Enterolobium contortisiliquum, Euphorbia punicea, Hibiscus, Maranta arundinacea, Morinda citrifolia, Morus nigra, Ocimum basilicum, Paulownia elongata, Syzygium aromaticum, Thunbergia, Tibouchina, Solanum tuberosum (potato), Bidens pilosa, Lactuca sativa (lettuce), and Cucumis sativus(cucumber) (CABI, 2014; EPPO, 2014, Paes-Takahashi et al. 2015, Overstreet et al., 2018).  Several weed plants have also been reported as hosts for the guava root-knot nematode: American black nightshade, Bristly hawkbit, Bull nettle, Common purslane, Dichondra, Ground cherry, Hairy beggarticks, Hairy crabweed, Pokeweed, Purple nutsedge, Redroot pigweed, Sicklepod, Smooth pigweed, Spiny amaranth, three-lobed morning glory, Wild, mustard, Wild, poinsettia, and Yellow nutsedge (Overstreet et al., 2018)

Symptoms:  Galls are produced on the roots of infected galls.  Galls may occur singly or coalesce to form compounded root swellings. Above-ground symptoms are general and typical of an impaired root system caused by biotic or abiotic factors.  Visible symptoms of infection usually include unthriftiness, yellowing of leaves, wilting, defoliation, reduced growth, and even death in three years.

Damage Potential:  Populations of Meloidogyne enterolobii are able to overcome resistance in tomato cv. Rossol, soybean cv. Forrest, and sweet potato cv. CDH in West Africa.  Damage to coffee has been observed in Cuba where the nematode is able to reproduce on resistant tomato varieties with the Mi 1.2 gene. The species may occur with and is considered more damaging than the commonly distributed species, M. incognita, M. arenaria , and M. javanica (Brito et al., 2002; CABI, 2014).  Severe damage to guava (stunted growth, reduced leaf size, and reduced yield) has been observed in South Africa and Brazil (CABI, 2014; Carneiro et al., 2001).

Movement and Dispersal:  Infected roots, bare root propagative material, and soil debris.

Worldwide Distribution: M. enterolobii was first reported from China (Yang & Eisenback, 1983).  Since then it has been reported from Asia: Vietnam; Africa: Burkina Faso, Congo (Democratic Republic), Cote d’Ivoire, Malawi, Senegal, South Africa, Togo; South America: Brazil, Venezuela; Central America and Caribbean: Cuba, Guadeloupe, Guatemala, Martinique, Puerto Rico, Trinidad, Tobago; North America: Mexico, USA (Florida, North Carolina, South Carolina, Louisiana);Europe: Switzerland (Brito et al., 2004; CABI, 2014; EPPO, 2014; Ramírez-Suárez et al., 2014; Ye et al.,2013, Overstreet et al., 2018; Rutter et al., 2019).

Official Control: Meloidogyne enterolobii is on the A2 list for EPPO since 2010, and on the Alert list for NAPPO since 2002 (EPPO, 2014).  Currently, it is on the Harmful Organism list for Costa Rica and the Republic of Korea (PCIT-APHIS, 2014).  In the USA, Meloidogyne enterolobii is on the quarantine list of nematodes in Florida, and Mississippi (National Plant Board, 2019). In North Carolina, there is an internal quarantine (Wilson, 2018).

California Distribution:  Meloidogyne enterolobii is not known to be present in California.

California Interceptions: There have been 13 detections of Meloidogyne enterolobii in incoming shipments of plants and soil to California. The origins of the shipments were China, Florida, Texas, and Puerto Rico. The hosts were Psidium sp., Scindapsus sp., Ochina sp., Plectranthus amboinicus and an unidentified genus of palm (CDFA PDR database, 2024).

The risk Meloidogyne enterlobii would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

-Low (1) not likely to establish in California; or likely to establish in very limited areas

-Medium (2) may be able to establish in a larger but limited part of California

– High (3) likely to establish a widespread distribution in California.

Risk is High (3).  California has suitable climate and hosts for M. enterolobii.  If introduced, the species is likely to establish a widespread distribution. 

2) Known Pest Host Range: Evaluate the host range of the pest:

-Low (1) has a very limited host range

-Medium (2) has a moderate host range

– High (3) has a wide host range.

Risk is High (3).  M. enterolobii has a wide and diverse host range.    

3) Pest Dispersal Potential: Evaluate the dispersal potential of the pest:

-Low (1) does not have high reproductive or dispersal potential

-Medium (2) has either high reproductive or dispersal potential

– High (3) has both high reproduction and dispersal potential.

Risk is High (3).  M. enterolobii has high reproduction.  A single female M. enterolobii may produce several hundreds to over one thousand eggs in an egg mass, similar to other Meloidogyne species.  Dispersal is mainly passive through the movement of infected roots and soils. The potential for spread is high.

4) Economic Impact: Evaluate the economic impact of the pest to California using these criteria:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines by other states or countries).

D. The pest could negatively change normal production cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

-Low (1) causes 0 or 1 of these impacts

-Medium (2) causes 2 of these impacts

– High (3) causes 3 or more of these impacts.

Risk is High (3).  M. enterolobii is able to break resistance in important crops carrying genes of resistance to the main Meloidogyne spp. thereby causing substantial reduction in crop yields, crop value, loss of markets, including the likely imposition of quarantines by other states and countries against California.  Pest management strategies may adversely affect normal cultural practices.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using these criteria:

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. Significantly impacting cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

– Low (1) causes none of the above to occur

– Medium (2) causes one of the above to occur

– High (3) causes two or more of the above to occur.

Risk is High (3). Several ornamental and perennial shrub plants are probable hosts of the nematode species.  Infestations of M. enterolobii may lower biodiversity and disrupt natural plant communities, endanger critical habitats.  Home gardening and ornamental plantings may also be impacted.

Consequences of Introduction to California for Common Name:  Score

Add up the total score and include it here. (Score)

Low = 5-8 points

Medium = 9-12 points

  High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 15.

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

–Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas

Surveys of sweet potatoes have not made any detections of M. enterolobii.

Final Score:

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 15.

Uncertainty: It is possible that the nematodes species may have entered the State undetected prior to 2005.  This is largely due to the fact that prior to 2005 Meloidogyne spp. were not always identified, at the CDFA Nematology Laboratory, to species level when detected in samples that originated outside and within California.  However, since 2005, M. enterolobii has never been detected in regulatory samples generated through CDFA’s nematode control and phytosanitary certification programs or through statewide nematode surveys of host plants grown in agricultural production sites and nurseries in California. Also, M. enterolobii has not been reported from California by other researchers/nematologists.  The status of M. enterolobii in non-cultivated and residential environments is not known.  Those environments may serve as sources of inoculum for infestations of cultivated production sites.  Identification to species level through DNA analysis is now essential for accurate identification of this species.  Future detection of the species in California soils may result in alteration of its current proposed rating.

Conclusion and Rating Justification: 

Based on the evidence above the proposed rating for Meloidogyne enterlobii is A.

References:

Brito, J. A., Stanley, J., Cetintas, R., Powers, T., Inserra, R., McAvoy, G., Mendes, M.L., Crow, B., and Dickson, D. 2004. Identification and host preference of Meloidogyne mayaguensis and other root-knot nematodes from Florida, and their susceptibility to Pasteuria penetrans. Journal of Nematology 36:308-309.

CABI.  2014.  Meloidogyne mayaguensis full datasheet.  Crop Protection Compendium.  www.cabi.org/cpc/.

EPPO.  2014.  Meloidogyne enterolobii (MELGMY).  PQR database.  Paris, France:  European and Mediterranean Plant Protection Organization.  http://newpqr.eppo.int .

Han, H., Brito, J.A., and Dickson, D.W. 2012.  First report of Meloidogyne enterolobii infecting Euphorbia puniceain Florida. Plant Disease 96 (11), p 1706.

Overstreet, C., McGawley, E.C., Clark, C., Rezende, J., Smith, T., and Sistrunk, M. 2018. Guava root knot nematode a potentially serious new pest in Louisiana. LSU Ag Center publication. https://msfb.org/wp-content/uploads/2018/11/guava-root-knot-nematode-adapdf.pdf

Paes-Takahashi, V. S., Soares, P. L. M., Carneiro, F. A., Ferreira, R. J., de Almeida, E. J., and dos Santos, J. M. 2015. Detection of Meloidogyne enterolobii in mulberry seedlings (Morus nigra L.). Ciência Rural 45(5):757-759.  http://dx.doi.org/10.1590/0103-8478cr20130350.

Ramírez-Suárez, A., Rosas-Hernández, l., Alcasio-Rangel, S., Pérez Valenzuela, G., and Powers, T.O.  2014.  First report of the root-knot Meloidogyne enterolobii parasitizing watermelon from Veracruz, Mexico.  Plant Disease, 98:428.3.

Rutter, W. B., Skantar, A. M., Handoo, Z. A., Mueller, J. D., Aultman, S.P., and Agudelo, P. 2019. Meloidogyne enterolobii found infecting root-knot nematode resistant sweetpotato in South Carolina, United States. Plant Disease 103:4

Tigano, M., de Siqueira, K., Castagnone-Sereno, P., Mulet, K., Queiroz, P., Dos Santos, M., Teixeira, C., Almeida, M., Silva, J., and Carneiro, R.  2010.  Genetic diversity of the root-knot Meloidogyne enterolobii and development of a SCAR marker for this guava-damaging species.  Plant Pathology 59:1054-1061.

USDA PCIT.  2014.  USDA Phytosanitary Certificate Issuance and Tracking System.  Phytosanitary Export Database.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp .

Wilson, P. 2018. NCDA&CS declares an internal quarantine for all North Carolina counties for the Guava knot nematode. http://www.ncagr.gov/paffairs/release/2018/10-18guavarootknotnematode.htm

Xu, J., Liu, P., Meng, Q., and Long, H.  2004. Characterization of Meloidogyne species from China using isozyme, phenotypes and amplified mitochondrial DNA restriction fragment length polymorphism. European Journal of Plant Pathology 110:309–15.

Yang, B., and Eisenback, J. D. 1983. Meloidogyne enterolobii n. sp. (Meloidogynidae), a root-knot nematode parasitizing pacara earpod tree in China. Journal of Nematology 15:381–91.

Ye, W., Koenning, M, S. R., Zhuo, K. and Liao, J. L.  2013.  First report of Meloidogyne enterolobii on cotton and soybean in North Carolina, United States. Plant Disease 97(9), p 1262.

Responsible Party: 

John J. Chitambar, and Heather J. Scheck, Former and Current Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, permits[@]cdfa.ca.gov

Comment Period:  CLOSED

The 45-day comment period opened on Aug 3, 2016 and closed on Sep 17, 2016.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment: 

Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

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♦  Comments may be edited prior to posting to ensure they are entirely germane.

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Pest Rating: A

Pest Rating Profile updated on 8/22/2024 by tn

Nematodes

Pratylenchus coffeae (Zimmermann) Filipjev & Schuurmans-Stekhoven


Pratylenchus_coffeae_USDA-ARS_Wikipedia
California Pest Rating for
Pratylenchus coffeae (Zimmermann) Filipjev & Schuurmans-Stekhoven
Pest Rating: B

 

PEST RATING PROFILE
Initiating Event:

None. The risk of introduction and establishment of Pratylenchus coffeae is evaluated and the current rating is reviewed.

History & Status:

Background:  For long, Pratylenchus coffeae has been considered a complex group of several morphologically indistinguishable species sharing a wide range of morphological variability within the group and within a single species or populations of a single species. Historically, this has resulted in a loss of the true identity of the species, and the creation of several new species based on questionable differences.  Consequently, the morphological identification of P. coffeae has been based on the species complex with its high variability and identified as P. coffeae sensu lato (latin: ‘in the broad/general sense’).  Numerous studies have been reported on the taxonomy of P. coffeae to clarify its identity. Molecular and phylogenetic analyses of the species complex group have now enabled the distinction of P. coffeae sensu stricto (latin: ‘in the strict/true sense’) from other distinguished representatives of the group through the development of species-specific molecular diagnostic tests.  Nevertheless, most reports on biology, ecology, geographical distribution, hosts, crop loss, and regulatory actions of the species are based on the species complex group of P. coffeae.  This is also true for P. coffeae detected within California.

The true status of P. coffeae (sensu stricto) in California is not known and early records, based solely on morphological analysis of the species, may be dubious. Siddiqui et al. (1973) reported the detection of P. coffeae, from 1952-1972, in residential and nursery greenhouse environments in several northern and southern coastal counties and few northern and southern valley counties, and 1 commercial site in Los Angeles County.  Much of their information was from University of California nematode distribution records, nematode detection records of certain County Agricultural Commissioner offices, and the CDFA Nematology Laboratory. Then, according to CDFA Nematode Detection Records, during the 1970s, P. coffee was infrequently detected in commercial soils in Glenn, Sonoma, and Merced counties.  However, there is a paucity of information on these detections and their related sites that would allow confirmation.   During the 1980s, P. coffeae was detected nine times in fruit tree nursery stock root samples submitted to CDFA for analysis and certification, and once in a plant root sample from a private residence in Riverside County.  The species was detected in several incoming shipments of ornamental plants imported to California nurseries under the External Quarantine Burrowing and Reniform Nematode Program.  From 1990-2016, the species was detected only three times, and again in fruit tree nursery stock, while several detections were made in imported nursery ornamental plants that were intercepted in California. Except for those few nursery stock detections, it is important to note that over the past 20 years or more, P. coffeae has not been found in California soils analyzed through CDFA’s nematode detection programs and surveys of agricultural production sites, nor has its in-state presence been reported from other sources.

Pratylenchus coffeae, the banana root nematode, is a migratory endoparasite of plant roots. Depending on the host infected, P. coffeae has a life cycle of 21-28 days at 25-30°C.  The nematode is able to spend its entire life cycle within root tissue and all developmental stages, adult females, and males are found within roots and rhizosphere soils of host plants.  Subsequently, infested plant root stock and associated soils are potential pathways for the transportation, introduction, and spread of this species. Also, in local situations, contaminated irrigation and run-off surface water from infested fields can help spread the species to non-infested areas.  The species produces lesions on feeder roots and other underground plant parts as a result of its feeding.  Damage caused by the nematode results in significant yield loss and reduction for several host plants.  It is likely that P. coffeae originated in the Pacific Rim/Southeast Asia region (Burke et al., 2015) and was first discovered infesting coffee roots and damaging production.  It is now distributed worldwide.

Hosts:  Pratylenchus coffeae attacks a wide variety of plants of over 250 plant species belonging to almost all plant families.  Hosts include Citrus spp., banana, plantain, coconut, coffee, cucurbits, fig, ginger, turmeric, cardamom, potato, maize, yams, caladium, vegetables, ornamentals, and weeds.

Damage Potential:  Pratylenchus coffeae infects roots, tubers, corms, and rhizomes of host plants causing damage to the cortical tissue which results in development of lesions, weakened root systems, rot, stunting, death of plant, reduction in crop production and yield loss.  Root lesions become avenues for secondary infections of fungi and bacteria.  Crop losses up to 80% in Musa sp. (banana) are reported from South Africa (Sarah, 1989) and 60% production loss of plantains in Ghana (Burke, et al., 2015).  In the United States, growth of citrus rootstock was reduced by 49-80% due to P. coffeae and fruit yields on rough lemon and sour orange rootstocks were reported 143% and 231% higher respectively, than trees infected with P. coffeae in the first bearing year, and 220% and 271% more in the second year (O’Bannon & Tomerlin, 1973).

Worldwide Distribution: Banana root nematode was originally discovered in Java, Indonesia.  It is found worldwide, although distributed primarily in tropical and subtropical regions.  Most reports record the occurrence of the species complex Pratylenchus coffeae sensu lato from Asia: Afghanistan, Bangladesh, Bhutan, Brunei Darussalam, China, India, Indonesia, Iran, Japan, Korea, Malaysia, Oman, Pakistan, Philippines, Sri Lanka, Papua New Guinea, Taiwan, Thailand, Turkey, Vietnam; Africa: Cameroon, Côte d’Ivoire, Ghana, Kenya, Madagascar, Malawi, Mauritius, Mozambique, Nigeria, Seychelles, South Africa, Swaziland, Tanzania, Uganda, Zambia, Zimbabwe; North America: Canada, Mexico, USA; Central America and Caribbean: Belize, Costa Rica, Cuba, Dominica, Dominican Republic, El Salvador, Grenada, Guadeloupe, Guatemala, Honduras, Jamaica, Martinique, Nicaragua, Panama, Puerto Rico, Trinidad and Tobago; Europe: Austria, Bulgaria, Italy, Slovenia, Spain; South America: Brazil, Chile, Colombia, Ecuador, French Guiana, Suriname, Venezuela; Oceania: Australia, Cook Island, Fiji, Kiribati, Niue, Palau, Papua New Guinea(CABI, 2014; Castillo & Vovlas, 2007; EPPO, 2014).

In the USA, Pratylenchus coffeae has been reported in Arkansas, California, Florida, Hawaii, North Carolina, and South Carolina (CABI, 2014; Castillo & Vovlas, 2007; EPPO, 2014).

Official Control: Pratylenchus coffeae is a phytosanitary risk in all tropical and subtropical countries (CABI, 2016).  Currently, P. coffeae is a C-rated pathogen in California.  The nematode species is on the ‘Harmful Organism Lists” for Argentina, Canada, Chile, French Polynesia, Indonesia, Madagascar, Morocco, New Caledonia, Timor-Leste, and Uruguay (USDA-PCIT, 2016).

California Distribution:  The true presence and distribution of Pratylenchus coffeae in California is not known as identification was based primarily on the species complex group (see “Background”).  However, from 1996 to May, 2016, P. coffeae was detected three times in CDFA’s Nursery Stock Nematode Certification Program: once in Los Angeles County (2002), once in Riverside County (1997), and once in Santa Barbara County (1998).

California Interceptions: Pratylenchus coffeae has been detected in several incoming shipments of ornamental plants imported to California nurseries under the External Quarantine Burrowing and Reniform Nematode Program.

This risk banana root nematode, Pratylenchus coffeae would pose to California is evaluated below.

Consequences of Introduction: 

 1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is Medium (2): Pratylenchus coffeae is likely to establish wherever its infected host is able to establish within California.  However, even with this capability, and since the early 1970s, P. coffeae has not been reported from California’s agricultural crop production sites, nor is it known to be established widely within California.  Therefore, a ‘medium’ risk is assessed for this category.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3):  Pratylenchus coffeae attacks a wide variety of plants of over 250 plant species belonging to almost all plant families.  Citrus, fruit trees, and ornamentals are some of the main susceptible hosts of concern for California.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3): Pratylenchus coffeae is spread over long distances primarily through infested plant root stock and associated soils.  Short-distance spread is through run-off irrigation water, infested and planting root stock, and movement of contaminated soil.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is Medium (2): Pratylenchus coffeae infects roots, tubers, corms, and rhizomes of host plants causing reduction in crop yield and possible loss of markets.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2): Pratylenchus coffeae could significantly impact cultural practices, home/urban gardening or ornamental plantings.

Consequences of Introduction to California for Pratylenchus coffeae:

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction to California = 12 (Medium).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

–Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

-High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is Medium (-2): The true presence and distribution of Pratylenchus coffeae in California is not known, however, from 1996 to May, 2016, P. coffeae was detected three times in CDFA’s Nursery Stock Nematode Certification Program: once in Los Angeles County (2002), once in Riverside County (1997), and once in Santa Barbara County (1998).

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10 (Medium).

Uncertainty:  

The status of Pratylenchus coffeae in California’s natural environment is not known.  Also, not known is the true identity of members of the species complex in California.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for banana root nematode, Pratylenchus coffeae is B.

References:

Burke, M., E. H. Scholl, D. Mck. Bird, J. E. Schaff, S. Coleman, R. Crowell, S. Diener, O. Gordon, S. Graham, X. Wang, E. Windham, G. M. Wright, and C. H. Opperman.  2015.  The plant parasite Pratylenchus coffeae carries a minimal nematode genome.  Nematology 17:621-637. http://dx.doi.org/10.1163/15685411-00002901.

CABI.  2014.  Pratylenchus coffeae (banana root nematode) basic datasheet.  http://www.cabi.org/cpc/datasheet/43903.

Castillo, P. and N. Vovlas.  2007.  Pratylenchus (Nematoda: Pratylenchidae): diagnosis, biology, pathogenicity and management.  Hunt, D. J., and R. N. Perry (Series Eds).Nematology monographs and perspectives. Brill Leiden-Boston. 529 p.

O‘Bannon, J. H., and A. T. Tomerlin.  1973.  Citrus tree decline caused by Pratylenchus coffeae. Journal of Nematology, 5(4):311-316.

Sarah, J. L.  1989.  Banana nematodes and their control in Africa. Nematropica, 19:199-215.

Siddiqui, I. A., S. A. Sher, and A. M. French.  1973.  Distribution of plant parasitic nematodes in California.  State of California Department of Food and Agriculture Division of Plant Industry.  324 p.

USDA-PCIT.  2016.  United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp .

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: (916) 262-1110, plant.health[@]cdfa.ca.gov.

Comment Period: CLOSED

The 45-day comment period opened on Jun 29, 2016 and closed on Aug 13, 2016.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment: 

Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: B

Posted by ls

Nematodes

Pratylenchus thornei Sher & Allen, 1953

Pratylenchus spp.
California Pest Rating for
Pratylenchus thornei Sher & Allen, 1953
Pest Rating: C 

 

PEST RATING PROFILE
Initiating Event:

During the 1950-60s, several species of plant parasitic nematodes were given a ‘D’ rating as they were regarded as parasites, predators or organisms of little or no economic importance that did not require State enforced regulatory action.  However, these nematode species were inaccurately assigned a D rating as most, if not all, are plant parasitic and therefore, capable of damaging plant production and causing significant economic losses especially at the county and local residential/grower level.  Furthermore, the detection of plant parasitic nematodes in nursery stock may be an indication of contamination in violation of the State’s standard of pest cleanliness required for nurseries. Pratylenchus thornei was originally rated D and its risk of infestation and permanent rating are re-assessed here.

History & Status:

Background: The root lesion nematode, Pratylenchus thornei, was first reported from soil around the roots of grass at Berkeley, California (Sher & Allen, 1953). Since then, P. thornei has been found to be associated with a variety of plants in different geographic locations and is a serious parasite of wheat in Utah, Australia, Yugoslavia, India, Italy, and Mexico (Fortuner, 1977).  The host status of associated plants is not always known. Pratylenchus thornei is one of the most widely distributed species of Pratylenchus and has been reported from every continent except Antarctica (Castillo & Vovlas, 2007).  In California, P. thornei is widely distributed statewide, even though it is known to prefer temperate soils (CABI, 2016).

Pratylenchus thornei, is an obligate migratory endoparasite that first feeds externally then enters plant roots, feeds, reproduces and moves freely within the tissue while spending its entire life cycle there.  The species can also be found in soil around roots.  Within the roots, feeding is confined to the root cortex.  Like other Pratylenchus species, P. thornei has six life stages: egg, four juvenile stages and adults.  Reproduction is by parthenogenesis (without fertilization). First stage juveniles develop within the egg, followed by a first molt to the second stage juvenile that hatches from the egg.  Each stage develops into the next via a molt of its cuticle (outer body covering).  All juvenile and adult stages are worm-shaped (vermiform).  All post-hatch stages are motile and can infect plants.  The time to complete a life cycle is dependent on temperature and moisture.  The life cycle of P. thornei was completed in about 25-35 days on carrot discs at 20-25°C (Castillo et al., 1995) and about 25-29°C on corn at 30°C (Siyanand et al., 1982).  Pratylenchus thornei survives the winter in infected roots or soil as eggs, juveniles or adults.  Under experimental conditions, survival of P. thornei in 200 g soil samples was reduced by drying to 5% moisture content and at 40°C was killed in less than 2 weeks, perhaps due to loss of moisture.   The nematodes become inactive at freezing to – 5°C Fortuner, 1977).  During spring, when plant growth is active, eggs hatch, nematodes are attracted to the plant roots and begin to feed and continue their life cycle within roots or in rhizosphere soil.  Within the root, the nematode feeds on cortical tissue causing necrosis of cortical cells, cell breakdown, and formation of cavities. Necrosis is apparent as lesions which expand as the nematodes move lengthwise within the infected roots.  Some nematodes may leave the root, enter soil and re-enter the root at a different site causing a new infection.

Hosts: Pratylenchus thornei is an important root parasite primarily of wheat and other cereals such as, barley and maize.  The nematode species has been associated with different plants from several countries.  The host status of associated plants is not always known.  Nevertheless, hosts/associated plants include, cereals, wheat, durum wheat, barley, chickpea, corn, oats, sorghum,  tobacco, carrot, celery, globe artichoke, asparagus, broccoli, cabbage, cauliflower, olive, onion, cotton, potato, strawberry, tomato, tea, ginger, strawberry clover, berseem clover, white clover, soybean, leguminous plants, sweet pea, lentil, alfalfa, pea, common bean, faba bean, lima bean, cowpea, papaya, red currant, apple, apricot, pear, peach, plum, cherry, walnut, almond, grapevine, blackberry, citrus, fig, sugarcane, groundnut, canola, watermelon, beetroot, various grasses, bent grass, safed musli (Chlorophytum borivillianum – medicinal plant),  rose, candytuft, chrysanthemum, iris, lily, pine, oak, peppermint, spearmint (CABI, 2016; Castillo & Vovlas, 2007; Siddiqui et al., 1973; Smiley et al., 2014).

Symptoms: In general, root lesion infection results in plant exhibiting symptoms of chlorosis, wilting, and stunting.  Infected roots show initial symptoms of small, water-soaked lesions that soon turn brown to black.  Lesions are formed along the root axis and may coalesce laterally to girdle the roots which are killed.  Affected root tissue may slough off leaving a severely reduced root system. Secondary infection by fungi and bacteria may further destroy the root system by causing sloughing off of the root tissues and rot.  Plant yield is reduced and in severe infections plants may be killed.

Damage Potential:  Pratylenchus thornei is capable to reducing root growth and function thereby, causing reduction in plant growth and yield of its associated host plants.

Spread:  On its own, Pratylenchus species move can move 1-2 m from an infected root.  The main mode of long and short distance spread is artificial. Infected roots, bare root propagative plant materials, soil debris, run-off and irrigation water, cultivation tools, equipment and human activity that can move soils from infested to non-infested sites.

Worldwide Distribution:  Pratylenchus thornei has been reported worldwide in Asia: Afghanistan, Azerbaijan, India, Iran, Israel, Japan, Jordan, Republic of Korea, Pakistan, Saudi Arabia, Syria, Tajikistan, Turkey; Africa: Algeria, Egypt, Kenya, Libya, Malawi, Morocco, Nigeria, South Africa, Sudan, Tunisia; Europe: Belgium, Bulgaria, Croatia, Cyprus, Denmark, France, Germany, Italy, Netherland, Poland, Portugal, Romania, Russian Federation, Slovakia, Slovenia, Spain, United Kingdom, Yugoslavia; North America: USA, Canada, Mexico; South America: Argentina, Chile, Venezuela; Oceania: Australia: New South Wales, Queensland, South Australia, Tasmania, Victoria, Western Australia (CABI, 2014; Castillo & Vovlas, 2007; Fortuner, 1977).

In the USA, Pratylenchus thornei has been reported in California, and several other states including, Colorado, Idaho, Maryland, Nebraska, Ohio, Oregon, Utah, Virginia, and Washington (CABI, 2014; Castillo & Vovlas, 2007; Fortuner, 1977).

Official Control: Currently, Pratylenchus thornei is rated ‘D’ by CDFA.  The following countries include the species on their Harmful Organism Lists: Brazil, Canada, Costa Rica, Honduras, Indonesia, Jordan, Panama, and Peru (USDA-PCIT, 2016).

California Distribution:  Pratylenchus thornei is widely distributed in California.

California Interceptions: Pratylenchus thornei has been detected in several incoming shipments of plants and soil to California.

The risk Pratylenchus thornei would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is High (3) – Pratylenchus thornei is able to establish throughout the State.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Medium (2) – Pratylenchus thornei is an important parasite of wheat and other cereals, but its diverse range of hosts are grown throughout the State and include, fruit trees, vegetable crops, and ornamentals.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3) –Long and short distance spread is mainly infected roots, bare root propagative plant materials, soil debris, run-off and irrigation water, cultivation tools, equipment and human activity that can move soils from infested to non-infested sites.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is Low (1) – At the local residential/grower level, Pratylenchus thornei infections could result in lowered crop yield.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2) – The impact of Pratylenchus thornei on natural environments is most likely not significant as the species is already widespread without causing apparent detriment to ecological balances and processes, however, the infestations of this root lesion nematode could affect home/urban gardening.

Consequences of Introduction to California for Pratylenchus thornei:

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Pratylenchus thornei to California = (11).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is High (-3).  Pratylenchus thornei is widely spread in several contiguous and non-contiguous climate and host regions throughout the state.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 8

Uncertainty: 

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the lesion nematode, Pratylenchus thornei, is C.

References:

CABI.  2014.  Pratylenchus thornei (nematode, California meadow) basic datasheet.  http://www.cabi.org/cpc/datasheet/43903.

Castillo, P. and N. Vovlas.  2007.  Pratylenchus (Nematoda: Pratylenchidae): diagnosis, biology, pathogenicity and management.  Hunt, D. J., and R. N. Perry (Series Eds).Nematology monographs and perspectives. Brill Leiden-Boston. 529 p.

Castillo, P., R. M. Jiménez Díaz, A. Gomez-Barcina, and N. Vovlas.  1995.  Parasitism of the root-lesion nematode Pratylenchus thornei on chickpea.  Plant Pathology 44:728-733.

Fortuner, R.  1977.  Pratylenchus thornei.  Commonwealth Institute of Helminthology (C.I.H.) descriptions of plant-parasitic nematodes set 7, No. 93.

USDA-PCIT.  2016.  United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp .

Sher, S. A. and M. W. Allen.  1953.  Revision of the genus Pratylenchus (Nematoda: Tylenchidae).  University of California Publications in Zoology 57:441-447.

Siyanand, A. R. Seshadri, and D. R. Dasgupta.  1982.  Investigation on the life cycles of Tylenchorhynchus vulgaris, Pratylenchus thornei and Hoplolaimus indicus individually and in combined infestations in corn.  Indian Journal of Nematology 12:272-276.

Siddiqui, I. A., S. A. Sher and A. M. French.  1973.  Distribution of plant parasitic nematodes in California. State of California Department of Food and Agriculture, Division of Plant Industry. 324p.

Smiley, R.W., G. Yan, J. A. Gourlie.  2014.  Selected Pacific Northwest rangeland and weed plants as hosts of Pratylenchus neglectus and P. thornei. Plant Disease 98: 1333-1340.

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Period: CLOSED

The 45-day comment period opened on Jun 2, 2016 and closed on Jul 17, 2016.

Comment Format:

♦  Comments should refer to the appropriate California Pest Rating Proposal Form subsection(s) being commented on, as shown below.

Example Comment: 

Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

♦  Posted comments will not be able to be viewed immediately.

♦  Comments may not be posted if they:

Contain inappropriate language which is not germane to the pest rating proposal;

Contains defamatory, false, inaccurate, abusive, obscene, pornographic, sexually oriented, threatening, racially offensive, discriminatory or illegal material;

Violates agency regulations prohibiting sexual harassment or other forms of discrimination;

Violates agency regulations prohibiting workplace violence, including threats.

♦  Comments may be edited prior to posting to ensure they are entirely germane.

♦  Posted comments shall be those which have been approved in content and posted to the website to be viewed, not just submitted.

Pest Rating: C 

Posted by ls

Nematodes

Tylenchorhynchus spp. Cobb, 1913

stunt nematode: symptoms, stunting of corn seedling

California Pest Rating for
Tylenchorhynchus spp.  Cobb, 1913
Pest Rating: C 

 

PEST RATING PROFILE
Initiating Event:

During the 1950-60s, several species of plant parasitic nematodes were given a ‘D’ rating as they were regarded as parasites, predators or organisms of little or no economic importance that did not require State enforced regulatory action.  However, these nematode species were inaccurately assigned a D rating as most, if not all, are plant parasitic and therefore, capable of damaging plant production and causing significant economic losses especially at the county and local residential/grower level.  Furthermore, the detection of plant parasitic nematodes in nursery stock may be an indication of contamination in violation of the State’s standard of pest cleanliness required for nurseries. Tylenchorhynchus spp. were originally rated D.  The risk of infestation and permanent rating of this genus group are re-assessed here.

History & Status:

Background:  Generally, pest risk assessments and assignment of pest ratings are conducted per individual pest species and not per genus group primarily due to differing pest biologies, geographical distributions, host ranges, damage potentials, and risk mitigating requirements. However, an exception to this rule is made here for the genus Tylenchorhynchus largely because of historical practice.  Over the past several decades, the genus, Tylenchorhynchus, was seldom differentiated to species level by CDFA Nematologists mainly due to i) the common occurrence and wide distribution of member species within California, ii) no state enforced regulatory action required subsequent to their detection, and iii) greater demands of time involved in diagnosing high risk and other nematode species considered to be of greater economic importance than those belonging to Tylenchorhynchus.

Members of the genus, Tylenchorhynchus, are sometimes known as ‘stunt nematodes’.  Species reproduce mainly by amphimixis (fertilization by female and male) producing eggs, three juvenile stages, and adults.  These nematodes usually inhabit the soil-root region of plants and feed as obligate migratory ectoparasites of roots using a stylet (sword-like hollow tooth) to feed on epidermal cells. All motile juvenile and adult stages feed.  (Mai et al., 1996; Maggenti, 1981).

Hosts: Tylenchorhynchus spp. are associated with the roots of a wide range of plants including tobacco, cotton, oats, and corn as well as other agricultural crops, fruit trees, ornamentals, nursery stock, forest trees and shrubs, desert shrubs, grasses, and weeds. The host status of associated plants is not always known.

Symptoms:  General plant damage associated with Tylenchorhynchus spp. includes stunting of the root system which is expressed aboveground by yellowing of foliage, stunted top growth, and sometimes wilt and defoliation (Maggenti, 1981).

Damage Potential:  Generally, Tylenchorhynchus spp. are considered mild pathogens of plants and are common associates of several plants (Norton, 1984).  However, plant damage caused by high populations of stunt nematodes may be more significant in small-area plant productions and/or containerized crops in nursery, residential and local situations than in large acreages and environments such as, pastures, parks, and cultivated fields. Crop losses under field conditions are not reported, however, under experimental conditions, reductions in root and plant growth have been demonstrated by certain species, e.g., T. annulatus on sugarcane and Bermuda grass; T. dubius on beans (Bridge, 1974; Siddiqi, 1976).  Tylenchorhynchus claytoni causes economic damage on tobacco (Mai et al., 1996).  Crop damage under field conditions may be difficult to assess as Tylenchorhynchus spp. are often mixed with other genera and/or two or more stunt nematode species occurring together.

Spread:  The main mode of long and short distance spread through artificial means: movement of nematode-contaminated soil, run-off and irrigation water, cultivation tools, equipment and any human activity that can move soils from infested to non-infested sites.

Worldwide Distribution: Tylenchorhynchus spp. are distributed worldwide.

Official Control:  Currently, Tylenchorhynchus spp. are D rated pests in California (see ‘Initiating Event’).  Tylenchorhynchus spp. are on the ‘Harmful Organism Lists” for Australia and the Republic of Nauru (USDA-PCIT, 2016).

California Distribution:  Tylenchorhynchus spp. are distributed throughout California.

California Interceptions: For the past several decades, Tylenchorhynchus spp. have been detected in several imported plant and soil shipments intercepted in California.

The risk Tylenchorhynchus spp. would pose to California is evaluated below.

 Consequences of Introduction:

1) Climate/Host Interaction: Evaluate if the pest would have suitable hosts and climate to establish in California. Score:

– Low (1) Not likely to establish in California; or likely to establish in very limited areas.

– Medium (2) may be able to establish in a larger but limited part of California.

– High (3) likely to establish a widespread distribution in California.

Risk is High (3) –Tylenchorhynchus spp. are able to establish throughout the State.

2) Known Pest Host Range: Evaluate the host range of the pest. Score:

– Low (1) has a very limited host range.

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3) –Tylenchorhynchus spp. are known to be associated with several diverse plant species, however, the host status of associated plants is not always known.

3) Pest Dispersal Potential: Evaluate the natural and artificial dispersal potential of the pest. Score:

– Low (1) does not have high reproductive or dispersal potential.

– Medium (2) has either high reproductive or dispersal potential.

– High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The main mode of long and short distance spread through artificial means: movement of contaminated soil, run-off and irrigation water, cultivation tools, equipment and any human activity that can move soils from infested to non-infested sites.  Increase in reproduction rates depends on the plant species parasitized.

4) Economic Impact: Evaluate the economic impact of the pest to California using the criteria below. Score:

A. The pest could lower crop yield.

B. The pest could lower crop value (includes increasing crop production costs).

C. The pest could trigger the loss of markets (includes quarantines).

D. The pest could negatively change normal cultural practices.

E. The pest can vector, or is vectored, by another pestiferous organism.

F. The organism is injurious or poisonous to agriculturally important animals.

G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.

– Medium (2) causes 2 of these impacts.

– High (3) causes 3 or more of these impacts.

Risk is Low (1) –Generally, Tylenchorhynchus spp. are considered mild pathogens of plants.  However, under high population levels in residential, nurseries and other small-area plantings, Tylenchorhynchus spp. infections could result in lowered crop yield.

5) Environmental Impact: Evaluate the environmental impact of the pest on California using the criteria below.

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.

B. The pest could directly affect threatened or endangered species.

C. The pest could impact threatened or endangered species by disrupting critical habitats.

D. The pest could trigger additional official or private treatment programs.

E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.

– Medium (2) causes one of the above to occur.

– High (3) causes two or more of the above to occur.

Risk is Medium (2) – The impact of Tylenchorhynchus spp. on natural environments is most likely not significant as the species is already widespread without causing apparent detriment to ecological balances and processes, however, heavy infestations of spiral nematodes could affect home/urban gardening.

Consequences of Introduction to California for Tylenchorhynchus spp.:

Add up the total score and include it here. (Score)

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Tylenchorhynchus spp. to California = (12).

6) Post Entry Distribution and Survey Information: Evaluate the known distribution in California. Only official records identified by a taxonomic expert and supported by voucher specimens deposited in natural history collections should be considered. Pest incursions that have been eradicated, are under eradication, or have been delimited with no further detections should not be included. (Score)

-Not established (0) Pest never detected in California, or known only from incursions.

-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).

-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.

–High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

Evaluation is High (-3).  Tylenchorhynchus spp. are widely spread in several contiguous and non-contiguous climate and host regions throughout the state.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score)

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 9

Uncertainty: 

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the spiral nematodes, Tylenchorhynchus spp., is C.

References:

Bridge, J.  1974.  Tylenchorhynchus dubius.  Commonwealth Institute of Helminthology (C. I. H.) descriptions of plant-parasitic nematodes. Set 4, No. 51.

Mai, W. F., P. G. Mullin, H. H. Lyon, and K. Loeffler.  1996.  Plant parasitic nematodes – a pictorial key to genera.  Fifth Edition.  Comstock Publishing Associates a division of Cornell University Press, Ithaca and London.  277 p.

Maggenti, A.  1981.  General nematology.  Springer-Verlag New York Heidelberg Berlin.  372 p.

Norton, D. C.  1984.  Nematode parasites of corn. In Plant and Insect Nematodes, edited by W. R. Nickle.  Marcel Dekker, Inc.  New York and Basel. 61-94 pp.

Siddiqi, M. R.  1976.  Tylenchorhynchus annulatus.  Commonwealth Institute of Helminthology (C. I. H.) descriptions of plant-parasitic nematodes. Set 6, No. 85.

USDA-PCIT.  2016.  United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp .

Responsible Party:

John J. Chitambar, Primary Plant Pathologist/Nematologist, California Department of Food and Agriculture, 3294 Meadowview Road, Sacramento, CA 95832. Phone: 916-262-1110, plant.health[@]cdfa.ca.gov.

Comment Period: CLOSED

The 45-day comment period opened on Jun 2, 2016 and closed on Jul 17, 2016.

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Consequences of Introduction:  1. Climate/Host Interaction: [Your comment that relates to “Climate/Host Interaction” here.]

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Pest Rating: C

Posted by ls