Tag Archives: nematode

Nematodes

Anguina funesta Price, Fisher & Kerr, 1979

June 5, 2017 Admin

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

Paratylenchus spp. Micoletzky, 1922

January 11, 2017 Admin

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

Rotylenchulus reniformis (Reniform Nematode)

January 5, 2016 Admin

California Pest Rating for

Rotylenchulus reniformis Linford & Oliveira, 1940

(Reniform Nematode)

Pest Rating: A

PEST RATING PROFILE

Initiating Event:

For the past several decades, CDFA Nematologists have detected the invasive reniform nematode, Rotylenchulus reniformis, mainly in imported nursery plants. For example, in 2012, the reniform nematode was detected in three separate shipments of 1,288 Beaucarnea sp. and 44 Beaucarnea recurvata and 174 Dracaena marginata plants from Florida destined to Orange County, one shipment of 24 Euphorbia sp. and 12 Dracaena marginata plants also from Florida destined to San Mateo County, and 250 Yucca elephantipes destined to San Diego County. While in 2013, 90 reniform nematode-infected Sansevieria sp. plants were intercepted in shipments from Florida to San Mateo County, and in 2015, 45 reniform nematode-infected Dracaena reflexa plants in shipments from Florida to San Diego County. Detection of this nematode species resulted in subsequent action taken to prevent its introduction and establishment in California. The pest rating proposal is used here to test the validity of the current rating of an already considered high-risk nematode pest.

History & Status:

Background: The reniform nematode, in its adult female stage, is an obligate sedentary semi-endoparasite of plant roots. All juvenile stages, immature females, mature males and eggs are found within rhizosphere soils of host plants. The species is bisexual and reproduces through cross fertilization and parthenogenesis, completely a life cycle from egg to egg in about 24-29 days on okra (17-23 days on cotton). Males do not feed. Soon after the final molt the vermiform, immature adult female becomes infective and seeks to penetrate host roots. After infecting the roots the young females become oriented perpendicularly to the longitudinal axis of the roots with usually only the anterior part of the body embedded within the root tissue. In cotton and other crops, Feeding occurs on tissue of the cortex, phloem and pericycle. Nurse cells are formed near the pericycle with hypertrophy of pericycle and endodermis cells. Epidermal and cortical cells are destroyed resulting in slight browning and necrosis of surrounding tissue. About one week after root penetration, the immature female body enlarges and matures to form the typical kidney shape and secretes a gelatinous matrix that encases her body on the surface of the root. It is within this matrix that the female lays 75-120 eggs per day. The nematode is capable of surviving in air-dried soil for extended periods of time: 7 months at 20-25C, for 6 months in dry soil, and has been reported to survive 29 months in the absence of the host. Two races have been reported in India, differentiated by reactions on cowpea, castor and cotton. Reproduction and development of the reniform nematode are favored by fine textured soils with a relatively high content of silt and/or clay.

The Reniform Nematode has been found to attack over 140 species of more than 115 plant genera in 46 families. Some of the economically important host plants are banana, cabbage, cantaloupe, citrus, kale, lettuce, mango, okra, pigeon pea, pineapple, sugarcane, cotton, corn, onion, beans, potato, carrot, plum, pear, cowpea, soybean, tobacco, eggplant, and tomato. Several ornamental foliage plants also are hosts. In California, potential damage and crop loss of cotton, grapes, citrus, tomato, and ornamentals would be of major concern. Yield loss in cotton up to 60% was reported in infested fields of Louisiana and Mississippi, also in tomato.

The nematode is readily transported over long distances in plant roots and associated soil, as well as spread over short distances in contaminated, run-off irrigation water, infested plant roots and soil. Therefore, imported nursery plants and farm -destined crops are potential pathways of entry.

Worldwide Distribution: The reniform nematode is widely distributed in many tropical and subtropical regions of the world. It has been reported in most of Africa, the Caribbean, Japan, the Middle East, South Pacific, Central America, Italy, Spain, Mexico, China and the Far East. Within the USA it is established in Alabama, Arkansas, Florida, Georgia, Hawaii, Louisiana, Mississippi, North Carolina, South Carolina and Texas.

Official Control: In 2012, the reniform nematode is included on a list of harmful organism under official control in Argentina, Bermuda, Chile, French Polynesia, Republic of Korea and Turkey. Within the USA it is under official control in the states of Arizona and California.

California Distribution: Reniform nematode is not established in California. In 1967, the nematode was detected in 13 residential properties in San Bernardino County. The infestation was traced to yuccas brought into California from Harlingen, Texas, and plant in the subdivision. In December, 1978, the nematode was officially declared eradicated after subsequent herbicide and fumigation (DBCP) trials of the infested areas.

California Interceptions: Over the past several decades, reniform nematode has been frequently detected in incoming quarantine shipments of nursery and household plants at nurseries and border stations.

The risk reniform 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). Rotylenchulus reniformis is likely to establish a widespread distribution in California especially in fine textured soils, and mainly wherever its host is able to grow.

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). Rotylenchulus reniformis has a wide 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). Rotylenchulus reniformis has both high reproduction and dispersal potential.

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 Rotylenchulus reniformis in California could result in the 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 application of irrigation water, to inhibit spread of the pathogen to non-infested sites. Cotton, grape, tomato, citrus and ornamental are the main industries that would be affected, additionally several other crops of lesser production 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 Rotylenchulus reniformis 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).

–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: Rotylenchulus reniformis is not established in California (0). The nematode species has never been detected within California. 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, and all published studies to date on plant parasitic nematodes in California have never resulted in the detection of R. reniformis.

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 reniform 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 Rotylenchulus reniformis is duly justified and is herein, proposed to remain unchanged.

References:

Birchfield, W., and W. J. Martin. 1967. Reniform nematode survival in air-dried soil. Phytopathology 57:804.

Chitambar, J. J. 1997. A brief review of the reniform nematode, Rotylenchulus reniformis. California Plant Pest & Damage Report, California Department of Food and Agricultural 16:71-73.

Dasgupta, D. R., and A. R. Seshadri. 1971. Races of the reniform nematode Rotylenchulus reniformis Linford and Oliviera, 1940. Indian Journal of Nematology 1:21-24.

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.

Jatala, P. 1991. Reniform and false root-knot nematodes, Rotylenchulus and Nacobbus spp. In Manual of Agricultural Nematology, edited by W. R. Nickle, Marcel Dekker, Inc., 1035p.

Koenning, S. R., S. A. Walters, and K. R. Barker. 1996. “Impact of soil texture on the reproductive and damage potentials of Rotylenchulus reniformis and Meloidogyne incognita on Cotton. Journal of Nematology, 28:527-536.

Robinson, A. F., C. M. Heald, S. L. Flanagan, W. H. Thames and J. Amador. 1987. Geographical distribution of Rotylenchulus reniformis, Meloidogyne incognita, and Tylenchulus semipenetrans in the lower Rio Grande valley as related to soil texture and land use. Annals of Applied Nematology 1:20-25.

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 Tuesday, January 5, 2016 and closed on February 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.]

♦ 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

Pratylenchus neglectus

January 5, 2016 Admin

California Pest Rating for

Pratylenchus neglectus (Rensch, 1924) Filipjev & Schuurmans-Stekhoven, 1941

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 is an indication of contamination in violation of the State’s standard of pest cleanliness required for nurseries. Pratylenchus neglectus was originally rated D and its risk of infestation and permanent rating are re-assessed here.

History & Status:

Background: The California meadow nematode, Pratylenchus neglectus (synonym P. minyus) 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. neglectus 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. Generally, root lesion nematodes have a life cycle 45-65 days, but in P. neglectus, the life cycle can take as few as 28 days on tobacco with greater reproduction at 38°C than at higher and lower temperatures (Townshend & Anderson, 1976). Pratylenchus neglectus survives the winter in infected roots or soil as eggs, juveniles or adults. It can survive at 2°C but not at sub-zero temperatures. 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 neglectus is primarily a parasite of grasses, but its diverse range of hosts include, fruit trees, pistachio, pear, apple, maize, potato, wheat, cereals, rapeseed, legumes, alfalfa, red clover, tobacco, peppermint, soybean, turf and pasture grasses, sugarcane, strawberry, carrots, cabbage (CABI, 2014; Castillo & Vovlas, 2007; Townshend & Anderson, 1976).

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 neglectus is capable to reducing root growth and function thereby, causing reduction in plant growth and yield of its associated host plants. It can cause significant losses in tobacco and peppermint production. In the Pacific Northwest of the United States, P. neglectus has been reported to reduce wheat yields individually or in mixed populations with a different root lesion nematode species, P. thornei (Smiley, et al., 2014).

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 neglectus has been reported worldwide in Asia: India, Iran, Japan, Oman, Pakistan, Turkey, Africa: Algeria, Tunisia, Morocco, South Africa; Australia: Western Australia, Tasmania; Europe: Bulgaria, Croatia, Estonia, France, Germany, Italy, Poland, Portugal, Russia, Slovakia, Slovenia, Spain, Yugoslavia; North America: USA, Canada, Mexico; South America: Argentina (CABI, 2014; Castillo & Vovlas, 2007; Townshend & Anderson, 1976).

In the USA, Pratylenchus neglectus has been reported in California, and several other states including, Idaho, Iowa, Montana, New York, Ohio, Oregon, Washington, and the Pacific Northwest United States (CABI, 2014; Castillo & Vovlas, 2007; Hafez et al., 2010; Smiley et al., 2004).

Official Control: Currently, Pratylenchus neglectus is rated ‘D’ by CDFA. Canada, Ecuador and Peru include the species on their Harmful Organism Lists (PCIT, 2015).

California Distribution: Pratylenchus neglectus is widely distributed in California. In statewide surveys for plant parasitic nematodes in California’s agricultural crop production site conducted by CDFA during 2005-2009, P. neglectus was found in almost every county.

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

The risk Pratylenchus neglectus 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 neglectus 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 neglectus is primarily a parasite of grasses, but its diverse range of hosts are grown throughout the State and include, fruit trees, pistachio, pear, corn, potato, wheat, cereals, rapeseed, legumes, alfalfa, red clover, tobacco, peppermint, soybean, turf and pasture grasses, sugarcane, strawberry, carrots.

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 neglectus 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 neglectus 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 neglectus:

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 neglectus to California = (11).

-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 neglectus 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 neglectus, is C.

References:

CABI. 2014. Pratylenchus neglectus (nematode, California meadow) basic datasheet. http://www.cabi.org/cpc/datasheet/43899

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

Hafez S. L, P. Sundararaj, Z. A. Handoo and M. R. Siddiqi. 2010. Occurrence and distribution of nematodes in Idaho crops. International Journal of Nematology, 20(1):91-98.

Smiley, R.W., K. Merrifield, L. M. Patterson, R. G. Whittaker, J. A. Gourlie, and S. A. Easley. 2004. Nematodes in dryland field crops in the semiarid Pacific Northwest United States. Journal of Nematology, 36:54-68.

Smiley, R. W., J. A. Gourlie, G. Yan., and K. E. L. Rhinhart. 2014. Resistance and tolerance of Landrace wheat in fields infested with Pratylenchus neglectus and P. thornei. Plant Disease, 98:797-805.

Townshend, J. L. and R. V. Anderson. 1976. Pratylenchus neglectus [=P. minyus]. C.I.H. Descriptions of Plant-parasitic Nematodes, Set 6, No. 82.

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 Tuesday, January 5, 2016 and closed on February 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.]

♦ 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

Xiphinema index Thorne & Allen, 1950 (Dagger nematode)

October 14, 2015 Admin

California Pest Rating for

Xiphinema index Thorne & Allen, 1950

(Dagger nematode)

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

None.

History & Status:

Background: Xiphinema index was first described by Thorne and Allen in 1950, from soil around roots of fig (Ficus carica, variety Calimyrna) growing near Planada, Merced County, California. By genetic analysis of a wide range of populations of X. index from grapevine vineyards throughout the world, Esmaenjaud et al. (2014) suggested that the dagger nematode, Xiphinema index originated from the Middle East from where it spread and was introduced into the grapevine countries in the Western Hemisphere. However, they also stated that their hypothesis needed to be confirmed and expanded to include new locations.

Xiphinema index is a migratory root ectoparasite that inhabits rhizosphere soils of host plants while feeding on the roots. The length of the life cycle is reported as geographically variable being 22-27 day at 24°C in California, and 7-9 months at 20-23°C in Israel. The life cycle of the dagger nematode involves development from egg through four vermiform, motile larval stages to adults. Eggs are laid singly in the soil and hatch in 6-8 days. A population may be generated by a single larva. Once hatched, each larval stage must feed in order to molt and develop to the next stage. Larvae and adults feed by means of a long stylet that is used to penetrate the vascular tissue of roots. Males are very rare and reproduction is apparently by parthenogenesis. The rate of reproduction is greatest at 29.4°C.

Research studies have shown that this nematode species can survive in moist sterile soil without food for 9-10 months, but survived for 4.5 years on grapevine roots left in field soil after the top growth had been removed (Raski & Hewitt, 1960; Taylor & Raski, 1964, Radewald & Raski, 1962). More recent studies indicate that X. index can survive in field soil for at least 4 years Esmaenjaud et al., 2014; Demangeat et al., 2005), and in non-irrigated, deep soil usually 50 cm below surface (Esmenjaud et al., 1992; Villate et al., 2008).

The nematode does well in light and medium-textured soils and in heavy soils with increases in rate of reproduction and shorter durations to complete its life cycle as soil temperatures increase from 16 to 28°C (Cohn & Mordechai, 1970). It prefers a pH of 6.5-7.5.

Xiphinema index is the vector of Grapevine fanleaf nepovirus (GFLV) which causes Fanleaf Degeneration Disease in grapevines and is considered the most economically important virus of grapevines worldwide. The nematode vector spreads the virus from plant to plant in the field and the spread of the virus in a field reflects the distribution of the nematode in the ground (Villate et al., 2008). During feeding, the nematode acquires the virus from infected plants and transmits it to virus-free plants. The virus is retained in the cuticle lining of the esophageal lumen of the nematode and adults and larvae can transmit the virus. The virus is not transmitted through the egg, but is lost at molting so that the nematode must feed again to acquire the virus. The virus does not affect the rate of reproduction of the nematode and a temperature of 13-24°C is favorable for transmission (Das & Raski, 1968). Early reports state that the nematode can transmit the virus for up to 4-8 weeks when feeding on virus-free plants, and that the virus can persist in starving X. index for at least 30 days (Taylor & Raski, 1964; Raski & Hewitt, 1960). However, Esmaenjaud et al., 2014, reported that the virus may survive in the adult nematode for at least 4 years and slightly less in fourth stage larvae, thereby indicating that elimination of the virus form soil mainly depends on the possibility of eliminating the nematode vector than on grape residues in infected field soils.

Damage Potential: Xiphinema index can cause crop yield reduction and loss. A reduction of 38% in root weight was caused by this nematode species (Van Gundy et al., 1965). More significant damage is caused due to vectoring of grape fanleaf virus. Feeding of X. index on roots of grapevine, fig, rose and mulberry results in mechanical and physiological expressed as 1) terminal swellings with necrosis, 2) cessation of root elongation and extensive necrosis of main roots resulting in a witches’-broom effect from lateral proliferation – in heavily parasitized roots, 3) unequal swelling on one side of rootlets which then produces a 45-90 degree curvature (Raski & Krusberg, 1984). The nematode may feed at the root tip or in the piliferous (root-hair zone) region, however, galls are produced only at the tip. Above ground symptoms caused by the nematode alone are general symptoms of an impaired root system, not diagnostic, and may not be present.

Hosts: Grapevine is the main host and X. index is associated with grapevine cultivation globally. Other hosts (natural and experimental) include fig, prune, apple, pistachio, citrus, sour orange, strawberry, walnut, rose, mulberry, bur marigold, Boston ivy, cactus, dwarf nettle, fruit, ornamentals and weeds.

Transmission: Infected rootings and soil, cultural practices that result in the movement of infected soil to clean, non-infected sites, and contaminated irrigation water.

Worldwide Distribution: Asia: Armenia, Azerbaijan, Republic of Georgia, India, Iran, Iraq, Israel, Lebanon, Pakistan, Tajikistan, Turkey, Turkmenistan, Uzbekistan; Africa: Algeria, South Africa, Tunisia; North America: USA, South America: Argentina, Brazil, Chile, Peru; Europe: Albania, Austria, Bulgaria, Croatia, Cyprus, Czech Republic, France, Germany, Greece, Hungary, Italy, Malta, Moldova, Poland, Portugal, Romania, Russian Federation, Serbia, Slovakia, Slovenia, Spain, Switzerland, Ukraine, Yugoslavia; Oceania: Australia, New Zealand (CABI, 2015; EPPO, 2015).

Official Control: Xiphinema index is on the “Harmful Organisms Lists” for Canada, Ecuador, Honduras, Japan, Republic of Korea, Taiwan, and Uruguay (USDA-PCIT, 2015).

California Distribution: The dagger nematode is most prevalent in vineyards in north and central coastal regions, and in the San Joaquin Valley. According to CDFA’s Pest Damage Records for 2000-2015, X. index was detected in Fresno, Napa, San Diego, San Luis Obispo, Sonoma and Tulare Counties mainly in grape (Vitis sp.), and occasionally on tangelo (Citrus sp.) and peach (Prunus sp.) samples collected during surveys. During the mid 1980s, the species was also detected in Mendocino and Monterey Counties. In 2013, McKenry (Nematologist (Retd.), UC Riverside) stated that X. index was increasing in Kern and Tulare County table grapes (Personal communications document: ‘Fifty years with a nematode-free nursery program’).

California Interceptions: The risk Xiphinema index 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) – Xiphinema index is able to establish in cool to warm climates. light and medium-textured soils and in heavy soils with increases in rate of reproduction and shorter durations to complete its life cycle as soil temperatures increase from 16 to 28°C.

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) – Grapevine is the main host and Xiphinema index is associated with grapevine cultivation globally. Other hosts (natural and experimental) include fig, prune, apple, pistachio, citrus, sour orange, strawberry, walnut, rose, mulberry, bur marigold, Boston ivy, cactus, dwarf nettle, fruit, ornamentals and weeds.

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 nematode’s life cycle and increase is dependent on soil temperature and plant host. Long and short distance spread is mainly through infested soils accompanying plant stock, farm machinery, runoff and splash contaminated irrigation water, human and animal activity and soil contaminated clothing.

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) – Infestations of Xiphinema index could result in lowered crop yield and value, loss in market, and change in cultural practices to mitigate risk of spread to non-infested sites. The main economic damage is due to the ability of X. index to vector the economically important grape fanleaf virus.

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 Xiphinema index on natural environments is not known, however, the infestations of the pest could affect cultural practices, home gardening and ornamental plantings.

Consequences of Introduction to California for Xiphinema index:

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 Xiphinema index to California = (13).

-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). Xiphinema index has been detected in at least two contiguous suitable climate areas 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 = 11.

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the dagger nematode, Xiphinema index, remains B.

References:

CABI. 2015. Xiphinema index (fan-leaf virus nematode) full datasheet report. Crop Protection Compendium. www.cabi.org/cpc/ .

Das, S. and Raski, D. J. 1969. Effect of grapevine fanleaf virus on the reproduction and survival of its nematode vector, Xiphinema index Thorne & Allen. Journal of Nematology, 1:107-110.

Demangeat, G., Voisin, R., Minot, J.C., Bosselut, N., Fuchs, M. and Esmenjaud, D. 2005.

Survival of Xiphinema index in vineyard soil and retention of Grapevine fanleaf virus

over extended time in the absence of host plants. Phytopathology 95:1151-1156.

EPPO. 2015. Xiphinema index (XIPHIN). European and Mediterranean Plant Protection Organization PQR database. http://www.eppo.int/DATABASES/pqr/pqr.htm .

Esmenjaud, D., Walter, B., Valentin, G., Guo, Z.T. and Cluzeau, D. 1992. Vertical

distribution and infectious potential of Xiphinema index (Thorne & Allen, 1950)

(Nematoda: Longidoridae) in fields affected by Grapevine fanleaf virus in vineyards in

the Champagne region of France. Agronomie 12:395-399.

Esmenjaud, D., Demangeat, G., van Helden, M. and Ollat, N. 2014. Advances in biology, ecology and control of Xiphinema index, the nematode vector of Grapevine Fan leaf virus. Proc. VIth Intl. Phylloxera Symp. Eds.: N. Ollat and D. Papura. Acta Hort. 1045, ISHS 2014; p. 67-73.

Fisher JM, Raski DJ, 1967. Feeding of Xiphinema index and X. diversicaudatum. Proceedings of the Helminthological Society of Washington, 34:68-72.

Radewald, J. D. and Raski, D. J. 1962. A study of the life cycle of Xiphinema index. Phytopathology, 52:748.

Raski, D. J. and Hewitt, W. B. 1960. Experiments with Xiphinema index as a vector of fanleaf of grapevines. Nematologica, 5:166-170.

Taylor, C. E. and Raski, D. J. 1964. On the transmission of grape fanleaf by Xiphinema index. Nematologica 10:489-495.

Thorne, G. and Allen, M. W. 1950. Paratylenchus hamatus n. sp. and Xiphinema index n. sp., two nematodes associated with fig roots, with a note on Paratylenchus ancepts Cobb. Proceedings of the Helminthological Society of Washington, 17:27-35.

USDA-PCIT. 2015. United States Department of Agriculture, Phytosanitary Certificate Issuance & Tracking System (PCIT). https://pcit.aphis.usda.gov/PExD/faces/ViewPExD.jsp .

Villate, L., Fievet, V., Hanse, B., Delemarre, F., Plantard, O., Esmenjaud, D. and van

Helden, M. 2008. Spatial distribution of the dagger nematode Xiphinema index and its

associated Grapevine fanleaf virus in French vineyard. Phytopathology 98:942-948.

http://www.ipm.ucdavis.edu/PMG/r302200111.html.

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.