Tag Archives: Nematodes

Paratrichodorus minor (Colbran, 1956) Siddiqi, 1974


California Pest Rating Proposal for

Paratrichodorus minor (Colbran, 1956) Siddiqi, 1974
Current Rating: D
Proposed Rating: C

Comment Period: 9/4/2019 through 10/19/2019


*NOTE:

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Posted by ka

Paratrichodorus porosus (Allen, 1957) Siddiqi, 1974


California Pest Rating Proposal for

Paratrichodorus porosus (Allen, 1957) Siddiqi, 1974
Current Rating: D
Proposed Rating: C

Comment Period: 9/4/2019 through 10/19/2019


*NOTE:

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Posted by ka

Quinisulcius spp. Siddiqi 1971


California Pest Rating Proposal for

Quinisculcius spp. Siddiqi 1971
Current Rating: D
Proposed Rating: C

Comment Period: 9/4/2019 through 10/19/2019



Responsible Party:

Heather J. Scheck, CDFA Primary Plant Pathologist/Nematologist. 204 West Oak Ave, Lompoc, CA
93463. 805-736-8050. plant.health[@]cdfa.ca.gov.

*NOTE:

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Posted by ka

Criconemoides (syn. Criconemella De Grisse and Loof 1965), Taylor 1936



California Pest Rating Proposal for

Criconemoides (syn. Criconemella De Grisse and Loof 1965), Taylor 1936
Current Rating: D
Proposed Rating: C

Comment Period: 9/4/2019 through 10/19/2019



Responsible Party:

Heather J. Scheck, CDFA Primary Plant Pathologist/Nematologist. 204 West Oak Ave, Lompoc, CA
93463. 805-736-8050. plant.health[@]cdfa.ca.gov.

*NOTE:

You must be registered and logged in to post a comment. If you have registered and have not received the registration confirmation, please contact us at plant.health[@]cdfa.ca.gov.


Posted by ka

Paratrichodorus spp. (Siddiqi 1974) and Trichodorus spp. (Cobb 1913)



California Pest Rating Proposal for

Paratrichodorus spp. (Siddiqi 1974) and Trichodorus spp. (Cobb 1913)
Current Rating: D
Proposed Rating: C

Comment Period: 9/4/2019 through 10/19/2019



Responsible Party:

Heather J. Scheck, CDFA Primary Plant Pathologist/Nematologist. 204 West Oak Ave, Lompoc, CA
93463. 805-736-8050. plant.health[@]cdfa.ca.gov.

*NOTE:

You must be registered and logged in to post a comment. If you have registered and have not received the registration confirmation, please contact us at plant.health[@]cdfa.ca.gov.


Posted by ka

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

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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

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

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


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

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. similisRadopholus 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.


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Pest Rating: A


Posted by ls

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:

BackgroundDitylenchus 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.

TransmissionThe 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 PotentialDitylenchus 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 potentialOn 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


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Pest Rating: A


Posted by ls