Category Archives: Nematodes

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

Pratylenchus alleni Ferris, 1961

 California Pest Rating for
Pratylenchus alleni Ferris, 1961
Pest Rating:  A

 


PEST RATING PROFILE
Initiating Event:

The risk of infestation of Pratylenchus alleni in California is evaluated and a permanent rating is proposed.

History & Status:

Background:  The root lesion nematode, Pratylenchus alleni, was first discovered in El Dorado, Illinois infesting nine varieties of soybeans cultivated in a single field (Ferris, 1961).  The nematode species can seriously affect soybean production and also is associated with other agricultural crops.

Pratylenchus alleni is a migratory endoparasite that can enter plant roots, feed, reproduce and move freely within the tissue while spending its entire life cycle there.  The species can also be found in soil around roots.  Within the roots, feeding is confined to the root cortex.  Like other Pratylenchus species, P. alleni has six life stages: egg, four juvenile stages and adults.  Reproduction requires both females and males. First stage juveniles develop within the egg, followed by a first molt to the second stage juvenile that hatches from the egg.  Each stage develops into the next via a molt of its cuticle (outer body covering).  All juvenile and adult stages are worm-shaped (vermiform).  All post-hatch stages are motile and can infect plants.  Generally, root lesion nematodes have a life cycle 45-65 days, but the duration is affected by temperature and moisture.  Pratylenchus alleni survives the winter in infected roots or soil as eggs, juveniles or adults. During spring, when plant growth is active, eggs hatch to commence the life cycle within roots or in rhizosphere soil.  Within the root, the nematode feeds on cortical tissue causing necrosis of cortical cells, cell breakdown, and formation of cavities. Necrosis is apparent as lesions which expand as the nematodes move lengthwise within the infected roots.  Some nematodes may leave the root, enter soil and re-enter the root at a different site causing a new infection.

Hosts: Soybean, vetch, chickpea, castor bean, cotton, wheat, corn, potato, tomato, Zygophyllum sp., raspberry, sunflower, chrysanthemum, marigold (Bernard & Keyserling, 1985; Castillo & Vovlas, 2007; Dickerman, 1979; Hackney & Dickerson, 1975).

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

Damage Potential:  Pratylenchus alleni is capable to severely reducing root growth and function thereby, causing reduction in plant growth and yield. In Canada, field-grown soybean suffered a 38 to 54 % reduction in yield due to Pratylenchus alleni (Bélair et al., 2013).  In temperate regions, poor potato growth has been caused by associated P. alleni (Brodie et al., 1993).

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

Worldwide Distribution:  Asia: India, Turkey, Europe: Martinique (France), Russia; North America: USA, Canada; South America: Argentina (Castillo & Vovlas, 2007).

In the USA, Pratylenchus alleni has been reported from Arkansas, Illinois, Iowa, and Ohio (Brown et al., 1980; Ferris, 1961; Robbins et al., 1987; Williams, 1982).

Official Control: None reported.

California DistributionPratylenchus alleni is not known to be present in California.

California Interceptions: Pratylenchus alleni has never been detected in incoming shipments of plants and soil to California.

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

Consequences of Introduction: 

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

– Low (1) not likely to establish in California; or likely to establish in very limited areas
– Medium (2) may be able to establish in a larger but limited part of California
High (3) likely to establish a widespread distribution in California.

Risk is High (3) Pratylenchus alleni is able to establish in cool and moist, as well as warmer regions of California, wherever its host plants are capable of growing.

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) Of what has been reported, Pratylenchus alleni has a moderate and diverse host range that includes several economically important agricultural crops.  Further studies on the host range of this species may be needed.  While soybean is not a major crop produced in California, other hosts such as potato, tomato, cotton and corn are cultivated under larger acreage.

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) – The nematode’s life cycle and increase is dependent on soil temperature and plant host. Long and short distance spread is mainly Infected roots, bare root propagative plant materials, soil debris, run-off and irrigation water, cultivation tools, equipment and human activity that can move soils from infested to non-infested sites.

4)  Economic Impact: Evaluate the economic impact of the pest to California using 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).
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) Pratylenchus alleni infections could result in lowered crop yield and value, loss in market, and change in cultural practices to mitigate risk of spread to non-infested sites.

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.   The pest significantly impacts 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) – The impact of Pratylenchus alleni on natural environments is not known, however, the infestations of this root lesion nematode could affect cultural practices, home gardening and ornamental plantings.

Consequences of Introduction to California for Pratylenchus alleni:

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

Low = 5-8 points
Medium = 9-12 points
High = 13-15 points

 Total points obtained on evaluation of consequences of introduction of Pratylenchus alleni 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)Pratylenchus alleni has never been detected 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: 

Pratylenchus alleni has never been detected through CDFA’s Nematode detection regulatory programs, nor has it been reported in California by other scientists.  Nevertheless, surveys for this species in agricultural production and environmental sites need to be conducted to ascertain its non presence in California.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the lesion nematode, Pratylenchus alleni, is A.

 References:

Acosta, N. 1982. Influence of inoculum level and temperature on pathogenicity and population development of lesion nematodes on soybean. Nematropica 12:189-197.

Acosta, N., and R. B. Malek. 1979. Influence of temperature on population development of eight species of Pratylenchus on soybean. Journal of Nematology 11:229-232.

Bélair, G., B. Mimee, M. O. Duceppe and S. Miller.  2013.  First report of the root-lesion nematode Pratylenchus alleni associated with damage on soybean in Quebec, Canada.  Plant Disease 97:292. http://dx.doi.org/10.1094/PDIS-03-12-0309-PDN .

Bernard, E. C., and M. L. Keyserling.  1985.  Reproduction of root-knot, lesion, spiral and soybean cyst nematodes.  Plant Disease 69:103-105.

Brodie, B. B., K. Evans and J. Franco.  1993.  Nematode parasites of potatoes.  In: Evans, K., D. L. Trudgill and J. M. Webster (Eds).  Plant parasitic nematodes in temperate agriculture.  Wallingford, UK, CABI Publishing, pp. 87-132.

Brown, M. J., R. M. Riedel and R. C. Rowe.  1980.  Species of Pratylenchus associated with Solanum tuberosum cv. Superior in Ohio.  Journal of Nematology 12:189-192.

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

Dickerson, O. J. 1979. The effects of temperature on Pratylenchus scribneri and P. alleni populations on soybeans and tomatoes. Journal of Nematology 11:23-26.

Ferris, V. R.  1961.  A new species of Pratylenchus (Nemata-Tylenchida) from roots of soybeans.  Proceedings of the Helminthological Society of Washington 28:109-111.

Hackney, R. W. and O. J. Dickerson. 1975. Marigold, Castor bean, and chrysanthemum as controls of Meloidogyne incognita and Pratylenchus alleni. Journal of Nematology 7:84-90.

Robbins, R. T., R. D. Riggs and D. Von Steen.  1987.  Results of annual phytoparasitic nematode surveys of Arkansas soybean fields, 1978-1986.  Annals of Applied Nematology 1:50-55.

Williams, D. D.  1982.  The known Pratylenchidae (Nematode) of Iowa.  Iowa State Journal of Research 56:419-424.

Responsible Party:

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


Comment Period:  CLOSED

The 45-day comment period opened on June 1, 2015 and closed on July 16, 2015.


Comment Format:

When commenting, please reference the section heading related to your comment, as shown in the example below.

Example Comment: 

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


Pest Rating:  A


Posted by ls

Longidorus elongatus: Needle nematode

California Pest Rating for
Longidorus elongatus (de Man, 1876) Micoletzky, 1922
(Needle nematode)
Pest Rating:  B

 


PEST RATING PROFILE
Initiating Event:

The CDFA’s latest record of detection of Longidorus elongatus was in 2013 during a statewide survey for plant parasitic nematodes associated with golf course turf and citrus orchards.  The nematode species was detected in turf (Poa sp.) samples from a golf course in Marin County, California.  Prior to this find, L. elongatus was last detected in California only few times during the early 60s to late 70s.    The current temporary Q-rating of the nematode species is reassessed here and a permanent rating is proposed.

History & Status:

BackgroundLongidorus elongatus is an obligate ectoparasite of host plants and feeds at or just behind root tips causing a characteristic swelling or galling of the tips as well as a general stunting of the root system.  Longidorus elongatus has four juvenile stages and most likely produces one generation a year especially under field conditions however, there is a two- to four-fold increase on favored hosts.  The nematode species is found in cool soils that may vary from peat to sandy loams, although the species appears to prefer coarse, well-drained soils. Adults may live for several years, and the time to complete its life cycle is dependent on soil temperature. At 20 ºC a generation takes 19 weeks with a twenty-fold increase in population on wild (Woodland) strawberry, and at 30 ºC the life cycle is completed in 9 weeks.  Males are rare and reproduction is usually by parthenogenesis, except where males are common, in which case bisexual reproduction occurs.

Damage Potential: Severe damage to certain crops has been caused by the direct feeding of the nematode.  However, the major economic impact caused by this nematode is due to its ability to vector plant viruses.  Longidorus elongatus transmits the Scottish strains of raspberry ringspot virus (RRV), tomato black ring virus (TBRV).  Strawberry roots are damaged both by the direct feeding of the nematode as well as transmitted RRV and TBRV.  Raspberry, although a poor host to the nematode, is readily infected by both viruses transmitted by the nematode resulting in severe crop loss.  Longidorus elongatus and Trichodorus spp. (stubby root nematode) and viruses are involved in ‘Docking Disorder” of sugarbeet.  The virus is carried on the inner surface of the guiding sheath of the nematode’s stylet.   The nematode species also transmits spoon leaf virus to red currants, certain raspberry varieties and weeds.

Hosts: The species can feed on over 60 plant species comprising of a wide variety of herbaceous annual and perennial crops and weeds.  Direct feeding by the nematode alone has caused severe crop damage to strawberry, sugarbeet, rye grass, potato, cereals (millets, wheat and barley), carrots and peppermint.  In the USA, there are reports of severe damage caused to carrots, rye grass and peppermint.

Transmission: The nematode species is able to spread over short and long distances when transported in infested soils accompanying plant stock, farm machinery, runoff and splash contaminated irrigation water, human and animal activity and soil contaminated clothing.

Worldwide Distribution: Longidorus elongatus occurs in a wide range of soils, especially, sandy and sandy loam soils, and has been found mainly in temperate regions.  Worldwide distribution of the species include, Asia: India, Kazakhstan, Pakistan, Tajikstan, Turkey, Uzbekistan, Vietnam; Africa: South Africa; North America: Canada, USA; Europe: Austria, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Latvia, Moldova, Netherlands, Norway, Poland, Portugal, Romania, Russian Federation, Slovakia, Spain, Sweden, Switzerland, United Kingdom, Ukraine; Oceania: New Zealand (CABI, 2014; EPPO, 2014).

In the USA, Longidorus elongatus has been found in Arkansas, Oregon and California (CABI 2014; EPPO, 2014; CDFA Nematode detection records – ‘Initiating event’).  Robbins and Brown (1991) noted that the accuracy of early reports of L. elongatus from Alabama, Florida, Idaho, Illinois, Michigan, New Jersey, New Mexico, Pennsylvania, Rhode Island, South Carolina, Texas, and Tennessee listed by Norton et al., (1984), was doubtful due to the wide morphometric variation in range values for L. elongatus that may refer to other Longidorus species.

Official Control: Longidorus elongatus is on the Harmful Organism lists of the following countries: Canada, Chile, Costa Rica, Ecuador, Honduras, Indonesia, and Taiwan (PCIT, 2015).

California Distribution:  CDFA’s Nematode detection records indicate that Longidorus elongatus was detected 34-40 years ago in two commercial sites: 1 in Borrego, San Diego County on Grape in 1962, and the other in Yountville, Napa County on Pear in 1977.  Also it was discovered on 3 private properties: San Leandro, Alameda County in 1962; Santa Barbara, Santa Barbara County in 1976; San Francisco, Harding Park Golf course, San Francisco County in 1979.   The nematode species was not detected in California until 2013 in Marin County during a statewide golf course survey.

California Interceptions: Since 1979, there has only been a single detection of Longidorus elongatus associated with an unknown houseplant that was intercepted at the Alturas Border Protection Station.

The risk Longidorus elongatus 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) Longidorus elongatus is able to establish in cool and moist regions of California.

 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) – Longidorus elongatus has a very wide host range which includes  herbaceous annual and perennial crops, turf grass, and weeds.

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

– Low (1) does not have high reproductive or dispersal potential.
– Medium (2) has either high reproductive or dispersal potential.
High (3) has both high reproduction and dispersal potential.

Risk is High (3) – The nematode’s life cycle and increase is dependent on soil temperature and plant host. Long and short distance spread is mainly through infested soils accompanying plant stock, farm machinery, runoff and splash contaminated irrigation water, human and animal activity and soil contaminated clothing.  

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

A. The pest could lower crop yield.
B. The pest could lower crop value (includes increasing crop production costs).
C. The pest could trigger the loss of markets (includes quarantines).
D. The pest could negatively change normal cultural practices.
E. The pest can vector, or is vectored, by another pestiferous organism.
F. The organism is injurious or poisonous to agriculturally important animals.
G. The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
High (3) causes 3 or more of these impacts.

 Risk is High (3) – Infestations of Longidorus elongatus could result in lowered crop yield and value, loss in market, and change in cultural practices to mitigate risk of spread to non-infested sites. The main economic damage is due to the ability of L. elongatus to vector Raspberry ringspot virus and Tomato black ring virus.

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

A. The pest could have a significant environmental impact such as lowering biodiversity, disrupting natural communities, or changing ecosystem processes.
B. The pest could directly affect threatened or endangered species.
C. The pest could impact threatened or endangered species by disrupting critical habitats.
D. The pest could trigger additional official or private treatment programs.
E. The pest significantly impacts cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact. Score:

– Low (1) causes none of the above to occur.
Medium (2) causes one of the above to occur.
– High (3) causes two or more of the above to occur.

Risk is Medium (2) – The impact of Longidorus elongatus on natural environments is not known, however, the infestations of the pest could affect cultural practices, home gardening and ornamental plantings.

Consequences of Introduction to California for Longidorus elongatus:

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

-Low = 5-8 points
-Medium = 9-12 points
-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Longidorus elongatus 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 Medium (-2)Including the earlier detections of Longidorus elongatus, the species has been detected in northern and southern cool coastal and sub coastal counties of California.

Final Score:

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

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

Uncertainty:

While Longidorus elongatus has not been detected in California’s agricultural production sites for the past 34 years, as determined through CDFA’s different nematode detection programs and special surveys, there is always the possibility that this species may be detected in future targeted surveys thereby increasing its distribution.  Such detections may alter the proposed rating of L. elongatus.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the needle nematode, Longidorus elongatus, is B.

References:

CABI.  2014.  Longidorus elongatus full datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/ .

EPPO.  2014.  Longidorus elongatus (LONGEL).  European and Mediterranean Plant Protection Organization PQR database.  http://www.eppo.int/DATABASES/pqr/pqr.htm .

Norton, D. C., P. Donald, J. Kimpinski, R. F. Meyers, G. R. Noel, E. M. Noffsinger, R. T. Robbins, D. C. Schmitt, C. Sosa-Moss, and T. C. VRAIN. (1984).  Distribution of plant-parasitic nematodes in North America. Society of Nematologists, Hyattsville, Maryland, 1-19.

PCIT.  2015.  USDA Phytosanitary Certificate Issuance & Tracking System.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp .

Robbins, R. T. and D. J. F. Brown.  1991. Comments on the taxonomy, occurrence and distribution of Longidoridae (Nematoda) in North America.  Nematologica 37:395-419.

Responsible Party:

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


Comment Period:  CLOSED

The 45-day comment period opened on Tuesday,  April 7, 2015 and closed on May 22, 2015.


Pest Rating:  B


Posted by ls

Asian Citrus Root-knot Nematodes

 California Pest Rating for
Asian Citrus Root-knot Nematodes:
Meloidogyne citri Zhang, Gao & Weng, 1990;
donghaiensis Zheng, Lin & Zheng, 1990;
fujianensis Pan, 1985
indica Whitehead, 1968;
jianyangensis Yang, Hu, Chen & Zhu, 1990;
kongi Yang, Wang & Feng, 1988;
mingnanica Zhang, 1993
Pest Rating: A

 


PEST RATING PROFILE
Initiating Event:

A statewide survey of California’s major commercial citrus production sites was conducted in 2012-13 for the probable detection of member species that comprise the Asian citrus root-knot nematode (ACRKN) complex.  The species are invasive and listed in the 2012 United States Department of Agriculture (USDA) CAPS Priority Pest List for survey.  A permanent rating is proposed here for the complex of species and each individual member.

History & Status:

Background:  The Asian citrus root-knot nematodes are a complex of species that in Asia attack the roots of Citrus spp.  The species have not been found outside of China and India where the climate ranges from semi-tropical to temperate.  Currently, there is a paucity of information on the biology and economic damage potential of each species, however, root-knot nematodes are known to economically damage crops and therefore ACRKN, if introduced to the United States, have the potential to negatively impact citrus production.

Life Cycle: The seven species comprising the complex of Asian citrus root-knot nematodes (Meloidogyne spp.) have life cycles and feeding behaviors similar to other root knot nematode species.  Meloidogyne spp are sedentary endoparasites that feed within host plant roots.  Adult females embedded in host roots produce eggs within a mass either on the surface of, or within roots.  The first stage juvenile develops within the egg and molts to develop into the second stage.  The second-stage juveniles (J2) are the infective stage that hatch from eggs, migrate in rhizosphere soil to host roots, reinfest the roots or are attracted to other nearby host roots which are then penetrated.  Within roots, J2 establish a specialized feeding site or giant plant cells that are formed at the head end of the nematode in response to its feeding.  The second stage juveniles become sedentary while feeding at the specialized site, increase in size and undergo two more molts and non-feeding stages before developing into mature adult females or males and completing the life cycle.  Very little is known about the biology of all ACRKN species.  Pan et al., (1999) provided information on the biology of M. fujianensis on Citrus reticulata in Fujian Province, China.  The species is active there throughout the year with peak infection occurring between September-October and March-April.  During that time juveniles of various stages may be present in the soil.  The life cycle of M. fujianensis is 55-60 days at 25° with 33-35 days from root penetration to egg production.  M. indica took 28-35 days from root penetration to egg production on Satsuma, sour orange and tomato (Vovlas & Inserra, 2000).

Hosts:  Citrus is the primary host for all ASRKN species.  Experimental hosts include pepper and tomato as non-citrus hosts.  Some of the nematode species show preferences to certain Citrus species over others. Meloidogyne citri: Citrus spp. (citrus), C. reticulata (mandarin/tangerine orange), C. unshiu (Satsuma orange), C. aurantium (sour orange), Solanum lycopersicum (tomato). M. donghaiensis: mandarin/tangerine orange. M. fujianensis: Imperata cylindrical (cogon grass), mandarin/tangerine orange.  M. indica: citrus, C. aurantifolia (lime), C. sinensis (orange), Morinda officianalis (morinda).  M. jianyangensis: citrus, mandarin/tangerine orange.  M. kongi: citrus, Capsicum sp. (pepper).  M. mingnanica: citrus, Satsuma citrus, Poncirus trifoliate (trifoliate or hardy orange), sour orange (as an experimental host) (Davis & Venette, 2004).

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

Damage Potential:  The damage potential and economic impact of ACRKN is not well known.  The impact of single species is difficult to determine as these nematodes usually occur in mixed populations.  In China and India, estimated losses in citrus production to ACRKN infestation are 20-50% (Pan, 1985; Vovlas & Inserra, 2000).  Information is sparse on the damage potential of individual members of the ACRKN group however, Meloidogyne spp. are known to be one of the most economically important plant parasitic nematodes attacking a wide range of crops worldwide and causes global economic losses that average 10-11%, although this figure is thought to be grossly underestimated.

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

Worldwide Distribution:   Asia: China (Meloidogyne citri, M. donghaiensis, M. fujianensis, M. indica, M. jianyangensis, M. kongi, and M. mingnancia) and India (M. indica).

Official Control: Of the seven species belonging to ACRKN, Meloidogyne fujianensis and M. kongi are on Taiwan’s Harmful Organism List, and M. indica is on the similar list for Indonesia and Timor-Leste.  M. citri and M. fujianensis are prevented into Florida through the movement of nursery stock and other plants and plant products (5B-3.0038: Quarantine Action, Department of Agriculture and consumer Services, division of Plant Industry).

California Distribution:  ACRKN are not known to be present in California.

California Interceptions: ACRKN have never been detected in incoming shipments of plants and soil to California.

The risk Asian citrus root-knot nematodes 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). If introduced, it is likely that ACRKN is able to establish a widespread distribution in California.  Meloidogyne citri, M. donghaiensis, M. fujianensis, M. indica, and M. mingnanica are favored by tropical and sub-tropical climates (Davis & Venette, 2004), while M. jianyangensis and M. kongi are more temperate climate species.  Based on what is currently known about the geographical distribution of ASRKN species, Davis and Venette (2004) suggested that because of their climate preference, the first group of species may not find suitable climate in California, while M. jianyangensis may find suitable climate in California in the northern region extending along an eastern-southern strip to Kern County.  However, their forecast is based on current known geographical distribution of the species and not of the associated hosts.  Most citrus are adapted to warm, tropical or subtropical climates.  There is always the possibility that California will support populations of the first group of species, especially as large acreages are under citrus, tomato and pepper production statewide. 

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).  ACRKN has a moderate host range of several Citrus species, tomato and pepper.  However, citrus and tomato are major crops grown over extensive acreage within 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).  ACRKN species have high reproduction and are easily spread to non-infected sites through the movement of infected plant roots, soil/planting media, contaminated cultivation equipment and irrigation 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).
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). Introduction and establishment of ACRKN could lower crop yield, crop value, result in reduction or loss of market due to the imposition of quarantines against California, require costly changes in normal production cultural practices including restriction and delivery of irrigation water within and between fields.

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.   The pest significantly impacts 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).   Introduction and establishment of ACRKN species to urban and commercial ornamental sites could significantly impact gardening/cultural practices thereby triggering additional official or private treatments.

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 = 14 (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:  ACRKN are not established in California (0).

Final Score:

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 14 (High).

Uncertainty:

It is possible that the Asian citrus root-knot nematode species may have entered the State undetected prior to 2005.  This is largely due to the fact that prior to 2005 Meloidogyne spp. were not always identified, at the CDFA Nematology Laboratory, to species level when detected in samples that originated outside and within California.  However, the likelihood that ACRKN species have already gained entry into California’s commercial citrus fields is minimal at best when the following is considered: ACRKN species were not detected by CDFA Nematology in statewide surveys of citrus, tomato and pepper commercial production sites in 2005-2008, and in citrus production sites in 2012-2013.  Also, none of the species belonging to the complex have been detected in regulatory samples generated through CDFA’s nematode control and phytosanitary certification programs; ACRKN species have not been reported from California by other researchers/nematologists.  The status of ACRKN species in non-cultivated and residential environments is not known.  Those environments may serve as sources of inoculum for infestations of citrus commercial production sites.  Identification to species level through DNA analysis is now essential for accurate identification of these species.  Future detection of ACRKN species in California soils may result in alteration of their current proposed rating.

Conclusion and Rating Justification: 

Based on the evidence presented above, the Asian citrus root knot nematodes, Meloidogyne spp., are pests of high risk to citrus production in California.

A permanent pest rating of “A” is proposed for each Asian citrus root-knot nematode species, namely, Meloidogyne citri, M. donghaiensis, M. fujianensis, M. indica, M. jianyagensis, M. kongi and M. mingnanica.   

References:

CABI.  2014.    Crop Protection Compendium.  www.cabi.org/cpc/ .

Davis, E. E. and R. C. Venette.  2004.  Mini risk assessment Asian Citrus Root-knot Nematodes: Meloidogyne citri Zhang, Gao & Weng; M. donghaiensis Zheng, Lin & Zheng; M. fujianensis Pan; M. indica Whitehead; M. jianyangensis Yang, Hu, Chen & Zhu; M. kongi Yang, Wang and Feng; and M. mingnanica Zhang [Nematoda: Meloidogynidae].  CAPS PRA. http://www.aphis.usda.gov/plant_health/plant_pest_info/pest_detection/downloads/pra/asiancitrusmmeloidogynepra.pdf .

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

Pan, C. S.  1985.  Studies on plant-parasitic nematodes on economically important crops in Fujian III.  Description of Meloidogyne fujianensis n. sp. (Nematode: Meloidogynidae) infesting Citrus in Nanjing County.  Acta Zoologica Sinica 31:263-268.

Pan, C., X. Hu and J. Lin. 1999. Temporal fluctuations in Meloidogyne fujianensis parasitizing Citrus reticulata in Nanjing, China. Nematologia Mediterranea 27: 327-330.

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

Vovlas, N. and R. N. Inserra.  2000.  Root-knot nematodes as parasites of Citrus.  Proceedings of the International Society of Citriculture, Vol. II 2:812-817.

Responsible Party:

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


Comment Period:  CLOSED

The 45-day comment period opened on Tuesday,  April 7, 2015 and closed on May 22, 2015.


Pest Rating: A


Posted by ls

Helicotylenchus multicinctus (Cobb, 1893) Golden, 1956

California Plant Pest Rating for
Helicotylenchus multicinctus (Cobb, 1893) Golden, 1956
Pest Rating: B

 


PEST RATING PROFILE
Initiating Event:

None. An evaluation of the risk involved with the possible introduction and spread of H. multicinctus in California is documented herein and a permanent rating is proposed for the species.

History & Status:

Biology and symptoms: The banana spiral nematode, Helicotylenchus multicinctus, is considered an endoparasite of host plant roots as it is able to complete its life cycle within the roots where all eggs, juvenile stages, and adult males and females may be found. Unlike other species of the genus, the banana spiral nematode invades outer layers of host cortical tissue producing characteristic small necrotic lesions which are initially yellow and then turn reddish brown to black in color. Apparently, the nematode does not invade deeper cortical tissue. In rare situations when infestation are high, root lesions can coalesce so that the necrosis becomes extensive resulting in root distortion and decay, stunting and toppling of top growth (McSorley & Parrado, 1986). The nematode species attacks rhizomes, corms, primary and secondary roots. Additionally, it is found in soil around plant roots. Because of its feeding and development biology the nematodes are easily introduced and spread to non-infested regions through infested soil, plant root and other root “seed stock”.

Hosts: The nematode is an important pest of banana and has also been recorded globally on several plant hosts of primary interest to California agriculture and environment. Hosts include mango, citrus, maize, rice, grapevine, fig, carrots, avocado, onions, peas, melon, common bean, cabbage, sugarbeet, garlic, grasses, and ornamentals (CABI, 2014; Vovlas, 1983). Ornamental banana plants are commonly propagated in regions of California.

Damage Potential: Knowledge of the extent of plant damage and loss has been gained through reports of laboratory and natural field studies conducted mainly on banana.  After the burrowing nematode, Radopholus similis, the banana spiral nematode, Helicotylenchus multicinctus is considered as the most damaging plant pathogenic nematode species on bananas under conducive environmental conditions of temperature greater than 15.6 C and minimum precipitation 127 cm (Gowen & Quénéhervé, 1990).  Both nematode species often occur together on bananas and plantains, however, in regions where the burrowing nematode is rare or absent, damage caused by H. multicinctus is more readily manifested (Gowen & Quénéhervé, 1990). Economic damage to banana has been reported from almost every region where banana and plantain are grown all which have similar climates and environments to California. Estimates of crop losses caused by H. multicinctus are not available and compounded as often other plant parasitic nematode species may be associated with the host and interact with environmental factors.

Disease Cycle: In experimental studies of H. multicinctus on banana roots, Blake (1966) reported that within 3 days of inoculation of adult nematodes, the latter fed on parenchymatous cells with their bodies partly embedded in the root. After 4 days, they were completely within the cortical tissue to a depth of 4-6 cells. Migration through the cortical tissue did not occur. Tissue surrounding infected cells was damaged with discoloration and necroses occurring near the infection points.

Transmission: Infected planting material: plant roots, bulbs, tubers, corms, rhizomes (suckers), seedlings, infested soil and growing medium with accompanying plants.

Worldwide Distribution: Banana spiral nematode is distributed wherever banana is cultivated globally. It has been recorded in several countries Europe, Asia, Pacific Islands, Africa, South America and North America (USA). In the USA, it has been reported in Alabama, Arkansas, California, Delaware, Florida, Georgia, Hawaii, Louisiana, Maryland, and Massachusetts (Birchfield, et al., 1978; CABI, 2014; Schenck & Schmitt, 1992).

Official Control: Helicotylenchus multicinctus is Chile’s Harmful Organism list (USDA PCIT, 2014). It is currently a Q-rated species in California.

California Distribution: There are early reports of Helicotylenchus multicinctus detected in Riverside, Los Angeles and San Diego Counties (Sher, 1966; Siddiqui et al., 1974).

California Interceptions: From 1989 to February 2015, there have been nine detections of Helicotylenchus multicinctus associated with Musa spp. and Ficus spp. imported to California nurseries (CDFA Nematode Detection Records).

The risk Helicotylenchus multicinctus 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) – Helicotylenchus multicinctus is likely to spread within California wherever host plants are grown in favorable climate.

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

– Low (1) has a very limited host range.
– Medium (2) has a moderate host range.
– High (3) has a wide host range.

Risk is Medium (2) – Banana is the main host, and ornamental banana plants are commonly grown in regions of California. There are several other plant species that are also hosts.

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) – Dispersal of the nematode pathogen is mainly through artificial means and infected planting materials, vegetative “seed” stock is the most common means of long distance spread. The nematode is also spread through infested soil and planting media, irrigation water, cultivation tools and equipments contaminated with infested soil.

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

A.  The pest could lower crop yield.
B.  The pest could lower crop value (includes increasing crop production costs).
C.  The pest could trigger the loss of markets (includes quarantines).
D.  The pest could negatively change normal cultural practices.
E.  The pest can vector, or is vectored, by another pestiferous organism.
F.  The organism is injurious or poisonous to agriculturally important animals.
G.  The organism can interfere with the delivery or supply of water for agricultural uses.

– Low (1) causes 0 or 1 of these impacts.
– Medium (2) causes 2 of these impacts.
– High (3) causes 3 or more of these impacts.

Risk is Medium (2) – The extent of crop damage and loss is mainly known for banana. Helicotylenchus multicinctus could lower crop value in banana plants including those grown in nurseries as ornamentals for commercial and residential purposes. Phytosanitary measures and the use of nematode-free planting stock would need to be adopted to mitigate risk of spread of this nematode species. The extent of damage and loss to other host plants, including agricultural crops is not known. Infected nursery plants are at risk of introducing the nematode species to outdoor favorable sites.

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 Low (1) – Banana, the main host, is not commercially cultivated in California, and the affect of the nematode species on other host plants is not fully known. However, it is likely that Helicotylenchus multicinctus could impact home/urban gardening and ornamental plantings causing changes in cultivation practices in order to mitigate potential damage.

Consequences of Introduction to California for Helicotylenchus multicinctus

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

– Low = 5-8 points
– Medium = 9-12 points
– High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Helicotylenchus multicinctus to California = (10).

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 Low (-1). Early reports indicate that Helicotylenchus multicinctus has been detected in San Diego, Los Angeles and Riverside Counties. However, to date this species has never been detected in California’s agricultural production site monitored through statewide nematode surveys or CDFA’s various nematode detection regulatory programs.

Final Score:

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

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

Uncertainty:

There may be some doubt associated with the true distribution of the banana spiral nematode in California partly due to the fact that for several years, members of the genus Helicotylenchus were given a general rating that required no State regulatory action against the pest. Subsequently, genus members were not always identified at the species level. On the other hand, it is quite unlikely that this was the case for H. multicinctus as its unique biology and morphology easily separates this species from all other species of the genus. Furthermore, H. multicinctus has not been detected in California’s commercial agricultural production sites monitored through various regulatory nematode detection programs. Future detections of H. multicinctus may indicate a wider distribution than presently known and result in a lower rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Helicotylenchus multicinctus is B.

References:

Birchfield W., J. P. Hollis and W. J. Martin. 1978. A list of nematodes associated with some Louisiana plants. Technical Bulletin, Louisiana State University, 101:22 p.

Blake, C. D. 1966. The histological changes in banana roots caused by Radopholus similis and Helicotylenchus multicinctus. Nematologica, 12:129-137.

CABI. 2014. Helicotylenchus multicinctus (banana spiral nematode) full datasheet. Crop Protection Compendium. www.cabi.org/cpc/

Gowen, S. & P. Quénéhervé. 1990. Nematode parasites of bananas, plantains and abaca. In: Luc, M., R. A. Sikora and J. Bridge, l (Eds). Plant parasitic nematodes in subtropical and tropical agriculture. Wallingford, UK, CAB International: 431- 460.

McSorley, R. and J. L. Parrado. 1986. Nematological reviews – Helicotylenchus multicinctus on bananas: An international problem. Nematropica, 16 : 73-91.

Schenck, S. and D. P. Schmitt. 1992. Survey of nematodes on coffee in Hawaii. Supplement to the Journal of Nematology 24:771-775.

Sher, S. A. 1966. Revision of the Hoplolaiminae (Nematoda) VI. Helicotylenchus Steiner, 1945. Nematologica 12:1-56.

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

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

Vovlas, N. 1983. Morphology of a local population of Helicotylenchus multicinctus from southern Italy. Revue de Nématologie 6: 327-329.

Responsible Party:

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


Comment Period:  CLOSED

The 45-day comment period opened on Monday, March 16, 2015 and closed on Thursday, April 30, 2015.

Comment Format:

When commenting, please reference the section heading related to your comment, as shown in the example below.

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


Pest Rating:  B


Posted by ls