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 thornei Sher & Allen, 1953

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

 


PEST RATING PROFILE
Initiating Event:

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

History & Status:

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

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

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

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

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

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

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

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

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

California DistributionPratylenchus thornei is widely distributed in California.

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

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

Consequences of Introduction:

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Pratylenchus thornei:

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

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty: 

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

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

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


Responsible Party:

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


Comment Period: CLOSED

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


Comment Format:

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

Example Comment

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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


Pest Rating: C 


Posted by ls

Tylenchorhynchus spp. Cobb, 1913

stunt nematode: symptoms, stunting of corn seedling

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

 


PEST RATING PROFILE
Initiating Event:

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

History & Status:

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

Members of the genus, Tylenchorhynchus, are sometimes known as ‘stunt nematodes’.  Species reproduce mainly by amphimixis (fertilization by female and male) producing eggs, three juvenile stages, and adults.  These nematodes usually inhabit the soil-root region of plants and feed as obligate migratory ectoparasites of roots using a stylet (sword-like hollow tooth) to feed on epidermal cells. All motile juvenile and adult stages feed.  (Mai et al., 1996; Maggenti, 1981).

Hosts: Tylenchorhynchus spp. are associated with the roots of a wide range of plants including tobacco, cotton, oats, and corn as well as other agricultural crops, fruit trees, ornamentals, nursery stock, forest trees and shrubs, desert shrubs, grasses, and weeds. The host status of associated plants is not always known.

SymptomsGeneral plant damage associated with Tylenchorhynchus spp. includes stunting of the root system which is expressed aboveground by yellowing of foliage, stunted top growth, and sometimes wilt and defoliation (Maggenti, 1981).

Damage Potential:  Generally, Tylenchorhynchus spp. are considered mild pathogens of plants and are common associates of several plants (Norton, 1984).  However, plant damage caused by high populations of stunt nematodes may be more significant in small-area plant productions and/or containerized crops in nursery, residential and local situations than in large acreages and environments such as, pastures, parks, and cultivated fields. Crop losses under field conditions are not reported, however, under experimental conditions, reductions in root and plant growth have been demonstrated by certain species, e.g., T. annulatus on sugarcane and Bermuda grass; T. dubius on beans (Bridge, 1974; Siddiqi, 1976).  Tylenchorhynchus claytoni causes economic damage on tobacco (Mai et al., 1996).  Crop damage under field conditions may be difficult to assess as Tylenchorhynchus spp. are often mixed with other genera and/or two or more stunt nematode species occurring together.

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

Worldwide Distribution: Tylenchorhynchus spp. are distributed worldwide.

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

California DistributionTylenchorhynchus spp. are distributed throughout California.

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

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

 Consequences of Introduction:

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Tylenchorhynchus spp.:

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

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty: 

None.

Conclusion and Rating Justification:

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

References:

Bridge, J.  1974.  Tylenchorhynchus dubius.  Commonwealth Institute of Helminthology (C. I. H.) descriptions of plant-parasitic nematodes. Set 4, No. 51.

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

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

Norton, D. C.  1984.  Nematode parasites of corn. In Plant and Insect Nematodes, edited by W. R. Nickle.  Marcel Dekker, Inc.  New York and Basel. 61-94 pp.

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

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


Responsible Party:

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


Comment Period: CLOSED

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


Comment Format:

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

Example Comment

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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


Pest Rating: C


Posted by ls 

Helicotylenchus spp. Steiner, 1945

helicotylenchus spp.
California Pest Rating for
Helicotylenchus spp.  Steiner, 1945
 Pest Rating: C 

 


PEST RATING PROFILE
Initiating Event:

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

History & Status:

Background:  Generally, pest risk assessments and assignment of pest ratings are conducted per individual pest species and not per genus group primarily due to differing pest biologies, geographical distributions, host ranges, damage potentials, and risk mitigating requirements. However, an exception to this rule is made here for the genus Helicotylenchus largely because of historical practice.  Over the past several decades, the genus, Helicotylenchus, was seldom differentiated to species level by CDFA Nematologists mainly due to i) the common occurrence and wide distribution of member species within California, ii) no state enforced regulatory action required subsequent to their detection, and iii) greater demands of time involved in diagnosing high risk and other nematode species considered to be of greater economic importance than those belonging to Helicotylenchus.  Alternately, certain species of the genus  that are capable of invading plant roots (e.g., H. multicinctus B-rated) may be assessed and rated individually as they can be more economically damaging to crop production and trade markets than non-root invading species.

Members of the genus, Helicotylenchus, are commonly known as ‘spiral nematodes’ since they assume a spiral form when relaxed with gentle heat.  Species reproduce mainly by parthenogenesis producing eggs, three juvenile stages, and adults.  These nematodes usually inhabit the soil-root region of plants and feed as obligate ectoparasites with their stylet (sword-like hollow tooth) inserted into the root. All motile juvenile and adult stages of Helicotylenchus feed. All species are parasitic on roots and other underground parts of plants (Siddiqi, 1972).

Hosts: Helicotylenchus spp. can attack a wide range of plants including agricultural crops, fruit trees, ornamentals, nursery stock, forest trees and shrubs, desert shrubs, grasses, and weeds. Species have been associated with different plants in soil around the root zone, however, the host status of associated plants is not always known.

SymptomsFeeding of Helicotylenchus spp. results in production of small discolored lesions in the root cortex and other underground parts.  Local lesions in the cortex result in death of cells on which the nematodes feed.  Feeding of high population levels of Helicotylenchus can severely damage roots by causing them to become slightly swollen, spongy, and discolored.  Eventually the cortex of such roots is sloughed off (Maggenti, 1981; Mai et al., 1960). Above ground symptoms may express yellowing of foliage, mild stunting, wilt and defoliation – depending on the population level of spiral nematodes present.

Damage Potential:  Plant damage caused by high populations of spiral nematodes may be more significant in small-area plant productions and/or containerized crops in nursery, residential and local situations than in large acreages and environments such as, pastures, parks, and cultivated fields.  Crop damage under field conditions is difficult to assess as Helicotylenchus spp. are often mixed with other genera and/or two or more spiral nematode species occurring together (Norton, 1984).  Helicotylenchus spp. are considered mild plant pathogens.  Crop losses under field conditions are not reported, however, under experimental conditions, reductions in root and total plant weight have been observed in cereals and grasses (Griffin, 1984).

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

Worldwide Distribution: Helicotylenchus spp. are distributed worldwide.

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

California DistributionHelicotylenchus spp. are distributed throughout California.

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

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

Consequences of Introduction:

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Helicotylenchus spp.:

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

-Low = 5-8 points

Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty: 

none.

Conclusion and Rating Justification:

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

References:

Griffin, G. D.  1984.  Nematode parasites of alfalfa, cereals, and grasses.  In Plant and Insect Nematodes, edited by W. R. Nickle.  Marcel Dekker, Inc.  New York and Basel.  243-321 pp.

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

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

Norton, D. C.  1984.  Nematode parasites of corn. In Plant and Insect Nematodes, edited by W. R. Nickle.  Marcel Dekker, Inc.  New York and Basel. 61-94 pp.

Siddiqi, M. R.  1972.  Helicotylenchus dihystera.  Commonwealth Institute of Helminthology (C. I. H.) descriptions of plant-parasitic nematodes. Set 1, No. 9.

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


Responsible Party:

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


Comment Period: CLOSED

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


Comment Format:

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

Example Comment

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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


Pest Rating: C 


Posted by ls 

Rotylenchulus reniformis (Reniform Nematode)

California Pest Rating for
Rotylenchulus reniformis Linford & Oliveira, 1940
(Reniform Nematode)
Pest Rating: A

 


PEST RATING PROFILE
Initiating Event:  

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

History & Status:

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

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

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

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

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

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

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

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

Consequences of Introduction: 

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

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

Risk is High (3)Rotylenchulus reniformis is likely to establish a widespread distribution in California especially in fine textured soils, and mainly wherever its host is able to grow.

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

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

Risk is High (3)Rotylenchulus reniformis has a wide host range.

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

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

Risk is High (3)Rotylenchulus reniformis has both high reproduction and dispersal potential.

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

A.  The pest could lower crop yield

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

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

D.  The pest could negatively change normal production cultural practices

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

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

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

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

Risk is High (3)The establishment of Rotylenchulus reniformis in California could result in the lowered crop yield and value, increased crop production costs, loss of markets, imposition of domestic and international quarantines against California export plant commodities, and alteration of normal cultural practices, including application of irrigation water, to inhibit spread of the pathogen to non-infested sites.    Cotton, grape, tomato, citrus and ornamental are the main industries that would be affected, additionally several other crops of lesser production are also at risk.

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

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

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

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

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

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

Score the pest for Environmental Impact:

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

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

Consequences of Introduction to California for Common Name:  Score

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

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

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

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:  Rotylenchulus reniformis is not established in California (0).  The nematode species has never been detected within California.  Eradicative actions taken subsequent to the detection of the nematode species in imported nursery and household plant shipments, vigilant screening of plant materials grown in California soils and inspected for plant parasitic nematodes through CDFA’s phytosanitary certification programs, and all published studies to date on plant parasitic nematodes in California have never resulted in the detection of R. reniformis.

Final Score:

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

Uncertainty:

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

Conclusion and Rating Justification: 

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

References:

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

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

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

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

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

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

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


Responsible Party:  

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


Comment Period:  CLOSED

The 45-day comment period opened on Tuesday, January 5, 2016 and closed on February 19, 2016.


Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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


Pest Rating: A


Posted by ls

Pratylenchus neglectus

California Pest Rating for
Pratylenchus neglectus (Rensch, 1924) Filipjev & Schuurmans-Stekhoven, 1941
Pest Rating: C

 


PEST RATING PROFILE
Initiating Event:

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

History & Status:

Background: The California meadow nematode, Pratylenchus neglectus (synonym P. minyus) is an obligate migratory endoparasite that first feeds externally then enters plant roots, feeds, reproduces and moves freely within the tissue while spending its entire life cycle there.  The species can also be found in soil around roots.  Within the roots, feeding is confined to the root cortex.  Like other Pratylenchus species, P. neglectus has six life stages: egg, four juvenile stages and adults.  Reproduction is by parthenogenesis (without fertilization). First stage juveniles develop within the egg, followed by a first molt to the second stage juvenile that hatches from the egg.  Each stage develops into the next via a molt of its cuticle (outer body covering).  All juvenile and adult stages are worm-shaped (vermiform).  All post-hatch stages are motile and can infect plants.  Generally, root lesion nematodes have a life cycle 45-65 days, but in P. neglectus, the life cycle can take as few as 28 days on tobacco with greater reproduction at 38°C than at higher and lower temperatures (Townshend & Anderson, 1976).  Pratylenchus neglectus survives the winter in infected roots or soil as eggs, juveniles or adults. It can survive at 2°C but not at sub-zero temperatures.  During spring, when plant growth is active, eggs hatch, nematodes are attracted to the plant roots and begin to feed and continue their life cycle within roots or in rhizosphere soil.  Within the root, the nematode feeds on cortical tissue causing necrosis of cortical cells, cell breakdown, and formation of cavities. Necrosis is apparent as lesions which expand as the nematodes move lengthwise within the infected roots.  Some nematodes may leave the root, enter soil and re-enter the root at a different site causing a new infection.

Hosts: Pratylenchus neglectus is primarily a parasite of grasses, but its diverse range of hosts include, fruit trees, pistachio, pear, apple, maize, potato, wheat, cereals, rapeseed, legumes, alfalfa, red clover, tobacco, peppermint, soybean, turf and pasture grasses, sugarcane, strawberry, carrots, cabbage (CABI, 2014; Castillo & Vovlas, 2007; Townshend & Anderson, 1976).

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

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

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

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

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

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

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

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

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

Consequences of Introduction: 

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

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

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

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

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

Risk is Medium (2) – Pratylenchus neglectus is primarily a parasite of grasses, but its diverse range of hosts are grown throughout the State and include, fruit trees, pistachio, pear, corn, potato, wheat, cereals, rapeseed, legumes, alfalfa, red clover, tobacco, peppermint, soybean, turf and pasture grasses, sugarcane, strawberry, carrots.

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

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

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

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

Consequences of Introduction to California for Pratylenchus neglectus:

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

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

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

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

-Not established (0) Pest never detected in California, or known only from incursions.
-Low (-1) Pest has a localized distribution in California, or is established in one suitable climate/host area (region).
-Medium (-2) Pest is widespread in California but not fully established in the endangered area, or pest established in two contiguous suitable climate/host areas.
High (-3) Pest has fully established in the endangered area, or pest is reported in more than two contiguous or non-contiguous suitable climate/host areas.

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

Final Score:

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

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

Uncertainty: 

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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


Responsible Party: 

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


Comment Period:  CLOSED

The 45-day comment period opened on Tuesday, January 5, 2016 and closed on February 19, 2016.


Comment Format:

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

Example Comment: 

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

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Pest Rating: C


Posted by ls

Bursaphelenchus coccophilus (Cobb) Baujard 1989

California Pest Rating for
Bursaphelenchus coccophilus (Cobb) Baujard 1989
Pest Rating: A

 


PEST RATING PROFILE
Initiating Event:

In 2011 the detection of the South American Palm Weevil in San Ysidro, a potential vector of the Red ring nematode, Bursaphelenchus coccophilus, led to laboratory examination of in-State detected weevils for the presence of the nematode.  Bursaphelenchus coccophilus is a federally regulated nematode pest.  Herein is proposed an official and permanent State rating for the nematode species.

History & Status:

Background: Red ring nematode (RRN) causes red ring disease of palms.  The nematode parasitizes the South American Palm Weevil, Rhynchophorus palmarum which in turn transmits it to palms.  Symptoms of red ring disease were first described on Trinidad coconut palms in 1905.  Although RRN has never been detected in California, its insect vector was first detected in the State in 2011 thereby marking a first U.S. find.

Life cycle:  The life cycle of RRN is intimately associated with the palm weevil.  The palm weevils are attracted to wounds or cuts in the trunks of the palms.  At an infected palm, a weevil ingests dispersal third stage juvenile nematodes or picks them up on the surface of its body.  When palm weevils disperse and invade healthy or stressed palms, the associated nematodes are usually deposited by the insect as it lays its own eggs.  Only a few nematodes are needed for a successful transmission.  Nematodes feed and reproduce in the palm tissue, causing the death of infected trees.  When the weevil eggs hatch, immature nematodes associate with immature weevils.  As many as 10,000 juveniles of B. cocophilus remain within a weevil through the latter’s metamorphosis, apparently without molting or reproducing, and appear to aggregate around the genital capsule of the adult weevil.  Adult weevils emerge from their cocoons and disperse to healthy or stressed and dying palms carrying new batches of third-stage juvenile nematodes with them, completing the life cycle.  The life cycle takes nine to ten days.

Hosts: Several species of tropical palms are hosts including date, Canary Island date and Cuban royal, but it is most common in oil and coconut palms, and date palm.  Over 17 species belonging to the family Palmae can be infected by the nematode.

Symptoms:  Symptoms of red ring disease vary greatly with palm species, cultivar, age of palm, and environmental conditions.  Palms younger than two and a half years are not infected with the nematode.  Most often 3-10 year old coconut palms and 5 year old African Oil palms are attacked by the nematode and die 2-4 months after nematode infection.  Older trees may live longer – up to 20 weeks or several years.  However, infested trees never fully recover from red ring nematode infestation. Those few that do recover have a recurrence of the disease in later years.

The main internal symptom is the presence of a red ring – seen as such in a cross section cut through the trunk of an infested palm, 3-5 cm wide, and found 1-7 ft above the soil line.  The color is commonly red but may vary from light pink or cream to dark brown.  The tissue of a healthy palm is creamy white.  Internal symptoms are visible within 2-3 weeks after the nematode enters a healthy plant. External symptoms in infested coconut palms include dwarfed, deformed, and yellow-bronzed leaves that turn deep reddish brown.  This color change starts at the tip of leaves, beginning in older leaves and progressing to younger ones.  Leaves eventually die and will often break close to the petiole or remain hanging from the stem.  In African oil palms and older coconut palms, small, deformed leaves remain green initially.  Similarly new leaves are also dwarfed and the central crown of the tree resembles a funnel.  This is a sign of little leaf disease, a chronic disease that can lead to red ring disease.  Eventually these little leaves become necrotic and often stop producing fruit. External symptoms take up to 2 months to appear after infection.

Damage Potential:  The disease kills palm trees. Losses of 80 and 35 percent in coconut and oil palm production respectively are reported in the tropics.  Palms are cultivated mainly for landscape, and date palms in particular are also grown for fruit production in California.  Red ring nematode is not present in the USA.  Introduction of the red ring nematode would devastate landscape/ornamental, tourism, date fruit palm industries, as well as domestic and international trade.

Transmission: RRN is spread mainly by the Palm Weevil, R. palmarum.  Studies on red ring disease conducted in Grenada showed that 22.3 percent of coconut palms were infected with the disease.  Of those infected, 92 percent had been invaded by palm weevils – and it was estimated that 72 percent of those weevils had vectored the nematode (Esser & Meredith, 1987).  Other vectors reported include ants, spiders, and other potential weevil vectors such as Metamasius hemipterus and Rhynchophorus cruentatus.  It can also be spread by tools used to cut down infested trees, and roots.

Survival:  The red ring nematodes survive less than a week in soil or on the body of a weevil.  They can survive 16 weeks in nut husks and 90 weeks in seedling tissue.  They can survive for long periods within an infected weevil.

Location/recovery of the nematode: 1. From the Palm weevil.  Male and female Palm Weevils are infested internally and externally with RRN juveniles.  Newly emerged weevils from cocoons carry high numbers of RRN.  Fewer nematodes have been found on the body of the insect than inside of it.  Empty cocoon (after weevil emergence) are rarely infested with the nematode.  2.  From Coconut palm.  RRN is located in the reddish tissue of the ring and immediately adjacent to it, especially in the inner circle. As many as 50,000 individuals have been found in 10 grams of infected stem tissue.  They can also be recovered from the top part of the trunk where the necrotic spots appear, and from petioles and necrotic lesions of older leaves.  3.  From Oil palm.  RRN is located in the discolored ring and the internal tissue adjacent to the ring.  Recovery from other plant parts: necrotic lesion on trunk, petioles, etc, is variable as the nematodes may be absent there.   4. From palm roots and soil.   Usually numbers of RRN in palm roots and soil are variable (low to absent).  In the soil they have been found as deep as 80 cm, however, most nematodes are found 30-40 cm deep.

Worldwide Distribution:   Central America, South America and many Caribbean islands: Belize, Brazil. Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Grenada, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Peru, Saint Vincent and the Grenadine Islands, Surinam, Tobago, Trinidad and Venezuela.  Reports of the presence of the nematode in Bahamas, Barbados, Dominica, Dominican Republic, Haiti, and Jamaica have not been confirmed.  Earlier reports of the nematode in Puerto Rico have been negated following targeted surveys.  In certain regions, mainly from Mexico to South America and in the lower Antilles, the red ring nematode is co-distributed with its primary vector the South American Palm Weevil (Brammer & Crow, 2008).

Official Control:   The following countries include Bursaphelenchus coccophilus on their ‘Harmful Organism Lists’: Antigua and Barbuda, Chile, China, Dominica, Honduras, Jamaica, Saint Lucia.  In the USA, B. coccophilus is a federally regulated pest per Federal Order issued January 25, 2010.

California Distribution: Bursaphelenchus coccophilus has not been detected in California.

California InterceptionsBursaphelenchus coccophilus has never been detected in host palm trees imported into California.

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) – RRN is able to establish a widespread distribution in California in regions where its palm tree host is able to grow and its insect vector is able to establish.

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) Several species of tropical palms are hosts, most commonly oil and coconut palms, and date palm.  Over 17 species belonging to the family Palmae can be infected by the nematode.

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) – High numbers of RRN is spread mainly by its insect vector.  It is also spread through infested trees, tools used to cut down infested trees, roots, and possibly other insects including ants, spiders, and other weevils moving from infested to non-infested plants.

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) – RRN kills palm trees. Introduction of the red ring nematode would devastate landscape/ornamental, tourism, date fruit palm industries, as well as domestic and international trade. As a result quarantines against this nematode pest would be implemented, normal cultural practices would be altered due to the detection and destruction of infested trees, and production costs would be negatively affected.  The pest is vectored by the pestiferous South American Palm Weevil.

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 High (3) –RRN infestations of palm trees would have significant impact on the environment by disrupting natural communities or changing ecosystem processes, significantly affect ornamental plantings, alter cultural practices, and trigger additional official or private treatment programs.

Consequences of Introduction to California for Bursaphelenchus coccophilus:

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 Bursaphelenchus coccophilus to California = (14).

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)Bursaphelenchus coccophilus 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 = 14

Uncertainty:

As the biology, introduction and distribution of Bursaphelenchus coccophilus is closely associated with that of its palm weevil vector, diligent survey for detection of the vector is critical for detecting the nematode species in palms.  The discontinuation or lack of a palm weevil detection survey program will hinder any knowledge gained about the possible introduction of the weevil-associated red ring nematode.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for red ring nematode, Bursaphelenchus coccophilus, is A.

References:

Esser, R.P. and J. A. Meredith. 1987. Red ring nematode. Nematology Circular No. 141, Florida Department of Agriculture and Consumer Services, Division of Plant Industry, Gainesville.

USDA APHIS-PPQ.  2011.  Detection of South American Palm Weevil (Rhynchophorus palmarum) in California.  Notice to State and Territory Agricultural Regulatory Officials, for Information and Action. DA-2011-45.

Brammer, A. S. and W. T. Crow.  2008.  University of Florida IFAS Extension. EENY-236, published September 2001, reviewed March 2008.

Chinchilla, C. M.  1991.  http://www.asd-cr.com/ASD-Pub/Bo101/b01c1.htm.

Giblin-Davis, R. M., P. S. Lehman and R. N. Inserra.  http://nematode.unl.edu/pest1.htm.

Gerber, K. and Giblin-Davis, R.  1990.  Journal of Nematology 22 (2):143-149.

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:

The 45-day comment period opened on Wednesday, October 14, 2015 and closed on November 28, 2015.


 Pest Rating:  A


Posted by ls 

Xiphinema index Thorne & Allen, 1950 (Dagger nematode)

California Pest Rating for
Xiphinema index Thorne & Allen, 1950
(Dagger nematode)
Pest Rating:  B

 


PEST RATING PROFILE
Initiating Event:  

None.

History & Status:

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

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

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

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

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

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

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

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

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

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

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

California InterceptionsThe risk Xiphinema index would pose to California is evaluated below.

Consequences of Introduction: 

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

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

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

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

Risk is High (3) Xiphinema index is able to establish in cool to warm climates.  light and medium-textured soils and in heavy soils with increases in rate of reproduction and shorter durations to complete its life cycle as soil temperatures increase from 16 to 28°C.

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

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

Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Medium (2) Grapevine is the main host and Xiphinema index is associated with grapevine cultivation globally.  Other hosts (natural and experimental) include fig, prune, apple, pistachio, citrus, sour orange, strawberry, walnut, rose, mulberry, bur marigold, Boston ivy, cactus, dwarf nettle, fruit, ornamentals and weeds.

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

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

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

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

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

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – Infestations of Xiphinema index could result in lowered crop yield and value, loss in market, and change in cultural practices to mitigate risk of spread to non-infested sites. The main economic damage is due to the ability of X. index to vector the economically important grape fanleaf virus.

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Xiphinema index:

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

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Xiphinema index to California = (13).

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).   Xiphinema index has been detected in at least two contiguous suitable climate areas in California.

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Responsible Party:

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


Comment Period:

The 45-day comment period opened on Wednesday, October 14, 2015 and closed on November 28, 2015.


Pest Rating:  B


Posted by ls

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