Category Archives: Nematodes

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

Nematodes

Radopholus similis (Cobb, 1893) Thorne, 1949

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

 

PEST RATING PROFILE
Initiating Event:  

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

 History & Status:

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

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

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

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

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

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

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

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

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

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

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

California Distribution: Radopholus similis is not established in California.

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

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

Consequences of Introduction: 

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

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

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

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

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

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

-Low (1) has a very limited host range

-Medium (2) has a moderate host range

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield

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

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

D. The pest could negatively change normal production cultural practices

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

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

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

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

-Medium (2) causes 2 of these impacts

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact:

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

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

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

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

Consequences of Introduction to California for Common Name:  Score

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

Low = 5-8 points

Medium = 9-12 points

High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

Uncertainty:

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

Conclusion and Rating Justification: 

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

References:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Responsible Party:

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

Comment Period:  CLOSED

Oct 5 – Nov 19, 2016

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: A

Posted by ls

Nematodes

Ditylenchus destructor Thorne, 1945

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

 

PEST RATING PROFILE
Initiating Event:

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

History & Status:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Consequences of Introduction: 

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Ditylenchus destructor:

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

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty:  

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

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

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

Responsible Party:

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

Comment Period:  CLOSED

Sep 27- Nov 11, 2016

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: A

Posted by ls

 

Nematodes

Scutellonema spp. Cobb, 1913

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

 

PEST RATING PROFILE
Initiating Event:

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

History & Status:

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

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

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

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

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

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

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

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

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

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

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

Consequences of Introduction: 

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Scutellonema spp.:

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

-Low = 5-8 points

  –Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty: 

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

Responsible Party:

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

Comment Period:  CLOSED

9/21/2016 – 11/5/2016

Pest Rating: C 

Posted by ls

Nematodes

Meloidogyne enterolobii Yang and Eisenback, 1983.

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

*Revised August 22, 2024

Initiating Event:  

None.

History & Status:

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

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

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

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

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

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

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

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

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

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

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

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

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

Consequences of Introduction: 

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

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

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

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

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

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

-Low (1) has a very limited host range

-Medium (2) has a moderate host range

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

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

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

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

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

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

-Medium (2) causes 2 of these impacts

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact:

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

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

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

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

Consequences of Introduction to California for Common Name:  Score

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

Low = 5-8 points

Medium = 9-12 points

  High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Conclusion and Rating Justification: 

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

References:

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Responsible Party: 

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

Comment Period:  CLOSED

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Nematodes

Pratylenchus coffeae (Zimmermann) Filipjev & Schuurmans-Stekhoven


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

 

PEST RATING PROFILE
Initiating Event:

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

History & Status:

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

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

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

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

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

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

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

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

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

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

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

Consequences of Introduction: 

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Pratylenchus coffeae:

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty:  

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

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

Responsible Party:

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

Comment Period: CLOSED

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: B

Posted by ls

Nematodes

Pratylenchus thornei Sher & Allen, 1953

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

 

PEST RATING PROFILE
Initiating Event:

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

History & Status:

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

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

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

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

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

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

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

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

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

California Distribution:  Pratylenchus thornei is widely distributed in California.

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

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

Consequences of Introduction:

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Pratylenchus thornei:

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty: 

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

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

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

Responsible Party:

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

Comment Period: CLOSED

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: C 

Posted by ls

Nematodes

Tylenchorhynchus spp. Cobb, 1913

stunt nematode: symptoms, stunting of corn seedling

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

 

PEST RATING PROFILE
Initiating Event:

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

History & Status:

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

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

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

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

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

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

Worldwide Distribution: Tylenchorhynchus spp. are distributed worldwide.

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

California Distribution:  Tylenchorhynchus spp. are distributed throughout California.

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

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

 Consequences of Introduction:

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Tylenchorhynchus spp.:

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

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

Final Score:

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

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

Uncertainty: 

None.

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

Responsible Party:

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

Comment Period: CLOSED

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

Comment Format:

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

Example Comment: 

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

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: C

Posted by ls 

Nematodes

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.

Symptoms:  Feeding 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 Distribution:  Helicotylenchus 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 

Nematodes

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

Nematodes

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

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

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

Consequences of Introduction: 

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

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

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

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

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

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

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

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

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

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

Consequences of Introduction to California for Pratylenchus neglectus:

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

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

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

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.]

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

♦  Comments may not be posted if they:

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

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

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: C

Posted by ls

Nematodes

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 Interceptions:  Bursaphelenchus 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 

Nematodes

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 Interceptions: The risk Xiphinema index would pose to California is evaluated below.

Consequences of Introduction: 

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

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

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

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

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

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

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

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

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

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

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

Consequences of Introduction to California for Xiphinema index:

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

-Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

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

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