Tag Archives: plant pathogens

Fungi, Plant Pathogens

Cronartium quercuum (Berk.) Miyabe ex Shirai 1899


California Pest Rating for

Cronartium quercuum (Berk.) Miyabe ex Shirai 1899

Pest Rating: C
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Responsible Party:

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

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Posted by ka

Fungi, Plant Pathogens

Plasmopara constantinescui Voglmayr & Thines 2007

California Pest Rating for
Plasmopara constantinescui Voglmayr & Thines 2007
Pest Rating: B
PEST RATING PROFILE

Initiating Event:

On August 8, 2017, diseased leaves of Impatiens walleriana plants were collected, from a retail nursery in Placer County, by Placer Agricultural County officials and sent to the CDFA Plant Pathology Laboratory for diagnoses.  The plants had been shipped from a different nursery in San Joaquin County.  Cheryl Blomquist, CDFA plant pathologist, identified the downy mildew pathogen, Plasmopara constantinescui, as the cause for the disease.  The pathogen was assigned a temporary ‘Q’ rating.  Consequently, the infected plants, received at Placer County, will be destroyed by County officials (Walber, 2017).  Impatiens walleriana plants related to the shipment from San Joaquin County were double-bagged and disposed at a landfill, by the nursery (Khan, 2017).  The risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is herein proposed.

History & Status:

Background:   Plasmopara constantinescui is an obligate oomycete plant pathogen that causes downy mildew disease in its host plants.  Presently, the host range for the pathogen only includes Impatiens species, belonging to the plant family Balsaminaceae.

Plasmopara constantinescui was originally described as Bremiella sphaerosperma from Impatiens in eastern Russia and northeastern North America (Constantinescu, 1991).  However, after molecular phylogenetic analyses of DNA sequences, B. sphaerosperma was found to belong to the genus Plasmopara and transferred there accordingly.  Furthermore, as there already existed, within Plasmopara, a species by the same epithet, the newly-transferred pathogen was given a new epithet, P. constantinescui (Voglmayr & Thines, 2007).  This species was also shown to be closely related to Plasmopara obducens, which is a common, widely distributed pathogen of several species of Impatiens in the Northern Hemisphere, including California (Constantinescu, 1991; Voglmayr & Thines, 2007).

Hosts:  Impatiens sp. (impatiens), I. capensis (jewel weed), I. noli-tangere (western touch-me-not), I. pallida (pale touch-me-not) (Constantinescu, 1991; Farr & Rossman, 2017).  Plasmopara constantinescui was recently detected in Impatiens walleriana (buzzy lizzy) plants (see: ‘Initiating Event’.) 

Symptoms:  Pale yellowish to ochre, round to irregular, and scattered spots appear on the upper surface of leaves.  These spots are small (1-6 mm-diam.), vein-limited, and with margins that are indistinct to reddish brown or violaceous.  They rarely coalesce and cover larger areas.  White to greyish or yellowish downy growth of sporangiophores of the oomycete develop in patches on the underside of the spots (Constantinescu, 1991).  It is likely that, similar to other downy mildew-causing pathogens, Plasmopara constantinescui attacks and spreads rapidly in young, tender green leaf, shoot, and blossom tissue (Agrios, 2005).

Disease development: Generally, downy mildew pathogens overwinter as thick-walled resting spores called oospores in plant debris in the soil or on weed hosts, and as mycelium in infected, but not dead, twigs.  Downy mildew develops and is severe under conditions that favor periods of prolonged leaf wetness and high relative humidity during cool or warm, but not hot, periods.  During rainy period in spring, the oospores germinate to produce a sporangium.  The sporangium or its zoospores are transmitted by wind or water to wet leaves near the ground where they infect through stomata of the lower leaf surface.  Mycelium develops and spreads into intercellular spaces of leaves.  When it reaches the sub-stomatal cavity, it forms a cushion from which sporangiophores arise and grow through the stoma.  Sporangia are produced at the tips of the sporangiophores and are transmitted by wind or rain to nearby non-infected plants (Agrios, 2005; Daughtrey et al., 1995).  In pathogenicity tests, Plasmopara constantinescui was able to cause systemic shoot infection of Impatiens walleriana (Personal communication: Suzanne Latham, CDFA plant pathologist).

Dispersal and spread: Wind, rain/water splash, infected plants and infected plant debris.

Damage Potential: While estimates of crop losses caused particularly by Plasmopara constantinescui have not been reported, generally, downy mildews can cause significant losses in short periods of time. Affected plants may result in defoliation, flower drop, and stem rot, similar to Impatiens walleriana plants infected with the closely related downy mildew species, P. obducens (Crouch et al., 2014).  Nurseries, private and public gardens, and landscape plantings may be at particular risk of contracting downy mildew disease caused by P. constantinescui.  Fungicidal control of the pathogen is possible, but may be difficult.  Under cool wet weathers, downy mildews are often uncontrollable and checked only when the weather turns dry and hot (Agrios, 2005).

Worldwide Distribution: Asia: Eastern Russia (formerly USSR); North America: Canada, USA (Indiana, Massachusetts, Wisconsin, Iowa, Maryland, Minnesota, Virginia, South Carolina, and California) (Constantinescu, 1991; Farr & Rossman, 2017; Voglmayr & Thines, 2007; CDFA Pest and Damage Record 2017).

Official Control:  Bremiella sphaerosperma (synonym of Plasmopara constantinescui) is on the ‘Harmful Organism List’ for Brazil (USDA PCIT, 2017).  Presently, P. constantinescui has a Q rating in California.

California Distribution:  Based on the source of diseased Impatiens, Plasmopara constantinescui is present in San Joaquin County

California Interceptions:  One intrastate interception in Placer County (see: Initiating Event).

The risk Plasmopara constantinescui would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: The downy mildew oomycete, Plasmopara constantinescui requires prolonged periods of leaf wetness and high relative humidity during cool or warm, but not hot, periods. These conditions for infection and development of the pathogen is likely to limit its establishment in California, to coastal regions in particular.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

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

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

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

2) Known Pest Host Range: The host range for the pathogen is limited to Impatiens

Evaluate the host range of the pest.

Score: 1

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Spores are produced in abundance. The pathogen is transmitted via infected plant material, winds, and rain/water splash.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: If left uncontrolled, downy mildews can cause significant losses in short periods of time. Affected plants may result in defoliation, flower drop, and stem rot, thereby lowering crop yield and value in increasing production costs largely due to administration of control measures.  Fungicidal control of the pathogen is possible, but may be difficult.  Under cool wet weathers, downy mildews are often uncontrollable and checked only when the weather turns dry and hot.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C, D.

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score:  3

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact:  Downy mildew disease caused by Plasmopara constantinescui could significantly impact home/urban, private and public gardens, and landscape plantings.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

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

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

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

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

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

Environmental Impact Score: 2

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

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

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

Consequences of Introduction to California for Plasmopara constantinescui:

Add up the total score and include it here. 11

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

Evaluation is ‘Low’.  Based on the source of diseased Impatiens, Plasmopara constantinescui is only present in San Joaquin County.

Score: (-1)

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

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

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

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

Final Score:

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

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

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Plasmopara constantinescui is B.

References:

Agrios, G. N.  2005.  Plant Pathology fifth edition.  Elsevier Academic Press, Massachusetts, USA.  922 p.

Calflora.  2017.  Information on California plants for education, research and conservation. [web application]. 2017. Berkeley, California. The Calflora Database [a non-profit organization].  http://www.calflora.org/

Constantinescu, O. 1991. Bremiella sphaerosperma sp. nov. and Plasmopara borreriae comb. nov. Mycologia 83: 473-479.

Crouch, J. A., M. P. Ko, and J. M. McKemy.  2014.  First report of impatiens downy mildew outbreaks caused by Plasmopara obducens through the Hawai’ian Islands.  Plant Disease, 98: 696.  DOI: https://doi.org/10.1094/PDIS-10-13-1017-PDN

Daughtrey, M. L., R. L. Wick, and J. L. Peterson.  1995.  Downey mildews.  Part I. infectious diseases, diseases caused by fungi.  Compendium of flowering potted plant diseases.  APS Press, the American Phytopathological Society.  38-38 p.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved September 7, 2017, from http://nt.ars-grin.gov/fungaldatabases/

French, A. M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento (Updated online version by T. Tidwell, May 2, 2017).

Khan, S.  2017.  Email from S. Khan, CDFA Pest Exclusion, to T. Walber, CDFA Interior Pest Exclusion, and J. Chitambar, CDFA, dated 9/19/2017. 4:43 pm.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved September 7, 2017. 4:19:24 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Voglmayr, H., and M. Thines.  2007.  Phylogenetic relationships and nomenclature of Bremiella sphaerosperma (Chromista, Peronosporales). Mycotaxon 100: 11-20.

Walber, T.  2017.  Email from T. Walber, CDFA Interior Pest Exclusion, to J. Chitambar, CDFA, dated 9/8/2017, 9:44 am.

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.

Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Cercospora ruscicola

California Pest Rating for
Cercospora ruscicola V. G. Rao & A. S. Patil 1972
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On April 28, 2017, a shipment of Ruscus (Ruscus sp.) plants with symptoms of leaf spots and destined to a private resident in Contra Costa County, was intercepted by Contra Costa County officials.  The shipment had originated in Florida.  A sample of diseased “leaves” was sent to the CDFA Plant Pathology Laboratory for diagnosis.  On May 8, 2017, Suzanne Latham, CDFA plant pathologist, identified the fungal pathogen, Cercospora ruscicola associated with the diseased leaf tissue. As there have not been any earlier reports of this pathogen in California, it was given a temporary ‘Q’ rating.  Subsequently, the consequences of introduction and establishment of C. ruscicola in California is assessed and a permanent rating is proposed herein.

History & Status:

Background:   The fungal pathogen, Cercospora ruscicola was originally identified from necrotic lesions on “leaves” (actually, ‘cladodes’ which are leaf-like modified stems) of several Ruscus plants at Poona, India (Rao & Patil, 1972).   There have not been any further reports of the global spread of this species, however, Cercospora spp., including C. ruscicola have been detected in federally intercepted samples of Ruscus plants, according to USDA’s National Mycologist (personal communications: S. Latham, CDFA plant pathologist).  Cercospora ruscicola is not known to be present in California.  The recent detection of this species in intercepted plants from Florida marked a first record.   Cercospora ruscicola is also known by its teleomorph (sexual) stage, Mycosphaerella ruscicola A. Pande 1980.

Disease development: In general, in infected plants, Cercospora species produce conidiophores (specialized hypha) that arise from the plant surface in clusters through stomata and form conidia (asexual spores) successively.  Conidia are easily detached and blown by wind often over long distances.  On landing on surfaces of a plant host, conidia require water or heavy dew to germinate and penetrate the host.  Substomatal stroma (compact mycelial structure) may form from which conidiophores develop.  Development of the pathogen is favored by high temperatures and the disease is most destructive during summer months and warmer climates.  High relative humidity is necessary for conidial germination and plant infection.  The pathogen can overwinter in or on seed and as mycelium (stromata) in old infected leaves (Agrios, 2005).

Dispersal and spread: air-currents, infected nursery plants, infected leaves, seeds (Agrios, 2005).

Hosts:  Ruscus aculeatus (butcher’s broom), Ruscus sp. (Farr & Rossman, 2017; Rao & Patil, 1972; CDFA Pest and Damage Record, May 8, 2017).

Symptoms:  Similar to most other Cercospora diseases, symptoms caused by C. ruscicola are leaf spots.  Spots may be irregularly circular to angular, with or without a distinct border, and usually coalesce to form extensive blighted regions.  Rao and Patil (1972) observed extensive, irregular necrotic regions on leaves of Ruscus plants.

Damage Potential:  Quantitative losses due to Cercospora ruscicola have not been reported.  Photosynthetic area can be reduced due to leaf spotting.  In severe infections, leaf wilt and drop may be expected.  Rao and Patil (1972) stated that the “severe’ disease ultimately resulted in defoliation and blight of Ruscus plants in India.  Generally, the damage potential due to this pathogen is likely to be similar to other Cercospora diseases which is usually low (Agrios, 2005).

Ruscus spp. are evergreen, perennial plants that are uncommon and not grown commercially in California, even though they are able to tolerate a wide range of temperatures, except freezing, and grow in shade under wet and dry conditions (Stamp, 2001).  In California, they may be found in ornamental nurseries, and residential and public gardens where they may be at risk of infection and damage by Cercospora ruscicola.  Furthermore, Ruscus stems and berries are used in dried or fresh floral arrangements.  Damage caused by C. ruscicola may significantly impact commercial and private florist businesses.

Worldwide Distribution:  Asia: India (Farr & Rossman, 2017; Rao & Patil, 1972).

Official Control:  Presently, Cercospora ruscicola is on the ‘Harmful Organism’ list for Paraguay (USDA-PCIT, 2017).

California Distribution:  Cercospora ruscicola is not known to be established in California.

California Interceptions:  Cercospora ruscicola was detected in a single shipment of Ruscus sp. intercepted by Contra Costa County officials in April 2017 (see: ‘Initiating Event’).

The risk Cercospora ruscicola would pose to California is evaluated below.

Consequences of Introduction:   

1) Climate/Host Interaction: Ruscus are not commonly grown in California. However, they are able to grow in shade under wet and dry conditions and can tolerate a wide range of temperature (except freezing). These conditions enable the plants to grow in several areas in California and, if introduced, Cercospora ruscicola would be able to establish wherever its host plant is grown under high relative humidity/moisture and warm climate.  However, as the plants are not commercially cultivated and are uncommonly grown in residential and public gardens and ornamental nurseries, the pathogen is given a low score in this category.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 1

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

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

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

2) Known Pest Host Range: Presently, the host range is only limited to Ruscus and R. aculeatus in the family Ruscaceae.

Evaluate the host range of the pest.

Score: 1

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Cercospora ruscicola has high reproductive potential resulting in the successive production of conidia which are dependent on air currents, infected plants, and seed for dispersal and spread.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: Diseased Ruscus plants exhibiting leaf spot symptoms could result in lowered value of plants and loss of markets to nurseries and florist businesses. Increased costs of production can be expected with the necessary use of appropriate fungicides and other disease management strategies.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: B, C

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score:  2

– 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.

4) Environmental Impact:  The pathogen could significantly impact ornamental plantings in home/ urban, public gardens and other recreational environments.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact: E

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

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

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

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

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

Environmental Impact Score: 2

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

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

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

Consequences of Introduction to California for Cercospora ruscicola: Medium (9)

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

Evaluation is ‘Not established’.

Score: 0

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

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

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

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

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information score: (Score: 9)

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 Cercospora ruscicola is B.

References:

Agrios, G. N.  2005.  Plant Pathology (Fifth Edition).  Elsevier Academic Press, USA.  922 p.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved May 10, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Rao, V. G., and A. S. Patil.  1972.  Cercospora ruscicola sp. nov. from India.  Transactions British Mycological Society, 58: 522.

Stamp, R. H.  2001.  Florida/Holland/Israeli Ruscus production and use.  University of Florida Extension, IFAS. Circular 1268 (ENH844).

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. May 10, 2017, 12:21:55 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Responsible Party:

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

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Pest Rating: B

Posted by ls 

Fungi, Plant Pathogens

Diaporthe pseudomangiferae

 California Pest Rating for
Diaporthe pseudomangiferae R. R. Gomes, C. Glienke & Crous
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On December 15, 2016, a shipment of Cacao seed pods with symptoms of necrotic spotting and rot and destined to a private citizen in Contra Costa County, was intercepted by the CDFA Dog Team at the United States Postal Service in Oakland, Alameda County.  The shipment was confiscated and destroyed and a sample of symptomatic seed pods was sent to the CDFA Plant Diagnostics Branch for disease diagnosis.  Suzanne Latham, CDFA plant pathologist identified the fungal pathogen, Diaporthe pseudomangiferae, as the cause for the disease and marked the first detection of D. pseudomangiferae in California.  The current status and rating of D. pseudomangiferae in California is assessed and a permanent rating is proposed.

History & Status:

Background:  Diaporthe pseudomangiferae is a fungal plant pathogen belonging to the order Diaporthales.  The species was named after its morphological similarity to the Phomopsis mangiferae, which was originally isolated from dead leaves of Mangifera indica in Pakistan, however, later reported to differ morphologically from P. mangiferae (Gomes et al., 2013).  Presently, D. pseudomangiferae has only been reported from the Dominican Republic, Puerto Rico, and Mexico (Farr & Rossman, 2017).

Diaporthe pseudomangiferae is not reported from the USA.  The pathogen is not established in California but was detected in a mail shipment of Cacao seed pods which was intercepted in California and subsequently, confiscated, bagged, frozen, and disposed.  However, its detection in Cacao marks a new host for the pathogen, which until now, has only been reported from mango (Gomes et al., 2013).

Disease development:  While specific information is lacking, it is likely that plant infection and disease development caused by Diaporthe pseudomangiferae are similar to those caused by other species of Diaporthe occurring as plant pathogens, endophytes or saprobes.  The fungus produces ascospores (sexual spores) in perithecia (sexual fruiting bodies) and conidia (asexual spores) in pycnidia on dead twigs and leaves.  Conidia are the main inoculum causing primary and secondary infections and are spread to host plants by splashing rains.  Ascospores may be involved in long distance dispersal of the pathogen.  The fungus is likely to overwinter as mycelium and/or as conidia within pycnidia (Agrios, 2005).

Dispersal and spread: Windblown/splashing rain and irrigation water, pruning tools, possibly insects, and animals can spread fungal spores to non-infected plants.

Hosts: Mangifera indica (mango) (Farr & Rossman, 2017; Gomes et al., 2013; Serrato-Diaz et al., 2014); Cacao sp. (CDFA Pest and Damage Record, 2016).

Symptoms:  In mango, Diaporthe pseudomangiferae causes inflorescence rot, rachis canker, and flower abortion.  Symptoms are characterized by blackening of plant tissue with soft rot lesions and sunken lesions on the rachis respectively.  In pathogenicity tests, initially white mycelia developed on inflorescences which later turned brown and flowers aborted (Serrato-Diaz et al., 2014).

Damage Potential:  Quantitative losses caused by Diaporthe pseudomangiferae have not been reported.  During a two-year disease survey in Puerto Rico, Serrato-Diaz et al., (2014) found 50% of mango symptomatic inflorescences to be infected with D. pseudomangiferae. The pathogen causes inflorescence rot, rachis canker, and flower abortion of mango. Therefore, if left uncontrolled, infections may result in reduced fruit production and marketability.  In California, nurseries and other growers of mango plants may be at risk of damage caused by this pathogen.

Worldwide Distribution: Caribbean: Dominican Republic, Puerto Rico; North America: Mexico (Farr & Rossman, 2016; Gomes et al., 2013; Serrato-Diaz et al., 2014).

Official Control: None reported.  In California, currently Diaporthe pseudomangiferae is a quarantine actionable pathogen with a temporary Q rating.

California Distribution: Diaporthe pseudomangiferae is not known to be established in California.

California Interceptions: There has been only one interception.  On December 15, 2016, the fungal pathogen was detected in a shipment of Cacao seed pods that originated in Puerto Rico and was intercepted at a United States Postal Service in Alameda County (see: ‘Initiating Event’).

The risk Diaporthe pseudomangiferae would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Mango is the only known host in California.  Diaporthe pseudomangiferae may be able to infect its host under wet conditions and is therefore, only likely to establish in very limited regions of the State where mango is grown mainly in the Coachella valley and foothill regions of southern California.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 1

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

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

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

2) Known Pest Host Range: The host range of the pathogen is presently limited to Mangifera indica and Cacao

Evaluate the host range of the pest.

Score: 1

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Diaporthe pseudomangiferae has high reproductive potential with an abundant production of spores, however, the spores are dependent on splashing water for dispersal.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 2

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

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

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

4) Economic Impact: Under favorable wet conditions for spread and disease development, Diaporthe pseudomangiferae has been found to cause inflorescence rot, rachis canker, and aborted flowers in mango, thereby possibly resulting in lowered fruit production, value, and loss of markets.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: Mango and cacao are the only known hosts, therefore no significant impact on the environment is expected.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  None

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

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

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

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

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

Environmental Impact Score: 1

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

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

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

Consequences of Introduction to California for Diaporthe pseudomangiferae: Low (8)

Add up the total score and include it here.

–Low = 5-8 points

-Medium = 9-12 points

-High = 13-15 points

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

Evaluation is ‘Not established’ (0).

Score: (0)

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

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

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

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

Final Score:

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

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

Uncertainty: 

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Diaporthe pseudomangiferae is C.

References:

Agrios, G. N.  2005.  Plant Pathology Fifth Edition.  Elsevier Academic Press.  922 p.

Anon.  1996. Mango Mangifera indica L. California Rare Fruit Growers, Inc.  http://www.crfg.org/pubs/ff/mango.html

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved January 18, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Gomes, R.R., C. Glienke, S. I. R. Videira, L. Lombard, J. Z. Groenewald, and P. W. Crous.  2013.  Diaporthe: a genus of endophytic, saprobic and plant pathogenic fungi. Persoonia 31: 1-41.

Serrato-Diaz, L.M., L. I. Rivera-Vargas, and R. D. French-Monar.  2014.  First report of Diaporthe pseudomangiferae causing inflorescence rot, rachis canker, and flower abortion of mango. Plant Disease 98(7): 1004

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 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.

Pest Rating: C

Posted by ls

Fungi, Plant Pathogens

Phytophthora parvispora Scanu & Denman, 2013

California Pest Rating for
Phytophthora parvispora  Scanu & Denman, 2013
Pest Rating: B 
PEST RATING PROFILE
Initiating Event: 

On August 19, 2016, non-official samples of pear baits of effluent collected from the bottom of four pots containing diseased Mexican orange blossom (Choisya ternata) plants, were sent by a private company to the CDFA Plant Pathology Lab for identification of the cultured pathogen.  The private company had prepared the pear baits after collection of the effluent drained from the four diseased plants that were contained in a commercial nursery in San Francisco County.  The associated pathogen was identified by Suzanne Latham, CDFA plant pathologist, as Phytophthora parvispora on September 9, 2016.  Subsequently, on September 22, 2016, San Francisco County Agricultural inspectors collected official samples of the same four symptomatic Mexican orange blossom plants originally sampled in San Francisco County.  The diseased plants exhibited root and crown rot symptoms and were sent to the CDFA Plant Pathology Lab for diagnosis.  On November 22, 2016, Suzanne Latham officially identified Phytophthora parvispora after baiting and culturing it from the roots of one of the four Choisya ternata plant samples (Latham, 2016).  This detection marked the first report of P. parvispora in the USA and therefore, a culture of the pathogen was sent from CDFA to the USDA APHIS CPHST in Beltsville for confirmation.  On November 15, 2016, the identity of P. parvispora was confirmed by CPHST.   Consequently, the pathogen was assigned a temporary ‘Q’ rating by CDFA.   The risk of introduction and establishment of this pathogen is assessed here and a permanent rating is proposed.

History & Status:

Background: Phytophthora parvispora was originally recorded from the stem bases of Beaucarnea sp. nursery plants grown in a greenhouse in Germany and was regarded a variety of the polyphagous fungal species, P. cinnamomi based on its morphology and temperature required for growth (Kröber & Marwitz, 1993).  However, Scanu et al., (2014) stated that P. parvispora was apparently isolated from citrus in Taiwan (Ann & Ko, 1985) prior to Kröber & Marwitz’ report and was suggested by several researchers to belong to a distinct species different from P. cinnamomi.   In subsequent years, studies based on molecular and phylogenetic analyses, combined with morphological characters, temperature-growth relations, and pathogenicity experiments, demonstrated that P. cinnamomi var. parvispora significantly differed from P. cinnamomi and therefore, was elevated to species status to become Phytophthora parvispora (Scanu et al., 2014).

Since its first records from Germany and Taiwan, P. parvispora has been also reported from Australia, isolated from potting mixes of nursery plants and an irrigation channel surrounded by cultivated agricultural fields; from South Africa, isolated from Arbutus unedo plants; from Brazil, isolated from the rhizosphere of cowpea; from Italy, isolated from Mandevilla sp. and A. unedo plants; and from Portugal isolated from potted Pinus pinea nursery plants (Scanu et al., 2014).   The current record of its detection in Choisya ternata in California marked its first detection in the USA.  As almost all reports of P. parvispora are associated with trade of plants intended for planting, the latter is considered a major pathway for introduction of the pathogen into ornamental, landscape and natural environments.  Choisya ternata is native to Mexico and not naturalized in the USA (NPGS).  The pathogen has never been recorded from natural environments (Scanu et al., 2014).  The origin of P. parvispora is considered to be south-east Asia as the earliest record came from Taiwan (Ann & Ko, 1985; Scanu et al., 2014).

Hosts: Although few plant hosts have been reported, they belong to six monocot, dicot, and coniferous plant families.  Rutaceae: Agathosma betulina (buchu) and Citrus sp.; Ericaceae: Arbutus unedo (strawberry tree); Asparagaceae: Beaucarnea recurvata (elephants foot, ponytail palm), Beaucarnea sp.; Apocynaceae: Mandevilla sanderi (Brazilian jasmine), M. splendens, Mandevilla sp., Mandevilla x amabilis; Pinaceae: Pinus pinea (Italian stone pine, umberella pine); Fabaceae: Vigna unguiculata (cowpea) (Farr & Rossman, 2016; Scanu et al., 2014).  Choisya ternata (Mexican orange blossom, Rutaceae; CDFA Pest and Damage Record, November 22, 2016) is included here as a newly reported host.

Symptoms:  Host plants infected with Phytophthora parvispora exhibit symptoms of root and collar rot, leaf chlorosis, shoot dieback and plant decline.  Two to three-year-old infected seedlings of Arbutus unedo showed symptoms of shoot tip dieback and root and collar rot (Scanu et al., 2014).

Disease Cycle:  Generally, species of Phytophthora that cause root and stem rots survive cold winters or hot and dry summers as resting spores (oospores and chlamydospores) or mycelium in infected roots, stems or soil.  For P. parvispora, it is suggested that the pathogen survives long terms in moderate dry conditions between consecutive rains as mycelial aggregations and selfed oospores than as chlamydospores as the former structures are produced in solid agar and in water, while chlamydospores are thin-walled and infrequently produced, thereby indicating short-term survival (Jung et al., 2013; Scanu et al., 2014).  During spring, the oospores and chlamydospores germinate to produce motile spores (zoospores) that swim around in soil water and roots of susceptible hosts. The pathogen infects the host at the soil line causing water soaking and darkening of the trunk bark. This infected area enlarges and may encircle the entire stem of small plants which wilt and eventually die.  On large plants, the infected, necrotic area may be on one side of the stem and become a depressed canker below the level of the healthy bark.  Collar rot canker may spread down the root system. Roots are invaded at the crown area or at ground level.   Mycelium and zoospores grow in abundance in cool, wet weather causing damage where the soil is too wet for normal growth of susceptible plants and low temperatures (15-23°C) prevail (Agrios, 2005).   The temperature range for the development P. parvispora in culture is from 10-11°C to 36-37°C, the optimum temperature being 16°C to 32°C (Kröber & Marwitz, 1993).  With high cardinal temperatures for growth, P. parvispora is well adapted to tropical and subtropical climates and greenhouse conditions (Scanu et al., 2014).

Dispersal and spread: Like most Phytophthora species, P. parvispora is soil-borne and water-borne and may be spread to non-infected sites through infected plants, nursery and planting stock, seedlings, pathogen-contaminated soil, run-off and splash irrigation and rain water, and contaminated cultivation equipment and tools.

Damage Potential:  Phytophthora parvispora causes root and crown rot on woody and semi-woody hosts.  At particular risk are nursery-grown plants for plantings in commercial and private garden, landscape, and horticultural environments.

Worldwide Distribution: Asia: Taiwan; Africa: South Africa; Europe: Germany, Italy, Portugal; North America: USA (California); South America: Brazil; Australia (Farr & Rossman, 2016; Scanu et al., 2014).

Official Control:  Presently, Phytophthora parvispora has a temporary, quarantine status and ‘Q’ rating by the CDFA.

California Distribution: San Francisco County.

California Interceptions: None.

The risk that Phytophthora parvispora would pose to California is evaluated below.

Consequences of Introduction:

1) Climate/Host Interaction: Phytophthora parvispora may be able to establish in cool to warm (10-11°C to 36-37°C, or 16-32°C optimal) and wet climates within California. Its in-state establishment is likely to be large but limited in accordance with the distribution of its hosts under climates favorable for infection.  Its hosts range from ornamentals such as Mandevilla which are grown in cool to warm coastal and inner valley regions, to citrus and stone pine which cover larger regions of the state.  The pathogen is well adapted to tropical and subtropical climates and greenhouse conditions, and requires wet weather for infection.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

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

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

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

2) Known Pest Host Range: Presently, the host range for Phytophthora parvispora is limited to relatively few, yet diverse hosts which are found in six monocot, dicot and coniferous families. Important hosts for California include mainly ornamentals (Arbutus unedo – strawberry tree, Mandevilla, Choisya ternata – Mexican orange blossom), conifer (Pinus pinea) and few fruit (Citrus sp.).  A low score is ascribed to this category.

Evaluate the host range of the pest.

Score: 1

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: Phytophthora parvispora is soil-borne and water-borne and therefore, primarily spreads artificially via infested soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools that may spread contaminated soil and plant materials to non-infected sites.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: Although losses caused solely by Phytophthora parvispora have not been quantified, the potential for the pathogen to infect mainly ornamental, conifer, and citrus plants in California could result in root and crown rot, and shoot dieback thereby decreasing healthy stands, causing yield losses, increasing production costs and causing loss of market of nursery stocks. Also, the pathogen’s potential to survive and spread in infected soils and irrigation water could require changes in normal cultivation practices of host plants.  A ‘High’ score is given for this category.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C, D, G.

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

4) Environmental Impact: Phytophthora parvispora may impact conifers and other ornamentals grown in commercial and private gardens and landscape environments.  The pathogen has never been reported from natural environments nevertheless, infected nursery plants provide a pathway for the introduction of the pathogen to outdoor environments, and the possibility of its establishment under favorable conditions. Infestations could trigger additional treatment programs.  Infections of perennial shrub and tree hosts could disrupt natural communities or alter ecosystem processes.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  A, D, E.

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

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

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

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

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

Score the pest for Environmental Impact.

Environmental Impact Score: 3

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

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

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

Consequences of Introduction to California for Phytophthora parvispora: Medium (12)

Add up the total score and include it here.

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

6) Post Entry Distribution and Survey Information: Presently, Phytophthora parvispora has only been officially reported from one region, namely, San Francisco County. California.

Score: (-1)

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

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

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

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

Final Score:

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

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

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Phytophthora parvispora is B.

References:

Agrios, G. N.  2005.  Plant Pathology fifth edition.  Elsevier Academic Press, Massachussetts, USA.  922 p.

Ann, P. J., and W. H. Ko.  1985.  Variants of Phytophthora cinnamomi extend the known limits of the species.  Mycologia 77: 946-950.

Farr D.F., & Rossman, A.Y.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved December 7, 2016, from http://nt.ars-grin.gov/fungaldatabases/

Jung, T., I. Colquhoun, G. E. St. J. Hardy.  2013.  New insights into the survival strategy of the invasive soilborne pathogen Phytophthora cinnamomi in different natural ecosystems in Western Australia. Forest Pathology 43: 266-288.  doi:10.1111/efp.12025.

Kröber, H., and R. Marwitz.  1993.  Phytophthora tentaculata sp. nov. und Phytophthora cinnamomi var. parvispora var. nov., zwei neue Pilze von Zierpflanzen in Deutschland. Zeitschrift fur Pflanzenkrankheiten und Pflanzenschutz 100, 250-258. [Original Description].

Latham, S.  2016.  Email to J. Chitambar et al., CDFA, on Monday, November 7, 2016, 10:12:21 am.

NPGS.  (Date unknown).  Taxon: Choisya ternata Kunth.  U. S. National Plant Germplasm System.  https://npgsweb.ars-grin.gov/gringlobal/taxonomydetail.aspx?315354

Scanu, B., Hunter, G.C., Linaldeddu, B.T., Franceschini, A., Maddau, L., Jung, T., and Denman, S. 2014. A taxonomic re-evaluation reveals that Phytophthora cinnamomi and P. cinnamomi var. parvispora are separate species. Forest Pathology 44: 1-20.

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 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

 

Fungi, Plant Pathogens

Colletotrichum sansevieriae M. Nakamura & M. Ohzono 2006

California Pest Rating for
Colletotrichum sansevieriae  M. Nakamura & M. Ohzono 2006 
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On November 11, 2016, diseased Sansevieria sp. plants exhibiting leaf spot symptoms, were intercepted by San Diego County Agricultural officials.  The plants had originated in Florida and were destined to a nursery in San Diego County.  A sample of diseased leaves was collected and sent by the County to the CDFA Plant Pathology Lab for diagnosis.  On December 7, 2016, Suzanne Latham, CDFA plant pathologist, detected Colletotrichum sansevieriae in culture from leaf spots and confirmed the identification by morphological and sequence analyses.  Then, on December 19, 2016, C. sansevieriae was detected once again in a shipment of Sansevieria trifasciata plants that had originated in Florida but were destined to a different nursery in San Diego County.  The samples submitted to the CDFA Lab had been collected on November 22, 2016 by San Diego County.  Consequently, the infested greenhouse-contained, potted Sansevieria plants were treated with fungicidal sprays and continue to be periodically monitored for detection of the pathogen (personal communication: Pat Nolan, plant pathologist, San Diego County).  Currently, C. sansevieriae has a temporary ‘Q’ rating.  The risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is proposed herein.            

History & Status:

Background: Colletotrichum sansevieriae is a fungal pathogen that causes anthracnose disease only in Sansevieria spp. plants (Nakamura et al., 2006).  The pathogen was first detected in Sansevieria plants in Japan and soon after reported from Australia (Aldaoud et al., 2010), India (Gautam et al., 2012), USA (Florida; Palmateer et al., 2012), and Korea (Park et al., 2013).  Its recent find in a California nursery marked its first detection in for the State.

Hosts: Sansevieria sp. (snake plant), S. trifasciata (mother-in-law’s tongue) (Farr & Rossman, 2016; CABI, 2016).

Symptoms:  Initially, round, water-soaked lesions are formed on leaves.  Lesions form on young and mature leaves and rapidly enlarge and coalesce resulting in foliage blight.  In mature lesions, numerous brownish-black and crustose cankers or acervuli (fungal fruiting bodies) in concentric rings are produced characteristic of anthracnose.  Abundant conidia are produced on these cankers (Makamura et al., 2006; Palmateer et al., 2012).

Damage Potential:  Anthracnose disease caused by Colletotrichum sansevieria can result in reduced plant quality and growth, and marketability.  In California, nursery production of potted host plants or in greenhouses are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species.  In California’s cultivated fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Disease Cycle:  It is likely that Colletotrichum sansevieria has a similar life cycle to that of other Colletotrichum species and survives between crops during winter as mycelium on plant residue in soil, on infected plants, and on seeds.  During active growth, the pathogen produces masses of hyphae (stromata) which bear conidiophores, on the plant surface. Conidia (spores) are produced at the tips of the conidiophores and disseminated by wind, rain, cultivation tools, equipment, and field workers.   Conidia are transmitted to host plants.  Humid, wet, rainy weather is necessary for infection to occur.  These requirements in particular may limit the occurrence of the pathogen in California fields and subsequently, the pathogen may be more of a problem under controlled environments of greenhouses.  Conidia germinate, penetrate host tissue by means of specialized hyphae (appresoria) and invade host tissue.  The optimum temperature for growth of C. sansevieria ranges from 25° to 28°C Nakamura et al., 2006).   In greenhouse tests, anthracnose disease developed within 10 days of inoculation of Sanseviera plants at 29°C with 70-85% relative humidity (Palmateer et al., 2012), or 6 days after inoculation in a humid chamber at 27°C under 12h fluorescent light/12 h darkness (Nakamura et al., 2006).

Transmission:  Wind, wind-driven rain, cultivation tools, and human contact.

Worldwide Distribution: Asia: India, Japan, Korea; North America: USA (Florida); Oceania: Australia (Farr & Rossman, 2016; CABI, 2016; Gautam et al., 2012).

Official Control:  In California C. sansevieriae is a quarantine actionable, Q-rated pathogen.

California Distribution: Colletotrichum sansevieriae was detected in two nursery greenhouses in San Diego.  Conseq  ently, infected plants were treated and continue to be monitored periodically for detection of the pathogen (see “Initiating Event”).  As the infected plants were contained in pots in greenhouses, the pathogen is not considered to be established in California.

California Interceptions:  Colletotrichum sansevieria has been intercepted twice in 2016, in shipments of Sansevieria plants that originated in Florida (see ‘Initiating event’).

The risk Colletotrichum sansevieriae would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Similar to other species of Colletotrichum, sansevieriae requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to fully establish and spread under dry field conditions in California.

Evaluate if the pest would have suitable hosts and climate to establish in California.

Score: 2

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

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

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

2) Known Pest Host Range: The host range of Colletotrichum sansevieriae is limited to Sansevieria

Evaluate the host range of the pest.

Score: 1

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

3) Pest Dispersal Potential: The pathogen has high reproductive potential and conidia are produced successively.  They are transmitted by wind, wind-driven rain, cultivation tools, and human contact however conidial germination and plant infection require long, wet periods.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: Under suitable, wet climates, the pathogen could lower plant growth, value, and trigger the loss of markets.

Evaluate the economic impact of the pest to California using the criteria below.

Economic Impact: A, B, C.

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

 Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

5)  Environmental Impact:  The pathogen could significantly impact cultural practices or home garden plantings.

Evaluate the environmental impact of the pest on California using the criteria below.

Environmental Impact:  E.

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

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

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

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

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

Score the pest for Environmental Impact.

Environmental Impact Score: 2

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

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

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

Consequences of Introduction to California for Colletotrichum sansevieriae: Medium (11)

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

6) Post Entry Distribution and Survey Information: Colletotrichum sansevieriae was detected in an incursion of plants held at a nursery in San Diego County and is not considered to be established within California.

Score: (-0)

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

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

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

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

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the anthracnose pathogen, Colletotrichum sansevieriae is B.

References:

Aldaoud, R., S. de Alwis, S. Salib, J. H. Cunnington, and S. Doughty.  2011.  First record of Colletotrichum sansevieriae on Sansevieria sp. (mother-in-law’s tongue) in Australia. Australasian Plant Disease Notes 6: 60-61

CABI.  2016.  Colletotrichum fructicola basic datasheet report.  Crop Protection Compendium.  www.cabi.org/cpc/

Farr, D. F., & A. Y. Rossman.  Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 3, 2016, from http://nt.ars-grin.gov/fungaldatabases/

Gautam, A. K., S. Avasthi, and R. Bhadauria.  2012.  Colletotrichum sansevieriae on Sansevieria trifasciata – a report form Madhya Pradesh, India.  Plant Pathology & Quarantine 2: 190-192.  doi 10.5943/ppq/2/2/12

Nakamura, M., M. Ohzono, H. Iwai, and K. Arai.  2006.  Anthracnose of Sansevieria trifasciata caused by Colletotrichum sansevieriae sp. nov. Journal of General Plant Pathology 72: 253-256.

Palmateer, A. J., T. L. B. Tarnowski, and P. Lopez.  2012.  First Report of Colletotrichum sansevieriae Causing Anthracnose of Sansevieria trifasciata in Florida. Plant Disease 96: 293.

Park, J. H., K. S. Han, J. Y. Kim, and H. D. Shin.  2013.  First Report of Anthracnose Caused by Colletotrichum sansevieriae on Sansvieria in Korea. Plant Disease 97: 1510

Weir, B. S., P. R. Johnston, and U. Damm.  2012.  The Colletotrichum gloeosporioides species complex.  Studies in Mycology, 73:115-180. DOI:10.3114/sim0011.

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 Format:

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

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♦  Comments may not be posted if they:

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Pest Rating: B

Posted by ls

Bacteria, Plant Pathogens

Candidatus Liberibacter solanacearum Liefting, Perez-Egusquiza & Clover, 2009

California Pest Rating for
Candidatus Liberibacter solanacearum Liefting, Perez-Egusquiza & Clover, 2009 
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

None.  The risk of entry and establishment of Ca. Liberibacter solanacearum in California is assessed and a permanent rating is proposed.

History & Status:

Background:  Candidatus Liberibacter solanacearum was first identified in 2008 simultaneously in the United States and New Zealand. In New Zealand, Liefting et al., (2008, 2009), detected the bacterial pathogen first in tomato and pepper and then in potato and other solanaceous plants.  The pathogen was tentatively named Candidatus Liberibacter solanacearum.  In the United States, the pathogen was detected in tomato plants and the potato/tomato psyllid Bactericera cockerelli and tentatively named Candidatus Liberibacter psyllaurous because of its association with psyllid yellows (Hansen et al., 2008; CABI, 2016).  Ca. L. psyllaurous is now considered a synonym of Ca. L. solanacearum.  The pathogen is the cause of ‘Zebra chip disease’ in potatoes, named because of the presence of dark stripes and blotches that develop from the rapid oxidative darkening of freshly cut tubers and become more distinct after frying infected potato chips (Crosslin, 2009).  Zebra chip disease of potatoes was first observed in the 1990s in Mexico and parts of Central America.  Foliar symptoms resembled those caused by phytoplasmas.  The disease is now widespread in south-western, central, and north-western USA, Mexico, Central America, New Zealand and restricted regions within Europe (see “Worldwide Distribution’ below).

In the United States, zebra chip disease of potatoes was first identified in 2000 in commercial potato fields in Texas and by 2004-2005, was reported to cause serious economic damage in parts of Southern Texas.  By 2007, zebra chip disease was observed in Nebraska, Colorado, Kansas, New Mexico, Arizona, Nevada, and California causing losses in the millions of dollars to potato producers and processors in affected regions.  Infested fields were often abandoned (Munyaneza et al., 2007b).

In California, while potato crops exhibiting symptoms of zebra chip disease were observed previously (Munyaneza et al., 2007b), the bacterium Ca. L. psyllaurous was first identified in 2009 from diseased potatoes grown in commercial fields in Lancaster, Los Angeles County (Crosslin, 2009; Crosslin et al., 2010).   Since then, the presence of Ca. L. solanacearum was also detected, in plant tissue and psyllid vector with real time PCR, in Riverside, Santa Barbara, Orange, and San Diego Counties (Trumble, 2015).  Substantial crop losses have occurred in southern California that resulted in abandonment of commercial fields, decline in potato and tomato productions, and significant increases in disease control costs (Trumble, 2015).  The pathogen is considered to be of rare occurrence and less of a problem in northern California (Nunez, 2015; Davis, 2015).   The psyllid can be found throughout southern California, in Kern County, on the coast up to Sacramento, and within the Sacramento Valley.  In the Sacramento area, dense psyllid populations have been reported on bell peppers.  For reasons not known, the peppers do not show symptoms of Ca. L. solanacearum (unlike peppers infested with psyllids in Utah, Arizona, New Mexico and New Zealand), and therefore, the presence of the bacterial pathogen in the populations cannot be definitely stated (Trumble, 2015).  Also, the psyllid vector is kept in control by growers, through routine insecticide applications primarily against aphid-vectored viruses (Nunez, 2015).

Biology: Candidatus Liberibacter solanacearum is a phloem-limited, insect hemolymph-limited, gram-negative, unculturable bacterium that is primarily spread from infected to healthy plants by psyllid insect vectors.  Presently, there are five known geographic haplotypes (a specific group of genes that are inherited together from a single parent) designated A, B, C, D, and E.  Haplotypes A and B are associated with Bactericera cockerelli and the diseases caused by this bacterium in potatoes and other solanaceous plants.  Haplotypes C and D are associated with diseased carrots, and Trioza apicalis and Bactericera trigonica respectively, and haplotype E is associated with diseased celery and carrot.  The five haplotypes are not yet known to elicit biological differences in plant or insect hosts.  Haplotype A has been found primarily from Central to North America (from Honduras and Guatemala through western Mexico to Arizona, California, the Pacific Northwest) and in New Zealand.  Haplotype B has been found in Mexico and North America (from eastern Mexico and northwards through central USA through Texas).  Some overlap of haplotypes A and B occurs in Texas, Kansas, and Nebraska.  Haplotype C occurs in Finland, Sweden, and Norway and is associated with T. apicalis. Haplotype ‘D’ was found in mainland Spain and the Canary Islands.  Haplotype E is present in mainland Spain, France, and Morocco (EPPO, 2013; Tahzima et al., 2014; Teresani et al., 2014, 2015).  Teresani et al., (2015) recently reported two additional new psyllid species, Bactericera tremblayi and B. nigricornis, as potential vectors of Ca. L. solanacearum that were detected with B. trigonica during surveys conducted from 2011 to 2014 in carrot, celery and potato plots in mainland Spain and the Canary Islands.

While there is not much known on the effects of environment on Ca. L. solanacearum, temperature is known to have a significant effect on the development of this bacterial pathogen.  Compared to the citrus greening Huanglongbing Liberibacter species, Ca. L. solanacearum appears to be heat sensitive and does not tolerate temperatures above 32°C

Dispersal and spread:  Ca. L. solanacearum is transmitted by its psyllid insect vector, Bactericera cockerelli, in a persistent (transovarially or vertically) way and during feeding on infected plant hosts (horizontally).  However, vertical transmission of the pathogen in the other psyllid species, Bactericera trigonica and Trioza apicalis, is currently not known.  The pathogen is also spread by grafting and infected plants, but not true seed (EPPO, 2013).  However, Bertolini et al., (2014) reported the detection of Ca. L. solanacearum in carrot seeds using real-time PCR thereby, indicating that seed transmission is involved in the natural spread of the bacterium via carrot seed in distant regions and countries in Europe.  Usually infected seed potatoes do not germinate but may occasionally produce infected plants which are often weak and short-lived and therefore, not a significant mode for spreading the disease (EPPO, 2013).

Hosts: Hosts are included in the plant families Apiaceae and Solanaceae.  Main hosts include, Capsicum annuum (bell pepper), Solanum lycopersicum (tomato), S. tuberosum (potato), and Datura stramonium (jimsonweed).  Other wild and incidental hosts include Solanum melongena (eggplant), S. pseudocapsicum (Jerusalem-cherry), S. dulcamara (climbing nightshade), Cyphomandra betacea (syn. Solanum betacea; tree tomato/tamarillo), Apium graveolens (celery), Daucus carota (carrot), Physalis peruviana (Cape gooseberry/tomatillo), and Nicotiana tabacum (tobacco) (CABI, 2016, EPPO, 2016).

Symptoms:  Characteristic above-ground symptoms in potato and other solanaceous host plants include stunting, erectness of new foliage, chlorosis and purpling of foliage with basal cupping of leaves through entire plant, resetting due to shortened and thickened terminal internodes, enlarged nodes, axillary branches or aerial tubers, leaf scorching, disruption of fruit set, and production of numerous small, misshaped and poor quality fruits. Below-ground symptoms in potato include collapsed stolons, browning of vascular tissue concomitant with necrotic flecking of internal tissues and streaking of the medullary ray tissues, all of which can affect the entire tuber.  These symptoms become more distinct upon frying and potato chips processed from affected tubers show very dark blotches, stripes or streaks thereby making them unacceptable for marketing.  It is due to the symptoms produced in potato tubers that the disease was named ‘zebra chip’ (EPPO, 2013).

Damage Potential: In potato, plant growth is affected.  Potato chips produced from zebra ship-infected tubers have dark stipes that are more distinct upon frying and therefore, not commercially acceptable. Infected tubers often do not sprout or produce hairy sprouts and weak plants.  Damage is also caused to other economically important solanaceous plants including tomato, pepper, eggplant, tamarillo, and tobacco.  Fields with infected crops may be rejected resulting in their abandonment (EPPO, 2013).  Ca. Liberibacter solanacearum can cause significant damage to crop quality and yield.  In the Americas and New Zealand, losses in millions of dollars have been caused by the pathogen and psyllid complex and to the carrot industry in Europe (Crosslin et al., 2010; Munyaneza 2007a, 2007b).  In Texas and New Zealand, annual potato yield losses at approximately US $22 million and US $40 million respectively were due to Ca L. solanacearum (Soliman, 2012 in CABI, 2016).  In Europe, up to 100% crop losses in carrot production due to Ca. L solanacearum – infected carrot psyllid were reported (CABI, 2016).

Worldwide Distribution: Africa: Morocco; North America: Mexico, USA; Europe (restricted distributions within): Finland, Germany (few occurrences), Norway, Spain, Spain – Canary Islands, Sweden; Central America:  Guatemala, Honduras, Nicaragua; Oceania: New Zealand (CABI, 2016; EPPO, 2013, 2016).

In Europe, Ca. L. solanacearum has not been detected in potato and tomato crops but has been detected mainly in carrot crops and to a lesser extent in celery in association with other psyllid species, Bactericera trigonica and Trioza apicalis (EPPO, 2013). Ca. L. solanacearum is considered “transient, under eradication” in Austria and France.

In the USA, the pathogen is present in Arizona, California, Colorado, Idaho, Kansas, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oregon, Texas, Utah, Washington, and Wyoming (CABI, 2016; EPPO, 2016).

Official Control: Candidatus Liberibacter solanacearum is on the Harmful Organisms Lists for Argentina, Australia, Brazil, Chile, Costa Rica, Guatemala, Honduras, Republic of Korea, Panama, and Taiwan (USDA PCIT, 2016).

California Distribution: Los Angeles, Riverside, Orange, San Diego, and Santa Barbara Counties.  The pathogen is considered to be of rare occurrence in northern California.

California Interceptions:  There are no reports of the detection of Ca. Liberibacter solanacearum in plant shipments imported to California.

The risk Ca. Liberibacter solanacearum 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: 3

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

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

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

Risk is High (3): Ca. L. solanacearum appears to be heat sensitive and does not tolerate temperatures above 32°C.  Presently, its distribution has been confirmed in some counties in southern California, while its occurrence in northern California is rare.  While the potato/tomato psyllid vector can be found on Ca L. solanacearum host plants throughout southern California, in Kern County, on the coast up to Sacramento, and within the Sacramento Valley, the presence of the bacterial pathogen has only rarely been found in the northern regions.  Furthermore psyllid populations are kept in check by growers through insecticides routinely applied primarily to control aphid-vectored viruses. In the absence of vector control measures, the bacterial pathogen is expected to establish a widespread distribution on prime hosts including, tomatoes, potatoes, peppers and eggplant.

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

Score: 2

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Medium (2):  The pathogen has a medium host range that includes major host plants such as tomatoes, potatoes, and peppers, cultivated under significant acreage in California.

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

Score: 3

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

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

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

Risk is High (3):  Ca. L. solanacearum is primarily transmitted by its psyllid insect vector, Bactericera cockerelli.  The bacterium has high reproduction and is dependent primarily on its vector for short and long-distance spread. The bacterium is also spread by grafting and infected plants.  [Usually infected seed potatoes do not germinate but may occasionally produce infected plants which are often weak and short-lived and therefore, not a significant mode for spreading the disease.]

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): Ca. L. solanacearum causes zebra chip disease of potatoes and has resulted in significant crop damage and economic loss in production and marketability. Significant losses have also been caused in other economic host crops.  The pathogen is vectored by the potato/tomato psyllid vector in California. 

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

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

The pest could directly affect threatened or endangered species.

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

The pest could trigger additional official or private treatment programs.

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

Score the pest for Environmental Impact.

Score: 2

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

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

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

Risk is Medium (2): Infestations of the bacterial pathogen could significantly impact home/urban gardening.

Consequences of Introduction to California for Candidatus Liberibacter solanacearum:

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:  -1

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

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

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

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

Evaluation is Low (-1): Presently, Ca. L. solanacearum is distributed within few counties of southern California, namely, Los Angeles, Riverside, Orange, San Diego, and Santa Barbara Counties and is considered to be only of rare occurrence in northern 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 = 12.

Uncertainty:  

Not much is known on the effects of environment on Ca. L. solanacearum.   Also, its presence in vector populations in northern California cannot be definitively stated.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the zebra chip pathogen, Ca. Liberibacter solanacearum is B.

References:

Bertolini, E., G. R. Teresani, M. Loiseau, F. A. O. Tanaka, S. Barbé, C. Martínez, P. Gentit, M. M. López, and M. Cambra.  2014.  Transmission of ‘Candidatus Liberibacter solanacearum’ in carrot seeds.  Plant Pathology: http://dx.doi.org/10.1111/ppa.12245 .

Crosslin, J. M.  2009. First report of ‘Candidatus Liberibacter psyllaurous’ in zebra chip symptomatic potatoes from California.  Plant Disease 93: 551. http://dx.doi.org/10.1094/PDIS-93-5-0551B .

Crosslin, J. M., J. E. Munyaneza, J. K. Brown, and L. W. Liefting.  2010.  Potato zebra chip disease: A phytopathological tale. Online. Plant Health Progress doi: 10.1094/PHP-2010-0317-01-RV.

Davis, M.  2015.  Email from M. Davis, Professor Emeritus, Plant Pathology Department, UC Davis, to J. Chitambar, Primary Plant Pathologist/Nematologist, CDFA, sent Wednesday, November 11, 2015, 7:13:45 pm.

Farr, D.F., & A. Y. Rossman.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved January 28, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

EPPO.  2013.  Candidatus Liberibacter solanacearum.  EPPO Data Sheets on pests recommended for regulation, European and Mediterranean Plant Protection Organization.  Bulletin OEPP/EPPO Bulletin 43: 197-201.  DOI: 10.1111/epp.12043.

EPPO.  2016.  Liberibacter solanacearum (LIBEPS).  New PQR database.  Paris, France:  European and Mediterranean Plant Protection Organization.  http://newpqr.eppo.int

Hansen, A. K., J. T. Trumble, R. Stouthamer, and T. D. Paine.  2008.  A new huanglongbing species, “Candidatus Liberibacter psyllaurous,” found to infect tomato and potato, is vectored by the psyllid Bactericera cockerelli (Sulc). Applied and Environmental Microbiology, 74(18):5862-5865. http://aem.asm.org .

Liefting, L. W., Z. C. Perez-Egusquiza, G. R. G. Clover, and J. A. D. Anderson.  2008.  A new ‘Candidatus Liberibacter’ species in Solanum tuberosum in New Zealand. Plant Disease, 92(10):1474.

Liefting, L. W., B. S. Weir, S. R. Pennycook, and G. R. G. Clover.  2009.  ‘Candidatus Liberibacter solanacearum’, associated with plants in the family Solanaceae. International Journal of Systematic and Evolutionary Microbiology, 59(9):2274-2276.

Munyaneza, J. E.  2012.  Zebra chip disease of potato: biology, epidemiology and management.  American Journal of Potato Research 89: 329-350.  http://dx.doi.org/10.1007/s12230-012-9262-3.

Munyaneza, J. E., J. M. Crosslin, and J. E. Upton.  2007a. Association of Bactericera cockerelli (Homoptera: Psyllidae) with “zebra chip”, a new potato disease in southwestern United States and Mexico.  Journal of Economic Entomology 100, 656–663.

Munyaneza, J.E., J. A. Goolsby, J. M. Crosslin, and J. E. Upton.  2007b.  Further evidence that zebra chip potato disease in the lower Rio Grande Valley of Texas is associated with Bactericera cockerelli.  Subtropical Plant Science 59, 30–37.

Nunez, J.  2015.  Email from J. Nunez, Vegetable/Plant Pathology Farm Advisor, UC Cooperative Extension, to J. Chitambar, Primary Plant Pathologist/Nematologist, CDFA, sent Wednesday, November 11, 2015, 4:35 pm.

Tahzima, R., M. Maes, E. H. Achbani, K. D. Swisher, J. E. Munyaneza, and K. De Jonghe.  2014.  First Report of “Candidatus Liberibacter solanacearum’ on carrot in Africa.  Plant Disease 98: 1426.  http://dx.doi.org/10.1094/PDIS-05-14-0509-PDN .

Teresani, G. R., E. Bertolini, A. Alfaro-Fernández, C. Martinez, F. A. O. Tanaka, E. W. Kitajima, M. Roselló, S. Sanjuán, J. C. Ferrándiz, M. M. López, M. Cambra, and M. I. Font.  2014.  Association of ‘Candidatus Liberibacter solanacearum’ with a vegetative disorder of celery in Spain and development of a real-time PCR method for its detection.  Phytopathology 104: 804-811.

Teresani, G., R. Hernández, E. Bertolini, F. Siverio, C. Marroquin, J. Molina, A. Hermoso de Mendoza, and M. Cambra.  2015.  Search for potential vectors of ‘Candidatus Liberibacter solanacearum’: population dynamics in host crops.  Spanish Journal of Agricultural Research, 13 (1): e10-002. http://dx.doi.org/10.5424/sjar/2015131-6551 .

Trumble, J. T.  2015.  Email from J. T. Trumble, Distinguished Professor of Entomology, University of California, Riverside, to J. Chitambar, Primary Plant Pathologist/Nematologist, CDFA, sent Thursday, November 12, 2015, 5:28:41 pm.

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

Responsible Party:

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

Comment 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

Fungi, Plant Pathogens

Phakopsora phyllanthi Dietel 1910

California Pest Rating for
Phakopsora phyllanthi Dietel 1910
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On December 4, 2015, a shipment of cut foliage of an unidentified plant species was intercepted at the USPS West Sacramento Distribution Center by the CDFA Dog Team.  The shipment had originated in Florida and was destined to a private owner in Merced County, California.  A sample of the symptomatic foliage was collected from the shipment and sent to the CDFA Plant Pathology Laboratory for pathogen diagnosis.  On January 20, 2016, Suzanne Latham, CDFA plant pathologist, identified the rust fungal pathogen, Phakopsora phyllanthi associated with the diseased leaves and confirmed the identification by PCR sequencings.  Subsequently, the shipment was destroyed (Martyn, 2016).  On further investigation, USDA APHIS PPQ and Florida Department of Agriculture and Consumer Services communicated to Suzanne Latham, CDFA, that P. phyllanthi had been detected in three locations in Florida on February 18, 2016 (Latham, 2016).  The risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is proposed.

History & Status:

Background:  Phakopsora phyllanthi is a fungal pathogen that causes rust disease in Phyllanthus spp. (‘gooseberry’).  The pathogen has only been detected on certain species of the plant genus primarily grown in tropical and subtropical regions of the globe.  In 2015, Phakopsora phyllanthi was first reported in the USA from Hawaii (Dietrich & Ko, 2015), and later in 2016, from Florida (Latham, 2016).  The pathogen is not known to be present in California and was detected for the first time in an intercepted shipment of cut foliage from Florida, which was subsequently destroyed (see ‘Initiating Event’).  The plant genus, Phyllanthus (Phyllanthaceae) contains several hundred species, however, only one species, P. caroliniensis subsp. caroliniensis (Carolina leaf-flower) native to the eastern United States, is known to be present in San Diego County as an introduced annual plant (Calflora, 2016).

Disease cycle:  The life cycle of Phakopsora phyllanthi is not fully known.  Teliospores (the sexual, overwintering stage of the fungus), have not been observed nor is it known if the pathogen needs an alternate host to complete its life cycle (Dietrich & Ko, 2015).  It is likely, but not proven, that P. phyllanthi is spread to non-infected hosts via production of urediniospores only.

Dispersal and spread: Urediniospores are spread by wind and splashing rain.  Insects, animals, and humans may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

Hosts:  Phyllanthus acidus (synonyms: Cicca acida, P. distichus; Tahitian gooseberry), P.benguetensis, P. emblica (Indian gooseberry), P. niruri (gale of the wind), P. phyllanthi, Phyllanthus sp. (Dietrich & Ko, 2015; Farr & Rossman, 2016).  Some Phyllanthus species such as, P. emblica and P. acidus are cultivated for fruit in warm climates, while other species are pantropical weeds or grown for medicinal uses – but these species are not present in California.

Symptoms:  Rust-infected Phyllanthus acidus (Tahitian gooseberry) trees may exhibit a general unthrifty appearance with thinning canopy, and barren branches or twigs.  Leaves exhibit discolored chlorotic or necrotic spots on upper and lower surfaces.  Small white-brownish raised spots or pustules containing numerous powdery urediniospores are produced on lower leaf surfaces.  Affected leaves eventually drop off.  Rust pustules and lesions are also formed on the surface of fruit (Dietrich & Ko, 2015).

Disease Potential:  Phyllanthus species, such as P. acidua (Tahitian gooseberry) and P. emblica (Indian gooseberry) grown for their fruit in tropical climates, are not commercially cultivated in California, but are probably sold by rare fruit nurseries within the State.  Infections of this rust pathogen could negatively impact production and value of plants.  In general, severe infestation of rust can result in defoliation and reduction in plant growth, vigor and stand.  Containment and management of the rust pathogen can be difficult as masses of air-borne spores produced can spread over long distances.  Backyard growers, other small, rare fruit production growers, hobbyists, and rare plant nurseries in warm and wet climates of southern California may be at particular risk.

Worldwide Distribution: Asia: China, India, Indonesia, Malaysia, Philippines, Thailand; North America: USA (Florida, Hawaii); South America: Brazil, Ecuador, French Guyana, Venezuela (Dietrich & Ko, 2015; Farr & Rossman, 2016).

Official Control: None reported.  Presently, Phakopsora phyllanthi has a temporary Q rating in California.

California Distribution:  The gooseberry rust pathogen, Phakopsora phyllanthi is not established in California.

California Interceptions:  The pathogen has only been detected once in a single intercepted quarantine shipment of unidentified cut foliage that originated in Florida (see “Initiating Event”).

The risk Phakopsora phyllanthi 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 Low (1):  Phakopsora phyllanthi may establish in very limited areas within southern California that have warm and wet climates where the tropical host, Phyllanthus spp. is able to grow.  Presently, only one species, Phyllanthus caroliniensis subsp. caroliniensis (Carolina leaf-flower) native to the eastern United States, is known to be present in San Diego County’s coastal region as an introduced annual plant. 

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 Low (1):  The host range for the pathogen is very limited and comprises of some species non-native, tropical plants belonging to the genus Phyllanthus.

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): Phakopsora phyllanthi has high reproduction and dispersal potential.  Spores are spread by wind and splashing rain.  Insects, animals, and humans may also aid in spreading spores to non-infected plants. Infected nursery plants also aid in introducing and spreading the pathogen.

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): Reported hosts of the gooseberry rust pathogen are not to be present in California and therefore, no major economic impact of this pathogen is expect within California.  However, if the pathogen was introduced, growers of rare, imported fruit plants, such as backyard growers, hobbyists, and rare plant nurseries in warm and wet climates of southern California may be at particular risk of reduced crop value.  The economic impact is evaluated to be low.

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):  Backyard growers, other small, rare fruit production growers, hobbyists, and rare plant nurseries in warm and wet climates of southern California may be at particular risk, if the pathogen were introduced into the State.

Consequences of Introduction to California for Myrtle Rust:

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 = 8 (Low).

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

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

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

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

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

Evaluation is ‘Not established’ (0).  

Final Score:

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

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

Uncertainty:

Details of the pathogen’s complete life cycle including the need of an alternate host to complete its life cycle are not presently known.  However, it is unlikely that this information will alter the proposed rating for the pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for gooseberry rust pathogen, Phakopsora phyllanthi is C.

References:

Calflora.  2016.  Calflora: Information on California plants for education, research and conservation [web application].  Berkeley, California: The Calflora Database [a non-profit organization].  http://www.calflora.org/

Dietrich, B., and M. Ko.  2015.  Phyllanthus Rust Phakopsora phyllanthi Dietel.  New Pest Advisory No. 15-02 October 2015, State of Hawaii Department of Agriculture.

Farr, D. F. and A. Y. Rossman.  2016.   Fungal databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved October 17, 2016 from http://nt.ars-grin.gov/fungaldatabases/.

Khan, S.  2016.  Email from K. Martyn, Yolo County, to S. Khan, CDFA, subject: “RE: Information request for A/Q/W reports”, dated February 11, 2016, forwarded to J. Chitambar, CDFA, by T. Walber, CDFA on October 18, 2016.

Latham, S.  2016.  Email from S. Latham (CDFA) to J. Chitambar (CDFA), subject: “FW: confirmed ID: Positive for gooseberry rust (Phakopsora phyllanthi) from St. Petersburg, Pinellas Co., FL.”, sent October 17, 2016.

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 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;

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♦  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

Fungi, Plant Pathogens

Pseudocercospora myrticola (Speg.) Deighton 1976

California Pest Rating for
Pseudocercospora myrticola (Speg.) Deighton 1976
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

None.  The risk of infestation of P. myrticola in California is evaluated and a permanent rating is herein proposed.

History & Status:

Background:  Pseudocercospora myrticola is a fungal plant pathogen that belongs to a larger group of Cercospora-like fungi most of which cause leaf spot symptoms in host plants. The pathogen was originally named Cercospora myrticola, and since then has also been known by several synonyms: Cercospora myrti, C. saccardoana, C. amadelpha and Fusariella cladosporioides (Crous et al., 2013; Farr & Rossman, 2016).   The pathogen is widely distributed globally and infects myrtle and several species within the family Myrtaceae, with few in Melastomataceae (Farr & Rossman, 2016). In the USA, P. myrticola has only been reported from myrtle (Myrtus communis).  In 1984, P. myrticola was first reported in the USA from Florida (Alfieri et al., 1984) and from San Diego, California in 2006 (CPPDR, 2007).  On December 4, 2013, the pathogen was detected in a decorative wreath comprising of symptomatic leaves of an unknown plant, most likely to be myrtle that had been shipped from the State of Nevada and intercepted in Sonoma County, California.

Disease cycle: Infected plants produce conidiophores (specialized hypha) that arise from the plant surface in clusters through stomata and form conidia (asexual spores) successively.  Conidia are easily detached and blown by wind often over long distances.  On landing on surfaces of a plant host, conidia require water or heavy dew to germinate and penetrate the host.  Sub-stomatal stroma (compact mycelial structure) may form from which conidiophores develop.  Development of the pathogen is favored by high temperatures and the disease is most destructive during summer months and warmer climates.  High relative humidity is necessary for conidial germination and plant infection.  The pathogen can overwinter in or on seed and as mycelium (stromata) in old infected leaves (Agrios, 2005).  

Dispersal and spread: air-currents, infected nursery plants, infected leaves, seeds.

Hosts: Blepharocalyx divaricatus, Metrosideros excela (New Zealand Christmas tree), M. parkinsonii (Parkinson’s rata), Monochaetum polyneurum, Myrciaria cauliflora (jaboticaba), Myrtus communis (common myrtle), M. communis var. latifolia, M. communis var. laurifolia, M. divaricata, Tristania suaveolens (swamp mahogany) (Farr & Rossman, 2016).

Symptoms:  Infected host plants exhibit irregular to angular, leaf spots on both leaf surfaces.  Spots are 2-4 mm in diameter, rusty-brown, abundant on the lower leaf surface, usually confluent.  Lesions or spots may be surrounded by a diffuse lighter halo (Nakashima et al., 2004).

Damage Potential: Specific losses due to Pseudocercospora myrticola have not been reported.  Photosynthetic area can be reduced due to leaf spotting.  In severe infections, leaf wilt and drop may be expected.  However, damage potential due to this pathogen is likely to be similar to other Cercospora diseases which is usually low (Agrios, 2005).  In California, myrtle is not native to California and is grown in lower coastal and some inner valley regions of the State (Calflora, 2016) in landscapes, commercial and private gardens.  Also, young branches and foliage are used in floral decorations and therefore, diseased plants could be of particular concern to production nurseries.

Worldwide Distribution: Africa: South Africa, Cape Province; Asia:  India, Japan; Europe: Cyprus, England, Republic of Georgia, Germany, Greece, Israel, Italy, Sicily, Scotland, Sweden, Yugoslavia; North America: USA (Florida, California); South America: Brazil, Chile, Paraguay; Oceania: Australia, New Zealand (Crous et al., 2013;  Farr & Rossman, 2016).

Official Control: None reported.  Presently, Pseudocercospora myrticola has a temporary ‘Q’ rating in California.

California Distribution: Pseudocercospora myrticola has been found in San Diego Counties (CDFA Plant Pest and Damage Records).

California Interceptions:  Pseudocercospora myrticola was detected in 2013 in an intercepted quarantine shipment of a plant wreath that originated in Nevada.

The risk Pseudocercospora myrticola 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): Pseudocercospora myrticola may be able to establish wherever myrtle and other hosts plants are able to grow.  Myrtle is a non-native plant in California and is grown in lower coastal and some inner valley regions in warm and humid climates.

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):  Pseudocercospora myrticola has a moderate host range that comprises common myrtle and other species within Myrtaceae, plus few species in Melastomataceae.

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):  Pseudocercospora myrticola has high reproductive potential resulting in the successive production of conidia which are dependent on air currents and infected plants and seed for dispersal and spread.

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):  Infected host plants with leaf spot symptoms could lower value of nursery-produced plants and trigger the 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): Pseudocercospora myrticola infections could significantly impact home/urban gardening and aesthetic plantings of myrtle in commercial environments, such as parks and public gardens.

Consequences of Introduction to California for Pseudocercospora myrticola:

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 = 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 Low (-1): Pseudocercospora myrticola has been found in San Diego County only.

Final Score:

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

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 10

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Pseudocercospora myrticola is B.

References:

Agrios, G. N.  2005.  Plant Pathology (Fifth Edition).  Elsevier Academic Press, USA.  922 p.

Alfieri Jr., S. A., K. R. Langdon, C. Wehlburg, and J. W. Kimbrough.  1984.  Index of Plant Diseases in Florida (Revised). Florida Department of Agriculture and Consumer Service, Division of Plant Industry Bulletin 11: 1-389.  In [Farr, D. F.  & A. Y. Rossman, 2016. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved October 19, 2016, from http://nt.ars-grin.gov/fungaldatabases/ ].

Crous, P.W., U. Braun, G. C. Hunter, M. J. Wingfield, G. J. M. Verkley, H. D. Shin, C. Nakashima, and J. Z. Groenewald.  2013.  Phylogenetic lineages in Pseudocercospora. Studies in Mycology 75: 37-114.

Calflora.  2016.  Information on California plants for education, research and conservation. [Web application].  Berkeley, California: The Calflora Database [a non-profit organization]. http://www.calflora.org/

CPPDR.  2007.  Plant pathology A & Q rated pathogen & hosts detected by county.  California Plant Pest & Disease Report, California Department of Food and Agriculture July 2005 through December 2006 23(1): 113-115.

Farr, D.F., & A. Y. Rossman.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved October 19, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

Nakashima, C., H. Horie, and T. Kobayashi.  2004.  Addition and reexamination of Japanese species belonging to the genus Cercospora and allied genera.  VI. Four Pseudocercospora species from Ohshima Island, Tokyo.  Mycoscience 45: 49-55.  DOI 10.1007/s10267-003-0151-y

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 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

Fungi, Plant Pathogens

Neofusicoccum mangiferae (Syd. & P. Syd.) Crous, Slippers & A. J. L. Phillips, 2006

California Pest Rating for
Neofusicoccum mangiferae (Syd. & P. Syd.) Crous, Slippers & A. J. L. Phillips, 2006
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

The current status and rating of Neofusicoccum mangiferae in California is reassessed and a permanent rating is proposed.

History & Status:

Background:  Neofusicoccum mangiferae is a fungal plant pathogen belonging to the family Botryosphaeriaceae.  The species was originally named Dothiorella mangiferae but since then has undergone several taxonomic revisions and is also been known as Nattrassia mangiferae, Fusicoccum mangiferae, and Hendersonula cypria (Crous et al., 2006; Farr & Rossman, 2016).

In California, Neofusicoccum mangiferae is widespread and has been found in different hosts including walnut and fig causing branch wilt and limb dieback (Michailides et al., 2007), in citrus causing branch and trunk canker (Eskalen et al., 2011) and Indian leaf-laurel fig causing ‘Sooty Canker’ disease (as syn. Nattrassia mangiferae) which severely damaged street plantings of Indian leaf-laurel fig in southern California (Hodel, et al., 2009; Mayorquin et al., 2012).  In addition, during 2015-16, CDFA plant pathologists identified the pathogen from diseased mango and avocado fruit that were intercepted in shipments from Florida to California. In natural infestations, the pathogen is often found in combination with other fungal species.

Disease development:  In Indian laurel-leaf fig and other host plants, Hodel et al., (2009) reported that the pathogen enters the tree primarily through bark wounds produced by mechanical damage, pruning, freezing weather, sunburn, insects, or other diseases.  Smooth, thin-barked trees or those stressed from insufficient water and other factors are especially susceptible to the disease.  The fungus and disease develops most rapidly in warm temperatures (85-105°F) under high humidity. Slightly sunken cankers develop at the wound and point of infection on branches and may expand as the disease progresses.  Once the disease expands to the trunk, the tree dies.  Small, black, pencil-point size fungal fruiting bodies are formed on the cankers while the underlying infected sapwood inside the bark is stained grey to black and sharply demarcated from adjacent light-colored, healthy tissue.   Masses of dark spores are produced by the fruiting bodies and dispersed by wind, rain splash, pruning tools, and insects.

Dispersal and spread: Wind, rain, water-splash, pruning tools, insects, and animals can spread fungal spores to non-infected plants.

Hosts: Agathis spp. (kauri; Araucariaceae), Castanea sativa (European chestnut; Fagaceae), Dioscorea rotundata (white yam; Dioscoreaceae), Eucalyptus grandis (flooded/rose gum; Myrtaceae), Mangifera indica (mango; Anacardiaceae), Manihot esculenta (cassava; Euphorbiaceae), Persea americana (avocado; Lauraceae), Prunus armeniaca (ansu apricot; Rosaceae), Phoenix dactylifera (date palm; Arecaceae), Cupressus (cypress; Cupressaceae), Robina pseudoacacia (black locust; Fabaceae), Tibouchina urvilleana (glory bush/purple glory tree; Melastomataceae), Ficus microcarpa (Indian laurel-leaf fig; Moraceae)) F. carica (edible fig: Moraceae), Juglans regia (English walnut; Juglandaceae), Citrus sp. (citrus; Rutaceae) (El-Trafi, 2010; Farr & Rossman, 2016; French, 1989; Heath et al., 2011; Mayorquin et al., 2012; Michailides et al., 2007; Nazerian et al., 2015).  Vitis vinifera (grape: Vitaceae) was reported as a host of Neofusicoccum mangiferae in China (Dissanayake et al., 2015).

Symptoms: Neofusicoccum mangiferae causes blight of inflorescences, rachis, and branches of infected host plants.  Symptoms include branch and trunk cankers, branch wilt and dieback, lesions and rot of fruit, rachis and flower discoloration and necrosis.

The pathogen has been reported to be associated with rachis necrosis and inflorescence blight in mango in Puerto Rico (Serrato-Diaz et al., 2014), lesions and progressive rot in mango and avocado fruit in Taiwan (Ni et al., 2009, 2010), Walnut branch wilt, fig branch dieback, citrus branch and/or trunk cankers, branch dieback and tree death symptoms of sooty canker disease in Indian laurel-leaf fig trees in California (Eskalen et al., 2011; Michailides et al., 2007; Hodel et al., 2009). In China, symptoms associated with grapevine dieback were characterized by partial or total death of affected cordons, with brown U-shaped necrotic sectors and brownish-black spot in cross-sections of affected trunks and arms (Dissanayake et al., 2015).

Damage Potential: In mango, disease incidences of 20-100% have been reported (Serrato-Diaz et al., 2014; El-Trafi, 2009) as well as 30-72% rot disease in stored mango fruit (Ni et al., 2010).  In several cities in Los Angeles County, California, the pathogen has devastated landscape plantings of Indian laurel-leaf fig tree by causing severe damage and death (Hodel et al., 2009).  Branch and trunk canker of citrus and other tree hosts may lead to decline or death of branches and whole plants (Eskalen et al., 2011; Michailides et al., 2007).

Worldwide Distribution: Asia: India, Iran, Myanmar, Pakistan, Taiwan; Africa: Benin, Nigeria, South Africa, Sudan; Europe: Cyprus; North America: Arizona, California, Hawaii, Washington, West Virginia; South America: Uruguay; Caribbean: Puerto Rico; Australia (CABI, 2016; USDA ARS, 2016; Farr & Rossman, 2016).

Official Control: None reported.

California Distribution: Neofusicoccum mangiferae is widespread in California in northern and southern coastal and valley counties including, Fresno, Los Angeles, Riverside, San Diego, San Luis Obispo, Tulare, and Ventura Counties (Eskalen et al., 2011; French, 1989; Hodel et al., 2009; Mayorquin et al., 2012).

California Interceptions:  From June 2014 to August 2016, Neofusicoccum mangiferae has been detected in eight shipments of mango and one shipment of avocado fruit imported to California (CDFA Pest and Damage Records).

The risk Neofusicoccum mangiferae 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):  Neofusicoccum mangiferae is able to establish in California under warm to hot and very humid climates.  Already, it is distributed within the State in certain southern and northern coastal and valley counties.

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):  Neofusicoccum mangiferae has a moderate and diverse host range. In California it has been found in Indian laurel-leaf fig tree, edible fig, citrus, avocado, and chestnut.  It has been detected in intercepted shipments of mango and avocado fruit.

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 Medium (2): Numerous numbers of spores are produced by this pathogen due to its high reproduction.  However, spore dispersal to non-infested hosts is dependent on external factor such as wind, water-splash, rain, infected pruning tools, insects, and animals. Therefore, it is given a Medium score.

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): Neofusicoccum mangiferae could lower crop yield, value, increase production costs, require changes in normal pruning practices, and can be spread by insects and animals, thereby, qualifying it for a high score for economic impact.

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): Infections of tree hosts used as commercial landscape, ornamental and private gardens plantings could result in disrupting natural communities in those environments, subsequently requiring official or private treatments.

Consequences of Introduction to California for Neofusicoccum mangiferae:

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 High (-3): Neofusicoccum mangiferae has been reported from certain southern and northern coastal and valley counties.

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 Neofusicoccum mangiferae is C.

References:

CABI.  2016.  Neofusicoccum mangiferae datasheet (basic).  http://www.cabi.org/cpc/datasheet/115758 .

Crous, P. W., B. Slippers, M. J. Wingfield, J. Rheeder, W. F. O. Warasas, A. J. L. Philips, A. Alves, T. Burgess, P. Barber, and J. Z. Groenewald.  2006.  Phylogenetic lineages in the Botryosphaeriaceae.  Studies in Mycology 55: 235-253.

Dissanayake, A. J., W. Jhang, X. Li, Y. Zhou, T. Chethana, E. Hukeatirote, K. D. Hyde, J. Yan, G. Zhang, and W. Zhao.  2015.  First report of Neofusicoccum mangiferae associated with grape dieback in China.  Phytopathologia Mediterranea temp25-30.  DOI: 10.14601/Phytopathol_Mediterr-15159.

El-Trafi, M. A.  2010.  Studies on mango branch wilt disease caused by Neofusicoccum mangiferae.  FAO Agris Records.  http://agris.fao.org/openagris/search.do?recordID=SD2010000222 .

Eskalen, A., A. Adesemoye, and D. Wang.  2011.  Identification of different species causing Botryosphaeriaceae canker in citrus reveal Neofusicoccum mangiferae with Scytalidium-like synanomorph.  Phytopathology, 101: S49.

Farr, D.F., & A. Y. Rossman.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved January 28, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

French, A.M. 1989. California Plant Disease Host Index. California Department of Food and Agriculture, Sacramento, 394 pages.

Heath, R.N., J. Roux, B. Slippers, A. Drenth, S. R. Pennycook, B. D. Wingfield, and M. J. Wingfield.  2011.  Occurrence and pathogenicity of Neofusicoccum parvum and N. mangiferae on ornamental Tibouchina species. Forest Pathology, 41: 48-51.

Hodel, D. R., A. J. Downer, and D. M. Mathews.  2009.  Sooty canker, a devastating disease of Indian laurel-leaf fig trees.  Western Arborist 35: 28-32.

Mayorquin, J. S., A. Eskalen, A. J. Downer, D. R. Hodel, and A. Liu.  2012.  First report of multiple species of the Botryosphaeriaceae causing bot canker disease of Indian laurel-leaf fig in California.  Plant Disease, 96:459. http://dx.doi.org/10.1094/PDIS-08-11-0714.

Michailides, T. J., D. P. Morgan, D. Felts, and H. Reyes.  2007.  Emerging fungal diseases in fruit and nut crops in California.  Phytopathology, 97: S170.

Nazerian, E., H. R. Naji, H. Abdul-Hamid, and M. Moradi.  2015.  Phenotypic and molecular characterization of Neofusicoccum mangiferae, the causal agent of black locust decline.  Journal of Plant Pathology and Microbiology, 6: 1. http://dx.doi.org/10.4172/2157-7471.1000250 .

Ni, H. F., R. F. Liou, T., H. Hung, R. S. Chen, and H. R. Yang.  2010. First report of fruit rot disease of mango caused by Botryosphaeria dothidea and Neofusicoccum mangiferae in Taiwan.  Plant Disease 94: 128. http://dx.doi.org/10.1094/PDIS-94-1-0128C

Ni, H. F., R. F. Liou, T., H. Hung, R. S. Chen, and H. R. Yang.  2009.  First report of a fruit rot disease of avocado caused by Neofusicoccum mangiferae.  Plant Disease 93: 760. http://dx.doi.org/10.1094/PDIS-93-7-0760B

Serrato-Diaz, L. M., L. I. Rivera-Vargas, and R. D. French-Monar.  2014.  First report of Neofusicoccum mangiferae causing necrosis and inflorescence blight of Mango (Mangifera indica) in Puerto Rico.  Plant Disease 98: 570. http://dx.doi.org/10.1094/PDIS-08-13-0878-PDN

USDA ARS.  2016.  Fungi on Mango in India, but not found in the U.S.A.  U.S. Department of Agriculture, Agricultural Research Service, Systematic Mycology and Microbiology Laboratory – Nomenclature Fact Sheets.  July 7, 2016. http://nt.ars-grin.gov/sbmlweb/onlineresources/nomenfactsheets/rptBuildFactSheet_onLine.cfm?thisName=Fungi%20on%20Mango%20in%20India&currentDS=specimens .

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

Responsible Party:

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

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Pest Rating: C

Posted by ls

Fungi, Plant Pathogens

Fusarium brachygibbosum Padwick 1945

California Pest Rating for
Fusarium brachygibbosum Padwick 1945
Pest Rating: C  
PEST RATING PROFILE
Initiating Event: 

On July 18, 2016, CDFA plant pathologists were notified by Dr. R. Bostock, Professor, Department of Plant Pathology, University of California, Davis, of a fungal pathogen, Fusarium brachygibbosum, detected in cold-stored, bare-root nursery almond trees in California. This detection marked a first report of the pathogen in California.  Therefore, a risk analysis of F. brachygibbosum to California agriculture and environment was conducted and a permanent rating is proposed here for the otherwise non-rated pathogen.

History & Status:

Background: In California, Seidle et al. (2016) reported the first detection of Fusarium brachygibbosum from asymptomatic, cold-stored, bare-root propagated almond (Prunus dulcis) trees.  Samples had been collected in fall 2013, from a nursery in Sutter County.

In 2011, that same nursery had experienced the re-emergence of a canker disease that occurred in the late 1900s.  During the winter of 1997-98, a severe canker disease developed during cold storage of dormant almond trees and other fruit tree species in several nurseries in California.  Fusarium acuminatum and F. avenaceum were identified as the primary causal agents of the disease.  The predominant symptoms were necrosis of the inner bark, cambium, and sapwood, which in severe cases, resulted in girdling and death of trees. However, in the absence of external symptoms, internal necrosis was not readily evident in dark-bark trees, but detectable in light-bark trees.  Notably, the canker phase of Fusarium-infected young trees did not become apparent unless predisposed by some physiological stresses.  Consequently, infected trees were distributed to growers and the disease that developed under abiotic stress factors, including desiccation and variable cold storage temperatures, resulted in loss of thousands of trees, newly planted orchards, and millions of dollars (Marek et al., 2013). Fusarium acuminatum and F. avenaceum were also detected along with F. brachygibbosum in the 2013 almond samples reported by Seidle et al. (2016).  The ability to detect F. brachygibbosum during the last few years than earlier was likely due to the availability of molecular tools for distinguishing this pathogen from other Fusarium species associated with nursery trees and storage/processing facilities and fields (Personal communication: Dr. R. M. Bostock, Professor, Department of Plant Pathology, University of California, Davis).

Fusarium brachygibbosum has been found on diverse host species within five plant families and reported from few countries in Asia, Africa, and North America (see ‘Worldwide Distribution’).

Hosts: Citrullus lanatus (watermelon; Cucurbitaceae), Euphorbia larica (spurge; Euphorbiaceae), Sorghum vulgare (broom corn; Poaceae), Triticum spp.  (wheat; Triticeae), Prunus dulcis (syn. P. amygdalus, almond; Rosaceae) (Al-Mahmooli et al., 2013; Farr & Rossman, 2016; Mirhosseini et al., 2014; Renteria-Martinez et al., 2015; Seidle et al., 2016; Van Coller et al., 2016).

Symptoms:  Fusarium brachygibbosum is associated with symptoms of wilting, dieback, and cankers and has often been found infecting plants with a complex of fungi species.  Therefore, symptoms particular to the species have only been demonstrated experimentally through pathogenicity tests.  In pathogenicity tests using almond branches inoculated with F. brachygibbosum and incubated at 15°C for two weeks, Siedle et al. (2016) found that canker lesions (area: 26.7 mm2 to 83.0 mm2) developed, comparable to those produced by F. acuminatum and F. avenaceum. Additionally, F. brachygibbosum was found in asymptomatic almond rootstock.  Experimentally in watermelon, F. brachygibbosum produced variable sized light brown colored lesion at neck and root causing wilting of leaves or whole plants (Renteria-Martinez et al., 2015). The pathogen produced dark brown to black, circular to elliptical leaf spots in oleander (Mirhosseini et al., 2014).  In South Africa, F. brachygibbosum was isolated along with several other Fusarium species from kernels of field-grown wheat exhibiting symptoms of Fusarium head blight disease (Van Coller et al., 2013).

Disease cycle: While the disease cycle has not been reported specifically for Fusarium brachygibbosum, it is likely that it is similar to other Fusarium species causing canker and wilt disease.  Generally, Fusarium species inhabit soils and plants.  They can exist saprophytically, but can also act as opportunistic pathogens.  On hosts predisposed by stress, as in cold storage temperatures, or in combination with other pathogens, symptoms may become severe.  The pathogen overwinters as mycelium or spores in infested crop residues and seed, or as chlamydospores (thick walled asexual spores) in soil, and produces asexual spores (microconidia and macroconidia) which are dispersed to plants and other plant debris by wind or rain-splash. Generally, under warm and humid conditions, sexual spores are produced which are forcibly discharged into the air and transmitted by wind currents to susceptible plants where infection and further development of the pathogen occur.

Damage Potential: Precise losses due to Fusarium brachygibbosum have not been reported.  More than one Fusarium species and/or other fungal species may be present in cold-stored canker diseased nursery stock (Marek et al., 2013).  Fusarium brachygibbosum may remain cryptic and asymptomatic within the host, and the canker phase does not become apparent unless young trees are subjected to some physiological stress. Asymptomatic, infected nursery trees may result in the development of the disease and losses in production in the field.

Transmission: Infected plants, roots, stems, leaves, seeds (Van Coller et al., 2016), plant debris, soil, air currents, rainwater splash, and contaminated equipment.

Worldwide Distribution: Asia: India, Iran, Oman; Africa: South Africa; North America: Mexico, USA (California) (Al-Mahmooli et al., 2013; Farr & Rossman, 2016; Mirhosseini et al., 2014; Renteria-Martinez et al., 2015; Seidle et al., 2016; Van Coller et al., 2016).

Official Control: None reported.

California Distribution: Sutter and Stanislaus Counties (Seidle et al., 2016). However, suspected to be widespread in California (R. M. Bostock, Professor, Department of Plant Pathology, University of California, Davis: personal communication).

California Interceptions:  None reported.

The risk Fusarium brachygibbosum 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) – In California, Fusarium brachygibbosum was detected in young almond nursery rooting predisposed to cold storage temperatures.  It was also isolated from soil under almond production (Seidle et al., 2016), and is suspected to be widespread within California.  The disease is likely to establish primarily in nurseries with bare-root propagative almond plants predisposed to abiotic stresses – including temperature variations in cold storage, and in almond production fields within California.  Watermelon is a reported host of the pathogen (although not reported from California) and may also be affected by the disease.

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 Low (1) – Presently, the known host range of Fusarium brachygibbosum is limited to watermelon, almond, wheat, spurge, and broom corn.

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) – Fusarium brachygibbosum has high reproduction and dispersal potential through infected plants, roots, stems, leaves, seeds, soil, plant debris, air currents, rainwater splash, and contaminated equipment.

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) – Quantitative estimates of losses in crop yield have not been reported, however, based on losses caused by the complex of other Fusarium species also detected in cold-stored almond tree seedlings in California (Marek et al., 2013), significant loss in crop production, value and yield is possible. However, development of the pathogen and production of visible disease symptoms in young trees is subject to predisposing physiological stresses.

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

 Risk is Low (1) – The pathogen has not been reported to significantly impact the environment.  However, leaf spots caused by the pathogen in infected ornamental oleander have been reported (but not from California). 

Consequences of Introduction to California for Fusarium brachygibbosum:

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 Fusarium brachygibbosum to California = (10).

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

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

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

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

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

Evaluation is Medium (-2).  Fusarium brachygibbosum has been detected in cold-stored young almond rootings in Sutter and Stanislaus Counties, however, the pathogen is suspected to be widespread 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 = 8

Uncertainty:

The full distribution of Fusarium brachygibbosum in California needs to be confirmed.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Fusarium brachygibbosum is C.

References:

Al-Mahmooli, I. H., Y. S. Al-Bahri, A. M. Al-Sadi, and M. L. Deadman.  2013.  First report of Euphorbia larica dieback caused by Fusarium brachygibbosum in Oman. Plant Disease, 97(5):687. http://apsjournals.apsnet.org/loi/pdis.

CABI.  2016.  Fusarium brachygibbosum basic datasheet.  Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/119707.

Farr, D.F., and A. Y. Rossman.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved January 28, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

Marek, S. M., M. A. Yaghmour, and R. M. Bostock.  2013.  Fusarium spp., Cylindrocarpon spp., and environmental stress in the etiology of a canker disease of cold-stored fruit and nut tree seedlings in California.  Plant Disease 97: 259-270.  http://dx.doi.org/10.1094/PDIS-04-12-0355-RE .

Mirhosseini, H. A., V. Babaeizad, and L. Hashemi.  2014.  First report of Fusarium brachygibbosum causing leaf spot on oleander in Iran. Journal of Plant Pathology, 96(2):431. http://www.sipav.org/main/jpp/.

Renteria-Martinez, M. E., A. Meza-Moller, M. A. Guerra-Camacho, F. Romo-Tamayo, A. Ochoa-Meza, S. F. Moreno-Salazar.  2015.  First report of watermelon wilting caused by Fusarium brachygibbosum in Sonora, Mexico. Plant Disease, 99(5):729. http://apsjournals.apsnet.org/loi/pdis.

Seidle, A. J., M. A. Yaghmour, S. C. Kirkpatrick, T. R. Gordon, and R. M. Bostock.  2016.  First report of Fusarium brachygibbosum causing cankers in cold-stored, bare-root propagated almond trees in California.  (Submitted for publication: Plant Disease, shared with J. Chitambar, CDFA, August, 2016).

Van Coller, G. J., A. -L. Boutigny, L. Rose, T. J. Ward, S. C. Lamprecht, and A. Viljoen.  2013.  Head blight of wheat in South Africa is associated with numerous Fusarium species and chemotypes.  Conference paper: 12th European Fusarium Seminar, at Palais de la Bourse, Bordeaux, France, May 2013.  https://www.researchgate.net/publication/269700231_Head_blight_of_wheat_in_South_Africa_is_associated_with_numerous_Fusarium_species_and_chemotypes

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.

Pest Rating: C

Posted by ls 

Plant Pathogens, Viruses and viroids

Freesia Mosaic Virus

California Pest Rating for
Freesia Mosaic Virus
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On March 21, 2016, two samples of diseased Lilium sp. (lily) plants exhibiting leaf spots, were collected from a nursery in San Luis Obispo County, during a regulatory nursery inspection by San Luis Obispo County Agricultural officials, and sent to the CDFA Plant Pathology Laboratory for analysis.  Tongyan Tian, CDFA plant pathologist, identified two pathogens associated with the sample, namely, Freesia mosaic virus (FreMV) and Freesia sneak virus (FreSV). Freesia mosaic virus was assigned a temporary Q rating by the CDFA, whereas FreSV already has a permanent B rating.  Subsequently, all infected propagative plant material was destroyed.  The risk of infestation of FreMV in California is evaluated and a permanent rating is proposed here.

 History & Status:

Background:  Freesia mosaic virus is a plant virus belonging to the genus Potyvirus in the family Potyviridae, and is vectored by the potato aphid, Macrosiphum euphoribae and green peach aphid, Myzus persicae.   Freesia mosaic virus (FreMV) was originally reported from Freesia refracta, in Lisse, the Netherlands, by Van Koot et al. in 1954 (Brunt, et al., 1996 onwards; Van Koot et al., 1954).  This pathogen, along with few other plant virus pathogens, has been reported to naturally infect freesia plants (Van Koot et al., 1954; Bouwen, 1994).  In the Netherlands, Freesia mosaic virus was frequently found in field samples of freesia plants with and without symptoms of freesia leaf necrosis disease and, more or less frequently in double infections with Freesia sneak virus in the same plants (Vaira et al., 2006; Meekes & Verbeek, 2011).  Freesia leaf necrosis disease has been reported in Europe since the 1970s and double infections of FreMv and FreSV in freesia plants were first described as “severe leaf necrosis” or “complex disease” which is progressive and may cause death of plants before flowering (Van Dorst, 1973; Meekes & Verbeek, 2011).  The natural occurrence of FreMV has also been found in Peruvian lily in Italy, and besides its spread in Europe, the pathogen has been reported from Freesia spp. in India, Australia, Korea, and New Zealand (Bellardi, 1992; Brunt et al., 1996 onwards; Kumar, et al., 2008; Jeong et al., 2014).

In the USA, Freesia mosaic virus was reported from infected Freesia spp. in Virginia in 2009 (Vaira et al., 2009).  The pathogen was first detected in California, in symptomatic freesia plant samples collected during April 2014, from a nursery in San Luis Obispo County, and identified by Tongyan Tian, CDFA plant pathologist.  Subsequently, all infected plant material was destroyed.

Hosts: Freesia spp. F. refracta, (common freesia; Iradaceae) and Alstroemeria sp. (Peruvian lily; Alstroemeriaceae).  Freesia and Peruvian lily are monocots and although presently naturalized in several countries including the USA, both plant species are native to South Africa and South America respectively (Bellardi, 1992; Brunt et al., 1996 onwards). Freesia mosaic virus was also detected in Lily (Lilium sp.) by the CDFA (see ‘Initiating Event’) and is included as an associated host.

Symptoms:  Symptoms of Freesia mosaic virus-infected freesia plants include mild chlorosis. The pathogen may also be present in symptomless plants (Brunt et al., 1996 onwards).  Experimentally, Alstroemeria sp. plants that were mechanical inoculated FMV infested plant sap, failed to show symptoms three months after inoculation, although the virus was detected serologically (Bellardi, 1992).

Complex infections of Freesia mosaic virus and Freesia sneak virus may result in severe leaf necrosis showing symptoms of chlorotic spots and stripes that appear on the first leaf of freesia plants grown from corms, and later turn grey-brown and necrotic as the disease progresses rapidly often resulting in rot of corms, and death of plants before flower formation (Van Dorst, 1973).

Damage Potential: In California, nursery and private productions of freesia and lily plants may be impacted if infected with FreMV.

Transmission: In nature, Freesia mosaic virus is transmitted by the potato aphid, Macrosiphum euphorbiae and green peach aphid, Myzus persicae.  It is also transmitted by mechanical inoculation and spread via infected nursery plants and propagative parts.   The virus pathogen is not transmitted by seed, pollen or contact between plants (Brunt et al., 1996 onwards).

Worldwide Distribution:  Asia: India, Korea; Europe: United Kingdom, Ireland, Italy, the Netherlands; North America: USA (Virginia); Australia; New Zealand (found, but with no evidence of spread) (Bellardi, 1992; Brunt, et al., 1996 onwards; Kumar et al., 2008; Jeong et al., 2014; Vaira et al., 2009).

Official Control: Freesia mosaic virus is on the ‘Harmful Organism List’ for Colombia, Georgia, Israel, Japan, Peru, and Taiwan (USDA-PCIT, 2016).  Currently, FreMV has a temporary Q-rating in California.

California Distribution: San Luis Obispo (nursery).

California Interceptions: There have not been any interceptions of Freesia mosaic virus-infected plants entering California.

The risk Freesia mosaic virus 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) – Freesia mosaic virus is likely to establish wherever freesia and Peruvian lily and lily plants are grown in limited areas of California. These host plant species have limited production in state, mostly in the north coast and mountain regions, and few southern coast regions, as well as cultivated in nursery and private production sites – including home gardens.       

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 Low (1) – Freesia mosaic virus is limited to Freesia spp. (Iradaceae), Alstroemeria sp. (Alstroemeriaceae), and Lilum spp. (Liliaceae).

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 Medium (2) – Freesia mosaic virus has high reproductive potential.  In nature, its spread to non-infected plants is through aphid vectors, Macrosiphum euphorbiae and Myzus persicae.  It is also transmitted by mechanical inoculation and spread via infected nursery plants and propagative parts.   The virus pathogen is not transmitted by seed, pollen or contact between 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) – Incidents of Freesia mosaic virus infections could lower plant value resulting in loss in market sales of nursery-grown freesia and lily plants.  The pathogen is vectored by the potato aphid and green peach aphid, Macrosiphum euphorbiae and Myzus persicae respectively.

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) – Plant infections caused by Freesia mosaic virus are likely to have a minimal impact on the overall environment but may significantly impact home gardening and ornamental plantings. The pathogen may impact California State and federal endangered western lily (Lilium occidentale) and Pitkin Marsh lily (L. pardalinum ssp. pitkinense (ref: State and Federally listed endangered, threatened, and rare plants of California, July, 2015, California Department of Fish and Wildlife, Biogeographic Data Branch, California Natural Diversity Database).

Consequences of Introduction to California for Freesia mosaic virus

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 Freesia mosaic virus to California = 10.

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

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

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

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

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

Evaluation is not established.  Freesia mosaic virus-infected freesia plants have only been detected in a contained nursery environment in California.  Those plants were subsequently destroyed and therefore, the pathogen is not considered established in 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 = 10.

Uncertainty:

Currently, the possible distribution of Freesia mosaic virus in California is not known.  Future confirmed detection of its in-state presence and distribution may affect its overall score and alter its current proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Freesia mosaic virus is B.

References:

Bellardi, M. G.  1992.  Natural occurrence of Freesia mosaic virus in Alstroemeria sp.  Plant Disease 76:643. DOI: 10.1094/PD-76-0643B.

Bouwen, I.  1994.  Freesia leaf necrosis: some of its mysteries revealed.  Virus Diseases of Ornamental Plants VIII, Acta Horticulturae 377: 311-318.

Brunt, A.A., K. Crabtree, M. J. Dallwitz, A. J. Gibbs, L. Watson, and  E. J. Zurcher. (eds.) (1996 onwards). `Plant Viruses Online: Descriptions and Lists from the VIDE Database. Version: 16th January 1997.’ URL http://biology.anu.edu.au/Groups/MES/vide/

Jeong, M. I., Y. J. Choi, J. H. Joa, K. S. Choi, and B. N. Chung.  2014.  First report of Freesia sneak virus in commercial Freesia hybrida cultivars in Korea.  Plant Disease 95:162. http://dx.doi.org/10.1094/PDIS-05-13-0484-PDN.

Kumar, Y., V. Hallan, and A. A. Zaidi.  2008.  First finding of Freesia mosaic virus infecting freesia in India.  New Disease Reports 18:3. http://www.ndrs.org.uk/article.php?id=018003.

Meekes, E. T. M., and M. Verbeek.  2011.  New insights in Freesia leaf necrosis disease.  Proceedings XIIth IS on Virus Diseases of Ornamental Plants; Editors A. F. L. M. Derks et al.  Acta Horticulturae  901, ISHA 2011.

USDA- PCIT.  2016.  USDA Phytosanitary Certificate Issuance & Tracking System. June 6, 2016.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp .

Vaira, A. M., V. Lisa, A. Costantini, V. Masenga, S. Rapetti, and R. G. Milne.  2006.  Ophioviruses infecting ornamentals and a probable new species associated with a severe disease in Freesia.  Proceeding XIth IS on Virus Diseases in Ornamentals, Ed. C. A. Chang.  Acta Horticulturae 722, ISHA 2006.

Van Dorst, H. J. M.  1973. Two new disorders in freesias.  Netherland Journal of Plant Pathology 79:130-137.

Van Koot, Y., D. H. M. van Slogteren, M. C. Cremer, and J. Camfferman.  1954.  Virusverschijnselen in freesia’s.  Tijdschrlfot over Planienziekten 60:157-192

Responsible Party:

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

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 Pest Rating: B

Posted by ls