Category Archives: Fungi

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.

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, Ratings

Stemphylium solani G. F. Weber 1930

California Pest Rating for
Stemphylium solani G. F. Weber 1930
Pest Rating: A
PEST RATING PROFILE
Initiating Event:

On March 31, 2017, the CDFA Permits and Regulations Program requested a rating for Stemphylium solani.  Therefore, the associated risk and current status of S. solani in California are assessed here and a permanent rating is proposed.

History & Status:

Background:   Stemphylium solani is a fungal pathogen that causes Gray leaf spot disease in tomato, and Stemphylium leaf blight disease in cotton, garlic, and other hosts.  Gray leaf spot in tomato is actually caused by three species of Stemphylium, one being S. solani and the other two species: S. lycopersici (Enjoji) W. Yaman (syn. S. floridanum Hannon & G. F. Weber) and S. botryosum Wallr. f. sp. lycopersici Rotem, Y. Cohen, & I. Wahl.  Gray leaf spot is regarded one of the most destructive diseases of tomato in the southeastern United States and throughout the world wherever warm and humid conditions prevail (Jones & Pernezny, 2014).

Gray leaf spot disease has been reported from several countries worldwide including the United States (see ‘Worldwide Distribution’). In the United States, the disease was first observed in 1924 and by 1928 had spread throughout Florida causing widespread defoliation. Since then, the pathogen has been reported from several states but has never been reported from California.

Disease development:  The disease begins in infested seedbeds and transplant houses or field-transplanted seedlings, usually when the plants are in the first true-leaf stage of growth.  Cotyledons are not severely infected.   The pathogen is spread when infected seedlings are transplanted to fields.  Conidia (asexual spores) can be spread over extensive distances by wind. The teleomorph or sexual stage of S. solani is not known.  The disease is favored by warm temperatures (24-27°C) and high humidity. Spore germination and infection of plant are dependent on the presence of free moisture (dew or rain) (Jones & Pernezny, 2014).  Leaf wetness is considered more important than temperature in establishment of infection (Cerkauskas, 2005).  Stemphylium solani survives as a saprophyte on infected plant debris or on volunteer tomato, pepper, gladiolus, blue lupine, and other wild solanaceous plants.  In the southern state climates, the pathogen remains viable on tomato plants which are grown throughout the year (Jones & Pernezny, 2014).  The pathogen can be seedborne (Koike et al., 2007).

Dispersal and spread: Infected plants, seedlings, and plant debris.  Conidia may be wind-blown over extensive areas or by splashing water (Jones & Pernezny, 2014).

Hosts: Hosts of Stemphylium solani are included primarily in the plant family Solanaceae.  Numerous other plant families are also included with their associated hosts, including Amaryllidaceae (Allium sp.), Asteraceae (Lactuca sp.), and Malvaceae (Gossypium hirsutum).  Hosts include, Aegiceras corniculatum (black mangrove), Allium sativum (garlic), Aster sp. (aster), Basella rubra (Malabar spinach), Capsicum annuum (bell pepper), C. annuum var. annuum (cayenne pepper), C. frutescens (chili pepper), Carthamus sp. (distaff thistles), Cirsium sp. (thistle), Citrus sp. (citrus), Convolvulus arvensis (field bindweed), Cucumis sativus (cucumber), Dactylis glomerata (orchardgrass), Dianthus caryophyllus (carnation), Gossypium hirsutum (upland cotton), Ipomoea reptans (synonym: I. aquatica, swamp morning-glory), Kalanchoe blossfeldiana (flaming katy), Lactuca sativa (lettuce), Lupinus angustifolius (narrowleaf lupine), Lupinus sp. (lupine), Lycopersicon esculentum (synonym: L. lycopersicum, tomato), Lycopersicon sp., Pelargonium zonale (horse-shoe pelargonium), Physalis pubescens (husk tomato), Physalis sp. (groundcherry), Solanum gilo (gilo), S. lycocarpum (wolf apple), S. lycopersicum (garden tomato), S. melongena (aubergine/eggplant), S. melongena var. esculentum, S. pseudocapsicum (Jerusalem cherry), S. tuberosum (potato), Vicia faba (fava bean), Vigna sinensis (synonym: V. unguiculata, cowpea) (CABI, 2017; Farr & Rossman, 2017).

Symptoms:  Gray leaf spots or lesions are almost entirely limited to the leaf blades, but under favorable conditions, lesions may develop on petioles and on the more tender parts of growing stems.  Lesions on stems are linear and parallel to the stem.  Fruit symptoms have not been observed.  In infected tomatoes, symptoms of gray leaf spot are first exhibited as minute brownish-black specks on the lower leaves.  Randomly scattered circular to oblong spots develop on adaxial and abaxial leaf surfaces without being restricted by leaf veins.  The spots may be surrounded by a narrow yellow halo and enlarge to about 2.1 mm in diameter while individual spots on the base of leaves may enlarge to twice that size or more in diameter and occasionally coalesce, thereby, killing large portions of the leaf blade. As the spots enlarge, the centers turn gray, eventually dry, crack, and fall out.  Frequently, at this stage entire leaves conspicuously turn yellow, especially if the infection is severe, and die rapidly, turning brown before dropping from the plants.  Seedbed infections result in marked defoliation without conspicuous yellowing (Jones & Pernezny, 2014; Damicone & Brandenberger, 2015).  In garlic, early symptoms of S. solani infection were observed as white spots (1-3 mm), which enlarged to sunken purple lesions, extending until the leaves withered (Zheng et al., 2008).

Damage Potential:  Gray leaf spot almost entirely affects leaves, and defoliation can be severe reducing available photosynthetic areas of infected plants thereby, resulting in reductions in plant development, quality, and fruit yields.  In China, garlic leaf blight caused by Stemphylium solani affected over 7,000 ha of field production and reduced yields up to 70% (Zheng et al., 2010).  During 1994 and 1995, a severe epidemic of leaf blight of cotton in Brazil resulted in yield losses up to 100% in some commercial fields (Mehta, 1998). Gray leaf spot disease limited tomato production in Venezuela and Malaysia (Cadeño & Carrero, 1997; Nasehi et al., 2012).   In California, processing tomatoes are grown in the warm and dry San Joaquin and Sacramento Valleys while fresh-market tomatoes are grown in the San Joaquin Valley, Central Valley, Central and Southern Coastal regions and the Imperial Valley.  It is less likely that S. solani will be able establish under warm and dry regions of the state’s tomato production acreages, as well as under the possible use of resistant varieties, protectant fungicides and cultural management strategies.  However, for tomato and other host plants under wet and warm climates, the pathogen may be able to establish within those regions.

Worldwide Distribution: Asia: Brunei Darussalam, China, Hong, Kong, Taiwan, Thailand, Korea, Malaysia; Africa: Libya, Mauritius, Senegal, Sudan, Tanzania; Europe: Greece, Spain; North America: Canada, USA (Alabama, Florida, Georgia, Indiana, Louisiana, Maryland, Mississippi, North Carolina, New Jersey, South Carolina, Tennessee, Texas, Virginia); South America: Brazil, Honduras, Venezuela; Central America and Caribbean: Cuba; Oceania: American Samoa (CABI, 2017; Cadeño & Carrero, 1997; Farr & Rossman, 2017).

Official Control: Presently, Stemphylium solani is on the Harmful Organisms list for Peru (USDA-PCIT, 2017).

California Distribution: Stemphylium solani has not been reported from California.

California Interceptions: None reported.

The risk Stemphylium solani would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: Although Stemphylium solani has a wide host range that includes several economically important agricultural crops in California as well as wild solanaceous plants, the pathogen is dependent on leaf wetness for plant infection and additionally on warm temperatures for disease development.  The disease is most severe under humid and overcast climate conditions that favor wet foliage mainly due to dew or rain.  These conditions would allow the pathogen to establish in a larger but limited part of 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: Stemphylium solani has a wide host range of plants included primarily in the family Solanaceae. However, numerous other plant families are also included with their associated hosts.  Economically important crops include tomato, pepper, cotton, citrus, cucumber, lettuce, garlic, eggplant and others.  Several wild solanaceous host plants could allow build-up of fungal inoculum.

Evaluate the host range of the pest.

Score: 3

– 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: Conidia are produced in abundance and readily dispersed by wind and splashing water. Also, the pathogen is spread through infected plants, seedlings, plant debris, and seed.

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: Stemphylium solani causes gray leaf spot in tomato and peppers as well as leaf blight in other hosts. Leaves are almost always entirely affected by the disease and defoliation can be severe reducing available photosynthetic areas of plants thereby, resulting in reductions in plant development, quality, and fruit yields.  If not controlled, significant reductions in crop yield and markets could occur.  Use of fungicides and cultural management practices could increase costs of crop production.

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:  The pathogen could significantly affect home/urban gardening of agricultural crops and ornamental hosts.

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 Stemphylium solani: High (13)

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’ in 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 = 13

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Stemphylium, solani is A.

References:

CABI, 2017.  Stemphylium solani (gray leaf spot) basic datasheet.  Crop Protection Compendium. http://www.cabi.org/cpc/datasheet/51531

Cerkauskas, R.  2005.  Tomato diseases, Gray leaf spot, Stemphylium solani, S. lycopersici found worldwide in warm climates.  AVRDC – The World Vegetable Center Fact Sheet.  AVRDC Publication 05-634.

Cadeño, L., and C. Carrero.  1997.  First report of tomato gray leaf spot caused by Stemphylium solani in the Andes Region of Venezuela.  Plant Disease 81: 1332. http://dx.doi.org/10.1094/PDIS.1997.81.11.1332B

Damicone, J. P., and L. Brandenberger.  2015.  Common diseases of tomatoes Part 1.  Diseases caused by fungi.  Oklahoma Cooperative Extension Service EPP-7625.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, U. S. National Fungus Collections, ARS, USDA. Retrieved April 3, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Jones, J. P., and K. L. Pernezny.  2014.  Gray Leaf Spot.  In Compendium of Tomato Disease and Pests Second Edition.  Ed. J. B. Jones, T. A. Zitter, T. M. Momol, and S. A. Miller, APS Press. The American Phytopathological Society.  29-30 p.

Koike, S. T., P. Gladders, and A. O. Paulus.  2007.  Stemphylium solani, S. lycopersici – gray leaf spot.  In Vegetables diseases a color handbook.  Academic Press, an imprint of Elsevier, Burlington, San Diego.  211-212 p.

Mehta, Y. R.  1998.  Severe outbreak of Stemphylium leaf blight, a new disease of cotton in Brazil. Plant Disease, 82: 333-336.

Nasehi, A., J. B. Kadir, M. A. Zainal Abidin, M. Y. Wong, and F. Mahmodi.  First report of tomato gray leaf spot disease caused by Stemphylium solani in Malaysia.  Plant Disease 96: 1226.  http://dx.doi.org/10.1094/PDIS-03-12-0223-PDN

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. April 3, 2017, 1:17:10 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Zheng, L., J. B. HUANG, and T. HSIANG.  2008.  First report of leaf blight of garlic (Allium sativum) caused by Stemphylium solani in China. Plant Pathology 57: 380.

Zheng, L., L. V. Rujing, J. Huang, D. Jiang, X. Liu, and T. Hsiang.  2010.  Integrated control of garlic leaf blight caused by Stemphylium solani in China.  Canadian Journal of Plant Pathology 32: 135-145.

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: A

Posted by ls

Fungi, Plant Pathogens

Diaporthe vaccinii Shear 1931

California Pest Rating for
Diaporthe vaccinii Shear 1931
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On February 3, 2017, CDFA was requested by the USDA APHIS for information on the export of Vaccinium plants from California to the EU, in preparation of a federal risk assessment of the introduction of a quarantine fungal pathogen, Diaporthe vaccinii into the EU through USA-originated Vaccinium spp.  Subsequently, the status and risk of this pathogen in California is assessed here and a permanent rating is proposed. 

History & Status:

Background:  Diaporthe vaccinii is also known by its asexual/anamorph name, Phomopsis vaccinii, and causes stem cankers, twig blight, leafspots, and fruit rot of Vaccinium spp. (blueberries and cranberries) (EFSA, 2014).  While D. vaccinii is considered the prominent species of Diaporthe on Vaccinium spp. worldwide, there are other species within Diaporthe and Phomopsis that attack Vaccinium spp. causing diseases that include stem cankers, twig blight, and fruit rot similar to D. vaccinii  (EFSA, 2014).  Also, as symptomless (latent) infections of D. vaccinii may occur, diagnosis of the disease based on symptoms alone is not reliable but can be obtained through molecular analysis.

Diaporthe vaccinii is regarded as native to North America and has been reported from Vaccinium-growing regions in the USA and Canada (Lombard et al., 2014). During the 1960-70s twig blight disease of blueberries became a serious problem in blueberry-growing regions of Wisconsin, Indiana, and southern Michigan, and in the 1980-90s increased tremendously in prevalence and severity in the southeastern USA, particularly North Carolina (Milholland, 1995).  However, D. vaccinii is not known to be present in California and Vaccinium spp. originating in California and shipped under certification to international trading partners, continue to test free of the pathogen by CDFA (Heaton, 2017).

In California, blueberry production has been increasing over the past decade.  Blueberry cultivation is done mostly in cool northern coastal regions, however, southern cultivars with low chilling-hour requirements needed to break dormancy are also farmed in the San Joaquin Valley and southern coastal regions Bremer et al., (2008).  In 2015, blueberries were cultivated on 5,700 harvested acres in California yielding a production of 624,000 cwt for a total value of $116,979 (CASR, 2015-2016).

Disease Development:  The epidemiology of the fungus has been studied in the USA.  The pathogen overwinters in infected and dead twigs, and possibly on plant debris (fallen twigs, leaves and fruits).  Ascospores and conidia are disseminated in the crop under wet and humid conditions.  In North Carolina, rain-dispersed conidia of the anamorph Phomopsis vaccinii have been trapped throughout the growing season with the largest numbers trapped between blossom budbreak to bloom (EPPOa, 2016; Milholland, 1982).

The pathogen enter host tissues mainly through wounds and to a lesser extent directly into the tips of young, succulent shoots,  Healthy unwounded blueberry plants were not infected even after one month of exposure to natural field inoculum (EFSA, 2014). Once the fungus enters the stem through the vascular tissue, it progresses downwards towards the base, girdling the old branches at their junction and killing the part of the plant above the girdle (CABI, 2017).  The fungus also enters host vascular tissues through open flower buds and, it is believed that blueberry blight develops primarily from infection of flower buds at budbreak through bloom in North Carolina (Milholland, 1982).   Conidia on germination enter berries throughout the growing season and remain dormant until maturation causing soft rot and leakage of juice at harvest (Milholland & Daykin, 1983).  Diaporthe vaccinii has been reported to be an endophyte of apparently healthy blueberry and cranberry stems (CABI, 2017).

Germ tubes of germinating conidia enter leaves producing spots.  About 2-3 weeks later, pycnidia with conidia are apparent on stems and leaf spots.  The pathogen has been isolated from fruiting bodies found on overwintered cranberry leaves in New Jersey, but not  in Wisconsin from vines collected in the spring from beds in which dieback had been very severe in the late summer of the preceding year (Friend & Boone, 1968).  Overwintering was indicated to be necessary for ascocarp (sexual fruiting body) development, completing the life cycle, perpetuating the species, and producing a source of inoculum for infection in the next season.  However, in the southeastern USA, the pathogen is reported to overwinter in infected blueberry twigs and produce conidia from pycnidia (asexual fruiting body) in the following year (EFSA, 2014).  A correlation has also been indicated between vine dieback and dry conditions, with the latter predisposing the plant to dieback (Friend & Boone, 1968).

The pathogen grows well in a wide temperature range of 4-32°C and optimum pH 5-6.  In experiments, the most favorable temperature range for conidium germination and growth was 21-24°C wherein 95% conidia germinated and either entered plants through wounds or directly at the tips of young succulent blueberry shoots held inside a damp chamber.  About 71% shoots became blighted four days after inoculation. In artificially inoculated plants, the fungus caused cankers and dieback symptoms above 30°C (Weingartner and Klos, 1975).

Dispersal and spread: Long distance dispersal occurs through movement of infected plant vines (EPPOa, 2016). Other modes for spread include infected plant debris, leaves, twigs, and fruit, rain/irrigation water splash.

Hosts: Principal hosts include Vaccinium macrocarpon (cranberry), V. oxycoccos (small cranberry), V. oxycoccos var. intermedium (Americana and European cranberries), V. corymbosum (highbush blueberry), V. ashei (rabbiteye blueberry).  While D. vaccinii is restricted to Vaccinium species, the wild European species, V. oxycoccos which usually occurs in mountain bogs could be a reservoir host for the pathogen (EPPOa, 2016).  Other hosts are Gaultheria shallon (salal), Rhododendron sp. (Farr & Rossman, 2017).

Symptoms:  In North Carolina, the predominant symptom was blighting in one-year-old susceptible blueberry cultivars. Systemic invasion has also been reported (Milholland, 1982).  Infected succulent, current-year shoots wilt in 4 days and are covered with minute lesions.  Major branches and frequently entire plants are killed as the fungus continues to travel downwards through the stem at an average rate of 5.5 cm in 2 months.  Regardless of the stem, cankers are long and narrow and are covered by the bark or epidermis.  On blueberry stems over two-years-old, a brown discoloration of the stem xylem below wilt symptoms can be observed.  However, inoculated stems only produce localized lesions.  Infected leaves develop spots which enlarge to 1 cm with pycnidia/conidiomata appearing in two weeks.  The pathogen may remain dormant until favorable conditions allow it to continue growing.  Infection of crowns frequently end in the death of stem originating from the crown.  Infected fruits turn reddish-brown, soft, mushy, often split and leak juice at harvest (CABI, 2017; EPPOa, 2016).  The fungus penetrated blueberry fruit at all stages of development and remains latent until maturation (Milholland and Daykin, 1983).

In cranberry, Diaporthe vaccinii does not cause twig blight disease similar to blueberry, but occurs on shoots and leaves without causing significant damage (CABI, 2017).  It is also a storage rot pathogen of cranberries, mainly causing a viscid rot of fruit, which becomes soft and discolored.  Also, infected upright stems turn yellow then orange and brown before dying back (Milholland, 1995).

It is important to note that in blueberry, symptoms similar to twig blight disease can be caused by other fungal pathogens such as Godronia cassandrae, Colletotrichum spp., Fusarium spp., and Botryosphaeria dothidea.  In cranberry, upright dieback is also caused by the fungus, Synchronoblastia crypta (EPPOc, 2009; CABI, 2017).

Damage Potential:    Fruit loss of two to three pints per bush with twig blight of blueberry disease were reported in North Carolina (Milholland, 1982).  Fruit loss of 0.5% out of 15.2% defective fruit were accredited to D. vaccinii (Milholland & Daykin, 1983).  The pathogen is not considered to cause appreciable economic loss in cranberry, except in Massachusetts.  Fruit loss has been considered minor due to D. vaccinii, being attributed more to the presence of other accompanying pathogens than to D. vaccinii (CABI, 2017).

Worldwide Distribution: Asia: China; Europe: Latvia (present with restricted distribution); North America: Canada, USA; South America: Chile (CABI, 2017; Farr & Rossman, 2017; EPPOa, 2016).   The pathogen was eradicated or no longer present in most of the EU (EPPOa, 2016).  In the USA, it has been found in Arkansas, Illinois, Indiana, Maine, Maryland, Massachusetts, Michigan, New Jersey, North Carolina, Oregon, Washington, and Wisconsin.

Official Control: Diaporthe vaccinii is listed as a quarantine pest for the European Union (EPPOb, 2016).  The pathogen is on the ‘Harmful Organism’ lists for Argentina, China, Ecuador, Guatemala, India, Israel, Mexico, Morocco, New Zealand, Norway, Peru, and Taiwan (USDA PCIT, 2017).

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

California Interceptions: None.

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

Consequences of Introduction: 

1) Climate/Host Interaction: Blueberry is the main host for Diaporthe vaccinii in California.  Blueberries are grown in northern coastal and southern coastal regions and in the San Joaquin Valley.  The pathogen grows well within a wide temperature range (4-32°C) and requires wet and humid conditions for spore dispersal and germination and fungal growth. Humid conditions along the coast may be more conducive for the pathogen than the drier environments of the San Joaquin Valley.  A ‘Medium’ score is given for climate-host interaction.

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: Vaccinium are the main host for Diaporthe vaccinii.

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 capability resulting in production of numerous ascospores, and conidia, however, these are primarily dependent on water splash for dispersal. Long distance spread occurs primarily through movement of infected plants. A ‘Medium’ rating is given to this category.

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 suitable environmental conditions, Diaporthe vaccinii may infect blueberries causing storage rot of mature fruit causing significant losses in crop yield, value and market.

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.

4) Environmental Impact: 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 vaccinii: Low (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’ (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 = 9

Uncertainty:  

None.

Conclusion and Rating Justification:

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

References:

Bremer, V., G, Crisosto, R. Molinar, M. Jimenez, S. Dollahite, and C. H. Crisosto.  2008.  San Joaquin Valley blueberries evaluated for quality attributes.  California Agriculture, 62 (3): 91-96.  http://CaliforniaAgriculture.ucop.edu

CABI.  2017.  Phomopsis vaccinii (Phomopsis twig blight of blueberry) full datasheet.  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/18747

CASR.  2015-2016. California agricultural statistics review 2015-2016.  California Department of Food and Agriculture.  https://www.cdfa.ca.gov/Statistics/PDFs/2016Report.pdf

EFSA.  2014.  Scientific opinion on the pest categorization of Diaporthe vaccinii Shear.  European Food Safety Authority (EFSA), Parma, Italy.  EFSA Journal 12: 3774.

EPPOa.  2016.  Diaporthe vaccinii data sheets on quarantine pests.  Prepared by CABI and EPPO for the EU under contract 90/399003.   https://www.eppo.int/QUARANTINE/data_sheets/fungi/DIAPVA_ds.pdf

EPPOb.  2016.  EPPO A2 list of pests recommended for regulation as quarantine pests (version 2016-09).  https://www.eppo.int/QUARANTINE/listA2.htm

EPPOc.  2009.  Diaporthe vaccinii Diagnostics.  OEPP/EPPO Bulletin 39, 18-24.

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 13, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Friend, R. J., and D. M. Boone.  1968.  Diaporthe vaccinii associated with dieback of cranberry in Wisconsin. Plant Disease Reporter, 52:341-344.

Heaton, J.  2017.  J. Heaton, CDFA, email to D. Schnabel, cc: T. Walber and J. Chitambar, CDFA, sent Friday, March 10, 2017 9:01:02 am.

Lombard, L., G. C. M. Van Leeuwen, V. Guarnaccia, G. Polizzi, P. C. J. Van Rijswick, K. C. H. M. Rosendahl, J. Gabler, and P. W. Crous.  2014.  Diaporthe species associated with Vaccinium, with specific reference to Europe.  Phytopathologia Mediterranea 53: 85-97.

Milholland, R. D.  1982.  Blueberry twig blight caused by Phomopsis vaccinii. Plant Disease, 66:1034-1036.

Milholland R. D. 1995.  Phomopsis twig blight and fruit rot.  In Compendium of Blueberry and Cranberry Diseases.  APS Press, The American Phytopathological Society, pg. 13-14.

Milholland, R. D., and M. E. Daykin.  1983.  Blueberry fruit rot caused by Phomopsis vaccinii.  Plant Disease 67: 325-326.

USDA PCIT.  2017.  USDA Phytosanitary Certificate Issuance & Tracking System. Retrieved March 13, 2017. 6:04:39 pm CDT.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp.

Weingartner, D. P., and E. J. Klos.  1975.  Etiology and symptomatology of canker and dieback diseases on highbush blueberries caused by Godronia (Fusicoccum) cassandrae and Diaporthe (Phomopsis) vaccinii. Phytopathology, 65(2):105-110

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

Ganoderma adspersum (Schulzer) Donk

 California Pest Rating for
Ganoderma adspersum (Schulzer) Donk
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On January 25, 2017, Dr. David Rizzo, Professor, Department of Plant Pathology, University of California, Davis, notified CDFA of his detection of Ganoderma adspersum in almond orchards in the San Joaquin Valley, during surveys which initiated during fall 2015, of almond trees for wood decay fungi. The fungus was noted to be very aggressive and had killed relatively young almond trees in some orchards.  Consequently, CDFA will collect official samples of the fungus for analysis at the CDFA Plant Pathology Laboratory, and for official record.  Ganoderma adspersum has not been reported earlier from California or North America (Rizzo, 2017a).  The potential risk of infestation of G. adspersum is assessed here and a permanent rating is proposed for the species.

History & Status:

Background:   Ganoderma adspersum is a wood-decaying fungus that occurs in a very wide range of tree species including deciduous trees and conifers throughout the world. The species has more frequently been detected in trees growing near human habitations, gardens, parks, and planted sites (Papp & Szabo, 2013; De Simone & Annesi, 2012).   Ganoderma adspersum is a pathogen of roots and butts of living trees causing white rot, and can continue to grow saprophytically on nonliving tissue such as, stumps of felled trees (De Simone & Annesi, 2012).  Ganoderma species often kill their hosts and frequently, a diseased tree breaks or is wind-thrown while still alive as a result of decay in the butt and base of the trunk (Sinclair & Lyon, 2005). Unlike other closely related species, G. adspersum is an aggressive species that is able to penetrate and break through intact reaction zones of infected wood causing progressive and extensive decay over a relatively short period of time (De Simone & Annesi, 2012).   In Italy, G. adspersum-infected pine stands were felled within two years of infection (De Simone & Annesi, 2012).

Ganoderma adspersum has been known by several names.  The fungus was originally found growing on Carpinus betulus (European hornbeam) in Croatia, and published by Schulzer 1878 as Polyporus adspersus, and later as P. linhartii Kalchbr. 1884, Ganoderma linhartii (Kalchbr.) Z. Igmándy 1968, and G. europaeum Steyaert 1961.  After studying all specimens under the different species names, in 1969, Donk concluded the correct name for the fungus, G. adspersum (Tortic, 1971). In European polypore monographs, G. adspersum was found under the name, G. australe (Fr.) Pat. 1889.  However, through molecular analysis, the European taxon (G. adspersum) was differentiated from the Australian taxon (G. australe).  Ganoderma adspersum is the name of the European species (Papp & Szabó, 2013).  Differentiation of species of Ganoderma is confusing and problematic with only seven species, including G. adspersum, being accepted in the European polypore monographs (Papp & Szabó, 2013).  Taxonomically, G. adspersum is a distinct species belonging to the G. applanatum – australe complex (Papp & Szabó, 2013).

The species was first reported from Europe and is primarily found in that continent. However, it has also been found in Argentina, Brazil, American Samoa, and recently in the USA (California) (see: ‘Worldwide Distribution’).

In California, Ganoderma adspersum was detected in nine and ten year old almond orchards trees in Kings County during surveys of almonds for wood decay fungi in February 2016 (Rizzo, 2017a)  Over a three-year period, the orchard had experienced almost 20% tree loss, resulting in its removal by the end of 2016.  This detection marked a first for the fungus in California and North America.  Another detection was made in August 2016, in a twelve-year old almond orchard in Fresno County, and in 2017, additional infections were detected in Tulare, Kern, and Madera Counties (Rizzo, 2017b).  Presently, in California, the fungus has been found only in almond, prune and peach. All surveyed almond trees were planted on peach rootstock (Rizzo, 2017b).

Disease development:  Generally, most infections are initiated by airborne basidiospores that enter wounds on roots and trunk bases.  Basidiocarps (fruiting bodies or conks containing numerous spore producing structures or basidia) usually grow from the vicinity of old wounds.  Basidiospores are produced in great numbers during evening hours when the air is humid.  Experimentally, infection by root contact with previously colonized wood is also possible, although tree-to-tree spread has not been indicated by field observations (Sinclair & Lyon, 2005).

Dispersal and spread: Primarily by airborne basidiospores (De Simone & Annesi, 2012).

Hosts: Abies sp. (fir), A. alba (silver fir), Acer saccharinum (silver maple), Aesculus hippocastanum (horse chestnut), Betula pendula (European white birch), Broussonetia papyrifera (paper mulberry), Carpinus betulus (European hornbeam), Cedrus deodara (deodar cedar), Celtis occidentalis (common hackberry), Cercis siliquastrum (Judas tree), Fagus sylvatica (European/common beech), Fraximus sp. (ash), F. angustifolia subsp. danubialis (narrow-leafed ash), F. ornus (manna ash), Gleditschia triacanthos (honeylocust), Gymnocladus dioicus (Kentucky coffeetree), Juglans nigra (black walnut), Laurus nobilis (bay laurel), Picea abies (Norway spruce), Pinus sp. (pine), P. pinea (Italian stone pine), Platanus sp. (sycamore/plane trees), Populus alba (white poplar), P. nigra (black poplar), Prunus avium (wild cherry), P. padus (European bird cherry), P. cerasus (sour cherry), P. domestica (European plum), P. dulcis (almond), P. persica (peach), Prunus sp. (plum), Robinia sp. (locusts), R. pseudoacacia (black locust),  Quercus sp. (oak), Q. cerris (Turkey oak), Q. petraea (sessile oak), Q. pubescens (downy oak ), Q. robur (English oak), Q. ilex (holly oak), Morus sp. (mulberry), Salix sp. (willow), Tilia sp. (basswood), T. cordata (littleleaf linden), Ulmus laevis (European white elm), Zelkova serrata (Japanese zelkova) (De Simone & Annesi, 2012; Farr & Rossman, 2017; Gottlieb et al., 1998; Papp, 2013; Rizzo, 2017b; Tortic, 1970);

Symptoms:  In general, trees affected by Ganoderma develop widespread decay of sapwood in the butt and major roots.  Other symptoms include loss of vigor, undersized and sometimes yellowing or wilting leaves, thin crowns, and dead branches.  Some infected trees may die while others are weakened and fall by windstorms as a result of decay.  In advanced stages of decay, wood is light colored and stringy or spongy.  Large, reddish brown basidiocarps of G. adspersum grow from roots or butts (Sinclair & Lyon, 2005).  Progression of decay may be favored by predisposing conditions such as wounds, excessive stem density, or water stress (De Simone & Annesi, 2012).

Damage Potential:  Ganoderma adspersum causes wood decay and root rot thereby decreasing structural strength, growth and stand of infected trees.  In California, Rizzo (2017b) reported 50% to 70% infection rates in almond and prune orchards, with tree loss being exponential over time. Very high infection levels were observed in 9-12 years old almond orchards.  The life span of a typical almond orchard is about 25 years.  However, extensive infections may be terminal for almond orchards.  Few orchards were removed entirely due to high infections of Ganoderma adspersum.

Worldwide Distribution: Europe: Belgium, England, Germany, Hungary, Italy, Yugoslavia; North America: USA (California); South America: Argentina; Brazil; Oceania: American Samoa (CABI, 2017; De Simone & Annesi, 2012; Farr & Rossman, 2017; Gottlieb et al., 1998; Tortic, 1971)

Official Control: No official controls are reported for Ganoderma adspersum.  However, Ganoderma spp. is on the “Harmful Organism Lists” for Colombia and Jamaica.  Shipments of Ganoderma spp.-free Phoenix dactylifera, (date palm) plants is required by Colombia (USDA PCIT, 2017).

California Distribution: Ganoderma adspersum has been found in almond and prune orchards in Fresno, Kings, Tulare, Kern, and Madera Counties (Rizzo, 2017b).

California Interceptions: None reported.

The risk Ganoderma adspersum would pose to California is evaluated below. 

Consequences of Introduction: 

1) Climate/Host Interaction: Presently, Ganoderma adspersum has been found in almond and prune orchards within the San Joaquin Valley.  It has therefore demonstrated its capability to establish under suitable climates for those hosts within the State.

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

Score: 3

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

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

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

2) Known Pest Host Range: Ganoderma adspersum has a wide host range which includes deciduous and confer trees reported worldwide.  However, in California, the fungus has presently been detected in almond, prune and peach (almond on peach root stock) (Rizzo, 2017b). Those fruit hosts are cultivated in significant acreage in California.

Evaluate the host range of the pest.

Score: 3

– 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: Numerous basidiospores are produced by the fungus but are dependent on wind currents for dispersal and spread to non-infected trees. Therefore, a Medium rating is given for high reproductive potential.

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: Rizzo (2017b) reported 50% to 70% infection rates in almond and prune orchards in California, with tree loss being exponential over time.  Ganoderma adspersum causes wood decay and root rot resulting in decreased structural strength, growth and stand of infected trees.  Few orchards were removed entirely due to high infections.

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: Ganoderma adspersum has been reported on several hosts that are found in California environments.  Internationally, the fungus has more frequently been detected in trees growing near human habitations, gardens, parks, and planted sites.  However, in California, the fungus has only been detected in cultivated almond and prune. Other hosts may be threatened if the almond isolate in California is able to infect them.  However, as presently this is not known, the fungus is given a Medium score for potentially impacting urban gardens and 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 Ganoderma adspersum: High (13).

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 Medium (-2).  Ganoderma adspersum has been reported (Rizzo, 2017a, 2017b) from Fresno, Kings, Tulare, Kern, and Madera Counties.

Score: (-2)

-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:  

Presently, in California, Ganoderma adspersum has only been found in almond, prune, and almond on peach rootstock.  The fungus has a wide host range, but it is not known if other hosts, in particular those in natural environments of California, have been infected or will be infected by the almond isolate of the fungus.  Future information on its distribution may alter the numerical score but less likely, the proposed rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Ganoderma adspersum is B.

References:

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

De Simone, D., and T. Annesi.  2012. Occurrence of Ganoderma adspersum on Pinus pinea.  Phytopathologia Mediterranea 51: 374-382.

CABI.  2017.   Ganoderma adspersum basic datasheet. http://www.cabi.org/cpc/datasheet/24922

Farr, D. F., and A. Y. Rossman.  2017.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved March 8, 2017, from http://nt.ars-grin.gov/fungaldatabases/

Gottlieb A. M., B. O Saidman, and J. E. Wright, 1998. Isoenzymes of Ganoderma species from southern South America. Mycological Research 102, 415‒426.

Papp, V. and I. Szabó.  2013.  Distribution and host preferences of poroid Basidiomycete in Hungary I. – Ganoderma.  Acta Silv. Lingn. Hung. 9: 71-83.  DOI: 10.2478/aslh-2013-0006

Rizzo, D.  2017a. Email from David Rizzo, University of California, Davis, to Cheryl Blomquist, CDFA, sent Wednesday, January 25, 2017 6:09 am, forwarded to John Chitambar, CDFA, Wednesday, January 25, 2017 8:03:08 am.

Rizzo, D.  2017b. Email from David Rizzo, University of California, Davis to John Chitambar, CDFA, Tuesday, March 7, 2017 12:33 pm.

Sinclair, W. A., and H. H. Lyon.  2005.  Diseases of trees and shrubs second edition.  Comstock Publishing Associates, a division of Cornell University Press, Ithaca and London.  660 p.

Tortic, M.  1971.  Ganoderma adspersum (s. Schulz.) Donk (Ganoderma europaeum Steyaert) and its distribution in Yugoslavia.  Acta Botanica Croatica. 30: 113-118.

USDA PCIT.  2017.  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

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:

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

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

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♦  Comments may not be posted if they:

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Pest Rating: B

Posted by ls

Fungi, Plant Pathogens

Calonectria pseudonaviculata (Crous, J. Z. Groenew. & C. F. Hill) L. Lombard, M. J. Wingf. & Crous, 2010

California Pest Rating for
Calonectria pseudonaviculata (Crous, J. Z. Groenew. & C. F. Hill) L. Lombard, M. J. Wingf. & Crous, 2010
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On November 22, 2016, non-official samples of diseased boxwood plants collected by a landscaper from a private property in Hillsborough, San Mateo County, were sent through the San Mateo County Agricultural Commissioner’s office to the CDFA Plant Pathology Lab for diagnosis.  The samples were examined by Kathy Kosta CDFA plant pathologist, and the associated pathogen was cultured and identified by Cheryl Blomquist CDFA plant pathologist, as Calonectria pseudonaviculata (Kosta, 2016).  Subsequently, on November 29, 2016, official samples were collected from the same private property by Kathy Kosta (CDFA) and Fred Crowder (San Mateo County) and processed at the CDFA Plant Pathology Lab for pathogen diagnosis.  The official identification of Calonectria pseudonaviculata was made by Cheryl Blomquist on December 7, 2016.  This detection marked a first record of the pathogen in California.  Consequently, the pathogen was assigned a temporary ‘Q’ rating.   The risk of introduction and establishment of the pathogen is assessed here and a permanent rating is proposed.

History & Status:

Background:  Calonectria pseudonaviculata is the fungal pathogen that causes boxwood blight or box blight disease.  The pathogen is also known by its asexual (anamorph) stage as Cylindrocladium pseudonaviculatum.  The disease was first reported in the United Kingdom in the early to mid-1990s and the pathogen was given the name Cylindrocladium buxicola.  The origin of C. pseudonaviculatum is not known.  The pathogen was considered an exotic species that had been introduced to the UK and by 1998, it had spread to Europe and New Zealand.  (CABI, 2016; Crous et al., 2002; Dart et al., 2012).  While most published literature refers to the fungus as C. buxicola, this pathogen was not formally reported in the literature until 2002 as Cylindrocladium pseudonaviculatum which later became synonymous with Calonectria pseudonaviculata, the sexual (teleomorph) stage of the fungus (Lombard et al., 2010).  The current scientific name of the pathogen is Calonectria pseudonaviculata (CABI, 2016; Crous et al., 2002; Ivors & LeBude, 2011).

Disease cycle:  The pathogen infects host plants rapidly in warm (18-25°C) and humid conditions and has a life cycle that is completed in one week (Henricot, 2006; Henricot et al., 2008).  The primary inoculum of spores are sticky and therefore, are best transmitted to healthy host plants by water-splash or carried by insects, birds or infested plants.  Spores germinate three hours after inoculation and penetrate leaves in as little as five hours (Henricot, 2006).  Hyphae penetrate through stomata on lower surface of leaves, or directly through the cuticle on upper surface of leaves without appressorium formation (specialized attachment and penetration structure).  The fungus continues to grow intercellularly in the mesophyll layers of the plant (Henricot, 2006).  Two to three days after infection, the fungus produces conidiophores and conidia (asexual spores) through stomata and after seven days, these cover the lower surface of the leaf.  Leaves are eventually killed (Henricot, 2006).   The fungus can form resting structures (microsclerotia) which can survive on leaf material and in the soil in the absence of a susceptible host (Henricot, 2006).  However, in a 5-year study on the survival of the fungus on decomposing plant material, Henricot et al., (2008) did not detect the presence of microsclerotia.  Apparently, the pathogen is able to survive as mycelium within decomposing plant tissue.   No sexual stage structures have been observed in nature or in culture (CABI, 2016).

C. pseudonaviculata is a low temperature fungus that can grow below 10°C but is inhibited at 30°C and killed at 33°C (Henricot, 2006).

Dispersal and spread: The pathogen is spread by wind-driven rain and splashing water over short distances.  Long distance spread occurs by movement of infected plants/nursery stock, infested plant debris, soil, contaminated tools and equipment, insects or birds.  The pathogen can survive in leaf debris on or beneath the soil surface for up to 5 years (Dart et al., 2012; Henricot, 2006; Henricot et al., 2008).  The disease may also be spread is through the movement of asymptomatic (or with very limited outward symptoms) boxwood plants or plants treated with fungicides that suppress but do not kill or eliminate the inhabiting pathogen (Douglas, 2011).

Hosts: Buxaceae: Buxus microphylla (little-leaf box), B. microphylla var. japonica, B. sempervirens (syn. B. colchica; common boxwood), B. sinica (Chinese box), B. sinica var. insularis (Korean boxwood), Buxus sp. (box), Pachysandra procumbens, P. terminalis (Japanese spurge), Sarcococca sp. (sweet box) (CABI, 2016; EPPO, 2016; Farr & Rossman, 2016).

The full host range of this pathogen is not currently known however, none of the Buxus species are immune to boxwood blight and susceptibility to the pathogen may vary among cultivars (Henricot et al., 2008).  Sarcococca sp. (sweet box) and Pachysandra terminalis (Japanese spurge) are experimental hosts (Henricot et al., 2008; LaMondia et al., 2012).

Symptoms:  Infections by Calonectria pseudonaviculata result in the production of dark brown or lighter brown leaf spots surrounded by a dark border.  Stems are also infected exhibiting characteristic black streaks.  Eventually severe defoliation and dieback occur.  The fungus does not infect the roots.  Entire foliage typically becomes blighted causing the leaves to turn ‘straw’ to light brown in color and defoliate.  Stems of blighted plants may remain green under the outer bark until infected by secondary or opportunistic pathogens and diseases resulting in decline and eventual death of entire plants.  Young seedlings can be killed by this pathogen (Henricot, 2006; Henricot et al., 2008; USDA-NCSU).

Damage Potential:   The disease has been described as ‘devastating’ to boxwood plants (Henricot et al., 2008). Foliage of infected plant is eventually killed and blighted plants are predisposed to infections by secondary pathogens also resulting in their eventual death.  At particular risk are boxwood plants grown in nurseries, commercial landscapes, parks and gardens, and at private residences under warm and wet climates conducive for the development and spread of the pathogen.  Rapid and widespread infection including over 10,000 American boxwood plants and 150,000 plants in production nurseries in North Carolina and Connecticut were reported (Ivors et al., 2012).  Buxus spp. (boxwood) are not native to the United States, and are widely cultivated as ornamental plants.  In California, depending on plant species and cultivar, boxwood is commonly grown throughout the State except in cold, mountainous regions, and are likely to prefer cooler climates in the State (Sunset Western Garden Book, 1992).  Three main species are grown as ornamentals in the USA, B. sempervirens, B. microphylla, and B. sinica var. insularis, all which are known hosts of C. pseudonaviculata (USDA-NCSU).

Worldwide Distribution: Asia: Iran, Republic of Georgia, Turkey; North America: Canada (restricted distribution in British Columbia, few occurrences in Ontario and Quebec), USA; Europe: Austria, Belgium, Croatia, Czech Republic, Denmark, France, Germany, Ireland, Italy, Netherlands, Norway, Slovenia, Spain, Sweden, Switzerland, United Kingdom; Oceania: New Zealand (CABI, 2016; EPPO, 2016; Farr & Rossman, 2016).

In the USA, C. pseudonaviculata has been reported from Alabama, Connecticut, Delaware, Kentucky, Maryland, Massachusetts, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, Rhode Island, Virginia (CABI, 2016; EPPO, 2016; Farr & Rossman, 2016), and by this report from California.

Official Control:  Cylindrocladium buxicola (synonym C. pseudonaviculata) is on the ‘Harmful Organism Lists’ for the Republic of Korea (USDA PCIT, 2016).  Presently, it has a temporary Q rating in California.

California Distribution:   San Mateo County.

California Interceptions:  None reported.

The risk Calonectria pseudonaviculata would pose to California is evaluated below.

Consequences of Introduction: 

1) Climate/Host Interaction: The boxwood blight pathogen, Calonectria pseudonaviculata rapidly infests host plants under humid and warm (18-25°C) climates – being inhibited at 30°C and killed at 33°C. Spores are transmitted to healthy host tissue under wet conditions, requiring wind-driven rains and water splash from overhead irrigation systems. Depending on species and cultivar selection, Buxus are grown throughout California, except in mountainous regions, and are likely to do best in cool climates, such as coastal regions of the State.  Plants grown in warm and humid climates are at possible risk of infection by the pathogen.  The pathogen may be able to establish in a larger but limited region in the State, suitable also to the growth of its host plants.  Therefore a ‘medium’ rating is given to this category.

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 Calonectria pseudonaviculata is currently limited to few Buxus species (boxwood) and several cultivars, as well as Sarcococca (sweet box) and Pachysandra spp. (Japanese spurge).

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: Calonectria pseudonaviculata has high reproductive potential.  Although its dispersal and spread over short distances to non-infected plants depends on wind-driven rain and water-splash, long distance spread occurs by movement of infected plants/nursery stock, infested plant debris, soil, contaminated tools and equipment, insects or birds. The disease may also be spread through the movement of asymptomatic (or with very limited outward symptoms) boxwood plants or plants treated with fungicides that suppress but do not kill or eliminate the inhabiting pathogen.  These modes of spread, plus the ability of the pathogen to survive in leaf debris on or beneath the soil surface for up to 5 years, places it as a ‘high risk’ in this category.

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: Boxwood blight disease could result in lower crop value, loss of foliage and plants, increased production costs, loss of markets, and changes in delivery of irrigation water so to avoid water splash and wetness of foliage.  Also, insects and birds could aid in spread of the pathogen to non-infected plants.  Therefore, economic impact, caused by the boxwood blight pathogen, is given a ‘High’ score.

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

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 3

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: Infections of Calonectria pseudonaviculata could significantly affect private and commercial plantings of boxwood plants commonly used as hedge and shrub ornamentals and result in additional treatments against the pathogen.  Therefore, risk on environmental impact is scored as ‘High’.

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

Environmental Impact: D, E.

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

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

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

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

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

Score the pest for Environmental Impact.

Environmental Impact Score: 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 Calonectria pseudonaviculata: 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: Presently, the boxwood blight pathogen has only been officially reported from one region, namely, San Mateo 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 = Medium (10)

Uncertainty:  

None.                              

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Calonectria pseudonaviculata is B.

References:

CABI, 2016.  Calonectria pseudonaviculata (buxus blight) full datasheet. http://www.cabi.org/cpc/datasheet/17414.

Crous, P.W., J. Z. Groenewald, and C. F. Hill.  2002.  Cylindrocladium pseudonaviculatum sp. nov. from New Zealand, and new Cylindrocladium records from Vietnam. Sydowia 54: 23-34.

Dart, N., M. A. Hansen, E. Bush, and C. Hong.  2012.  Boxwood blight: a new disease of boxwood found in the eastern U.S.  Virginia Cooperative Extension, Virginia State University Publications and Educational Resources PPWS-4.  http://pubs.ext.vt.edu/PPWS/PPWS-4/PPWS-4.html

Douglas, S. M.  2011.  Boxwood blight – a new disease for Connecticut and the U. S.  The Connecticut Agricultural Experiment Station.  www.ct.gov/caes .

Farr, D.F., and A. Y. Rossman.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved December 1, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

Henricot, B., C. Gorton, G. Denton, and J. Denton. 2008. Studies on the control of Cylindrocladium buxicola using fungicides and host resistance. Plant Disease, 92(9):1273-1279.  http://www.apsnet.org

Ivors, K. and A. LeBude.  2011.  A new pest to the U. S. ornamental industry: the “box blight” pathogen Cylindrocladium pseudonaviculatum = Cylindrocladium buxicola.  NC Pest Alert. http://plant-clinic.bpp.oregonstate.edu/files/plant_clinic/webfm/NC_pest_alert_box_blight1-1.pdf

Ivors, K. L., L. W. Lacey, D. C. Milks, S. M. Douglas, M. K. Inman, R. E. Marra, and J. A. LaMondia.  2012.  First report of boxwood blight caused by Cylindrocladium pseudonaviculatum in the United States.  Plant Disease.  96: 1070. http://dx.doi.org/10.1094/PDIS-03-12-0247-PDN.

Kosta, K.  2016.  Personal communication to J. Chitambar, CDFA Primary Plant Pathologist/Nematologist via email on November 30, 2016, 5:03:15 pm.

LaMondia, J. A., D. W. Li, R. E. Marra, and S. M. Douglas.  2012.  First report of Cylindrocladium pseudonaviculatum causing leaf spot of Pachysandra terminalis.  Plant Disease 96: 1069. http://dx.doi.org/10.1094/PDIS-03-12-0235-PDN.

Lombard, L., P. W. Crous, B. D. Wingfield, and M. J. Wingfield.  2010.  Phylogeny and systematics of the genus Calonectria.  Studies in Mycology. 66: 31-69.  www.studiesinmycology.org , doi:10.3114/sim.2010.66.03

USDA-NCSU.  (Date not known).  The ‘box blight’ pathogen: Cylindrocladium pseudonaviculatum = Cylindrocladium buxicola (Teleo.  Calonectria pseudonaviculata).  Datasheet developed by USDA-APHI-PPQ-CPHST and NCSU Department of Plant Pathology, Mountain Horticultural Crops Research and Extension Center (MHCREC) staff. caps.ceris.purdue.edu/dmm/1603

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

Coleophoma empetri (Rostr,) Petr. 1929

California Pest Rating for
Coleophoma empetri (Rostr,) Petr. 1929
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On April 27, 2016 a mail shipment containing cut foliage of Galax sp. was intercepted by the Santa Barbara County Dog Team, at the FedEx Service Center in Goleta, Santa Barbara County.  The shipment had originated in Florida and was destined to a nursery in Carpinteria, Santa Barbara County.  Samples of diseased leaves exhibiting leaf spots were collected by the County and sent to the CDFA Plant Pathology Laboratory for disease diagnosis.  On April 29, 2016 Suzanne Latham, CDFA plant pathologist, identified the fungal pathogen, Coleophoma empetri, as the cause for the disease.   The pathogen has not been previously reported in California and therefore, was assigned a temporary Q rating.  Subsequent action taken by the County resulted in the destruction of the intercepted shipment of Galax sp. foliage (CDFA, 2016). The risk of infestation of Coleophoma empetri in California is evaluated and a permanent rating is herein proposed.

History & Status:

Background: Originally described as Septoria empetri, the fungal pathogen Coleophoma empetri is also known by other synonyms, Rhabdostromina empetri, Sporonema oxycocci, and Coleophoma rhododendri, and Coleophoma ericae.  The pathogen is widely distributed and found on living and dead leaves and fruit of many different plant species (Farr & Rossman, 2016; Sutton, 1980).

Disease cycle:   There is a paucity of specific information on Coleophoma empetri.  However, it is likely that the development of disease caused by the pathogen would be similar to other pycnidia-forming fungal pathogens.   The pathogen overwinters as mycelium or immature pycnidia in infected fruit and diseased plant debris. Under high moisture and cool temperature conditions, pycnidia swell and release conidia which are spread by splashing rain, irrigation, water, and so on.  Seed transmission is not known for C. empetri.  Infection of host plants and severity of disease development is likely to require high moisture and cool temperatures.  In the development of fruit rot of berries, conidia initiate infection during bloom and early berry development.  As infected fruit mature, hyphae continue to invade the fruit and rot symptoms do not develop until the late growing season and mostly in storage (Kusek, 1995).

Dispersal and spread: Splashing rain and irrigation water, air currents, infected plants, infected plant debris, cultivation tools, animals, and contaminated clothing.

Hosts:  Archontophoenix alexandrae (Alexander palm), Arctostaphylos sp. (Manzanita), A. uva-ursi, Arctous alpine (bearberries), Betula sp. (birch), Camellia sp., Cajanus cajan (pigeon pea), Canavalia ensiformis (Jack bean), Capsicum annuum (bell peppers), Croton sp., Diapensia sp., D. obovata (pincushion plant), Elaeagnus sp. (oleaster), E. macrophylla, Empetrum sp., E. nigrum (black browberry), Erica carnea (winter heath), Eucalyptus sp. E. tereticornis (forest red gum), Ficus sp., Fraxinus sp. (ash), Galax aphylla (beetleweed/coltsfoot), Gaultheria shallon (shallon), Gaylussacia brachycera (box huckleberry), Juniperus sp. (juniper), Kalmia angustifolia (sheep laurel), Laurus sp., L. nobilis (sweet bay), Leucothoe sp., Loiseleuria sp., L. procumbens, Lonicera sp. (honeysuckle), L. periclymenum, Malus sylvestris (European crab apple), Paxistima canbyi (Canby’s mountain-lover), Plea europaea, Prunus laruocerasus (cherry laurel), P. ponticum, Rhododendron sp., R. maximum, Solanum tuberosum (potato), Stransvaesia sp., Taxus baccata (English yew), Vaccinium sp. (blueberry), V. macrocarpon (American cranberry), V. ovatum (California huckleberry), V. oxycoccos (bog cranberry), V. vitis-idaea (lingonberry) (Farr & Rossman, 2016; Kusek, 1995; Sutton, 1980).

Symptoms:  Coleophoma empetri causes leaf spot, fruit rot and tuber skin spot disease on numerous hosts in numerous families.  Symptoms of ripe rot on cranberry fruit initially appear as a small soft area which expands over the entire fruit.  Diseased fruit appear off-red or reddish orange, and internally watery, squirting a watery fluid when squeezed.  However, as not all watery-soft fruit is caused by the pathogen, the latter must be isolated from the diseased fruit to confirm an association with the symptoms (Kusek, 1995).

Disease Potential:  Specific information on quantitative crop losses caused by Coleophoma empetri has not been reported. Photosynthetic area can be reduced due to leaf spotting.  In severe infections, leaf wilt and drop may be expected. Symptomatic host plants infected with the pathogen may be more of a serious problem for nursery greenhouse productions where favorable wet requirements for disease development and spread are more likely to occur under controlled environments than in open field environments in California.  The disease could negatively impact value and marketability of nursery-grown plants including ornamental and landscape plants such as Manzanita, Camellia, Rhododendron, and Eucalyptus. The pathogen causes fruit rot that is apparent during late growing season and mainly in storage.

Worldwide Distribution: Coleophoma empetri is globally widely distributed.  Asia: India, USSR; Europe: Finland, Lithuania, Poland, USSR, United Kingdom, Ukraine, Scotland, Germany; North America: Alaska, Maryland, Massachusetts, Maine, Michigan, New Jersey, Oregon, Tennessee, Virginia, Washington, Wisconsin, and Northwestern states (Farr & Rossman, 2016).

Official Control:  Currently, has a temporary Q rating in California.

California Distribution:  is not established in California.

California Interceptions: A single shipment of Coleophoma empetri-infected Galax sp. foliage was intercepted on April 27, 2016 at the FedEx Service Center in Goleta, Santa Barbara County (see ‘Initiating Event’).

The risk Coleophoma empetri 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: 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.

Risk is Medium (2): Coleophoma empetri may be able to establish on suitable host plants growing in high moisture and cool to warm climate conditions.  These conditions would likely limit natural establishment to northern coastal regions of California.

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):  Coleophoma empetri has a moderate host range that includes many host species in different plant families.  Most hosts grow under cool and wet climates.  In California, main hosts include ornamental, landscape, and fruit berry plants such as, Manzanita, Camellia, Rhododendron, Eucalyptus, blueberry, and cranberry.

3) Pest Dispersal Potential: 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.

Risk is High (2): Coleophoma empetri has high reproduction and dispersal potential.  The pathogen can be spread over short and long distance by splashing rain and irrigation water, air currents, infected plants, infected plant debris, cultivation tools, animals, and contaminated clothing.

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

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.

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.

Risk is Medium (2):  The pathogen may be more of a serious problem for nursery greenhouse productions where favorable wet requirements for disease development and spread are more likely to occur under controlled environments than in open field environments in California.  The disease could negatively impact value and marketability of nursery-grown plants including ornamental and landscape plants.  Also, the pathogen may cause fruit rot that is apparent during late growing season and mainly in storage.

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: 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.

 Risk is High (3): Severe infections caused of Coleophoma empetri could impact ornamental plantings.  Under suitable conditions that result in severe disease, threatened or endangered plant species, namely, manzanita (Arctostaphylos spp.) could be affected and disrupt critical habitats.  

Consequences of Introduction to California for Coleophoma empetri:

Add up the total score and include it here:

-Low = 5-8 points

–Medium = 9-12 points

        -High = 13-15 points

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

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

Score: 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.

Evaluation is Not Established (0).  Coleophoma empetri is not established in California.   

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Coleophoma empetri is B.

References:

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

CDFA.  2016.  Santa Barbara County Dog Team Interception.  CDFA AQW Pest Report No. 18-2016, weekly AQW report: for the week of April 28 to May 04, 2016.

Duan, J. X., W. P. Wu, and X. Z. Liu.  2007.  Reinstatement of Coleonaema for Coleophoma oleae and notes on Coleophoma.  Fungal Diversity 26: 187-204.

Farr, D. F. and A. Y. Rossman.  2016.   Fungal databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved August 24, 2016 from http://nt.ars-grin.gov/fungaldatabases/.

Kusek, C. C.  1995.  Cranberry Ripe Rot.  In Compendium of Blueberry and Cranberry Diseases Edited by F. L. Caruso and D. C. Ramsdell.  APS Press, The American Phytopathological Society, page 43.

Sutton, B. C. 1980. The Coelomycetes. Fungi Imperfecti with pycnidia, acervuli and stromata. Commonwealth Mycological Institute, Kew, Surrey, England, 696 pages

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.]

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♦  Comments may not be posted if they:

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Pest Rating: B

Posted by ls

Fungi, Plant Pathogens, Ratings

Pseudocercospora purpurea (Cooke) Deighton 1976

California Pest Rating for
Pseudocercospora purpurea (Cooke) Deighton 1976
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On November 17, 2016, USDA APHIS PPQ inquired if CDFA had conducted a pest risk assessment of the fungal pathogen, Pseudocercospora purpurea on avocados in California.  Subsequently, the risk of infestation of P. purpurea in California is evaluated and a permanent rating is herein proposed.

History & Status:

Background:  Pseudocercospora purpurea is a fungal plant pathogen that causes Pseudocercospora (Cercospora) spot (blotch) disease exhibiting leaf and fruit spot symptoms in Persea spp., including avocado (P. americana) plants. The pathogen was originally known as Cercospora purpurea. In South Africa, the disease is known as black spot or Cercospora spot and is the most serious pre-harvest disease affecting all cultivars of avocado, particularly, cv. Fuerte (Crous et al., 2000; Pohronezny et al., 1994).  The disease occurs in warm, humid and rainy climates and is found in southeastern USA, South America, northern Australia, Asia, Africa, and the Caribbean (CABI, 2016; Menge & Ploetz, 2003).  The pathogen has not been reported from California.

Disease cycle:  Initial inoculum of conidia (asexual spores) mostly comes from infected leaves.  New shoot tissues are infected wherever this disease occurs.  The pathogen penetrates host tissue either directly or through wounds. 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.  In South Africa, the pathogen remains latent for about 3 months after penetration.  Infected plants produce conidiophores (specialized hypha) that arise from the plant surface in clusters through stomata and form conidia successively.  Substomatal stroma (compact mycelial structure) may form from which conidiophores develop.  Fruit are susceptible when developed to a quarter to three-quarter of their full size.  Very small fruit (< 4 cm diameter) and those at or near maturity are almost immune.  Disease development is severe during warm, rainy weather when fruit are about a quarter size (Agrios, 2005; Menge & Ploetz, 2003; Pohronezny et al., 1994).  High relative humidity is necessary for conidial germination and plant infection.  The pathogen can overwinter as mycelium (stromata) in old infected leaves (Agrios, 2005).  

Dispersal and spread: Wind, rain, irrigation water, infected nursery plants, infected leaves, insects (Menge & Ploetz, 2003).

Hosts: Avocado is the main host; Persea spp. in the family Lauraceae, namely, P. americana (syn. P. gratissima, avocado), P. borbonia (redbay), P. drymifolia (Mexican avocado), P. palustris (swamp bay), and Persea sp. (Farr & Rossman, 2016).

Symptoms: Symptoms occur on leaves, stems, and fruit (Pohronezny et al., 1994).  On leaves, lesions initially appear as small (1-5 mm) angular, purple to purplish brown flecks or spots near leaf margins.  Over time, chlorotic halos surround older spots and are visible on both leaf surfaces.  The fungus sporulates under high humid conditions, appearing as gray, felty mycelial growths in the center of lesions. Individual lesions may coalesce forming larger regions of necrotic tissue.  Leaves become curled, deformed and may fall.

On fruit, lesions initiate as small flecks which later become slightly sunken, expand or coalesce becoming somewhat circular, and turn brown to brownish black in color.  Fissures or cracks usually develop in fruit lesions and serve as avenues for infection by other pathogens.  In certain cases, if the disease is temporarily arrested, the lesions appear as minute, raised, shiny, black specks associated with the corking of lenticels.  While blotch is usually confined to the rind of fruit, in advanced cases, the flesh may be invaded.  Once defoliation occurs, fruit may turn chlorotic, shrivel and drop.  Dark brown to black, 2-10 mm lesions may also form on green twigs and fruit pedicels (Pohronezny et al., 1994; Menge & Ploetz, 2003).

Damage Potential:  Pseudocercospora spot (blotch) is one of the most common diseases of avocado in Florida (Pohronezny et al., 1994).  Losses in avocado production may be severe and have been reported to be up to 69% in non-sprayed orchards in South Africa (Pohronezny et al., 1994; Menge & Ploetz, 2003).  Photosynthetic area can be reduced due to leaf spotting.  In severe infections, leaf wilt and drop may be expected.  In California, avocado production is a major industry producing 75% and 92% of the nation’s avocado fruit supplies (Lazicki et al., 2016).  Therefore, losses due to this pathogen is of particular concern.

Worldwide Distribution: Pseudocercospora purpurea is widespread in subtropical and tropical regions.  Asia:  India, Japan, Philippines; Africa: Cameroon, Democratic Republic of Congo, Côte d’Ivoire, Guinea, Kenya, South Africa; North America: Bermuda, Mexico, USA; Central America and Caribbean: Dominica, El Salvador, Honduras, Jamaica, Nicaragua, Panama, Puerto Rico, Trinidad and Tobago, United States Virgin Islands; South America: Argentina, Bolivia, Brazil, Chile, Guyana, Peru, Venezuela; Oceania: Australia, Palau (CABI, 2016; Farr & Rossman, 2016).

In the USA, the pathogen has been found in the states of Florida, Georgia, and Mississippi (CABI, 2016).

Official Control:  Presently, Cercospora purpurea (syn. Pseudocercospora purpurea) is on the ‘Harmful Organism Lists’ for Namibia and South Africa and P. purpurea is on the ‘Harmful Organism Lists’ for French Polynesia and New Caledonia (USDA PCIT, 2016).

California Distribution: Pseudocercospora purpurea has not been reported from California.  The pathogen is not known to be established in California.

California Interceptions:  None reported.

The risk Pseudocercospora purpurea 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: 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.

Risk is Medium (2): In California, Pseudocercospora purpurea may be able to establish on avocado, under high moisture and warm climate conditions.  In the State, avocados are grown mostly along the southern coast (Lazicki et al., 2016).

2) Known Pest Host Range: 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.

Risk is Low (1):  The host range for Pseudocercospora purpurea is limited to Persea spp. with avocado being the main host.

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):  Pseudocercospora purpurea has high reproductive potential resulting in the successive production of conidia which are mainly dependent on wind, rain, and infected plants for dispersal and spread.

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

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.

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.

Risk is High (3):  Infected host plants with leaf and fruit spot symptoms caused by Pseudocercospora spot (blotch) disease could lower value and yield of commercially produced avocado plants as well as affect nursery productions resulting in 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: 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):  The pathogen could significantly impact avocado plants grown for fruit and aesthetic value in private residential and public environments.

Consequences of Introduction to California for Pseudocercospora purpurea:

Add up the total score and include it here:

-Low = 5-8 point

–Medium = 9-12 point

-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: 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.

Evaluation is not established (0):  Pseudocercospora purpurea is not established in California.

Final Score:

7) The final score is the consequences of introduction score minus the post entry distribution and survey information 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 Pseudocercospora purpurea is B.

References:

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

CABI.  2016.  Pseudocercospora purpurea (spot blotch) (basic) datasheet.  Crop Protection Compendium.  http://www.cabi.org/cpc/datasheet/12266 .

Crous, P.W., A. J. L. Phillips, A. P. and Baxter.  2000.  Phytopathogenic fungi from South Africa. University of Stellenbosch, Department of Plant Pathology Press, 358 pages (referenced by Farr & Rossman, 2016).

Farr, D. F., & A. Y. Rossman.  2016.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA.  Retrieved August 18, 2016, from http://nt.ars-grin.gov/fungaldatabases/.

Lazicki, P., D. Geisseler, and W. R. Horwath.  2016.  Avocado production in California. https://apps1.cdfa.ca.gov/FertilizerResearch/docs/Avocado_Production_CA.pdf. (Last updated April, 2016.)

Menge, J. A., and R. C. Ploetz.  2003.  Disease of Avocado.  In Diseases of Tropical Fruit Crops, Edited by R. C. Ploetz, CABI Publishing, CAB International, UK, USA, 527 p.

Pohronezny, K. L., G. W. Simone, and J. Kotzé.  1994.  Pseudocercospora spot (blotch).  In Compendium of Tropical Fruit Diseases, Edited by R. C. Ploetz, G. A. Zentmeyer, W. T. Nishijima, K. G. Rohrbach, and H. D. Ohr, APS Press, The American Phytopathological Society, 79-80 p.

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;

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

Violates agency regulations prohibiting workplace violence, including threats.

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

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

Pest Rating: C

Posted by ls

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