Category Archives: Plant Pathogens

Plant Pathology (plant diseases)

Fungi, Plant Pathogens

Peronosclerospora philippinensis (W. Weston) C. G. Shaw, 1978

peronosclerospora philippinensis | photo by Bob Kemerait, Univ of Georgia, Bugwood.org
California Pest Rating for
Peronosclerospora philippinensis (W. Weston) C. G. Shaw, 1978
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

Peronosclerospora philippinensis was recently proposed by the USDA to be removed as a select agent from the 2016 updated Select Agents Registration List and Select Agent Regulations.  Currently, the pathogen is not rated in California.  Therefore, the risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is proposed herein.

History & Status:

Background: Peronosclerospora philippinensis is an oomycete pathogen that causes Philippine downy mildew disease.  The disease is destructive mainly to corn in tropical Asia, endemic to the Philippines, and has also been reported from China, India, Indonesia, Nepal, Pakistan, Taiwan, and Congo, Mauritius, and South Africa (CABI, 2016; EPPO, 2016; Farr & Rossman, 2016).  The pathogen has not been reported within the USA (Farr & Rossman, 2016; USDA, 2013).

In 2002, the USDA designated Peronosclerospora philippinensis a ‘select agent’ deemed to be very damaging to susceptible maize and sources of resistance, if any, had not been established for U. S. maize varieties (USDA, 2013).  However, on January 14, 2016, after its fourth biannual review, the USDA proposed to remove P. philippinensis from the updated Select Agents Registration List and Select Agent Regulations.  Removal of select agents, by the USDA, was based on either the absence of viable samples present in the U.S., no climate conducive to growth, or the availability of adequate treatments for the agents (USDA, 2016).

Hosts: Hosts include species within the family Poaceae.  Zea mays (maize) is the main host.  Other hosts include, Andropogon sorghum (Sorghum bicolor, sorghum), Avenae sativa (oats), Euchlaena luxurians, Saccharum officinarum (sugarcane), S. spontaneum (wild sugarcane), Sorghum halepense (Johnson grass), Zea mays subsp. mexicana (teosinte) (CABI, 2016; EPPO, 2016; Farr & Rossman, 2016).

Symptoms: Systemic symptoms are expressed in the first true leaf stage as stripes or overall yellowing of an entire leaf.  Local symptoms are expressed as long chlorotic streaks with downy growth of conidia (spores) and conidiophores.  This downy growth is the site of spore production and may be present on both upper and lower leaf surfaces, but is more common on the lower surface.  Tassels may be malformed and produce less pollen, and ears may be aborted.  Early infected plants are stunted and may die.  Infected stems do not show external symptoms, but may be stunted (CABI, 2016).  The pathogen invades the stem, and becomes established in the shoot apex producing chlorotic areas, which are initially confined to the base of the lower leaf but later increase in size in succeeding leaves.  The youngest leaf emerging from the whorl becomes completely chlorotic.  The pathogen becomes established within seed, as mycelium in the pericarp layer, and also within the embryo and endosperm.  However, no external symptoms on seed are expressed and seed quality is not affected (CABI, 2016).

Disease cycle:  Although the Philippine downy mildew pathogen was reported to produce oospores (overwintering sexual spores) on corn leaf, there have been no subsequent reports.  Even though the Philippine downy mildew pathogen was reported in 1967 to produce overwintering sexual spores (oospores), on corn leaf, there have not been any subsequent reports since then and therefore, the role of oospores has not been established in the life cycle or disease caused by this pathogen (USDA, 2013). Airborne conidia (spores) released from infected crops or weeds form primary source of inoculum for infection. Germinating conidia produce germ tubes which penetrate stomata of leaves.  The optimum temperature for germination and germ tube growth is 18-30°C.  Penetration is followed by invasion of the mesophyll.  Soon the disease becomes established and lesions are formed in leaves.  Conidia are produced under night temperatures ranging from 21 to 26°C and free moisture.  Moisture is critical for infection.  Secondary infections occur that eventually result in the spread of the disease throughout an entire crop.  Seed transmission can occur at low rates from seeds harvested with higher moisture content (CABI, 2016).

Dispersal and spread:  Peronosclerospora philippinensis is commonly spread by wind and rain.  Production of conidia requires night temperatures ranging from 21 to 26°C and free moisture.  Disease severity is highest in areas that receive 39-78 inches of rain annually and in tropical climates.  The pathogen is dispersed short distances by wind.  Although the pathogen is present within infected seed, it has been demonstrated that once the seed or grain is dried to below 14% it will not produce an infected plant (Adenle & Cardwell, 2000; USDA 2013).

Damage Potential: Before resistant varieties became widely available in the Philippines, annual yield losses of maize were often 40 to 60%.  Yield losses of sweet corn were 100%. Disease severity is highest in areas that receive 39-78 inches of rain annually and in tropical climates (USDA, 2013).  In California, the required warm temperature and long wet periods (heavy rain durations) for disease development and spread are not present.  Therefore, the potential for damage caused by the pathogen to California’s maize production, can be considered to be minimal, if at all.  Furthermore, the pathogen is seed transmissible, but transmission will not occur once the seed has been dried to the moisture content required for storage.  Seed treatments are available to eradicate the pathogen (CABI, 2016).

Worldwide Distribution: Asia: China, India, Indonesia, Japan, Nepal, Pakistan, Philippines, Taiwan, Thailand; Africa: Mauritius, Congo, South Africa (CABI, 2016; Farr & Rossman, 2016).

Official Control: Presently, Peronosclerospora philippinensis is on the ‘Harmful Organism Lists’ of the following countries: Colombia, French Polynesia, Guatemala, Honduras, Indonesia, Japan, Republic of Korea, Morocco, Namibia, New Caledonia, New Zealand, Peru, South Africa, and Timor-Leste  (USDA-PCIT, 2016).  The USDA designated S. rayssiae var. zeae a select agent in 2002, however, on January 14, 2016, the USDA proposed to remove S. rayssiae from the updated Select Agent Registration List and Select Agents Regulations (see ‘Background’).

California Distribution: Peronosclerospora philippinensis is not present in California.

California Interceptions:  There are no reports of the detection of Peronosclerospora philippinensis in plant and soil shipments imported to California.

The risk Philippine downy mildew disease 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):   Peronosclerospora philippinensis is not likely to establish in California as the required warm temperature and long wet periods (12 hours or more) for disease development and spread are not present.

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 is limited to include species within the family Poaceae.  Maize is the main host, cultivated sugarcane, oats, sorghum cultivars, and weedy grass species including Euchlaena luxurians, wild sugarcane, Johnson grass, and Zea mays subsp. mexicana (teosinte).

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):  Under favorable wet conditions, Peronosclerospora philippinensis has high reproductive potential.  The pathogen is dispersed primarily through infected soil, plant debris, and maize seeds.  Short distance spread is by wind and rain splash or physical contact with infected plants.  Long distance transmission by wind is reported to be unlikely.

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):  In California, the required warm temperature and long wet periods (heavy rain durations) for disease development and spread of the pathogen, are not present, thereby, making it most unlikely for the pathogen to establish and cause infections to the State’s maize cultivation. However, within contained and artificially controlled conditions as in greenhouses, it is possible for pathogen infections to occur. Seed transmission of the pathogen will not occur once the seed has been dried to the moisture content required for storage and the pathogen can be eradicated from seed through seed treatments. The economic impact is therefore, regarded 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 Low (1):  No environmental impacts due to the pathogen are expected to occur in California.

Consequences of Introduction to California for Brown stripe downy mildew of maize:

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 = 7

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 = 7

Uncertainty:  

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Peronosclerospora philippinensis is C.

References: 

Adenle, V. O., and K. F. Cardwell. 2000.  Seed transmission of maize downy mildew (Peronosclerospora sorghi) in Nigeria. Plant Pathology 49:628-634.

CABI.  2016.  Peronosclerospora philippinensis (Philippine downy mildew) full datasheet.  http://www.cabi.org/cpc/datasheet/44646

EPPO.  2016.  Peronosclerospora philippinensis (PRSCPH).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://www.newpqr.eppo.int.

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

Fry, W. E. and N. J. Grűnwald.  2010.  Introduction to Oomycetes.  The Plant Health Instructor.  DOI:10.1094/PHI-I-2010-1207-01

Payak, M. M., and B. L. Renfro.  1967.  A new downy mildew disease of maize.  Phytopathology, 57:394-397.

USDA.  2013.  Recovery plan for Philippine downy mildew and brown stripe downy mildew of corn caused by Peronosclerospora philippinensis and Sclerophthora rayssiae var. zeae, respectively.   http://www.ars.usda.gov/SP2UserFiles/Place/00000000/opmp/Corn%20Downy%20Mildews%20Recovery%20Plan%20Revised%202013.pdf

USDA, 2016.  Stakeholder announcement: USDA proposes updates to select agents registration list and select agent regulations.  USDA APHIS. Published January 14, 2016.

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: C

Posted by ls

Plant Pathogens, Viruses and viroids

Freesia Mosaic Virus

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

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

 History & Status:

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

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

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

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

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

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

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

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

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

California Distribution: San Luis Obispo (nursery).

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

The risk Freesia mosaic virus would pose to California is evaluated below.

Consequences of Introduction: 

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

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

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

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

Risk is Medium (2) – Freesia mosaic virus is likely to establish wherever freesia and Peruvian lily and lily plants are grown in limited areas of California. These host plant species have limited production in state, mostly in the north coast and mountain regions, and few southern coast regions, as well as cultivated in nursery and private production sites – including home gardens.       

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

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

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

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

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

Risk is Medium (2) – Freesia mosaic virus has high reproductive potential.  In nature, its spread to non-infected plants is through aphid vectors, Macrosiphum euphorbiae and Myzus persicae.  It is also transmitted by mechanical inoculation and spread via infected nursery plants and propagative parts.   The virus pathogen is not transmitted by seed, pollen or contact between plants.

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – Incidents of Freesia mosaic virus infections could lower plant value resulting in loss in market sales of nursery-grown freesia and lily plants.  The pathogen is vectored by the potato aphid and green peach aphid, Macrosiphum euphorbiae and Myzus persicae respectively.

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

Risk is Medium (2) – Plant infections caused by Freesia mosaic virus are likely to have a minimal impact on the overall environment but may significantly impact home gardening and ornamental plantings. The pathogen may impact California State and federal endangered western lily (Lilium occidentale) and Pitkin Marsh lily (L. pardalinum ssp. pitkinense (ref: State and Federally listed endangered, threatened, and rare plants of California, July, 2015, California Department of Fish and Wildlife, Biogeographic Data Branch, California Natural Diversity Database).

Consequences of Introduction to California for Freesia mosaic virus

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Freesia mosaic virus to California = 10.

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

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

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

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

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

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

Final Score:

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

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

Uncertainty:

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

Conclusion and Rating Justification:

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

References:

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

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

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

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

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

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

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

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

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

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

Responsible Party:

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

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

Calonectria pteridis Crous, M. J. Wingf. & Alfenas, 1993

California Pest Rating for
Calonectria pteridis Crous, M. J. Wingf. & Alfenas, 1993
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

On April 19, 2016, diseased Ravenea rivularis (majesty palm) plants exhibiting leaf spots were intercepted by San Luis Obispo County Agricultural officials. The shipment of plants had originated in Florida and was destined to a nursery in San Luis Obispo County.  Symptomatic leaves were sent to the CDFA Plant Pest Diagnostics Branch for diagnosis.  Suzanne Latham, CDFA plant pathologist, identified the associated pathogen as Calonectria pteridis.  Then on May 23, 2016, C. pteridis was detected again in a different shipment of majesty palm plants destined to the same nursery in San Luis Obispo.  In both detections, the pathogen was assigned a temporary Q rating by the CDFA and consequently, all infected plant materials were destroyed. The risk of infestation of C. pteridis in California is evaluated and a permanent rating is proposed here.

History & Status:

Background:  Calonectria pteridis is the sexual (telemorph) stage of the fungal pathogen, while its asexual (anamorph) stage is Cylindrocladium pteridis.  Calonectria pteridis causes leaf spot and blight, stalk and root rot diseases in various hosts.  In the continental United States, Calonectria pteridis primarily causes symptoms of leaf spots and blights in palm.  Symptoms are indistinguishable from those caused by three other species in the genus (Yu & Elliot, 2013).  In Brazil, C. pteridis is one of the most common species associated with eucalyptus trees causing Calonectria leaf blight disease (Alfenas et al., 2013). In China, C. pteridis caused serious damage to Serenoa repens – an important medicinal and ornamental garden plant (Yang, et al., 2014).  In the USA, C. pteridis has been found on several hosts including palm from Tennessee, Georgia, Florida, and Hawaii (Uchida, 2004; Farr & Rossman, 2016). Recently, the pathogen was detected in infested majesty palm plants shipped from Florida to California.  The pathogen is widespread especially in subtropical and tropical regions.

Disease cycle:  The disease cycle generally involves the pathogen’s anamorphic or asexual stage resulting in the production of conidia (spores) and telemorphic or sexual stage resulting in perithecia (fruiting structure) and ascospores. Conidia, produced on infected plants are dispersed by insects, tools, gloves, plant handling, wind and splashing water, while ascospores are discharged from fruiting bodies by air currents and splashing water.  Discharged spores land on plant host tissue and germinate and penetrate tissue when leaves are wet or under high relative humidity.  The pathogen grows within the host and after about one week produces conidiophores and conidia.  Perithecia and ascospores are formed on infected tissue (Uchida, 2004; Yu & Elliot, 2013).

Hosts: Calonectria pteridis can attack a number of hosts including ornamentals, forest and environmental trees and shrubs, and few agricultural crops.  In the USA, palms have been reported as the main host attacked by the pathogen.  Hosts include: Arachis hypogaea (peanut), Arachnoides adiantiformis  (syn. Rumohra adiantiformis, Polystichum adiantiformis; leatherleaf fern), Arecastrum romanzoffianum (syn. Sygarus romanzoffiana; queen palm); Asparagus plumosus (asparagus fern), Callistemon citrinus (crimson bottlebrush), C, rigidus (erect bottlebrush), Chamaedorea elegans (syn. Collinia elegans; neanthe bella palm/parlor palm), C. cataractarum (cat palm), Chrysalidocarpus sp. (syn. Dypsis sp.; palm); Cissus rhombifolia (grape ivy), Cocos nucifera (coconut), Crassula sp., C. argentea (jade plant), Dictyosperma album (princess palm), Dracaena marginata (Marginate Dracaena), Drosera sp. (sundews), Dryopteris sp. (woodfern), Elaeis guineensis (African oil palm), Eucalyptus spp.,(eucalyptus), Guzmania wittmackii (bromeliad/Guzmanea), Heliconia bihai (macawflower), Howeia belmoreana, H. forsteriana (kentia palm/curly palm), Laccospadix australasica (Atherton palm), Leucadendron sp., Livistona chinensis (Chinese fan palm), Lupinus sp., (lupine), Mauritia flexuosa (moriche palm), Melaleuca leucadendra (weeping paperback), M. quinquenervia (broad-leaved paperback), Musa sp. (banana), Nephrolepis sp., Nephrolepis exaltata (sword fern), Phoenix canariensis (Canary Island date palm), Pinus sp., P. caribaea (Caribbean pine), P. caribbaea var. hondurensis,  P. oocarpa (Mexican yellow pine), Pouteria dulcifica (syn. Synsepalum dulcificum; miracle fruit/sweet berry), Ravenea rivularis (majesty palm), Rhapis humilis (slender lady palm), Rhododendron obtusum (Hiryu azalea/Kurume azalea), Serenoa repens (saw palmetto), Scolopendrium sp., Solanum tuberosum (potato), Strelitzia reginae (bird of paradise), Tillandsia wagneriana (bromeliad), Washingtonia sp., W. filifera (California or desert fan palm), W. robusta (Mexican fan palm) (Crous et al., 1993; Crous & Wingfield, 1993; Farr & Rossman, 2016; Yu & Elliot, 2013).

Symptoms:  Symptoms caused by Calonectria pteridis in palm begin as flecks of small, water-soaked lesions that develop to irregular shades of gray, yellow, reddish brown, brown, or black.  Newly formed lesions are circular or elliptical, 3-5 mm long, and on enlarging develop a tan or gray center surrounded by a brownish halo. The rachis and petiole may become infected with small flecks and eventually leaves and leaflets dry as the disease progresses and lesions coalesce.  Leaf spots may appear on leaves of all ages, although mature leaves are most susceptible (Yu & Elliot, 2013).

Spread:   Conidia are readily spread by insects, pruning tools, plant handling, air currents, rain or splashing irrigation water, while ascospores can be released from their fruiting bodies and spread by air currents and splashing water (Uchida, 2004; Yu & Elliot, 2013).

Damage Potential:  Leaf spot and blight disease caused by Calonectria pteridis can result in reduced plant growth, quality, and marketablility.  Estimates of yield/crop loss due to this pathogen have not been reported.  However, under nursery controlled environments, production of palms, ferns, eucalyptus, and other ornamental host plants may be at heightened risk for pathogen infection and reduced plant production. Seedling and immature palms without trunks are likely to be most susceptible to this leaf spot disease (Yu & Elliot, 2013).  Infection of outdoor growths of palm and eucalyptus trees require warm and humid to wet climate for disease development.  In Brazil, C. pteridis is one of the most important causal agents of Calonectria leaf blight disease of Eucalyptus spp. and has significantly reduced eucalyptus growth (Alfenas, et al., 2013).  In China, up to 100% incidence of leaf spot disease in Serenoa repens, medicinal plant, often lead to plant death (Yang, et al., 2014).

Worldwide Distribution: Asia: China, India, Malaysia, Singapore; Africa: Cameroon, Ivory Coast, Mauritius, South Africa; Europe: Spain, North America: USA (Florida, Hawaii), West Indies; South America: Brazil, Costa Rica, Martinique, Venezuela (Crous & Wingfield, 1993; Farr & Rossman, 2016).

Official Control: None reported.  Currently, Calonectria pteridis is a quarantine, actionable pathogen with a Q rating in California.

California Distribution: Calonectria pteridis is not known to be established in California.  Diseased plants detected in a San Luis Obispo nursery were destroyed (see “Initiating Event).

California Interceptions:  There have been two interceptions of Calonectria pteridis- infested Ravenea rivularis (majesty palm) plants that originated in Florida (see ‘Initiating Event’).

The risk Calonectria pteridis 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):  Calonectria pteridis requires humid, wet, rainy and warm climates to infect plants and develop.  Therefore, the pathogen may only be able to establish in limited parts of California.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3): Calonectria pteridis has a very wide host range and can attack a number of diverse hosts including ornamentals, forest and environmental trees and shrubs, and few agricultural crops.  In the USA, palms have been reported as the main host attacked by the pathogen.

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

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

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

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

Risk is High (3):  The pathogen has high reproductive potential.  Conidia and ascospores are transmitted by wind, wind-driven rain and splashing irrigation water, cultivation tools, and plant handling.  However conidial germination and plant infection require long, wet periods.

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): Infections of Calonectria pteridis could lower crop value and cause loss of markets.  Under controlled wet and warm environments, nursery productions of palms and other ornamental host plants may be at particular risk for pathogen infection and reduced plant production.

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):  Under conducive climate for development, the pathogen could significantly impact cultural practices or home garden plantings.  Its overall impact on California’s environment is assessed as ‘medium’. 

Consequences of Introduction to California for Calonectria pteridis:

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

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

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

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

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

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

Evaluation is Not established (0):  Interceptions of Calonectria pteridis-infected nursery plants were destroyed and therefore, the pathogen is not considered 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 = 12.

Uncertainty:  

Periodic surveys and/or subsequent detection may confirm the presence/absence of C. pteridis in commercial and private production regions within California.  Subsequent results may alter the herein proposed rating for the pathogen.

Conclusion and Rating Justification:

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

References:

Alfenas, R. F., O. L. Pereira, R. G. Frietas, C. S. Freitas, M. A. D. Dita, and A. C. Alfenas.  2013.  Mass spore production and inoculations of Calonectria pteridis on Eucalyptus spp. under different environmental conditions.   Tropical Plant Pathology, 38:406-413.

Crous, P. W., M. J. Wingfield, and A. C. Alfenas.  1993. Additions to Calonectria.  Mycotaxon 46:217-234.

Crous, P. W., and M. J. Wingfield. 1993.  Calonectria pteridis.  IMI Descriptions of Fungi and Bacteria. No. 116 pp. Sheet 1153.

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

Uchida, J. Y.  2004.  Calonectria leaf spot (Cylindrocladium leaf spot).  In ‘Compendium of Ornamental Palm Disease and Disorders’ Eds. M. L. Elliott, T. K. Broschat, J. Y. Uchida, and G. W. Simone.  The American Phytopathological Society, pgs. 12-14.

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

Yang, W., L. Zheng, C. Wang, and C. -P. Xie.  2014.  The first report of Calonectria pteridis causing a leaf spot disease on Serenoa repens in China. Plant Disease. 986: 854.

Yu, J. and M. L. Elliott.  2013.  Calonectria (Cylindrocladium) leaf spot of palm.  University of Florida Institute of Food and Agricultural Sciences.  http://edis.ifas.ufl.edu/PP302.

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

Posting by ls

Fungi, Plant Pathogens

Phytophthora quercina T. Jung 1999

California Pest Rating for
Phytophthora quercina T. Jung 1999
Pest Rating: B 
PEST RATING PROFILE
Initiating Event: 

On April 25, 2016, two soil samples with roots of valley oak (Quercus lobata) trees that showed symptoms of stunting in a restoration site in Santa Clara County, were collected by Santa Clara County Agricultural officials and sent to the CDFA Plant Pathology Laboratory, for diagnosis.  DNA was extracted from soil baits and determined to be 100% similar to the pathogen, Phytophthora quercina, by Suzanne Rooney-Latham, CDFA plant pathologist.   DNA samples were sent by CDFA to the USDA APHIS PPQ CPHST Laboratory in Beltsville, Maryland, and on June 10, 2016, USDA confirmed the identity of P. quercina.  This detection marked the first confirmed presence and new record of the pathogen in the United States (USDA APHIS PPQ, 2016).  Currently, P. quercina has a temporary ‘Q’ rating in California.  The risk of introduction and establishment of this pathogen in California is assessed and a permanent rating is proposed herein.

History & Status:

Background: Oak decline is a serious and frequently recurring disease in Europe since the beginning of the twentieth century (Jung et al., 1999).  During the early 1990s, several Phytophthora spp. including a newly described P. quercina were found to be associated with oak decline and root rot in central and southern Europe.  In pathogenicity tests on oak, Quercus robur, P. quercina was found to be most pathogenic in comparison to the other associated Phytophthora species (Jung et al., 1999).  Subsequent reports associated P. quercina with oak decline from Turkey, Austria, and Italy (Balcý & Halmschlager, 2002a, 2002b; Vettraino et al., 2002).  Phytophthora quercina is an oomycete, and Cooke et al, (1999) provided molecular evidence that verified P. quercina as a distinct species.

Phytophthora quercina was recently detected in soil samples obtained from the root zone area of diseased valley oak trees grown at a California restoration site.  The USDA marked this detection as the first known confirmation of the pathogen in the United States.  Details are given above in “Initiating Event”.   The species was reported in 2007 on being detected in a soil bait around a declining oak tree in Central Missouri (Schwingle et al., 2007), however, the identification was not confirmed by USDA APHIS and there have not been any further publications on the species in the USA (USDA APHIS PPQ, 2016).

Hosts: Quercus spp. (oak): Q. cerris, Q. hartwissiana, Q. frainetto, Q. ilex, Q. robur, Q. petraea, Q. pubescens, Q. suber, and Q. vulcanica (Balcý & Halmschlager, 2002a, 2002b; EPPO, 2016; Farr & Rossman, 2016; NPRG, 2010).

Symptoms:  Phytophthora quercina, along with several other Phytophthora species, occur in oak decline stands in Europe (Balcý & Halmschlager, 2002; Jung et al., 2008).  Above ground symptoms of oak decline include dieback of branches and parts of the crown, formation of epicormic shoots, high transparency of the crown, yellowing and wilting of leaves and tarry exudates from the bark.  These symptoms are indicative of water stress and poor nutrition (Jung et al., 2008).  Below ground symptoms in declining European oak species resulted in deterioration of oak fine roots, including a progressive destruction of the fine root system, dieback of long roots, and necrotic lesions on suberized and non-suberized roots.  Although these symptoms occur in both healthy and declining oaks, the damage is generally more severe in declining oaks (Jung, et al., 2008).  The pathogen also causes abnormal root branching, and produces elicitins, viz. toxic substances that induce wilting and yellowing and leaf necrosis in declining oaks (NPRG, 2010).   In pathogenicity test, P. quercina-infected Quercus robur (oak) seedlings with severe root rot showed wilting and necrosis of leaves, root necrosis and dieback of the shoot. Under natural conditions, mature Q. robur trees showed reductions in fine root length (Jung et al., 1999).

Damage Potential:  The extent of damage caused by Phytophthora quercina has not been reported.  Several Phytophthora species including P. quercina are associated with oak decline disease.  However, P. quercina has been shown to be pathogenic to some European Quercus species, such as Q. robur (Jung et al., 1999), and to be one of the most aggressive and most common species found in reported surveys in Europe (Jung et al., 1999, 2008; Balcý and Halmschlager 2002a, 2002b).  In Italy, P. quercina was the only species significantly associated with declining oak trees (Vettraino et al., 2002).

Disease Cycle: Although present in roots and rhizosphere soil of oaks exhibiting symptoms of oak decline, the precise role of Phytophthora quercina in this disease is not known and very little is known about its biology.  Jung et al. (2008), reported that at least two different complex diseases are referred to as ‘oak decline’.  On sites with a mean soil pH 3.5 or greater and sandy-loam to clayey soil texture, Phytophthora species were commonly isolated from rhizosphere soil, and highly significant correlations existed between crown transparency and various root parameters.  However, in sites with a mean soil pH less than 3.9 and sandy to sandy-loam soils, Phytophthora species were not found. Biotic and abiotic stress factors such as drought and frost, may often act synergistically and accelerate Phytophthora-mediated decline of oaks.

Generally, species of Phytophthora that cause root and stem rots survive cold winters or hot and dry summers as thick-walled, resting spores (oospores and chlamydospores) or mycelium in infected roots, stems or soil.  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). Phytophthora quercina is homothallic.  Optimum growth in culture is at 20°C and 25°C, however, it is able to grow at temperatures as high as 27.5°C (Jung et al., 1999; Barzanti et al., 2001).

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

Worldwide Distribution: Asia: Turkey; Europe: Austria, Belgium, France, Germany, Hungary, Italy, Luxemberg, Montenegro, Serbia, Spain, Sweden, Scotland, United Kingdom: North America: USA (California) (Balcý & Halmschlager, 2002a, 2002b; EPPO, 2016; Farr & Rossman, 2016; Jung et al., 1999; NPRG, 2010).

Official Control: Phytophthora quercina is listed as an exotic forest pathogen in USDA APHIS PPQ Federal New Pest Response Guidelines for Phytophthora species (NPRG, 2010).  The species has been on the North American Plant Protection Organization (NAPPO) alert list since 2002.  Currently, P. quercina has a temporary ‘Q’ rating in California.

California Distribution: Phytophthora quercina has been detected in a California native plant restoration site in a Santa Clara County.

California Interceptions: None.

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

Consequences of Introduction:

1) Climate/Host Interaction: Evaluate and score the pest for suitability of hosts and climate to establish in California.  Score:

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

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

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

Risk is High (3) – Although Phytophthora quercina has been reported to be associated primarily with European oak species in Europe, its recent detection in valley oak rhizosphere soil extends the capability of this pathogen to be associated with California native oaks.  Valley oak is endemic to California and present throughout the State.  Thereby, making it likely for the pathogen to establish a widespread distribution in California.  It is not yet known, but probable that other California native oaks may be affected by P. quercina.

2) Pest Host Range: Evaluate and score the pest as it pertains to host range.  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) – Phytophthora quercina has a host range limited to Quercus spp. that includes Q. cerris, Q. hartwissiana, Q. frainetto, Q. ilex, Q. robur, Q. petraea, Q. pubescens, Q. suber, and Q. vulcanica.  In California, it was found to be associated with Q. lobata.

3) Pest Dispersal Potential: Evaluate and score the pest for dispersal potential using these criteria.  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) – Phytophthora quercina is soil-borne and water-borne and therefore, primarily spread artificially via infested soils, plants, nursery and planting stock, seedlings, run-off and splash irrigation water, cultivation equipment and tools, and boots that may spread contaminated soil and plant materials to non-infected sites.

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is Medium (2) – The extent of damage caused by Phytophthora quercina has not been reported.  Several Phytophthora species including P. quercina are associated with oak decline disease. In Europe, P. quercina was most commonly associated with the disease than were other Phytophthora species.  The pathogen could impact nursery-produced oaks thereby triggering possible loss of markets and requiring changes in normal cultural practices to avoid spread of the soil and water-borne pathogen.  

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

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 could significantly impact cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

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

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

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

 Risk is High (3) – Phytophthora quercina is listed as an exotic forest pathogen in USDA APHIS PPQ Federal New Pest Response Guidelines for Phytophthora species (NPRG, 2010).  The species has been on the North American Plant Protection Organization (NAPPO) alert list since 2002.  Although the extent of damage potentially caused by this pathogen is not yet known, its spread within California could cause serious impact on native oaks, disrupt critical habitats by killing critical species necessary for species diversity and soil stability, necessitate official or private treatment programs to preserve critical, rare, or endangered species, and significantly impact cultural practices, home/urban and/or ornamental plantings.

Consequences of Introduction to California for Phytophthora quercina:

Add up the total score and include it here

Low = 5-8 points

Medium = 9-12 points

High = 13-17 points

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

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

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

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

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

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

Evaluation is Low (-1).

Final Score

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.

Uncertainties:

The extent of economic damage caused by Phytophthora quercina is not known. Also not known is the exact role of the pathogen in oak decline disease, and details of the biology of the pathogen species.

Conclusion and Rating Justification:

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

References:

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

Balcý, Y. and E. Halmschlager.  2002a. First confirmation of Phytophthora quercina on oaks in Asia.  Plant Disease 86:442. http://dx.doi.org/10.1094/PDIS.2002.86.4.442C

Balcý, Y. and E. Halmschlager.  2002b. First report of Phytophthora quercina in Austria.  New Disease Reports volume 6, August 2002-January 2003. http://www.bspp.org.uk/ndr/jan2003/2002-28.htm

Barzanti, G. P., P. Capretti, and A. Ragazzi. 2001. Characteristics of some Phytophthora

species isolated from oak forest soils in central and northern Italy.

Phytopathologia Mediterranea 40(2): 149-156.

Cooke, D.E.L., T. Jung, N. A. Williams, R. Schubert, G. Bahnweg, W. Oswald, and J. M. Duncan.  1999.  Molecular evidence supports Phytophthora quercina as a distinct species. Mycological Research, 103:799-804.

EPPO.  2016.  Phytophthora quercina (PHYTQU).  New PQR database.  Paris, France:  European and Mediterranean Plant Protection Organization.  http://newpqr.eppo.int

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

Jung, T., D. E. L. Cooke, H. Blaschke, J. M. Duncan, and W. Oswald. 1999.  Phytophthora quercina sp. nov., causing root rot of European oaks. Mycol. Res. 103: 785-798.

Jung, T., H. Blaschke and W. Oßwald.  2008.  Involvement of soilborne Phytophthora species in Central European oak decline and the effect of site factors on the disease.  Plant Pathology, 49:706-718. DOI: 10.1046/j.1365-3059.2000.00521.x

Schwingle, B. W., J. Juzqik, J. Eggers, and B. Moltzan.  2007.  Phytophthora species in soils associated with declining and nondeclining oaks in Missouri Forests.  Plant Disease 91:633. http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-91-5-0633A

NPRG.  2010.  New Pest Response Guidelines: Phytophthora species in the Environment and Nursery Settings. USDA MRP APHIS PPQ Cooperating State Departments of Agriculture, July 09 2010. 229 pages.

USDA APHIS PPQ.  2016.  Email from J. H. Bowers, National Survey Coordinator National Policy Manager, Cooperative Agricultural Pest Survey, USDA, APHIS, PPQ, PHP, to Nick Condos, Director, CDFA, sent Friday, June 10, 2016, 11:56 am.

Vetrraino, A. M., G. P. Barzanti, M. C. Bianco, A. Ragazzi, P. Capretti, E. Paoletti, N. Luisi, N. Anselmi, and A. Vannini.  2002.  Occurrence of Phytophthora species in oak stands in Italy and their association with declining oak trees.  Forest Pathology, 32:19-28.  DOI: 10.1046/j.1439-0329.2002.00264.x

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 fructicola Prihastuti, L. Cai & K. D. Hyde, 2009

California Pest Rating for
Colletotrichum fructicola Prihastuti, L. Cai & K. D. Hyde, 2009
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:

On March 29, 2016, a shipment of Chinese evergreen (Aglaonema sp.)  cuttings showing leaf spotting symptoms and destined to a nursery in San Luis Obispo County, was intercepted and sampled by San Luis Obispo County Agricultural officials.  The shipment had originated in Costa Rica.  Diseased plant samples were sent to the CDFA Plant Diagnostics Branch for diagnosis.  Suzanne Latham, CDFA plant pathologist, identified the anthracnose and fruit rot pathogen, Colletotrichum fructicola, as the cause for the disease.  This species was first detected within California on August 26, 2015, in mango fruit shipped from Puerto Rico and intercepted by the California Dog Team.  The fruit shipment was destined to a private citizen in Sacramento County.  The identity of the fungal pathogen was confirmed on August 18, 2015, by the USDA National Identification Services at Beltsville, Maryland.  Several detections of C. fructicola followed the initial find: on August 14, 2015, in Cymbidium orchid leaves from a nursery in San Diego County; on August 19, 2015, on mango fruit from Florida and destined for Stanislaus County; on November 9, 2015, in Dracaena massangeana cuttings from Costa Rica and destined to a nursery in San Diego County; on March 15, 2016, in black sapote fruit from Florida and destined to a private citizen in Los Angeles County.  In all these cases, subsequent to the detection of C. fructicola, all fruit and plant shipments/nursery stock were either destroyed or rejected from entering California.  Currently, C. fructicola 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 fructicola was originally reported to be associated with coffee berries (Coffea arabica) in northern Thailand (Prihastuti et al., 2009) and as a leaf endophyte from Central America (as C. ignotum). Since then, C. fructicola has been found on several tropical and subtropical hosts from diverse geographical regions. In the USA, C. fructicola was reported in 2012 from Florida and North Carolina on strawberry crown and apple fruit respectively (Weir et al., 2012). During 2015-16, the pathogen was also detected in California associated with several quarantine nursery plant/fruit shipments and regulatory nursery samples.

The pathogen is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides complex and is generally identified from other species of the complex only by gene sequencing.  However, C. ignotum and Glomerella cingulata var. minor are synonyms of C. fructicola (Prihastuti et al., 2009; Rojas et al., 2010; Weir et al, 2012).

Hosts: Aglaonema sp. (Chinese evergreen), Annona reticulata (custard apple), A. squamosa (sugar apples), Artocarpus heterophyllus (jackfruit), Coffea arabica (coffee), Coffea sp., Camellia japonica (Japanese camellia), Camellia sinensis (tea), Camellia sp., Capsicum frutescens (chili pepper), Carica papaya (papaya), Cestrum parqui (green cestrum), Citrullus vulgaris (watermelon), Citrus limon (lemon), C. reticulata (Mandarin orange), C. sinensis (sweet orange), Citrus x paradisi, Crinum asiaticum (spider lily), Cucumis sativus (cucumber), Cymbidium sp. (orchid), Dendrobium sp. (orchid), Dioscorea alata (purple yam), D. rotundata (white yam), Diospyros nigra (black sapote), Dracaena massangeana (corn plant/cornstalk Dracaena), Epidendrum sp. (orchid), Ficus carica (common fig), F. edulis (fig), F. pumila (creeping fig), Fortunella margarita (oval kumquat) Fragaria ananassa (strawberry), Limonium sinuatum (statice), Limonium sp., Lobularia maritima (sweet alyssum), Lupinus angustifolius (blue lupine), Lycopersicon esculentum (tomato), Lycium chinensis (boxthorn), Malus domestica (apple), M. sylvestris (crab apple), Mangifera indica (mango), Matthiola incana (stock), Medicago polymorpha (burclover), Musa acuminata (edible banana), Nerium oleander (oleander), Nicotiana tabacum (tobacco), Passiflora edulis (passion fruit), Persea americana (avocado), Phalaenopsis sp. (moth orchid), Phormium tenax (flax), Portulaca oleracea (little hogweed/common purslane), Psidium guajava (guava), Pyrus bretschneideri (Chinese white pear), P. pyrifolia (pear), Saccolabium sp. (orchid), Tetragastris panamensis, Theobroma cacao (cocoa), Vanda sp. (orchid) (Farr & Rossman, 2016; Li et al., 2014; Prihastuti et al., 2009; Wang et al., 2016, Weir et al., 2012; Zhang et al., 2015).

Symptoms:  Generally, Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots, fruit rot, and wilting of leaves which often result in dieback and reduction in plant quality.  In China, early stages of the disease in pear was characterized by the presence of black spots on young fruit which was always followed by severe bitter rot in matured fruit, and less than 1 mm black spots on leaves resulting in severe defoliation and loss of fruit (Jiang et al., 2014; Zhang et al., 2015). Anthracnose symptoms on tobacco leaves initiate as discrete, yellow-green spots which coalesce into larger lesions with white centers and dark brown margins (Wang et al., 2016).

Damage Potential:  Anthracnose disease caused by Colletotrichum fructicola can result in reduced plant quality and growth, fruit production and marketability.   In China, sudden outbreaks of the disease resulted in severe defoliation and a loss of pear fruit quality and yield resulting in fresh market losses ranging from 60-90% which, in 2008, were estimated at US$150 million. (Li, et al., 2013; Zhang, et al., 2015).  In 2014, also in China, 90% of tobacco leaves on ~2% plants in a 3-ha commercial tobacco field were infected with C. fructicola (Wang, et al., 2016).  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 fructicola 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.

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

Worldwide Distribution: Asia: China, India, Israel, Japan, Korea, Thailand; Africa: Angola, Nigeria; Europe: United Kingdom; North America: Canada, Panama, USA (California, Florida, North Carolina); Australia (Farr & Rossman, 2016; Li et al., 2014; Prihastuti et al., 2009; Wang et al., 2016, Weir et al., 2012; Zhang et al., 2015).

Official Control:  In California C. fructicola is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.

California Distribution: Colletotrichum fructicola was detected in a nursery in San Diego County (see “Initiating Event”).

California Interceptions:  During 2015-16, Colletotrichum fructicola has been intercepted several times mainly in shipments of mango and black sapote fruits, Dracaena and Chinese evergreen cuttings that originated in Costa Rica, Puerto Rico, and Florida (see ‘Initiating event’).

The risk Colletotrichum fructicola 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) – Similar to other species of Colletotrichum, C. fructicola 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.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is High (3) – The host range of Colletotrichum fructicola is relatively wide and diverse and includes several tropical and subtropical plants, as well as agricultural and ornamental crops grown in California.

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

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

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

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

Risk is High (3) – 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.

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) –Under suitable, wet climates, the pathogen could lower plant growth, fruit production and value and trigger the loss of markets.

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

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

The pest could directly affect threatened or endangered species.

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

The pest could trigger additional official or private treatment programs.

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

Score the pest for Environmental Impact. Score:

– 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 cultural practices or home garden plantings.

Consequences of Introduction to California for Colletotrichum fructicola:

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

-Low = 5-8 points

-Medium = 9-12 points

–High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Colletotrichum fructicola to California = (13).

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

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

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

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

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

Evaluation is Low (-1) – Colletotrichum fructicola was detected in a nursery in San Diego County.

Final Score:

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

Final Score:  Score of Consequences of Introduction – Score of Post Entry Distribution and Survey Information = 12.

Uncertainty:

Periodic surveys need to be conducted to confirm the presence/absence of C. fructicola in commercial and private production regions within California.  Subsequent results may alter the herein proposed rating for the pathogen.

Conclusion and Rating Justification:

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

References:

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/

J. Jiang, Zhai, H. Li, Z. Wang, Y. Chen, N. Hong, G. Wang, G. N. Chofong, and W. Xu. 2014. Identification and characterization of Colletotrichum fructicola causing black spots on young fruits related to bitter rot of pear (Pyrus bretschneideri Rehd.) in China.  Crop Protection 58:41-48.

Li, H.N., Jiang, J.J., Hong, N., Wang, G.-P., and Xu, W.X. 2013. First Report of Colletotrichum fructicola Causing Bitter Rot of Pear (Pyrus bretschneideri) in China. Plant Disease 97:1000. http://dx.doi.org/10.1094/PDIS-01-13-0084-PDN.

Prihastuti, H., L. Cai, H. Chen, E. H. C. McKenzie, and K. D. Hyde.  2009. Characterization of Colletotrichum species associated with coffee berries in northern Thailand. Fungal Diversity 39: 89-109.

Wang, H. C., Y. F. Huang, Q. Chen, M. S. Wang, H. Q. Xia, S. H. Shang, and C. Q. Zhang.  2016.  Anthracnose caused by Colletotrichum fructicola on tobacco (Nicotiana tabacum) in China.  Plant Disease (posted on line March 8, 2016). http://dx.doi.org/10.1094/PDIS-06-15-0724-PDN.

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.

P. F. Zhang, L. F. Zhai, X. K. Zhang, X. Z. Huang, N. Hong, W. Xu, and G. Wang. Characterization of Colletotrichum fructicola, a new causal agent of leaf black spot disease of sandy pear (Pyrus pyrifolia).  European Journal of Plant Pathology 143:651-662.

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

Ascochyta aquilegiae (Rabenh.) Boerema, Fruyter & Noorder, 1997

California Pest Rating for
Ascochyta fungi (photo source: forestryimages.org)
Ascochyta fungi; Ascochyta spp. Lib.
Ascochyta aquilegiae (Rabenh.) Boerema, Fruyter & Noorder, 1997
Pest Rating:  C
PEST RATING PROFILE
Initiating Event:

On March 28, 2016, a sample of diseased Aquilegia sp. (columbine) plants showing symptoms of dieback, was voluntarily submitted by a nursery in Contra Costa County to the CDFA Plant Pathology Laboratory for disease diagnosis.  Suzanne Latham, CDFA plant pathologist, identified the associated fungus plant pathogen, Ascochyta aquilegiae, as the cause for the disease.  The pathogen was assigned a temporary “Z” rating as it has been reported earlier in California and is considered widely distributed.  That rating is reassessed here and a permanent rating is proposed.

History & Status:

Background:  Ascochyta aquilegiae causes dark leaf spots, stem lesions, and crown rots in plants belonging to the family Ranunculaceae, including several species in the genera Aquilegia and Delphinium.  The fungal species has undergone several name changes in fungal taxonomy and is known by several synonyms including, Stagonosporopsis aquilegiae, Actinonema aquilegiae, Ascochyta laskarisii, Diplodina delphinii, Phoma aquilegiicola, Phyllosticta aquilegiae, and Phyllosticta aquilegicola (Farr & Rossman, 2016).

Disease development and spread:  Ascochyta aquilegiae attack primarily plant leaves by means of spores (conidia) and, following infection, produce numerous condia that are spread to other plants by wind, wind-blown rain, water, and insects.  Conditions that favor prolonged leaf-wetness in warm climates often favor development of the pathogen. The pathogen is also transmitted to non-infected sites through the movement of infected plant materials and debris. The fungus overwinters primarily in fallen leaves or infected leaf debris, or as mycelium in infected tissues of perennial plants (Agrios, 2005; Pscheidt & Ocamb, 2016a, 2016b).

Hosts: Aquilegia spp. (columbine), Aconitum spp. (aconite/wolf’s bane), Clematis sp. (clematis), Consolida spp. (larkspur), Coptis chinensis (goldthread), Delphinium spp. (delphinium/larkspur) (Farr & Rossman, 2016; French, 1989; Garibaldi et al., 2011; Yu et al., 2014).

Symptoms and damage potential: Ascochyta aquilegiae causes leaf spots, stem cankers and crown rots.  Leaf lesions of infected Aquilegia and Coptis plants are extensive, usually beginning at the leaf margin and extending to the central leaf blade eventually coalescing to cover entire leaf, irregular, brown to black, necrotic, slightly sunken with a well-defined border and surrounded by a violet-brown halo.   As the disease progresses, stems are also affected causing death of the apical part of the plant (Garibaldi et al., 2011; Yu et al., 2014). In Delphinium spp., petioles develop brown water-soaked lesions near the base of succulent plants.  Less vigorous plants show black local lesions on the petiole.  Inflorescences and seed pods develop a blackish decay.  Generally, crown rot may be found in plants two years or older (Pscheidt & Ocamb, 2016a, 2016b).  Small, dark brown to black fungal fruiting bodies (pycnidia) may be present in the lesions.

Damage Potential:  While information on the economic importance of the disease caused by Ascochyta aquilegiae is limited, the development of leaf spots, stem cankers and crown rots in infected plants may result in reduced plant production, yield, and marketability of columbine and other host plants used in residential gardens and commercial landscapes.  Plants are particularly at risk of pathogen infection in warm and moist natural climates of California, and in nursery-controlled productions.  In China, A. aquilegiae caused yield losses of 15-75% in gold thread, an important herbaceous plant used in traditional Chinese medicine (Yu et al., 2014).

Worldwide Distribution:  Asia:  Armenia, China, Japan, Russia; Africa: South Africa, Zimbabwe, Europe: Bulgaria, Czechoslovakia, Germany, Italy, Netherlands, Poland, Scotland, United Kingdom; North America: Canada, USA; Oceania: New Zealand.  It is widespread within the USA in Alaska, California, Connecticut, Iowa, Idaho, Maryland, New Jersey, New York, Oregon, Pennsylvania, Texas, Washington, Wisconsin (Farr & Rossman, 2016; Garibaldi et al., 2011; Pscheidt & Ocamb, 2016a, 2016b; Yu et al., 2014).

Official Control: None reported. Currently, the pathogen has a temporary ‘Z’ rating in California, which indicates that it is a previously unrated organism of known economic and/or environmental detriment but generally distributed in the state.

California Distribution: Ascochyta aquilegiae has been detected in California’s northern and southern coastal counties which include: Del Norte, Humboldt, Mendocino, Sonoma, Marin, San Francisco, San Mateo, Santa Cruz, Alameda, Santa Clara, San Benito, Monterey, San Luis Obispo, Santa Barbara, Ventura, Los Angeles, Orange, and San Diego Counties (French, 1989).

California Interceptions: None reported.

The risk Ascochyta aquilegiae 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): Conditions that favor prolonged leaf-wetness in warm climates often favor development of Ascochyta aquilegiae.  The pathogen is already known to be present in northern and southern coastal counties in California.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1): Presently, the host range is limited to few species within Ranunculaceae. 

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

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

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

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

Risk is Medium (2): Ascochyta aquilegiae produces numerous condia the infect plants, however, to spread to other plants, they are dependent on wind, wind-blown rain, water, and insects.  Furthermore, prolonged leaf-wetness in warm climates is needed to favor development of the pathogen in plants. The pathogen is also transmitted to non-infected sites through the movement of infected plant materials and debris.

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): While information on the economic importance of the disease caused by Ascochyta aquilegiae is limited, the development of leaf spots, stem cankers and crown rots in infected plants may result in reduced plant production value and marketability of columbine and other host plants used in residential gardens and commercial landscapes.  Plants are particularly at risk of pathogen infection in warm and moist natural climates of California, and in nursery-controlled productions

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

Risk is High (3): Commercial landscape and home garden plantings could be negatively impacted if infected by Ascochyta aquilegiae under favorable moist climate conditions.  The pathogen could directly affect certain species of larkspur, namely, Delphinium bakeri (Baker’s larkspur), D. hesperium ssp. cuyamacae (Cuyanaca larkspur), D. luteum (golden larkspur), and D. variegatum ssp. kinkiense (San Clemente Island larkspur) included in the ‘State and Federally Listed Endangered, Threatened, and Rare Plants of California, July 2015’ thereby, potentially lowering biodiversity, natural communities or ecosystem processes.

Consequences of Introduction to California for Ascochyta aquilegiae:

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 = 10

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

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

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

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

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

Evaluation is Medium (-2): Presently, Ascochyta aquilegiae is known to be present in northern and southern coastal counties in California.

Final Score:

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

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

Uncertainty:   

The impact and spread of this pathogen to other intrastate regions where host species are grown, is not known.  Future reports of the detection of P. digitalidis in California could lower the overall score for the pathogen although it is unlikely to affect its final rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Ascochyta aquilegiae is C.

References:

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

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

Garibaldi, A., D. Bertetti, M. T. Amatulli, and M. L. Gullino.  2011.  First report of leaf spot of fan columbine (Aquilegia flabellata) caused by Phoma aquilegiicola in Italy.  Plant Disease 95:880.  http://dx.doi.org/10.1094/PDIS-05-10-0391.

Pscheidt, J.W., and Ocamb, C.M.  2016a. Columbine (Aquilegia spp.) leaf spots.  Pacific Northwest Plant Disease Management Handbook. © Oregon State University. pnwhandbooks.org/plantdisease/node/3020. http://pnwhandbooks.org/plantdisease/columbine-aquile.

Pscheidt, J.W., and Ocamb, C.M.  2016b. Delphinium – leaf spot and crown rot.  Pacific Northwest Plant Disease Management Handbook. © Oregon State University. pnwhandbooks.org/plantdisease/node/3118.  http://pnwhandbooks.org/plantdisease/delphinium-leaf-spot-and-crown-rot.

Yu, Y., Z. C. Su, W. Z. Tan, and C. W. Bi.  2014.  First report of a leaf spot on goldthread (Coptis chinensis) caused by Phoma aquilegiicola in China. Plant Disease 98:1428. http://dx.doi.org/10.1094/PDIS-01-14-0010-PDN.

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

Puccinia kuehnii (W. Krűger) E. J. Butler 1914

California Pest Rating for
Puccinia rusts. Photo credit: Cesar Calderon, USDA APHIS PPQ. Bugwood.org
Puccinia rusts. Photo credit: Cesar Calderon, USDA APHIS PPQ. Bugwood.org
Puccinia kuehnii (W. Krűger) E. J. Butler 1914
Pest Rating:  C
PEST RATING PROFILE
Initiating Event:

On February 9, 2016, USDA’s Animal and Plant Health Inspection Service (APHIS) notified the CDFA that the rust pathogen, Puccinia kuehnii was added on February 2, 2016, to their ‘List of Pests no Longer Regulated at U.S. Ports of Entry’ under the Federally Recognized State Managed Phytosanitary (FRSMP) program (USDA APHIS 2016).  Consequently, USDA APHIS will no longer take regulatory action against this pathogen at ports of entry.  Therefore, and at the request of Stephen Brown, Assistant Director, CDFA, the risk of infestation for P. kuehnii is assessed here and a permanent rating is proposed.

History & Status:

Background:  Puccinia kuehnii is one of two major rust fungi on sugarcane and causes orange rust.  The other rust fungi known as P. melanocephala, causes brown rust and is relatively common.  The orange rust of sugarcane pathogen, P kuehnii, most likely originated in Asia-Oceania regions where Saccharum spp. are native.  In other countries where the pathogen occurs, such as Indonesia and the South Pacific, sugarcane has existed for several centuries and it is assumed that P. kuehnii was likewise introduced and also existed in those countries for the same period of time.  The pathogen is now wide spread in Asia and Australia and was recently discovered in West Africa and the Western Hemisphere and from sugarcane-growing regions in the southeastern United States, Central and South America, and the Caribbean Basin (Dixon & Castlebury, 2016). It is likely that the pathogen was introduced to Australia along with sugarcane that was introduced about 150 years ago as there are no known native hosts present in that region (CABI, 2016).  In the USA, P. kuehnii was first reported from Florida having been detected in infected, brown rust-resistant, sugarcane cultivars. The disease appears to be distributed widely in the South Florida sugarcane-growing region (Comstock et al., 2008).  In 2013, orange rust was also reported from the southern region of Louisiana’s sugarcane production area (Grisham, et al., 2013).  Puccinia kuehnii has not been reported from California nor is sugarcane a major production crop of the State.

Disease cycle:  Puccinia kuehnii completes its life cycle on the same host and has an incomplete lifecycle. Spermagonia and aecia spore states are unknown.    Urediniospores are produced abundantly under natural conditions, but the production of teliospores and basidiospores are comparatively less common.    Under favorable conditions of humidity and temperature, urediniospores present on host germinate to penetrate the tissue.  As the fungus grows, uredinia (fruiting structures) are formed and urediniospores are produced in abundance.   Urediniospores are produced between 10°C and 34°C and optimally at 15-25°C for urediniospores and 26°C for teliospores.  Relative humidity above 97% favors urediniospore germination (Hsieh & Fang, 1983; CABI, 2016).

Dispersal and spread: The main risk for natural dispersal of spores over long distances (over 2000 km) is by wind and wind-blown rain.  Other potential means for spread are the movement of infected leaves and spore-contaminated clothing (CABI, 2016).

Hosts:  Saccharum officinarum (sugarcane) is the main host.  Other hosts include few weeds and ornamental grasses belonging to Saccharum spp. within Poaceae: Saccharum arundinaceum, S. barberi, S. bengalense, S. edule, S. munja, S. narenga, S. rufipilum, S. sinense, S. spontaneum; S. ravennae (syn. Erianthus ravennae); Sclerostachya fusca (Afshan & Khalid, 2013; CABI, 2016; Dixon & Castlebury, 2013; EPPO, 2016; Farr & Rossman, 2016 )

Symptoms:  Orange rust disease is characterized by the development of lesion that initiate as small (0.5 mm diameter) spots on leaves and enlarge into elongated brown lesions (2-8 mm x 0.5-2 mm wide).  As the lesions enlarge, fungal mycelium protrudes through the leaf surface, usually on its underside, producing abundant urediniospores. These pustules usually occur in patches or groups, but cover entire leaf surfaces in severe infections. Severely infected leaf tissue becomes necrotic leading to early senescence. Affected crops appear brown with very little green tissue remaining at all. Symptom development may take 3-4 weeks from infection, depending on weather conditions (CABI, 2016).

Disease Potential:  Orange rust of sugarcane is considered a disease of low economic impact that has rarely caused significant economic losses.  The only severe economic loss was reported in Australia in 2000 on the introduced, highly susceptible Q124 sugarcane variety that was subsequently replaced (CABI, 2016).  The potential for establishment and spread of the pathogen in California is reasonably low as sugarcane, the main host, is grown in limited acreage in dry climates of the Imperial Valley.

Worldwide Distribution: Africa: Cameroon, Cote d’Ivore; Asia: China, India, Indonesia, Japan, Malaysia, Myanmar, Nepal, Pakistan, Philippines, Singapore, Sri Lanka, Taiwan, Thailand, Vietnam; Central America and Caribbean:  Costa Rica, Cuba, Dominican Republic, Guatemala, Jamaica, Nicaragua, Panama; North America: USA, Mexico; South America: Brazil, Colombia, Ecuador; Oceania: American Samoa, Australia, Cook Islands, Fiji, French Polynesia, Guam, Micronesia, New Caledonia, Papua New Guinea, Samoa, Solomon Islands (CABI, 2015; Dixon & Castlebury, 2013; EPPO, 2016; Farr & Rossman).

In the USA it has been reported from Florida and Louisiana (Comstock et al., 2008; Grisham et al., 2013).

Official Control: Puccinia kuehnii is on the “Harmful Organisms Lists” for Brazil, Costa Rica, Egypt, Honduras, and Morocco (PCIT, 2016). Currently, the pathogen has not been rated for California.

California Distribution:  Puccinia kuehnii is not established in California.

California Interceptions: None reported.

The risk Orange Rust of Sugarcane 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):   The potential for establishment and spread of the orange rust pathogen in California is likely to be low as sugarcane, the main host, is grown in limited acreage under dry climates of the Imperial Valley.  Spore germination and plant infection are not expected to be favored under climates of low relative humidity common to that region.

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):  Sugarcane is the main host of P. kuehnii.  The pathogen is largely limited to Saccharum spp. and the related species Sclerostachya fusca.    

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): Puccinia kuehnii has high reproduction and dispersal potential via its windblown spores that are primarily transmitted by strong winds over distances of several hundred kilometers.  Also, they may be spread over long distances via infected plant leaves and spore-contaminated human clothing. 

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is Low (1): The economic impact of Puccinia kuehnii to California is considered low as the potential for establishment and spread of the pathogen is reasonably minimal within a state where sugarcane is not a majorly cultivated crop and requires high relative humidity for pathogen infection.  Potential incidents of the disease occurring under conducive climates could lower crop yield.  

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

Risk is Medium (2):  Puccinia kuehnii infections could affect production of ornamental grasses belonging to Saccharum spp. and grown in private and/or public commercial environments.    

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).  Puccinia kuehnii 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 = 8 (Low).

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Puccinia kuehnii is C.

References:

Afshan, N.S., and A. N. Khalid.  2013.  Checklist of the rust fungi on Poaceae in Pakistan. Mycotaxon 125: 1-17.

Comstock, J. C., S. G. Sood, N.C. Glynn, J. M. Shine Jr., J. M. McKemy, and L. A. Castlebury.  2008.  First report of Puccinia kuehnii, causal agent of orange rust of sugarcane, in the United States and Western Hemisphere. Plant Disease, 92(1):175. http://www.apsnet.org.

Dixon, L. and L. Castlebury.  2016.  Systematic Mycology and Microbiology Laboratory, ARS, USDA. . Invasive Fungi. Orange rust of sugarcane – Puccinia kuehnii. Retrieved March 10, 2016, from /sbmlweb/fungi/index.cfm.

EPPO.   2016.  Puccinia kuehnii (PUCCKU).  PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://www.newpqr.eppo.int.

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/.

Grisham, M. P., J. W. Hoy, J. S. Haudenshield, and G. L. Hartman.  2013.  First report of orange rust caused by Puccinia kuehnii in sugarcane in Louisiana. Plant Disease, 97(3):426-427. http://apsjournals.apsnet.org/loi/pdis.

Hsieh, W. H., and F. G. Fang.  1983.  The uredospore production of Puccinia melanocephala and Puccinia kuehnii in sugarcanes. Plant Protection Bulletin, Taiwan, 25(4):239-244.

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

Peronospora digitalidis Gäum, 1923

California Pest Rating for
Foxglove, Downy Mildew Plant Symptoms
Downy mildew does occur in the landscape in Washington. Note lesions with angular margins. ~ Photo Credit: Jenny Glass, 2011.
Peronospora digitalidis Gäum, 1923
Pest Rating: C
PEST RATING PROFILE
Initiating Event:

On February 9, 2016, USDA’s Animal and Plant Health Inspection Service (APHIS) notified the CDFA that the downy mildew pathogen, Peronospora digitalidis, was added on February 2, 2016, to their ‘List of Pests no Longer Regulated at U.S. Ports of Entry’ under the Federally Recognized State Managed Phytosanitary (FRSMP) program (USDA APHIS 2016).  Consequently, USDA APHIS will no longer take regulatory action this pathogen at ports of entry.  Therefore, and at the request of Stephen Brown, Assistant Director, CDFA, the risk of infestation and the current rating for P. digitalidis is re-assessed here.

History & Status:

Background:  Peronospora digitalidis is an oomycete in the order Peronosporales, which causes downy mildew disease of foxglove (Digitalis spp.).  The pathogen has been reported in Europe, Asia, and New Zealand, and was first reported from the United States, in 2002, on potted common foxglove plants in commercial nurseries in Santa Cruz County, California (Tjosvold & Koike, 2002).  It is likely that all affected nursery plants were destroyed, however, following its initial detection, in 2003, the pathogen continued to be found in several nurseries in California coastal counties and most recently in 2015 (CDFA Pest and Damage Records).

Disease cycle:  Peronospora digitalidis is an oomycete belonging to the family Peronosporaceae.  Generally, downy mildews overwinter as thick-walled resting spores called oospores that are produced through the fertilization of two mating types.  However, no oospores have so far been reported for this pathogen.  It is likely that the pathogen survives as mycelium and/or condia (spores) in infected plant buds, plant debris, leaf tissue and shoots.  Downy mildews are severe in cool or warm (but not hot), high humid climates and when a film of water is present on plant tissue.  They primarily cause foliar blights and rapidly spread in young green leaf, twig and fruit tissues.  Under favorable weather conditions, condia are carried by wind or water to wet leaves near the ground where they infect through stomata of the lower leaf surface.  A conidium germinates via a germ tube that grows through leaf stomata into intercellular spaces within the leaf tissue and eventually penetrates plant cells through special structures called haustoria.  Developing hypha that spreads intercellularly forms a cushion of mycelia just below the stomata.  From this cushion, conidophores arise and emerge through stomata.  At their tips, conidia (sporangia/spores) are produced simultaneously and are carried by wind and rain to new infection sites of the same or different plant.

Dispersal and spread:  The pathogen can spread through contaminated plant cuttings, transplants, fresh leaves and within seeds.  Also, it produces airborne conidia (spores) can disperse and be carried by moist winds.  It can also be present in soil associated with host and non-host plants and therefore, can spread by any means that aids in the movement of soil and/or water from infected plants to non-infected ones.

Hosts: Digitalis spp. (foxglove): D. purpurea, D. grandiflora, D. lutea, and Digitalis sp. (Farr & Rossman, 2016). Foxy hybrids are very susceptible and D. grandiflora was symptomless when grown in a heavily diseased region (Tjosvold & Koike, 2002).

Symptoms and damage potential: On leaves, initial symptoms consist of light green, rectangular areas that are delimited by veins.  Later, these spots become chlorotic, coalesce and turn necrotic and purplish-gray sporulation of the pathogen develops primarily on the underside of leaves and sometimes on upper surfaces of leaves (Pscheidt & Ocamb, 2016).

Damage Potential: While estimates of crop losses caused in particular by Peronospora digitalidis have not been reported, downy mildews can cause rapid and severe losses of young plants in seedbeds and in the field. Nursery stock producers and landscape growers of foxglove species may be at risk of damages caused by this downy mildew pathogen.

Worldwide Distribution: Europe: Czech Republic, Poland, Germany, Italy, United Kingdom, Scotland, Wales; North America: USA (California, Oregon, Washington) (Farr & Rossman, 2016; Garibaldi et al., 2013; Tjosvold & Koike, 2002; Pscheidt & Ocamb, 2016).

Official Control: Since 2002, Peronospora digitalidis has been on the North American Plant Protection Organization (NAPPO) “Alert List” (EPPO, 2016).  Since February 2, 2016, it has not been regulated by the USDA (see ‘Initiating event’). Currently, it has a “C” rating in California.

California Distribution: Orange, San Diego, San Luis Obispo, Santa Barbara, and Santa Cruz (CDFA Pest and Damage Records).

California Interceptions:  Peronospora digitalidis was detected in two nursery foxglove shipments imported to California in 2003.

The risk Downy mildew of foxglove 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):  Peronospora digitalidis is likely to establish in cool to warm and very humid to wet climates where foxglove grows in California.  According to the California Invasive Plant Council (2006-2016), foxglove is found along the coast northward from Santa Barbara, infesting moist meadows and roadsides and also in the northern Sierra Nevada foothills.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is Low (1): Presently, the host range is limited to few reported species of Digitalis. 

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): Conidia are easily produced simultaneously and in abundance.  The pathogen is transmitted via infected plant material; conidia are dispersed by winds, water and associated soil.   

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3): While estimates of crop losses caused by Peronospora digitalidis have not been reported, presence of the pathogen in open fields/landscapes and/or in nursery stock produced in greenhouse environments are expected to cause severe damage under cool or warm and humid climates resulting in significantly lower crop value and yield.  Infected, symptomatic nursery stock plants are not marketable resulting in total loss in recovery of production costs.  Markets for crop sale are directly affected.  Normal cultivation practices, including delivery and supply of irrigation water, would need to be altered to prevent spread of the pathogen.

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): Commercial landscape and home garden plantings of foxglove can be significantly impacted if infected by the downy mildew pathogen.  Under favorable climate conditions, disruption of natural communities and changes in ecosystem could occur with severe and widespread infestations of downy mildew. 

Consequences of Introduction to California for Downy mildew of foxglove:

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 Medium (-2): Presently, the downy mildew pathogen, Peronospora digitalidis, has been reported from at least five coastal counties.

Final Score:

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

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

Uncertainty:   

The impact and spread of this pathogen to other intrastate regions where Digitalis spp. is grown, is not known.  Future reports of the detection of P. digitalidis in California could lower the overall score for the pathogen although it is unlikely to affect its final rating.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Peronospora digitalidis is C.

References:

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

California Invasive Plant Council.  2006-2016. Invasive Plants of California’s Wildland Digitalis purpurea: http://www.cal-ipc.org/ip/management/ipcw/pages/detailreport.cfm@usernumber=42&surveynumber=182.php?print=y .

EPPO.  2016.  Peronospora digitalidis (PERODG).  New PQR database.  Paris, France: European and Mediterranean Plant Protection Organization.  http://newpqr.eppo.int.

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

Garibaldi, A., D. Bertetti, A. Poli, and M. L. Gullino.  2013.  Outbreak of downy mildew caused by Peronospora digitalidis on common foxglove (Digitalis purpurea) in Italy.  Journal of Plant Pathology 95:659-668. doi: 10.4454/JPP.V95I3.021.

Pscheidt, J. W., and C. M. Ocamb (Senior Eds.).  2016.  Foxglove (Digitalis spp.) downy mildew.  PNW Plant Disease Management Handbook: http://pnwhandbooks.org/plantdisease/foxglove-digitalis-spp-downy-mildew.

USDA APHIS.  2016.  FRSMP: Pests no longer regulation at U. S. ports of entry.  United States Department of Agriculture Animal and Plant Health Inspection Service.  https://www.aphis.usda.gov/aphis/ourfocus/planthealth/plant-pest-and-disease-programs/frsmp/ct_non-reg-pests.

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

Plant Pathogens, Viruses and viroids

Squash Vein Yellowing Virus (SqVYV)

California Pest Rating for
Squash Vein Yellowing Virus (SqVYV)
Pest Rating:  B
PEST RATING PROFILE
Initiating Event:

None.  The risk of introduction of Squash vein yellowing virus to California is assessed and a permanent rating for SqVYV is herein proposed.

History & Status:

Background:    In 2003 in Hillsborough County, Florida, an unknown virus was detected in squash plants (Cucurbita pepo) exhibiting vein yellowing symptoms and soon after in 2005, this virus was found to cause watermelon vine decline in watermelon plants in Florida (Webb et al., 2003; Adkins et al., 2007).  In 2006, the virus was identified and characterized as a new species, Squash vein yellowing virus.  SqVYV is a whitefly-transmitted member of the genus Ipomovirus in the family Potyviridae which induces necrosis of watermelon stems and petioles resulting in rapid wilt and death of plants at or near harvest. In the field, SqVYV is often detected in watermelon in mixed infections with other viruses (Adkins et al., 2013).

Squash vein yellowing virus was reported from California in 2015 following the fall of 2014 detection of diseased pumpkin plants grown from seed at the University of California Desert Research Extension Center in Holtville, California. Molecular analysis of pathogens associated with the diseased plants revealed mixed infections with the crinivirus Cucurbit yellow stunting disorder virus, the begomovirus Squash leaf curl virus and SqVYV. Symptoms of infection and association of a divergent strain of SqVYV were confirmed through pathogenicity trials and molecular diagnostic tests of infected pumpkin and squash plants.  SqVYV-infected melon plants were also detected in commercial fields in the Imperial Valley (Batuman et al., 2015).   Subsequently, during December 2014, official melon and pumpkin samples from the infected sites were collected by Imperial County Agricultural Commissioner’s staff and sent to CDFA Plant Pathology Laboratory for diagnosis.  Tongyan Tian, CDFA plant pathologist, detected SqVYV from the samples using a RT-PCR protocol and sequence analysis.  The detection of SqVYV in Imperial County marked the first report of an Ipomovirus in California (Batuman et al., 2015).

Hosts: The host range is limited to species in Cucurbitaceae with more dramatic symptoms produced in squash (inc. pumpkin) and watermelon.  Plant hosts include two varieties of cucurbit weeds, namely, Momordica charantia (Balsam-apple) and Melothria pendula (creeping cucumber) (Adkins et al., 2008). The weeds may serve as reservoir hosts for SqVYV.

Symptoms: Initial symptoms consist of a slight yellowing of leaves. This is followed by browning and collapse of entire vines within weeks of the first symptoms.  These symptoms appear as the fruit develops to a harvestable size.  Infected fruit internally often exhibit discolored and necrotic blotches in the rind, discolored flesh (too red) and an off-taste (Baker et al., 2008).  SqVYV-infected cucurbit weed hosts are asymptomatic (Adkins et al., 2008).   In Puerto Rico, symptoms of watermelon vine decline on field-grown watermelon included leaf curling, mosaic, and internode necrosis. During the early stage of plant growth reduced vigor and general stunting occurred, and at the flowering stage, symptoms progressed to necrosis and wilting of vines (Acevedo, et al., 2013).  Adkins et al. (2013) reported that symptoms of vine decline in watermelon appeared 12-16 days after inoculation regardless of plant age at time of inoculation and greenhouse or field location. However, younger watermelon plants exhibited more severe symptoms than older ones.

Damage Potential:  In Florida, watermelon plants suffering from vine decline and fruit rot disease caused by SqVYV has resulted in severe losses in spring and fall plantings.   During this period the disease may rapidly increase in incidence from 10 to >80% within a week (Adkins et al., 2007). The disease can result in total crop loss with collapsed vines and unmarketable fruit with discolored and necrotic rinds.

Transmission:  SqVYV is transmitted by the whitefly Bemisia tabaci.  The pathogen is not transmitted by aphids unlike other common cucurbit-infecting species of the family Potyviridae (Adkins et al., 2003). Experimentally, Adkins and others determined that whiteflies required 1-2 days to feed and acquire the virus from infected plants followed by 2 hours or 2 days to inoculate or transmit the virus to non-infected squash and watermelon plants.  Transmission occurs in a semi-persistent mode by the whitefly which remains infective for 4-6 hours after acquiring the virus.  Adkins et al. (2008) experimentally demonstrated that the whitefly vector was able to acquire SqVYV from inoculated cucurbit weed host Momordica charantia and subsequently transmit it to squash and watermelon to produce typical symptoms.  While the virus has been artificially inoculated to plants under greenhouse conditions, the main mode of natural field transmission is through its whitefly vector.

Worldwide Distribution: North America: USA (California, Florida, Georgia, Indiana, South Carolina, Puerto Rico (Acevedo et al., 2013; Egel & Adkins, 2007; Adkins et al., 2013).

Official Control: Squash vein yellowing virus currently holds a temporary Q rating by the CDFA.  No other official control for SqVYV has been reported.

California Distribution: Currently, Squash vein yellowing virus has only been detected in Imperial County.

California Interceptions:  There are no official records of interceptions of Squash vein yellowing virus in California.

The risk Squash vein yellowing virus would pose to California is evaluated below.

Consequences of Introduction: 

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

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

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

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

Risk is Medium (2) – SqVYV has already been able to establish in Imperial County, southern California  Its further spread to non-infected sites cultivated to cucurbits is limited by the distribution of its vector, Bemisia tabaci, which to date, has not been found in natural cooler climates of northern California counties.

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

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

Risk is low (1) – The natural host range is limited to plant species in the family Cucurbitaceae (which are grown extensively in the lower Sacramento Valley and in limited production in San Joaquin and Imperial Valleys). 

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

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

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

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

Risk is High (3) – The virus is able to thrive in climates that are favorable for its vector. Its potential for spread is always artificial being completely dependent on the distribution of its vector and infected plant materials.  Therefore, factors that increase movement and activity of the vector and infected plants will also influence that of the virus.  

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – SqVYV infections could lower crop yield and value, increase production costs, trigger loss of market, and the virus is vectored by the whitefly, Bemisia tabaci which would require implementation of management strategies to minimize the risk of the introduction and establishment of the virus in non-infected regions within California.

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

Risk is Medium (2) – Infestations of  SqVYV could significantly impact home/urban gardening of cucurbit host plants resulting in the imposition of additional official or private treatment programs in order to prevent spread of the virus and virus-carrying whitefly vector.

Consequences of Introduction to California for Squash vein yellowing virus

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of SqVYV 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). 

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:

While SqVYV is established in the Imperial Valley and there have been no further reports of its spread to other intrastate regions, targeted surveys for the pathogen have not been conducted in other cucurbit production sites.  The distribution and establishment of the virus is largely dependent on the distribution and established infestations of virus-carrying Bemisia tabaci.  Subsequently, detections outside the Imperial Valley may alter the proposed rating for this virus pathogen.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Squash vein yellowing virus is B.

References:

Acevedo, V., J. C. V.  Rodrigues, C. E. de Jensen, C. G. Webster, S. Adkins and L. Wessel-Beaver.  2013.  First report of Squash vein yellowing virus affecting watermelon and bitter gourd in Puerto Rico.  Plant Disease 97:1516.

Adkins S., T. G. McCollum, J. P. Albano, C. S. Kousik, C. A. Baker, C. G. Webster, P. D. Roberts, S. E. Webb and W. W. Turechek.  2013.  Physiological effects of Squash vein yellowing virus infection on watermelon.  Plant Disease 97:1137-1148.

Adkins, S., S.E. Webb, D. Achor, P. Roberts, and C.A. Baker. 2007. Identification and characterization of a novel whitefly-transmitted member of the family Potyviridae isolated from cucurbits in Florida.  Phytopathology 97: 145-154.

Adkins, S.T., S. Webb, C. Baker, and C.S. Kousik. 2008. Squash vein yellowing virus detection using nested polymerase reaction demonstrates the cucurbit weed Momordica charantia is a reservoir host. Plant Disease 92: 1119-1123.

Baker, C., S. Webb and S. Adkins.  2008.  Squash vein yellowing virus, causal agent of watermelon vine decline in Florida. Plant Pathology Circular No. 407, Florida Department of Agriculture and Consumer Services, Division of Plant Industry.

Egel, D. S. and S. Adkins. 2007.  Squash vein yellowing virus identified in watermelon (Citrullus lanatus) in Indiana.  Plant Disease, 91:1056.2.

Batuman, O., E. T. Natwick, W. M. Wintermantel, T. Tian, J. D. McCreight, L. L. Hladky, and R. L. Gilbertson.  2015.  First report of an Ipomovirus infecting cucurbits in the Imperial Valley of California.  Plant Disease 99:1042.  http://dx.doi.org/10.1094/PDIS-12-14-1248-PDN.

Webb, S. E., E. Hiebert and T. A. Kucharek.  2003.  Identity and distribution of viruses infecting cucurbits in Florida.  Phytopathology 93:S89.

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

Phytophthora tentaculata Kröber & Marwitz 1993

California Pest Rating Proposal for
Phytophthora tentaculata Kröber & Marwitz 1993
Pest Rating: B
PEST RATING PROFILE
Initiating Event: 

During January 2016, samples of two diseased Diplacus hybrids (monkey flower hybrid varieties) and one of diseased Artemisia palmeri (Palmer sagewort) were collected by Kathleen Kosta, CDFA, from a nursery in Santa Clara County.  The samples were processed and analyzed at the CDFA Plant Pathology Laboratory and Phytophthora tentaculata was tentatively identified as the associated pathogen by Suzanne Rooney-Latham, CDFA plant pathologist.  The identity of the pathogen was later confirmed by the USDA APHIS PPQ CPHST Laboratory in Beltsville, Maryland.  The three afore mentioned plant varieties are new hosts records for P. tentaculata.  Several detections of this pathogen have been made in California during the past few years.  Therefore, the current rating for P. tentaculata is reassessed here.

History & Status:

Background: In 1993, Phytophthora tentaculata was first isolated from roots and stems of greenhouse-grown Argyranthemum frutescens (syn. Chrysanthemum frutescens), Leucanthemum vulgare  (syn. C. leucanthemum), Delphinium ajacis, and Verbena sp. in nurseries in the Netherlands and Germany in 1993 (Kröber & Marwitz, 1993).  Later, the pathogen was also reported from Spain (Moralejo et al., 2004; Álvarez et al., 2006), Italy (Cristinzio et al., 2006; Martini et al., 2009) and China (Meng & Wang, 2006; Wang and Zhao, 2014) after detection in nursery-potted and field-grown plants.  In 2012, P. tentaculata was first detected in North America, in sticky monkey flower, Diplacus aurantiacus (syn. Mimulus aurantiacus) growing in a native plant nursery in Monterey County, California.  Plant samples collected by Monterey County and CDFA staff were submitted to CDFA for analysis and the pathogen P. tentaculata was identified by Suzanne Rooney-Latham and Cheryl Blomquist, CDFA plant pathologists (Rooney-Latham & Blomquist, 2014), and later confirmed by the USDA APHIS National Identification Services. The source of the Diplacus (Mimulus) plants was traced back to plants that were grown from seed and cuttings from a historical site in Monterey County.  No Diplacus (Mimulus) plants had been shipped from the native plant nursery prior to the initial detection.  Consequently, all positive Diplacus (Mimulus) plants and materials were destroyed.  The California detection marked the first detection on a native host, albeit in a native plant restoration nursery and a host that has a wide geographical native range in California.  Since its initial Monterey County find, P. tentaculata has also been detected in native plant nurseries in Placer, Butte, Santa Cruz, San Mateo, Orange, and Santa Clara Counties, and in out-planted nursery stock in habitat restoration sites in Alameda, Monterey, and Santa Clara Counties. The pathogen was detected and reported from several new hosts that are listed below (see ‘Hosts’) and include Artemisia douglasiana, A. californica, A. dranunculus, A. palmeri, Diplacus x “Apricot”, Diplacus x “Red brick”, Monardella villosa, and Salvia sp.  Several of these detections were made during a 2014-2015 survey of California native plant nurseries and restoration sites conducted by the collaborative efforts of CDFA, USDA and a private research company.  The survey resulted in the detection of P. tentaculata in 8 out of 16 counties.  The origin of P. tentaculata is unknown.  Presently in California, Phytophthora tentaculata has only been detected in nursery-grown plants that were out-planted in the environment.  The pathogen has persisted on those plants in the field for at least 4.5 years. Therefore, it is likely that in California, the pathway of pathogen spread is from infected nurseries to restoration field sites, and that the pathogen has been spread between and within nurseries by the use of infested pots and plants (Rooney-Latham, et al., 2015).

Hosts: The currently known hosts are included in the plant families Asteraceae, Lamiaceae, Phrymaceae,  Ranunculaceae, Rhamnaceae, Rosaceae, and Verbenaceae.  The host range includes the following plants, diseases and geographical locations:

Apium graveolens (celery); stem and root rot; China (Wang & Zhao, 2014).

Argyranthemum frutescens (syn. Chrysanthemum frutescens) (marguerite daisy); root and stem base rot; Germany & the Netherlands; Root, collar & stalk rot (Kröber & Marwitz 1993).

Artemisia douglasiana (California mugwort); root rot; California, USA (Rooney-Latham, et al., 2015).

Artemisia dracunculus (tarragon); root rot; California, USA (Rooney-Latham et al., 2015). Artemisia californica (California sagebrush); root rot; California, USA (Rooney-Latham et al., 2015).

Artemesia palmeri (Palmer sagewort); root rot; California, USA (see “Initiating Event”).

Aucklandia lappa (rhizomatous medicinal herb); China; stalk rot & wilt (Meng & Wang 2008).

Calendula arvensis (field marigold) (Li et al., 2011).

Ceanothus cuneatus (buckbrush); root rot; California, USA (Rooney-Latham et al., 2015).

Cichorium intybus (chicory, endive); Italy; collar and root rot (Garibaldi et al. 2006).

Delphinium ajacis (nursery stock); Germany & the Netherlands; root, collar & stalk rot (Kröber & Marwitz 1993).

Diplacus aurantiacus (syn Mimulus aurantiacus) (sticky monkey-flower); California, USA.  root and collar rot (Rooney-Latham & Blomquist, 2014).

Diplacus x “Apricot” (Diplacus hybrid variety); root and collar rot; California, USA (see “Initiating Event”).

Diplacus x “Red brick” (Diplacus hybrid variety); root and collar rot; California, USA (see “Initiating Event”).

Frangula californica (syn. Rhamnus californica) (coffeeberry); California; root and collar rot (Frankel et al., 2015; NPAG, 2014).

Gerbera jamesonii (African daisy); Italy; Crown & stem rot (Cristinzio et al. 2006).

Heteromeles arbutifolia (toyon) California, USA (Frankel et al., 2015; NPAG, 2014).

Leucanthemum vulgare (syn. Chrysanthemum leucanthemum) Germany & the Netherlands; Root, collar & stalk rot (Kröber & Marwitz 1993).

Monardella villosa (coyote mint); California, USA (Rooney-Latham et al., 2015).

Origanum vulgare (oregano); Italy.  Leaf russeting & chlorosis, wilt, defoliation, twig dieback,basal stem rot, root rot, entire plant collapse (Martini et al. 2009).

Salvia spp. (sage) California, USA (Frankel et al., 2015; NPAG, 2014).

Santolina chamaecyparissus (lavender cotton); Spain; Root rot (Alvarez et al. 2004).

Verbena sp. (nursery stock); Germany, Netherlands; nursery potted plant in Spain; root, collar & stalk rot (Moralejo et al. 2004).

Symptoms:  Depending on the host species, Phytophthora tentaculata causes moderate to severe root and crown rot, and death in highly infected plants. The symptoms are not unique to P. tentaculata by similar to infections caused by other Phytophthora species, root and stem pathogens and drought.   According to Rooney-Latham et al (2015) symptoms can vary in field-planted nursery stock.  Infected sticky monkey flower plants are stunted, with dull yellowish leaves that turn red as the disease progresses.  Roots and stem collars have necrotic, sunken lesions with few feeder roots and discolored leaves. In some cases, plants may exhibit poor growth and eventually collapse within their first season, while some plants may grow for a year or more before exhibiting severe dieback during hot summers. Transplanted infected Artemisia douglasiana plants did not show dieback, but exhibited stunting and chlorosis more that 4.5 years after being out-planted (Rooney-Latham et al., 2015; Frankel et al., 2015; Kröber & Marwitz 1993).

Damage Potential:  Phytophthora tentaculata causes moderate to severe root and crown rot on woody and semi-woody hosts.  Introduction of P. tentaculata-infected native plants to restoration sites could negatively impact native plants in their natural environment.

Disease Cycle: Generally, species of Phytophthora that cause root and stem rots survive cold winters or hot and dry summers as thick-walled, resting spores (oospores and chlamydospores) or mycelium in infected roots, stems or soil.  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). Little information is known about the life cycle or biology of Phytophthora tentaculata other than what was provided by the original species description by Kröber and Marwitz. The temperature range of the pathogen is 7°C to 32°C, the optimum temperature being 15°C to 25°C.

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

Worldwide Distribution: Asia: China; Europe: Italy, Germany, the Netherlands, Spain; North America: USA (California).

Official Control: USDA lists Phytophthora tentaculata in the top 5 Phytophthora species of concern and threat to nurseries and forests in Federal New Pest Response Guidelines (USDA APHIS, 2010).  USDA APHIS New Pest Advisory Group determined that P. tentatculata is “actionable and reportable.

California Distribution: Phytophthora tentaculata has been detected in native plant nurseries in Monterey, Placer, Butte, Santa Cruz, San Mateo, Orange, and Santa Clara Counties, and in out-planted nursery stock in habitat restoration sites in Alameda, Monterey, and Santa Clara Counties.

California Interceptions: None.

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

Consequences of Introduction:

1) Climate/Host Interaction: Evaluate and score the pest for suitability of hosts and climate to establish in California.  Score:

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

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

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

Risk is High (3) – To date, Phytophthora tentaculata has been detected in native plant nurseries in eight counties and in habitat restoration sites (in out-planted nursery stock) in three of those eight counties.  Several native plant hosts are widespread in California.  Since the pathogen is known to attack many plants in the nursery trade, it is possible that the pathogen could appear and survive wherever nurseries, including native plant nurseries, are present in California.  Therefore, there is the potential for this pathogen to establish a widespread distribution in California.

2) Pest Host Range: Evaluate and score the pest as it pertains to host range.  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) – Presently, 23 plant hosts belonging to 7 families have been reported.  Of these, almost half the number of hosts have been reported from California, and are native to the State.  While several new hosts have been reported after the initial detection of the pathogen in Monterey County, based on the present known host range, the risk of the pathogen is evaluated as medium.

3)   Pest Dispersal Potential: Evaluate and score the pest for dispersal potential using these criteria.  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) – Phytophthora tentaculata is soil-borne and water-borne and therefore, primarily spread 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.

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – The presence of Phytophthora tentaculata could cause severe economic impacts in nursery trade, impacting a number of nursery-produced native and ornamental plants that are commonly used in California landscapes as well as some of which play a significant role in the State’s florist trade.  In addition to lowered crop yields and lowered crop values due to increased need for protective treatments, the management of infestations of a soil- and water-borne pathogen such as Phytophthora spp. in a commercial nursery may be a laborious and expensive problem that would involve alterations in the normal cultural practices such as choice of sites to grow susceptible hosts, and water and growth medium management practices to ensure pathogen propagule-free irrigation water and growth media.

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

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 could significantly impact cultural practices, home/urban gardening or ornamental plantings.

Score the pest for Environmental Impact:

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

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

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

 Risk is High (3) – The USDA APHIS lists Phytophthora tentaculata in the top 5 Phytophthora species of concern and threat to nurseries and forests in Federal New Pest Response Guidelines (USDA APHIS, 2010).  The presence of P. tentaculata could cause serious impact on native plants, threatened or endangered species, disrupt critical habitats by killing critical species necessary for species diversity and soil stability, necessitate official or private treatment programs to preserve critical, rare, or endangered species, and significantly impact cultural practices, home/urban and/or ornamental plantings.

Consequences of Introduction to California for Phytophthora tentaculata:

Add up the total score and include it here

– Low = 5-8 points

– Medium = 9-12 points

– High = 13-17 points

Total points obtained on evaluation of consequences of introduction of Phytophthora tentaculata to California = (14).

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

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

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

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

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

Evaluation is Medium (-2). To date, Phytophthora tentaculata has been detected in native plant nurseries in Monterey, Placer, Butte, Santa Cruz, San Mateo, Orange, and Santa Clara Counties, and in out-planted nursery stock in habitat restoration sites in Alameda, Monterey, and Santa Clara Counties 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 = 12.

Uncertainties:

While more is known about the presence of Phythophthora tentaculata in California since its original detection in Monterey County, more researched information is needed on the distribution, behavior and threat of Phytophthora tentaculata in California’s natural soils and plant communities under diverse climatic environments.  

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for Phytophthora tentaculata remains B.

References:

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

Álvarez, L. A., A. Pérez-Sierra, M. León, J. Armengol, and J. García-Jiménez.  2006.  Lavender cotton root rot: a new host of Phytophthora tentaculata found in Spain. Plant Disease 90:523. http://dx.doi.org/10.1094/pd-90-0523A

Cristinzio, G., I. Camele and C. Marcone.  2006.  Phytophthora tentaculata su gerbera in Italia.  First report of Phytophthora tentaculata on gerbera in Italy.  Informatore Fitopatologico 56:23-25. http://www.cabdirect.org/abstracts/20063066005.html;jsessionid=C23F9F14D93FF641EEE94948EFEB99D5.

Frankel, S., S. Rooney-Latham, C. L. Blomquist, and E. Bernhardt.  2015.  Pest Alert: Phytophthora tentaculata.  Technical Report, February 2015, United States Department of Agriculture. http://www.suddenoakdeath.org/wp-content/uploads/2015/02/P.tentaculata.

Garibaldi A., G. Gilardi, M. L. Gullino.  2010. First report of collar and root rot caused by Phytophthora tentaculata on witloof chicory (Cichorium intybus) in Italy. Plant Disease 94:1504.

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]

Martini, P., A. Pane, F. Raudino, A. Chimento, S. Scibetta, and S. O. Cacciola.  2009.  First report of Phytophthora tentaculata causing root and stem rot of oregano in Italy. 93:843. http://dx.doi.org/10.1094/PDIS-93-8-0843B.

Meng, J., and Y. C. Wang.  2008.  First Report of Stalk Rot Caused by Phytophthora tentaculata on Aucklandia lappa in China. Plant Disease 92 (9): 1365.

doi:10.1094/PDIS-92-9-1365B. http://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-92-9-1365B.

Moralejo, E., M. Puig, and W. A. Man in’t Veld.  2004.  First report of Phytophthora tentaculata on Verbena sp. in Spain. The British Society for Plant Pathology.

http://www.bspp.org.uk/publications/new-disease-reports/ndr.php?id=009038. May 31, 2009.

USDA APHIS.  2010.  New Pest Response Guidelines: Phytophthora species in the Environment and Nursery Settings. 229 pages.

Rooney-Latham, S., and C. L. Blomquist.  2014. First report of root and stem rot caused by Phytophthora tentaculata on Mimulus aurantiacus in North America. Plant Disease 98(7):996.

Rooney-Latham, S., C. L. Blomquist, T. Swiecki, and E. Bernhardt.  2015.  Phytophthora tentaculata.  Forest Phytophthoras 5(1):  doi:10.5399/osu/fp.5.1.3727.

Schwartzburg, K., H. Hartzog, C. Landry, J. Rogers, and B. Randall-Schadel.  2009. Prioritization of Phytophthora of Concern to the United States. USDA APHIS PPQ CPHST PERAL (Plant Epidemiology and Risk Analysis Laboratory), Raleigh, NC. 61 pages.

Wang, T. and W. Zhao.  2014.  First report of Phytophthora tentaculata causing stem and root rot on celery in China. http://dx.doi.org/10.1094/PDIS-06-13-0592-PDN.

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

Plant Pathogens, Viruses and viroids

Freesia Sneak Virus (FreSV)

California Pest Rating forFreesia Sneak Virus
Freesia Sneak Virus
Pest Rating: B
PEST RATING PROFILE
Initiating Event:

None.     

History & Status:

Background:  Freesia sneak virus (FreSV) is associated with freesia leaf necrosis disease. The disease has been reported in Europe since the 1970s.  Although FreSV has been most closely correlated with freesia leaf necrosis symptoms in freesia plants, other species within the same genus may also be correlated (e.g., Freesia mosaic virus FreMV) and, therefore, the causal agent(s) is/are still being determined (Bouwen, 1994; Meekes & Verbeek, 2011).

Freesia sneak virus is a plant virus belonging to the genus Ophiovirus in the family Ophioviridae.  Freesia sneak virus is soil-borne and vectored by the soil-borne fungus, Olpidium brassicae. Initially, the virus was provisionally called Freesia Ophiovirus, but is now known as Freesia sneak virus (Vaira et al., 2006).

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

Hosts: Freesia spp. (Iradaceae) and Lachenalia spp. (Hyacinthaceae) (Jeong, et al., 2014; Meekes & Verbeek, 2011; Vaira et al., 2007, 2009).  Both hosts are monocots native to South Africa.

Symptoms: Symptoms may be affected by environmental conditions (Vaira et al., 2006).

Freesia leaf necrosis disease mainly affects the leaves exhibiting chlorotic spots and stripes that start at the leaf tip and usually spread over the entire leaf.  Later these chlorotic spots turn grey-brown and become necrotic.  Mildly infected plants show light chlorotic symptoms only on the lower leaves.  Flowers and corms do not seem to be affected by the disease (Van Dorst, 1973; Bouwen, 1994; Meekes & Verbeek, 2011).

Damage Potential: In detection surveys conducted in Korea, Freesia sneak virus was detected from 71.7% of 138 plants tested (Jeong et al., 2014).  Infection rates of 10-25% percent of plants shipped to the USA have been reported (Hansen, 2008; Vaira et al., 2009).  In California, nursery and private productions of freesia and lachenalia plants, in particular, may be impacted if infected with Freesia sneak virus.

Transmission: in nature, Freesia sneak virus is vectored by the soil-borne fungus, Olpidium brassicae, and not by mechanical transmission.  Resting spores of O. brassicae are very persistent and can survive for more than twenty years in soil without losing the capacity to transmit the disease (Meekes & Verbeek, 2011).   Therefore, spread of FreSV is also through movement of contaminated soils and plants.

Worldwide Distribution:  Asia: Korea; Africa: South Africa; Europe: Northern Europe including the Netherlands, Italy; North America: USA (Virginia) (Jeong et al., 2014; Meekes & Verbeek, 2011; Vaira, et al., 2007, 2009).

Official Control: None reported.

California Distribution: San Luis Obispo (nursery).

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

The risk Freesia sneak virus would pose to California is evaluated below.

Consequences of Introduction: 

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

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

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

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

Risk is Medium (2) – Freesia sneak virus is likely to establish wherever freesia and lachenalia plants are grown in limited areas of California. Freesia has limited production in state and is naturalized mostly in the north coast region, as well as cultivated in nursery and private production sites – including home gardens.    Lachenalia is grown mainly in nurseries and in private productions as a hobbyist’s 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) – Freesia sneak virus is limited to Freesia spp. (Iradaceae) and Lachnenalia spp. (Hyacinthaceae).

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

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

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

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

Risk is Medium (2) – Freesia sneak virus has high reproductive potential.  In nature, its spread to non-infected plants is dependent on the presence of the soil-borne fungus vector, Olpidium brassicae.  Resting spores of O. brassicae are very persistent and can survive for more than twenty years in soil without losing their viability. Therefore, FreSV is also spread through movement of contaminated soils and plants.  The pathogen is not mechanically transmitted.

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

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – Incidents of Freesia sneak virus infections could lower plant value resulting in loss in market sales of nursery-grown freesia and lachenalia plants.  The pathogen is vectored by the soil fungus, Olpidium brassicae.    

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

Risk is Low (1) – Plant infections caused by Freesia sneak virus are likely to have a minimal impact on the overall environment but may significantly impact home gardening and ornamental plantings.

Consequences of Introduction to California for Freesia sneak virus

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Freesia sneak virus to California = 9.

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

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

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

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

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

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

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

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

Hansen, M. A.   2008.  Freesia sneak virus – a new find for the United States.  Virginia Cooperative Extension, Virginia Tech Plant Disease Clinic: https://www.cals.ncsu.edu/plantpath/activities/societies/ornamental/2008_talks/freesia_sneak_virus_4.pdf.

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

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

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

Vaira, A. M., R. Kleynhans, and J. Hammond.  2007.  First report of Freesia sneak virus infecting Lachenalia cultivars in South Africa.  Plant Disease 91:770.  http://dx.doi.org/10.1094/PDIS-91-6-0770A.

Vaira, A. M. , M. A. Hansen, C. Murphy, M. D. Reinsel, and J. Hammond.  2009.  First report of Freesia sneak virus in Freesia sp. in Virginia.  Plant disease, 93:965. http://dx.doi.org/10.1094/PDIS-93-9-0965B.

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

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

Greeneria uvicola (Berk. & M. A. Curtis) Punith. 1974

California Pest Rating Proposal for
Greeneria uvicola (Berk. & M. A. Curtis) Punith. 1974
Pest Rating: B
PEST RATING PROFILE
Initiating Event:  

On December 16, 2015, a shipment of grape leaves from Texas, destined to a retail store in California, was intercepted by the Los Angeles County officials.  The leaves had symptoms of leaf spots and a sample was collected and sent to the CDFA Plant Pathology Laboratory for disease diagnosis.  The fungal pathogen, Greeneria uvicola, was identified as the cause for the leaf spots, by Suzanne Rooney Latham, CDFA plant pathologist.  The pathogen was given a Q rating and subsequently the shipment of grape leaves was destroyed.  The risk of infestation of Greeneria uvicola in California is evaluated and a permanent rating is herein proposed. 

History & Status:

Background:  Greeneria uvicola is the cause of ‘Bitter Rot’ of grapes. The disease is cosmopolitan and common in the southern eastern United States, while being an occasional problem in the northern region as far as Long Island and New England states.  Greeneria uvicola is an asexually reproducing fungus with no known sexual state. Taxonomically, the pathogen is also known by several synonyms (including, Greenaria fuliginea, Melanconium fuligineum, and Phoma uvicola) and based on molecular data was placed in Ascomycetes, Diaporthales (Farr et al., 2001; Sutton, 2015).

Hosts: Grapevine (Vitis spp.).

Symptoms:  The pathogen infects all above ground vegetative plant parts including stem, leaves, tendrils and fruits.  Leaf symptoms, which are more common on muscadine grapes than on bunch grapes, appear as tiny, sunken, reddish-brown flecks with yellow halos.  Stem and petiole infects result in round to elliptical, reddish brown to black lesions which may be slightly raised or sunken.  Flecking of sepals and blighting of flower buds may also occur.  The fungus initially invades the berry from the berry stem (pedicel) at the onset of ripening. Infected light-skinned berries turn brown and form multiple, prominent fungal asexual fruiting bodies (acervuli) once the berries reach their full size.  As the rot progresses through the infected berries, the acervuli form in concentric rings, but are more uniformly distributed once the fruit is completely rotted.  These symptoms are less visible on dark-skinned berries which rough-skinned and iridescent.  Eventually, infected berries soften, shrivel, may be completely covered with acervuli, and may abscise or become mummified and remain attached (Sutton, 2015).

Damage Potential:  Infected fruit becomes rotted and as rotted fruit begins to soften they have a distinct bitter taste which is carried through the winemaking process resulting in a finished wine with an unpleasant, burnt or bitter taste.  Therefore, the marketability of diseased fruit for table or wine use is reduced.

Disease Cycle: The pathogen overwinters as a saprophyte on fallen fruit, cold-damaged shoot tips, and necrotic bark of the trunk and cordons.  In spring, gelatinous masses of spores (conidia) are produced from acervuli and washed by rain to green vegetative parts including the pedicels.  Disease development requires long and warm rains in spring, followed by warm, humid summers.  Infections occur during wet periods at 12-30°C, and optimally at 22.4-24.6°C, with 6-12 hrs wetness.  The fungus invades the pedicel and remains latent until fruit mature.  At that time the pathogen actively grows from the infected pedicel into the maturing fruit resulting in berry rot.  Conidia are produced in infected berries and rain splashed onto other ripening fruit causing secondary infections.  Infections usually occur in fruit wounded by insects, birds, hail, heavy rainstorms, or mechanically.  Berries are most susceptible at the onset of ripening however they may be infected by conidia anytime between bloom and harvest (Sutton, 2015).

Transmission:   The pathogen is spread through infected above ground vegetative plant materials and dead plant debris (leaves, stems, tendrils, and mummied fruits), rain/water splash.

Worldwide Distribution: Greeneria uvicola is distributed worldwide and reported from Asia: India, China, Taiwan, Thailand; Africa: South Africa; Europe: Bulgaria, Poland, Ukraine; North America: USA, Mexico; South America: Brazil, Costa Rica; Uruguay; Australia (Farr & Rossman, 2016; Samuelian, et al., 2013; ChaoYu et al., 2015).  Greece, Japan, and New Zealand have also been reported (Sutton, 2015).

In the USA, Greeneria uvicola has been reported mainly from the south eastern states.  Its distribution includes Florida, Georgia, Missouri, Mississippi, Ohio, Oklahoma, North Carolina, South Carolina, and West Virginia (Farr & Rossman, 2016).

Official Control:  Greeneria uvicola is on the ‘Harmful Organism List’ for China (PCIT, 2015).  Presently, G. uvicola has a temporary (Q) rating as a quarantine, actionable pathogen by the CDFA.

California Distribution:  Greeneria uvicola is not reported from California.

California Interceptions: There has been only one interception of Greeneria uvicola-infected grape leaves in California (see ‘Initiating Event”).

The risk Greeneria uvicola 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) – The requirements for a suitable climate of long periods of warm rains in spring, followed by warm, humid summers would not likely favor or greatly limit the establishment of Greenaria uvicola in California where grape is usually cultivated under warm and dry conditions.

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) – Grape (Vitis spp.) is the only host.  Although the host range is very limited, in California grape is a major crop that is cultivated over significant acreage.

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

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

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

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

Risk is Medium (2) – Greeneria uvicola is highly reproductive, producing gelatinous masses of conidia for primary and secondary infections.  Dispersal of conidia is dependent on rain splash for delivery to, and infection of non-infected above ground parts of the grapevine.

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

A.  The pest could lower crop yield.

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

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

D.  The pest could negatively change normal cultural practices.

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

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

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

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

– Medium (2) causes 2 of these impacts.

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

Risk is High (3) – Bitter rot diseased fruit is rotted and has a bitter taste that results in finished wine with an unpleasant bitter or burnt flavor.  Therefore, Greeneria uvicola-infected fruit could lower crop yield of healthy fruit bunches, lower crop value, and trigger loss of markets of table and wine grapes.   

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) – Home gardens cultivated with table and/or wine grapes could be significantly impacted if infected with the bitter rot pathogen.

Consequences of Introduction to California for Greeneria uvicola:

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

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

Total points obtained on evaluation of consequences of introduction of Greeneria uvicola to California = 9

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 in California (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 = 9.

Uncertainty:

None.

Conclusion and Rating Justification:

Based on the evidence provided above the proposed rating for the bitter rot pathogen, Greeneria uvicola is B .  

References:

ChaoYu, Cui, Jiang JunXi, Ouyang Hui, Li Cheng, Liu DengQuan, and Huang Ting.  2015.  First report of Greeneria uvicola causing bitter rot of grape in China.  Journal of Phytopathology, 163:780-782.

http://www.eppo.int/DATABASES/pqr/pqr.htm .

Farr, D. F., and A. Y. Rossman.  2015.  Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved January 12, 2016, from http://nt.ars-grin.gov/fungaldatabases/

Farr. D. F., L. A. Castlebury, A. Rossman, and O. Erincik.  2001.  Greeneria uvicola, cause of bitter rot of grapes, belongs in Diaporthales.  Sydowia-Horn, 53:185-199.

PCIT.  2015.  USDA Phytosanitary Certificate Issuance & Tracking System. July 21, 2015.  https://pcit.aphis.usda.gov/PExD/faces/ReportHarmOrgs.jsp .

Samuelian, S. K., L. A. Greer, K. Cowan, M. Priest, T. B. Sutton, S. Savocchia, and C. C. Steel.  2013.  Phylogenetic relationships, pathogenicity and fungicide sensitivity of Greeneria uvicola isolates from Vitis vinifera and Muscadinia rotundifolia.  Plant Pathology, 62: 829-841.

Sutton, T. B.  2015.  Diseases caused by biotic factors, diseases caused by fungi and Oomycetes: Bitter Rot.  Compendium of Grape Disease, Second Edition.APS Press, The American Phytopathological Society, pg. 24-26.

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