Colletotrichum henanense

California Pest Rating for

Colletotrichum henanense F. Liu & L. Cai 2015

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

On October 12, 2017, the California Dog Team a shipment of nuts of Castanea sativa (European chestnut) at a parcel distribution facility in Alameda County. The shipment had originated in Indiana and was destined to a private citizen in Contra Costa County. A sample of nuts were collected by Alameda County Agricultural officials, and sent to the CDFA Plant Diagnostics Branch for Diagnosis. Suzanne Latham, CDFA plant pathologist detected the pathogen, Colletotrichum henanense in culture from the nuts. The identity of the associated pathogen was later confirmed by USDA National Identification Services at Beltsville, Maryland, and marked the first domestic detection of C. henanense in the USA. Consequent to the California detection, all infected plant materials were destroyed. The risk of infestation of C. henanense in California is evaluated and a permanent rating is proposed.

History & Status:

Background: Colletotrichum henanense is a distinct fungus species belonging to the vastly morphological and physiological variable C. gloeosporioides and is genetically identified from other species of the complex. The species was originally described in 2015 from tea plants (Camelia sinensis) and Japanese thistle (Cirsium japonicum) in Xinyang, Henan Province, and Beijing, China respectively (Liu et al., 2015). The pathogen causes anthracnose disease in its host plants. Camellia species were affected by anthracnose disease in China where the plant species are used as in production of edible oil, processed tea and as ornamentals (Li et al., 2018; Liu et al., 2015). The pathogen has only been reported from China until its 2017 detection in the California.

Symptoms: Generally, Colletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves which often result in dieback and reduction in plant quality.

Hosts: Camellia sinensis (tea tree), C. oleifera (tea-oil tree. Theaceae); Cirsium japonicum (Japanese thistle. Asteraceae) (De Silva et al., 2017; Li et al., 2018; Liu et al., 2015). The detection of Colletotrichum henanense in Castanea sativa (European chestnut) is included here (see: Initiating Event).

Symptoms: Colletotrichum henanense causes leaf spot symptoms. Leaf spots or lesions in tea-oil tree are semicircular or half-oval, brown to black with greyish-white centers. Severely infected leaves wither and drop (Li et al., 2018).

Disease Cycle: It is likely that Colletotrichum henanense 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 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.

Damage Potential: In China, 40% of tea-oil tree yield loss has been suggested (Li et al., 2018). A 42.5% incidence of anthracnose disease caused by C. henanense was observed in 85 of 200 young tea-oil plants grown in a nursery in Kunming, Yunnan Province, China (Li et al., 2018). Generally, anthracnose disease can result in reduced plant quality and growth, and marketability. Nursery productions of Camellia and chestnut are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum species. In open fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions.

Worldwide Distribution: Asia: China; North America: USA (De Silva et al., 2017; Li et al., 2018; Liu et al., 2015).

Official Control: None reported.

California Distribution: Colletotrichum henanense is not established in California (see “Initiating Event”).

California Interceptions: The risk Colletotrichum henanense would pose to California is evaluated below.

Consequences of Introduction:

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

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

Score: 2

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

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

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

2) Known Pest Host Range: Presently, the host range is limited to Camellia sinensis, C. oleifera, Cirsium japonicum, and Castanea sativa.

Evaluate the host range of the pest.

Score: 1

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

– Medium (2) has a moderate host range.

– High (3) has a wide host range.

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

Evaluate the natural and artificial dispersal potential of the pest.

Score: 3

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

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

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

4) Economic Impact: Anthracnose-infected chestnut and camellia plants may result in lower crop value and market loss. Nursery productions of Camellia and chestnut are particularly at risk as nursery conditions are often conducive to infection by Colletotrichum In open fields, disease development may be sporadic as it is affected by levels of pathogen inoculum and environmental conditions. Its economic impact is evaluated as a Medium risk.

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

Score: B, C

A. The pest could lower crop yield.

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

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

D. The pest could negatively change normal cultural practices.

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

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

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

Economic Impact Score: 2

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

– Medium (2) causes 2 of these impacts.

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

5) Environmental Impact: Chestnut trees cultivated and growing in open environments in California are not expected to be significantly affected by Colletotrichum henanense due to the high moisture conditions required for the development of the pathogen. However, under humid and moist environments, the pathogen may be more of a problem particularly in ornamental plantings of Camellia in home/urban and private/public settings.

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

Environmental Impact: E

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

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

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

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

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

Environmental Impact Score: 2

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

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

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

Consequences of Introduction to California for Colletotrichum henanense: 10

Add up the total score and include it here.

-Low = 5-8 points

–Medium = 9-12 points

-High = 13-15 points

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

Evaluation is ‘Not Established’

Score (0). Colletotrichum henanense is not known to be established in California and is known only from its detected in an intercepted shipment of chestnut.

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

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

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

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

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

De Silva, D. D., P. K. Ades, P. W. Crous and P. W. J. Taylor. 2017. Colletotrichum species associated with chili anthracnose in Australia. Plant Pathology 66 (2): 254-267.

Farr, D. F., and A. Y. Rossman. Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Retrieved March 16, 2018, from https://nt.ars-grin.gov/fungaldatabases/

Li, H., G. Y. Zhou, X. Y. Qi and S. Q. Jiang. 2018. First report of Colletotrichum henanense causing anthracnose on tea-oil trees in China. Plant Disease “First Look” paper, accepted for publication, posted 01/03/2018. https://doi.org/10.1094/PDIS-08-17-1302-PDN

Liu, F., Weir, B.S., Damm, U., Crous, P.W., Wang, Y., Liu, B., Wang, M., Zhang, M., and Cai, L. 2015. Unravelling Colletotrichum species associated with Camellia: employing ApMat and GS loci to resolve species in the C. gloeosporioides complex. Persoonia 35: 63-86.

Responsible Party:

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

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