Colletotrichum spaethianum | Pest Rating Proposals and Final Ratings

California Pest Rating for

Colletotrichum spaethianum (Allesch.) Damm, P. F. Cannon & Crous, 2009

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

On March 27, 2015, a mail shipment containing Iris sp. plants with leaf spots was intercepted by the CDFA Dog Team, at the United States Postal Service Center in West Sacramento, Yolo County. The plants had been shipped by a private owner in Gowen, Oklahoma. Samples collected were submitted to the CDFA Plant Pathology Laboratory and the fungal pathogen, Colletotrichum spaethianum, was isolated from the diseased plants and identified by Suzanne Latham, CDFA plant pathologist. The species identity was confirmed on August 18, 2015, by the USDA PPQ National Mycology Laboratory. This detection was considered a new US record and reportable by the USDA. Consequently, the shipment of Iris sp. plants was destroyed. The risk of infestation of C. spaethianum in California is evaluated and a permanent rating is proposed.

History & Status:

Background: The fungal pathogen Colletotrichum spaethianum was originally described in 1895 under the name Vermicularia spaethiana from dead stems of Funkia univittata (synonym Hosta sieboldiana) in Berlin, Germany. A living strain of the original material of pathogen is no longer available however, as a result of taxonomic and phylogenetic studies, Damm et al., (2009) combined V. spaethiana to the genus Colletotrichum becoming C. spaethianum and designated an epitype (representative specimen in place of the non-available original specimen) from the same host in the same city as the original fungal species.

Hosts: Hosta sieboldiana, Hemerocallis sp.(daylily), H. flava, H. fulva, H. citrine, Hymenocallis americana (northern spider lily), Lilium sp. (Lily), Peucedanum praeruptorum (Qian Hu), Allium fistulosum (Welsh onion), (Damm et al., 2009, 2012; Yang et al., 2009; Yang et al., 2014; Guo et al., 2013; Vieria et al., 2014; Farr & Rossman, 2015). The CDFA detection of Colletotrichum spaethianum in Iris sp. is a new host record.

Symptoms: Colletotrichum spaethianum infected host plants exhibit symptoms of anthracnose which include reddish brown to dark brown leaf and stem necrotic spots and wilting of leaves which often result in dieback and reduction in plant quality.

Damage Potential: Anthracnose disease caused by Colletotrichum spaethianum can result in reduced plant quality and growth, fruit production and marketability. Estimates of yield/crop loss due to this pathogen have not been reported. 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 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 spaethianum 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: Europe: Germany; Asia: South Korea; North America: Florida, South America: Oceania: New Zealand (Cai, et al., 2009; Damm et al., 2009; Farr & Rossman, 2015; Yang, et al., 2009; Yang et al., 2014).

Official Control: In California C. spaethianum is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection. The species is considered ‘reportable’ by the USDA.

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

California Interceptions: There has been one interception of Colletotrichum spaethianum –infected (Iris) plants that originated in Oklahoma (see ‘Initiating event’).

The risk Colletotrichum spaethianum 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. spaethianum requires humid, wet, rainy weather for conidia to infect host plants. This environmental requirement may limit the ability of the pathogen to establish and spread in less conducive climates. Also confining is the limited host range comprising primarily of lily and iris ornamental plants which are cultivated in nurseries, residential and commercial community environments such as parks and gardens. The pathogen could establish within these limited regions when grown under favorable moist 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) – Presently, the host range of Colletotrichum spaethianum is limited to hosta, daylilies, northern spider lily, lily, iris, Qian Hu (Chinese medicinal plant), and Welsh onion.

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 Medium (2) – In particular, nursery and private productions of lily, hosta, and iris ornamental plants can be limited by their susceptibility to anthracnose under wet conditions. Therefore, under suitable climates, the pathogen could lower plant growth, value and trigger the loss of markets.

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

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

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

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

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

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

Score the pest for Environmental Impact. Score:

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

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

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

Risk is High (3) – The pathogen could significantly impact cultural practices or home/urban garden plantings. Also, the pathogen could impact endangered lily plants in California, namely: western lily (Lilium occidentale) and Pitkin Marsh lily (Lilium pardalinum ssp. Pitkinense) (State and federally listed endangered, threatened and rare plants of California, California Natural Diversity Database, California Department of Fish and Wildlife, July 2015).

Consequences of Introduction to California for Colletotrichum spaethianum:

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 spaethianum 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 not established (0). Colletotrichum spaethianum is not established in California. The intercepted C. spaethianum-infected iris plants were either rejected or destroyed.

Final Score:

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

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

Uncertainty:

None.

Conclusion and Rating Justification:

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

References:

Cai, L., Hyde, K.D., Taylor, P.W.J., Weir, B.S., Waller, J.M., Abang, M.M., Zhang, J.Z., Yang, Y.L., Phoulivong, S., Liu, Z.Y., Prihastuti, H., Shivas, R.G., McKenzie, E.H.C., and Johnston, P.R. 2009. A polyphasic approach for studying Colletotrichum. Fungal Diversity 39: 183-204.

Farr, D. F., & A. Y. Rossman. Fungal databases, systematic mycology and microbiology laboratory, ARS, USDA. Retrieved April 7, 2015, from

http://nt.ars-grin.gov/fungaldatabases/

Guo, M., Y. M. Pan, Y. L. Dai, and Z. M. Gao. 2013. First report of leaf spot caused by Colletotrichum spaethianum on Peucedanum praeruptorum in China. Plant Disease, 97:1380.

Kitterly, W. R., and A. P. Keinath. 1996. Fungal disease of aerial parts: Anthracnose. In ‘Compendium of Cucurbit Diseases’. Edited by T. A. Zitter, D. L. Hopkins, and C. E. Thomas, APS Press The American Phytopathological Society Minnesota, USA, p. 24-25.

Santana, K. F. A., C. B. Garcia, K. S. Matos, R. E. Hanada, N. R. Sousa, G. F. and Da Silva. 2015. First report of anthracnose caused by Colletotrichum spaethianum on Allium fistulosum in Brazil. Plant Disease (Accepted for publication) posted on line on 3Aug 2015, First Look. http://dx.doi.org/10.1094/PDIS-07-15-0737-PDN.

Vieira, W. A. S., S. J. Michereff, A. C. Oliveira, A. Santos and M. P. S. Câmara. 2014. First report of anthracnose caused by Colletotrichum spaethianum on Hemerocallis flava in Brazil. Plant Disease, 98:997. http://dx.doi.org/10.1094/PDIS-10-13-1026-PDN

Yang, Y. L., Z. Y. Liu, L. Cai, K. D. Hyde, Z. N. Yu and E. H. C. McKenzie. 2009. Colletotrichum anthracnose of Amaryllidaceae. Fungal Diversity 39: 123-146

Yang, H. C., J. S. Haudenshield and G. L. Hartman. 2014. Colletotrichum incanum sp. nov., a curved-conidial species causing soybean anthracnose in USA. Mycologia 106: 32-42.

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

Responsible Party:

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