Colletotrichum karstii Yan L. Yang, Zuo Y. Liu, K. D. Hyde & L. Cai 2011

California Pest Rating for
Colletotrichum karstii Yan L. Yang, Zuo Y. Liu, K. D. Hyde & L. Cai 2011
Pest Rating: B


Initiating Event:    

During May 2015, the pathogen Colletotrichum karstii, was detected in culture from infected Aglaonema plants that were collected from a nursery in Ramona, San Diego County, California.  The plants were part of an incoming nursery shipment from Fallbrook, San Diego County, California and originated in a nursery in Guatemala.  The pathogen was cultured from leaf spots, sequenced, and identified by Suzanne Latham, CDFA plant pathologist.  A permanent rating for Colletotrichum karstii is proposed herein.        

History & Status:

Background Colletotrichum karstii was originally discovered in an infected leaf of Vanda sp. (Orchidaceae) and several other orchids in southwest China (Yang et al., 2011).  The pathogen is a fungus species belonging to the complex species group C. boninense which was originally described in 2003 as a segregate of the vastly morphological and physiological variable C. gloeosporioides complex (CABI, 2014; Morikwaki et al., 2003).  In the past, isolates of C. boninense were often identified as C. gloeosporioides.  However, after segregation from C. gloeosporioides, researchers found that C. boninense actually comprised of a complex of several species and by 2012, through molecular phylogenetic analyses of 86 strains of C. boninense, Damm et al. (2012) were able to recognize 18 separate and distinct species within the C. boninense complex including C. karstii based on DNA sequence data and morphology.

In the USA, Colletotrichum karstii was first detected in white Phalaenopsis orchid flowers growing in a greenhouse in San Francisco, California (Jadrane et al., 2012).

Hosts: Colletotrichum karstii is pathogenic on many host plants and is the most common and geographically diverse species in the C. boninense complex (Damm et al., 2012).  Hosts include, Aglaonema sp. (Araceae: CDFA plant pathology detection record), Anona cherimola (custard-apple), Arundina graminifolia (bamboo orchid), Bletilla ochracea (Chinese ground orchid), Calanthe argenteo-striata (orchid), Carica papaya (papaya), Cucurbita spp., Diospyros australis, Leucospermum sp., Olea dioica (rose sandalwood), Musa sp. Musa acuminata, Mangifera indica (mango), Malus domestica (apple), Maytenus ilicifolia, Passiflora edulis (passion fruit), Passiflora spp., Persea americana (avocado), Phalaenopsis amabilis, P. aphrodite (orchid), Pleione bulbocodioides (orchid), Vaccinium sp. Vanda sp.,(orchid) (Damm et al., 2012; Farr et al., 2015; Sharma & Shenoy, 2013; Jadrane et al., 2012).

SymptomsColletotrichum-infected host plants exhibit symptoms of anthracnose which include dark brown leaf, stem and fruit spots and wilting of leaves often resulting in dieback and reduction in plant quality.  In white Phalaenopsis orchid flowers, petals infected with C. karstii show anthacnose-like lesions where necrotic tissue is surrounded by a ring of green tissue (Jadrane et al., 2012)

Damage Potential:  Anthracnose disease caused by Colletotrichum boninense can result in reduced plant quality and growth.  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 karstii  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:  Australia, Brazil, China, India, Mexico, New Zealand, Thailand, and USA (California, Florida). Damm et al. (2012) determined an isolate of C. boninense from Florida USA, and ITS (internal transcribed spacer) sequences of strains of C. gloeosporioides “group 2” from Thailand to be identical or similar to C. karstii.

Official Control:  None.

California Distribution: San Francisco and San Diego County (see “Initiating Event”).

During the early 1980s, CDFA plant pathologists identified C. gloeosporioides in several hosts belonging to several families.  At that time specific molecular diagnostic tests were not available to enable the distinction of C. karstii.  It is, therefore, possible that these detections may have included C. karstii.  No eliminative action would have been taken against C. gloeosporioides as the species is known to be widespread in California.

California Interceptions Colletotrichum karstii has been intercepted once in shipments of Algaonema sp. that originated in Guatemala (see ‘Initiating event’).

The risk Colletotrichum karstii 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. karstii 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. Limited regions with conducive climates within California could enable the pathogen to establish.  In particular, C. boninense s. str. can effectively infect and spread to host plants grown under conducive climate conditions in nurseries.

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 karstii is very diverse and includes several plant families.

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 climates, the pathogen could lower plant growth and 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 Medium (2) – The pathogen could significantly impact cultural practices, home gardening or ornamental plantings.

Consequences of Introduction to California for Colletotrichum karstii:

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 karstii 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 karstii has been found in San Francisco and San Diego County – coastal regions.  Early detection of the complex species group C. gloeosporioides in several plant families in California have not be verified by the use of specific molecular diagnostic tests for the distinction of C. karstii as it is possible that these detections may have included C. karstii.

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.


The possibility that the 1980 detections of C. gloesporioides may have included the now segregate species, C. karstii, can only be ascertained through survey and molecular testing for the pathogen isolated from infected host plants particularly those obtained from suspect counties included in early detection reports of C. gloeosporioides .  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 karstii is B.


CABI.  2014.  Colletotrichum karstii basic datasheet report.  Crop Protection Compendium.

Damm, U., P. F. Cannon, J. H. C. Wouldenberg, P. R. Johnston, B. S. Weir, Y. P. Tan, R. G. Shivas and P. W. Crous.  2012.  The Colletotrichum boninense species complex.  Studies in Mycology 73:1-36;

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

Jadrane, I., M. Kornievsky, D. E. Desjardin and Z. H. He. 2012.  First report of flower anthracnose caused by Colletotrichum karstii in white Phalaenopsis orchids in the United States.  Plant Disease 96:1227.

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.

Moriwaki, J., T. Sato and T. Tsukiboshi.  2003.  Morphological and molecular characterization of Colletotrichum boninense sp. nov. from Japan.  Mycoscience 44:47-53.

Sharma, G. and B. D. Shenoy.  2013.  Multigene sequence-based identification of Colletotrichum cymbidiicola, C. karstii and C. phyllanthi from India.  Czech Mycology 65:79-88.

Yang, Y. L., L. Cai, Z. N. Liu, Z. N. Yu and K. D. Hyde.  2011.  Colletotrichum species on Orchidaceae in southwest China.  Cryptogamie Mycologie 32:229-253.

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,[@]

Comment Period:

The 45-day comment period opened on Monday, October 12, 2015 and closed on November 26, 2015.

Pest Rating: B

Posted by ls