California Pest Rating for
Colletotrichum petchii Damm, P. F. Cannon & Crous, 2012
Pest Rating: B
PEST RATING PROFILE
In January 2015, the fungal pathogen Colletotrichum petchii, was detected in infected potted Dracaena deremensis (corn plant) in a nursery in Vista, San Diego County, California. The plants were shipped from a nursery in Keaau, Hawaii. The pathogen was cultured from infected leaves and identified by Suzanne Latham, CDFA plant pathologist. This detection was considered a new US record and reportable by the USDA. The species identity was confirmed by the USDA PPQ National Mycology Laboratory. Consequently, the shipment of plants was destroyed. A permanent rating for Colletotrichum petchii is proposed herein.
History & Status:
Background: Colletotrichum petchii was originally discovered in 1925 by Petch and described under a previously existing name, Colletotrichum dracaenae that was detected in dark brown patches on leaves of Dracaena brauni (syn. D. sanderiana) in Sri Lanka. However, Damm et al., (2012) published the name C. petchii to replace C. dracaenae Petch 1925 which was an illegitimate name according to the International Code of Nomenclature for fungi. [The legitimate name for C. dracaenae is the same name but described by Allescher: C. dracaenae Allesch., 1902.]
The more recent development of species-specific molecular diagnostic tests, particularly since the early 2000s, resulted in changes in taxonomy and nomenclature of fungi within the genus Colletotrichum and eventually led to the recognition of Colletotrichum petchii. During 2003 to 2012, prior to its being legitimately named, C. petchii was included as a strain of the species C. boninense. However, researchers indicated that C. boninense actually comprised of a complex of several species. Then by 2012, through molecular phylogenetic analyses of 86 strains of C. boninense, Damm et al. were able to recognize C. petchii as a separate species. Furthermore, C. boninense 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 (Damm et al., 2012).
Hosts: Dracaena spp., Dracaena aletriformis (syn. D. latifolia).D. braunii, D. fragrans (syn. D. deremensis), D. sanderiana,
Symptoms: Colletotrichum-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.
Damage Potential: Anthracnose disease caused by Colletotrichum petchii can result in reduced plant quality and growth. Estimates of yield/crop loss due to this pathogen have not been reported. Nursery production of Dracaena as potted 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 petchii 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. Condia 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: Sri Lanka, Italy, China, Netherlands, Germany, and USA.
Official Control: Colletotrichum petchii is considered a new USA record and reportable to the USDA.
California Distribution: There is no official record of the establishment of Colletotrichum petchii in California, however in 2013 CDFA plant pathologists identified C. gloeosporioides in Dracaena warnickii plants grown in a nursery in San Luis Obispo County, California. At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense and C. petchii. It is, therefore, possible that this detection may have included C. petchii (Suzanne Latham, CDFA, personal communication). No eliminative action would have been taken against the 2013 nursery detection of C. gloeosporioides which is known to be widespread in California.
California Interceptions: Colletotrichum petchi has been intercepted once in shipment of potted Dracaena deremensis from Hawaii (see ‘Initiating event’).
The risk Colletotrichum petchii 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. petchii 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. petchii can effectively infect and spread to host plants (Dracaena spp.) grown under conducive climate conditions in nurseries.
2) Known Pest Host Range: Evaluate the host range of the pest:
– 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 of Colletotrichum petchi is limited to Dracaena spp.
3) Pest Dispersal Potential: Evaluate the dispersal potential of the pest:
– 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 these criteria:
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 these criteria:
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:
– 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 petchii:
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 petchii 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. However, while there is no official record of the establishment of Colletotrichum petchii in California, in 2013 CDFA plant pathologists identified C. gloeosporioides in Dracaena warnickii plants grown in a nursery in San Luis Obispo County, California. At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense and C. petchii. It is, therefore, possible that this detection may have included C. petchii (Suzanne Latham, CDFA, personal communication).
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.
The possibility that the 2013 detection of C. gloesporoides may have included the now segregate species, C. petchii and that the latter may already be established in California, can only be ascertained through survey and testing of infected host plants particularly in San Luis Obispo County and neighboring counties. 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 petchii is B.
CABI. 2014. Colletotrichum boninense datasheet report. Crop Protection Compendium. www.cabi.org/cpc/
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; www.studiesinmycology.org
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.
Petch, T. 1925. Additions to Ceylon fungi. III. Annals of the Royal Botanical Gardens. Peradeniya 9:313-328.
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.
PEST RATING: B
Posted by ls