Colletotrichum boninense Moriwaki, Toy. Sato & Tsukib. 2003

California Pest Rating for

Colletotrichum boninense Moriwaki, Toy. Sato & Tsukib. 2003

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

During February 2015, the fungal pathogen Colletotrichum boninense was detected in infected Aglaonema commutatum (Aglaonema/Chinese evergreen) cuttings in a nursery in Vista, 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 Costa Rica. A month later, the pathogen was detected twice in San Diego in two different shipments of Aglaonema sp. plants: one sent to the Vista nursery by the same shipper as before, and the other sent by a different shipper to a different nursery. The latter two shipments had also originated in Costa Rica. The pathogen was cultured from leaf spots, sequenced, 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 boninense is proposed herein.

History & Status:

Background: Colletotrichum boninense was first discovered associated with Crinum asiaticum var. sinicum (Amaryllidaceae) in the Bonin Islands, Japan (Moriwaki et al., 2003). These scientists also found the species in Japan to be associated with several other hosts plants of different plant families. 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). Prior to its segregation as a species, isolates of C. boninense were often identified as C. gloeosporioides. However, after the segregation, 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 species within the C. boninense complex including C. boninense in its strict sense (s. str.) based on DNA sequence data and morphology. The current proposed rating is for C. boninense s. str.

Hosts: Host plants of C. boninense s. str. are very diverse and include members in the plant families Amaryllidaceae, Bignoniaceae, Podocarpaceae, Proteaceae, Solanaceae and Theaceae (Damm et al., 2012). The CDFA 2015 detection of C. boninense s. str. on Aglaonema commutatum would also include the family Araceae.

The range of host plants for Colletotrichum boninense s. str. is not well understood from reports published prior to 2012 as many of those reports refer to the broad C. boninense complex (sensu lato). Subsequently, those reported hosts would need to be molecularly verified to be C. boninense s. str. and include members of the genera Bletilla, Camellia, Capsicum, Cattleya, Clivia, Coffeae, Crinum, Cucumis, Cymbidium, Dacyrarpus, dendrobium, Dracaena, Eucalyptus, Hippaestrum, Leucospermum, Oncidium, Pachira, Panax, Passiflora, Pleione, Protea, Prunus, and Solanum (Farr & Rossman, 2015).

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 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 boninense 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: Australia, Brazil, China, Colombia, Japan, Korea, the Netherlands, New Zealand, South Africa, and Zimbabwe (Farr & Rossman, 2015).

Except for Japan, Australia, and New Zealand where the presence of Colletotrichum boninense s. str. was verified (Damm et al., 2012), reports from other countries should be independently verified for C. boninense s. str.

The 2010 report of Colletotrichum boninense in Florida, USA, reported by Tarnowski & Ploetz, is now not considered to be C. boninense s. str. but actually a different species within the C. boninense species complex (personal communication: Aaron Kennedy, National Identification Services, USDA-APHIS-PPQ-PM). The Florida report was published before the C. boninense complex was split into several species in 2012.

Official Control: Colletotrichum boninense is considered a new USA record and reportable to the USDA.

California Distribution: There is no official record of the establishment of Colletotrichum boninense in California however during the early 1980s, CDFA plant pathologists identified C. gloeosporioides in Camelia japonica (Theaceae) and other hosts in the plant family Araceae which are included as host for C. boninense s. str. These detections were made in northern and southern coastal counties. At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense. It is, therefore, possible that these detections may have included C. boninense s. str. (Suzanne Latham and Cheryl Blomquist, CDFA, personal communication). No eliminative action would have been taken against C. gloeosporioides as the species is known to be widespread in California.

California Interceptions: Colletotrichum boninense has been intercepted at least thrice in shipments of Algaonema sp. from Costa Rica (see ‘Initiating event’).

The risk Colletotrichum boninense 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. boninense 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:

– 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 boninense s. str. is very diverse and includes member in the plant families Amaryllidaceae, Bignoniaceae, Podocarpaceae, Proteaceae, Solanaceae, Theaceae, and Araceae.

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 boninense:

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 boninense 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 not established. However, while there is no official record of the establishment of Colletotrichum boninense in California, during the 1980s, CDFA plant pathologists identified C. gloeosporioides in Camelia japonica (Theaceae) and other hosts in the plant family Araceae which are included as host for C. boninense s. str. These detections were made in northern and southern coastal counties. At that time specific molecular diagnostic tests were not available to enable the distinction of C. boninense. It is, therefore, possible that these detections may have included C. boninense s. str.

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 = 13.

Uncertainty:

The possibility that the 2013 detection of C. gloesporoides may have included the now segregate species, C. boninense st. str. and that the latter may already be established in California, can only be ascertained through survey and testing of infected host plants particularly in 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 boninense s. str. is B.

References:

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

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/

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.

Tarnowski, T. L. B. and R. C. Ploetz. 2010. First report of Colletotrichum boninense, C. capsici, and a Glomerella sp. as causes of postharvest anthracnose of passion fruit and Florida. Plant Disease 94:786. http://dx.doi.org/10.1094/PDIS-94-6-0786C .

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.