Colletotrichum queenslandicum B. Weir & P. R. Johnst. 2012

California Pest Rating for

Colletotrichum queenslandicum B. Weir & P. R. Johnst. 2012

Pest Rating: B

PEST RATING PROFILE

Initiating Event:

On October 29, 2015 California Dog Teams intercepted Persea americana (avocado) fruit at parcel distribution facilities in Los Angeles and Santa Clara Counties. The shipments had originated in Florida and Puerto Rico and were destined to private citizens in Los Angeles and Santa Clara Counties accordingly. Diseased avocado fruit with necrotic spots were collected by County Agricultural officials, and sent to the CDFA Plant Diagnostics Branch for diagnosis. Suzanne Latham, CDFA plant pathologist identified the fungal fruit spot and anthracnose pathogen, Colletotrichum queenslandicum as the cause for the disease. The identity of the associated pathogen was later confirmed by USDA National Identification Services at Beltsville, Maryland, and marked the first detection of C. queenslandicum in continental USA. [According to USDA APHIS, the first US domestic detection of C. queenslandicum was reported from Hawaii on October 19, 2015.] Consequent to the California detection, all infected plant materials were destroyed. The risk of infestation of C. queenslandicum in California is evaluated and a permanent rating is proposed.

History & Status:

Background: Colletotrichum queenslandicum 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 (Weir et al, 2012). The species was originally described in 1965 as C. gloeosporioides var. minus Simmonds from Carica papaya (papaya) in Queensland, Australia. The new name, C. queenslandicum was proposed by Weir and Johnston in 2012.

Hosts: Colletotrichum queenslandicum is known from few different hosts in different countries: Carica papaya, Carica sp. Persea americana, and Passiflora edulis (Australia); Coffea sp. (Fiji) (Farr & Rossman, 2015; James et al., 2014; Vieira et al., 2014; Simmonds, 1965).

Symptoms: Colletotrichum queenslandicum causes leaf and fruit spots. 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.

Damage Potential: Anthracnose disease caused by Colletotrichum queenslandicum 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 productions of papaya and avocado plants 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.

Disease Cycle: It is likely that Colletotrichum queenslandicum 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: Colletotrichum queenslandicum is distributed in Australia and Fiji (Farr & Rossman, 2015; James et al., 2014; Vieira et al., 2014; Simmonds, 1965).

Official Control: In California C. queenslandicum is an actionable, Q-rated pathogen, and infected plant material is subject to destruction or rejection.

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

California Interceptions: There have been two reported interceptions of Colletotrichum queenslandicum-infected avocado fruit. (see ‘Initiating event’).

The risk Colletotrichum queenslandicum 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 queenslandicum 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 in mainly in southern California.

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) – Colletotrichum queenslandicum has a limited host range comprising mainly of avocado, papaya, coffee and purple Granadilla (Passiflora edulis). The Latter two hosts are not grown in California and avocado and papaya have limited productions mainly in the southern regions of the State.

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) –Anthracnose-infected papaya and avocado fruit may result in lower crop value and market loss. Its economic impact is evaluated as a medium risk.

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 backyard productions of papaya and avocado wherever grown in California.

Consequences of Introduction to California for Colletotrichum queenslandicum:

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 queenslandicum to California = (10).

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 queenslandicum is not established in California.

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 queenslandicum is B.

References:

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/

James, R.S., J. Ray, Y. P. Tan and R. G. Shivas. 2014. Colletotrichum siamense, C. theobromicola, and C. queenslandicum from several plant species and the identification of C. asianum in the Northern Territory, Australia. Australasian Plant Disease Notes : 1-6.

Simmonds, J. H. 1965. A study of the species of Colletotrichum causing ripe fruit rots in Queensland. Queensland Journal of Agricultural and Animal Sciences 22: 437-459.

Vieira, W.A.S., S. J. Michereff, M. A. de Morais, Jr., K. D. Hyde and M. P. S. Camara. 2014. Endophytic species of Colletotrichum associated with mango in northeastern Brazil. Fung. Diversity 67: 181-202.

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.