Screening for non-host rotation crops of Colletotrichum acutatum for strawberry nurseries in California

Screening for non-host rotation crops of Colletotrichum acutatum for strawberry nurseries in California

Summary

Our results show the fungus can colonize nearly all plants tested thus far. This includes a number of the common strawberry nursery cover crops such as triticale, Sudan grass, Austrian winter pea and bell bean. We can isolate the fungus from both living and dead tissue of most of the species inoculated. We are also able to induce sporulation from surface sterilized plant debris. We have not confirmed sporulation from tissue on living plants.
Extracts from various plants did not inhibit the fungus. However, essential oils from several plants did show inhibitory properties.

Objectives/Performance Targets

1. Determine whether or not the commonly used strawberry nursery cover crops are a host for C. acutatum or if not a primary host, determine what role they may play in the survival of this fungus during the rotation period. Screen crops that have possible inhibitory effects on the germination and growth of C. acutatum. Evaluate their potential as novel rotation crops.

Accomplishments/Milestones

Experiments on infection of plants under growth chamber and greenhouse conditions have been completed. Experiments on sporulation of C. acutatum from plants under growth chamber and greenhouse conditions have been completed. Field tests have been completed and a data analysis is under way and should be completed by February 2009. Experiments on the effect of plant extracts have been completed. An additional field trial will be initiated in February 2009 and should be completed by June 2009.

Impacts and Contributions/Outcomes

Growers with a history of anthracnose should consider it possible that the fungus is perpetuating itself on rotation crops. The fungus is clearly able to asymptomatically colonize a variety of rotation crops. It is also able to produce secondary conidia on the leaves of the plants tested. The fungus does not produce lesions under the conditions tested and therefore does not produce sporulating acervuli on living plant tissue. Yet, the fungus has the ability to lie dormant in dry plant debris for at least 1 month and then sporulate profusely upon exposure to moist conditions. There are significant differences, between the plant species tested and the degree to which the fungus sporulates. Though we are attempting to find non-host plants, this information on how the pathogen overwinters on several of the known rotation crops will allow a further vigilance in our efforts to know when infection occurs and from what source.

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