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Biological Control of Phytophthora diseases of Taro

Grant Recipient:

Department of Plant Pathology
University of Hawaii at Manoa
St. John 307
3190 Maile Way
Honoulu, HI 96822-2279

Project Period:

August 1999 to July 2002

Principal Investigator:

Janice Y. Uchida

Description
Phytophthora causes serious losses in the production of taro (Colocasia esculenta) in Hawaii and currently no effective pesticides are registered in Hawaii for wetland taro. Phytophthora is a fungus that commonly occurs in the soil and attacks the leaves, roots and corms of taro. The project is trying to develop a successful biological control agent for Phytophthora. They evaluate the effects of an antagonistic (competing) Pythium species that shows promise in restricting the growth of Phytophthora in laboratory studies. They then propose to test potential biological control agents in greenhouse trials, present those results to growers and follow up with field studies in commercial taro fields on Oahu and Kauai as a demonstration. The project also provides more basic information on disease epidemics in wetland paddy fields.

Project goals and objectives
1) Evaluate the effectiveness of a Pythium species that is anatagonistic to Phytophthora in greenhouse trials.
2). Conduct field studies in a commercial taro field on Oahu and Kauai as a demonstration.

Outcomes
Preliminary greenhouse trials showed that the biological control agent, Pythium, is not a pathogen of Maui Lehua taro, the most widely grown commercial cultivar in Hawaii. The trials also confirmed a strong affinity of Pythium for mycelium of Phytophthora colocaisae, a major pathogen of taro. The first greenhouse trials testing Pythium against Phytophthora were inclusive. A second trial incorporating modifications based on the first trial showed that Pythium could protect taro plants from Phytophthora and plants grew better when Pythium was added. Pythium also appeared to protect taro leaves against leaf blight in some cases when leaves were isolated on agar culture.

The taro project continued with help from other funding sources and the cooperators conducted more tests. However, it now appears that resistant varieties of taro along more effective nutrient management and cultivation techniques show more promise.

Project Links
Data not required at time of project

American Farmland Trust