Compost tea, powdery mildew and botrytis


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This project seeks to assess the ability of different compost teas to reduce diseases in grapes.

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Compost tea, powdery mildew and botrytis

  1. 1. PROJECT REPORT h RESEARCH AND EDUCATION h SARE Annual Results SW00-039 Control of Botrytis by Compost Tea Applications on Grapes in Oregon Location: OBJECTIVES Oregon This project seeks to assess the ability of different compost teas to reduce diseases in grapes. Funding Period: Aug. 15, 2000 - Dec. 31, 2003 ACCOMPLISHMENTS/MILESTONES Applications of compost tea were made through the summer to assess several Grant Award: diseases that might be controlled with the application of compost tea. Mildew $126,707 was a serious problem in the summer of 2001, so the study assessed the effects Project Coordinators: of compost tea on mildew in addition to the effects on botrytis. In untreated Elaine Ingham grapes, mildew and botrytis were serious problems. In vineyards treated with Soil Foodweb Inc. compost tea that contained adequate organism activity and density, and in 1128 NE 2nd St., Suite 120 vineyards treated with conventional fungicides, the diseases were controlled. Corvallis, OR 97330 (541) 752-5066 The research team noted that to control the diseases required that the compost teas have adequate bacterial and fungal cover on leaf surfaces. The mechanism Terry Grove of the control were clearly related to preventing disease organisms from Sustainable Studies Institute 3359 Videra Dr. reaching the leaf or grape surface; preventing disease organisms from having Eugene, OR 97405 exudates produced by the leaves as those foods were consumed by the non- disease bacteria and fungi; and preventing infection sites from being occupied Major Participants: by the disease-causing organisms. Shepard Smith Sunbow Farms Philmath, OR In the Reeds and Reynolds vineyard, no mildew occurred where the compost tea had been applied. In the other two vineyards, mildew was controlled where there Cooperators: was adequate organism coverage of the leaves. Where organism coverage on the Kevin Chambers leaves was low, mildew outbreaks did occur, but they were easily controlled Reed and Reynolds Farm with one application of fungicide. Further outbreaks were prevented with McMinnville, OR adequate coverage of leaves with compost tea organisms. Dai Crisp Wren Vineyards While the teas was effective in preventing or suppressing both mildew and Wren, OR botrytis when organism numbers were adequate in the tea, the tea did not appear Tim Broadly to be effective as a pesticide; once mildew was established, compost tea Broadly Vineyard organisms were ineffective at preventing outbreaks from continuing. However, a Monroe, OR one-time fungicide application, followed by tea applications, prevented further disease. To be effective, the teas must have adequate organisms to achieve adequate coverage. The critical level of coverage appears to be 50-70% with bacteria and 2-5% with fungi. “This would prevent the spores of mildew or botrytis from finding space on the leaf, prevent the spores from obtaining food sources, or exudates, produced by the leaf and prevent infection sites from being open to colonization,” says the project report. “Thus, disease will not be able to germinate, grow or infect the leaves.” The densities of the organisms per ml of teas that resulted in adequate coverage were 2 micrograms of active bacterial biomass, 10 micrograms of total bacterial biomass, 2 micrograms of active fungal biomass, 10 micrograms of total fungal biomass and 2,000 protozoa. IMPACTS AND CONTRIBUTIONS/OUTCOMES During the past year, producers who switched from conventional applications to compost tea reduced input costs of chemical pesticide applications. Producer Tim Broadly had been applying a copper fungicide in his vineyard to control mildew at a cost of $500 an acre. The applications of compost ran around $5 an acre. 2002 i SW00-039i 1
  2. 2. “When the tea contained the organisms required to combat mildew and botrytis, the diseases were contained at much lower cost than with the chemical alternative,” says the project report. Two vineyards working in the project have indicated they will commit more of their vineyards to the application of compost teas, while the third needs another year of demonstration to be assured the tea is repeatedly beneficial. Several other producers, in addition to the three directly involved, are helping with the project and anticipating its results. Indeed, the project report says the second year of the testing will need to be finished before recommendations are made on timing, dose rates and quality control aspects of the tea. This project and the use of compost teas were presented at the Kansas Turfgrass Association meeting in November 2001 with 65 attending; to ACRES USA in December 2001, 55 attending a workshop and 850 present during the keynote address; and a Portland, Ore., community supported agriculture meeting with 25 members present. It was also discussed on Oregon Public Broadcasting during the week of Dec. 15, 2001. Presentations in 2002 were scheduled for the Virginia Horticulture Show in January, the Southern Sustainable Agriculture Working Group in January, the Tulare Ag Show in Tulare, Calif., in February and during a speaking tour in Australia and New Zealand in March 2002. 2002 i SW00-039i 2