This project sought to assess the ability of compost teas to reduce diseases in grapes in Oregon vineyards. Applications of compost tea were made through the summer of 2001 to study effects on powdery mildew and botrytis. Where compost teas had adequate microbial coverage, diseases were controlled similarly to conventional fungicides. However, established mildew required a fungicide application. For effective disease control, compost teas required bacterial biomass of 2 micrograms and fungal biomass of 2 micrograms per ml. This reduced input costs compared to chemical pesticides and led some vineyards to adopt compost tea applications.

1. PROJECT REPORT h RESEARCH AND EDUCATION h SARE
Annual Results
SW00-039
Control of Botrytis by Compost Tea
Applications on Grapes in Oregon
http://wsare.usu.edu
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
info@soilfoodweb.com 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. “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