Control of Botrytis by Compost Tea Applications on Grapes in Oregon Vineyards

Control of Botrytis by Compost Tea Applications on Grapes in Oregon Vineyards

Summary

It was decided early on that tea applications would be made through the summer, in order to assess several different diseases that might be controlled using compost tea.

This summer in the Willamette Valley, OR, mildew was a serious problem, and so this study assessed control of mildew as well as botrytis. In untreated grapes, both mildew and botrytis were significant problems, but the vineyards treated with compost tea containing adequate organism activity and density, as well as areas treated with conventional fungicides, these diseases were controlled.

It was critical to have adequate bacteral and fungal coverage of leaf surfaces, and thus adequate density of bactera and fungi in the teas sprayed on the plant surfaces in order to have control of fungal diseases. Mechanisms of control were clearly related to preventing disease organisms from reaching the leaf or grape surface, preventing disease organisms from having exudates produced by the leaves because those foods were consumed by the non-disease bacteria and fungi, and preventing infection sites from occupation by the disease-causing organisms.

Objectives/Performance Targets

To assess the ability of different compost teas to reduce disease in grapes.

Why are differences in ability to control diseases observed? Why is control of foliar diseases nearly 100% in some cases, but in other cases, control is no better than without tea? The probable explanation for such variation between teas is that tea quality is not the same way in each case. Differences in tea recipe, in tea aeration, in the initial compost used (and therefore the complement of organisms present to compete with and control disease) are probably the explanation for the differences. Which tea recipe, production method, application method, or compost gives the best control of disease?

Potential Benefits or Impacts on Agriculture
During this last year, producers switching from conventional chemical applications to using compost tea reduced input costs by reducing applications of chemical pesticides. Compost tea was produced and applied instead. For example, per acre, Broadly used applications of a copper fungicide in the vineyard to control mildew. Per spray, the cost was $500/ac. Tea applications were approximately $5.00 per acre. In the tea area, when the tea contains the organisms required to combat mildew and Botrytis, control was possible and much less expensive than the chemical alternative.

Farmer Adoption and Direct Impact
Two of the growers we are working with are undoubtedly going to commit more of their vineyards to compost tea use, while the third needs another year of demonstration to be assured that tea is repeatedly beneficial. We need to finish the second year of testing before we can recommend timing, dose rates, and quality control aspects of tea.

Farmer Adoption and Direct Impact
Two of the growers we are working with are undoubtedly going to commit more of their vineyards to compost tea use, while the third needs another year of demonstration to be assured that tea is repeatedly beneficial. We need to finish the second year of testing before we can recommend timing, dose rates, and quality control aspects of tea.

Accomplishments/Milestones

In the Reeds and Reynolds vineyard, no mildew occurred in any tea-applied area. In the other vineyards, mildew was controlled in the areas where adequate organism coverage of the leaves occurred. Where organism coverage on leaves was too low, mildew outbreaks occurred but were easily controlled using one application of fungicide, and following adequate coverage of the leaves with compost tea organisms, prevention of further outbreaks were achieved.

The not-sprayed-at-all plot (neither compost tea or conventional controls measures), a true control, severe disease occurred. Fungicides were required to control the disease in these areas. Tea was very effective in preventing or suppressing both mildew and botrytis when organism numbers were adequate in the tea to give preventative control.

As a “pesticide”, however, compost tea did not appear to be effective. Once mildew was established, compost tea organisms were ineffective at preventing outbreaks from continuing. A single-time application of fungicide was adequate to stop the disease, and then compost tea applications were effective at preventing further disease.

Thus, leaf-coverage with the organisms is critical. Having adequate organisms in the tea, in order to obtain adequate coverage, is thus critical. The critical level of coverage appears to be between 50 and 70% coverage with bacteria, and 2 to 5% coverage with fungi. This would prevent the spores of mildew or botrytis from finding space on the leaf, prevent the spores from obtaining food resources, or exudates, produced by the leaf, and prevent infection sites from being open to colonization. Thus, disease will not be able to germinate, grow or infect the leaves.

The density of organisms, per ml of tea, which resulted in adequate coverage were:

2 micrograms active bacterial biomass
10 micrograms total bacterial biomass
2 micrograms active fungal biomass
10 micrograms total fungal biomass
2000 protozoa
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In January 2001, Dr. Bob Ames was hired to oversee the grant in the place of Mr. Michael Alms who attended the initial grant meeting with all the growers in October of 2000, lead two Microb-Brewer training sessions, and then dropped out of the grant with only the explanation that he was too busy to continue working on the grant.

Dr. Ames developed an experimental calendar, met with the growers several times to make sure things were in order. Unfortunately, he overspent the equipment budget and the Sustainable Studies Institute had to use non-grant funds to cover these expenditures. As a result the Institute did not have the funds to keep Dr. Ames further employed.

Shepard Smith stepped in as one of the grower field representatives to act as coordinator of the project in the field. Mr. Smith collected all compost, ingredients for the teas and took them to the growers, helped deal with mechanical failures with the sprayers and Microb-Brewers, collected finished teas for transport to SFI, as well as taking soil samples and leaf samples.

Applications of tea were started between April 1 and May 15, depending on weather conditions and frost protection equipment in the field in the specific vineyards. Teas were sprayed either once a week or twice a week, but only bacterial-dominated teas could be produced, since the Microb-Brewers could not extract enough fungal biomass from the composts, although the fungi were clearly presenting the composts. Each tea was made using a standard recipe with a cup of molasses and kelp in the sprayer tank before spraying. The same vermi-compost was used throughout after an initial problem with mushroom “compost” killing most of the organisms in the teas.

Plots were set up to be similar areas in each vineyard, of approximately 1 acre per plot. In the Broadly vineyard, 6 rows of vines were in each plot (1/wk, 2/month, control). In the Wren vineyard, 6 rows were in each plot, while in Reeds and Reynolds, there were 8 rows per plot.

Since the organism numbers in the tea were below desired levels in 5 gallons, but at adequate levels when 12 gallons were applied, twelve gallons of tea were applied to each plot. Plot 1 received tea every two weeks, while plot 2 received weekly tea sprays. Controls received standard applications of chemicals, while a completely non-treated area was maintained until disease was noted. In weeks where both plot 1 and 2 were sprayed with tea, plot 1 received tea on day 1 while plot 2 received tea on day 2, so that batches of tea could be brewed separately. Later in the summer, when the Microb-Brewer pump at Sunbow Farm failed and could not be fixed, 50 gallons of tea were brewed using a Compara brewer, and then 12 gallons of tea were applied in each plot on the same day.

Tractor speeds were measured, so that rate of application of the tea per foot of row was the same. However, while the plots were thought to be the same size initially, the size of the plots in each vineyard were different, so the application rate was different in each vineyard. No dilution of tea occurred in Reed and Reynolds Vineyard (12 gal/ acre), but water was added to the tea in Wren vineyard to “stretch” the applications, so that only 10 gal per acre were actually applied. In Broadly vineyard, the application rate was actually about 8 gal per acre.

Thus, due to incomplete communication, the experiment became a dose-response experiment. The data from the initial soil samples, compost, compost teas and leaf samples through the summer canbe obtained from Soil Foodweb Inc on request (www.soilfoodweb.com).

Soil samples will be taken again at 1 year, based on plant phenology, following the first tea spray, to ascertain a one-year summary effect of foliar tea application.

An additional conclusion that can be made is that the concentrations of organisms in the teas were remarkably similar through the year, despite differences in season, location and microclimates through the Willamette Valley (the vineyards are a good 2 hours distance from each other).

Fungal-dominated teas were never achieved, no matter how fungal the compost. When adequate fungal biomass was placed onto the leaves, disease suppression occurred. However, it was not possible to achieve fungal teas, and so the fungal-tea plots could not be performed.

The tea brewer and then the tractor at Broadly Vineyard broke down the second week of July. No spraying of tea was performed for three weeks. Thus, when mildew was first noted in the Broadly twice-a-month sprayed plot on August 5, well after mildew had been found in other vineyards in the area, and long after a mildew alert had been issued by Dr. Scheidt at Oregon State University (June 15, 20001), it was not perhaps not unexpected.

The mildew spread from the first plot (twice a month spray) to the second plot (once a week). An extra sprau of tea was applied to both areas to attempt to shut down the disease, but the curative spray was ineffective. Kaligreen was sprayed in both plots, followed by an application of fungicide the next Monday.

After the tractor was fixed, and a different tea maker obtianed, a Compara brewer was used, and both plots were sprayed weekly at 12 gal/ac until color change in the grapes. After that time, mildew is not of concern, but botrytis can become a problem. No botrytis was observed in any area sprayed with tea, although only spot areas of botrytis were observed in some of the vineyards. This was not a year when botrytis was of concern in the Willamette Valley because conditions were not appropriate for it’s growth.

In the Wren vineyard, a few areas of mildew were observed in the twice a month plot, and spread to a shaded, poorly air circulation area of the vineyard. These areas were sprayed once with Kaligreen, and the normal spray schedule was re-instituted, except, the tea was no longer diluted. With the Compara brewer, there was no need to “stretch” the tea. No further mildewwas observed. Clearly, the tea can be used in conjunction with the fungicidal applications.

Anaerobic teas were tested, and contained no measurable bacteria or fungi. There was some leaf-burning noted when these teas were applied.

Dissemination of Findings

Current:
Summary in the Compost Tea Brewing Manual, 2nd Ed (please contact www.soilfoodweb.com for copy)

Presentations of work:
Kansas Turfgrass Association meeting, Nov, 2001 (65 attendees)

ACRES USA, Dec, 2001 (55 attendees at workshop, 550 attendees at final address)

Portland CSA meeting, Dec 2001 (25 members present)

Interview with Kevin Chambers and Elaine Ingham, Oregon Public Broadcasting, week of Dec 15, 2001

Future
Virginia Horticulture Show, January 2002
Southern Sustainable Agriculture Working Group,
January 2002
Tulare Ag Show, Tulare, CA Feb 2002
Speaking tour of Australia and New Zealand,
March, 2002

Publication of results following the end of the two-years of field research planned

Impacts and Contributions/Outcomes

In this next year, using Compara/Sotillo tea makers, we will be able to maintain more uniform organism numbers in the teas. Since there will not be a limitation of tea volume, the entire area in both the once a week and in the twice a month areas will receive the same amount of tea in all three vineyards.

We will again, expand the scope of the proposal to assess mildew as well as grey mold prevention and control.

It was reassuring that the organisms in the teas were shown to be similar week after week throughout the summer. The compost source proved to be consistent through the summer.

It was apparent that although mushroom compost was high in fungi, other metabolic compounds in the mushroom compost were quite detrimental to bacterial and fungal activity.

Collaborators: