This was a joint project between the Fruit Research and Extension Center (FREC) and the Lake Erie Regional Grape Research and Extension Center (LERGREC). The primary objective was to explore the potential of compost teas, made from locally available composts for the suppression of grapevine powdery mildew and Botrytis. Greenhouse and laboratory assays were conducted to determine the effects of compost type, brewing method, and nutrient additives on the microbial composition and disease control efficacy of compost teas.

Two types of compost teas were use. One was manure based from Roth Vineyards, Fairfield, PA and the other was vermicompost obtained from Orner Farms, Rockton, PA. Compost teas were made via two methods; non-aerated compost teas (NCTs) and aerated compost teas (ACTs).

Microbial profiles, which included bacterial and fungal counts, were determined for each compost tea and brewing method. In addition, various nutrients were added to the teas to see if they would enhance disease suppression.

A Brief Summary

Control of Powdery Mildew, NCTs
In trial 1, the compost type, fermentation time (3 days and 6 days), and presence/absence of added nutrients did not have a significant effect on the control of powdery mildew. Although none of the NCTs provided significant control over the water check, the addition of nutrients numerically improved the efficacy of NCTs made with Roth compost, regardless of fermentation time. In trial 2, the addition of 1 % whole milk to teas just before application appeared to consistently provide complete control.

Control of Powdery Mildew, ACTs
Some reduction in the severity of powdery mildew on leaves was observed with the addition of nutrients applied every 6 to 12 days.

Botrytis Control on Berries -None of the NCTs or ACTs, with the exception of the Roth 7 day tea without nutrients (10 days after inoculation), significantly reduced Botrytis on grape berries. Aerated teas generally provided higher levels of control of incidence than non-aerated teas.

Discussion
The bacterial and fungal profiles of NCTs were generally superior to that of ACTs, however, ACTs were generally more efficacious than NCTs of the same compost. Brewing methods were not directly compared in the assays. In assays at FREC, powdery mildew control was improved in some ACTs when reapplied every 6-12 days after inoculation, indicating some potential for powdery mildew management when applied early and frequently under low disease pressure. Despite the rather modest disease control efficacy of these teas, the results of these assays have provided a basis for further exploration with compost teas in integrated control programs.

For a more detailed report which includes descriptions of microbial populations as reflected by compost type, brewing times and methods, the specific nutrients used, Methods and Materials, tables of data and statistical analyses, please see the entire report (The Suppression of Grapevine Diseases with Compost Tea in the Greenhouse ).

Click on IMages for larger view.
Phil Roth turning compost used to make compost tea	Non-aerated open bucket brewing system	Chardonnay vine inoculated with compost tea + milk	Vines showing no PM when sprayed with milk and vines with high PM infection (water control)