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Poster: Biology & Disease Mgmt: Cultural Control


Utility of compost tea for disease management in grapes.
G. KOTAMRAJU (1), R. Sysak (1), J. Gillett (1), A. Schilder (1) (1) Michigan State University, U.S.A.

Compost tea is a fermented watery extract of compost used for disease suppression and plant nutrition. A replicated trial was conducted in a ‘Niagara’ vineyard in Clarksville, Michigan to evaluate the efficacy of compost tea for disease control. Non-aerated manure-based compost tea was prepared over a 2-wk period, and foliar applications were made with a handheld sprayer every 7 or 14 days from 10 June through 27 Aug, 2016. Undiluted compost tea with NuFilm-P adjuvant applied every 7 days provided good control of black rot, powdery mildew, downy mildew, and Phomopsis cane and leaf spot. In general, less frequent and more dilute applications were less effective. 'Niagara' leaves were sampled daily for 7 days after application of aerated manure-based compost tea. Bacterial populations were higher on leaves sprayed with compost tea compared to non-treated leaves but declined to almost background levels after a week. Both yeast and fungal populations were reduced immediately after the application, but later increased over the control. Bacteria from various manure- and plant-based compost teas were isolated and evaluated for antagonism against Botrytis cinerea by dual plating. The majority of isolated bacteria belonged to the Bacillaceae family as determined by 16s rRNA sequencing. This study shows that compost tea may be used for disease suppression in grapes but further evaluation is warranted.