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United States Department of Agriculture

Agricultural Research Service

Title: In Vitro Sensitivity and Resistance Profiles of Botrytis Cinerea Isolates from Louisiana Strawberry Farms

Authors
item Wedge, David
item Boudreaux, J - LOUISIANA STATE UNIVERSIT
item Pace, P - AGNO-TECH
item Curry, K - UNIVERSITY OF SOUTHERN MS
item Smith, B - USDA ARS SFRS

Submitted to: North American Strawberry Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: March 12, 2001
Publication Date: October 12, 2001

Interpretive Summary: Botrytis fruit rot (gray mold) is one of the most destructive diseases of strawberry. Fungicidal sprays have been widely used for the control of Botrytis cinerea, but in some areas B. cinerea has become resistant to many antifungal compounds. Few fungicides are now available for effective control of Botrytis disease. New approaches for control of B. cinerea have become necessary as the effectiveness and availability of commercial fungicides decrease. Preliminary testing of the five strawberry-gray mold isolates indicated that B. cinerea isolates from southeastern Louisiana were resistant or becoming resistant to two commercial herbicides. This study provided extension personnel with a guide to work with growers in implementing new disease control and resistance management strategies. Implementation of disease control measures that utilize low application rates of effective chemicals is imperative to maintaining cost-effective disease controls and farm profitability. Evaluation of new fungicides to control gray mold with low mammalian and environmental toxicity use will help assure the safety of our food supply and the sustainability of US agriculture.

Technical Abstract: Botrytis fruit rot (gray mold) is one of the most destructive diseases of strawberry. Fungicidal sprays have been widely used for the control of Botrytis cinerea, but in some areas B. cinerea has become resistant to many antifungal compounds. Few fungicides are now available for effective control of Botrytis disease. New approaches for control of B. cinerea have ebecome necessary as the effectiveness and availability of commercial fungicides decrease. Five isolates of B. cinerea were collected from southeastern Louisiana strawberry farms and one from blueberry was used for comparison. A standardized 96-well microtiter plate assay was used to evaluate B. cinerea for sensitivity to benomyl, azoxystrobin, captan, chlorothalonil, cyprodinil, dodine, fosetyl-A1, iprodione, metalaxyl, thiabendazole, thiram, vinclozolin, butrizol, PCNB, quinomethionate, and thiophanate-methyl. Each fungus was challenged in a dose-response format with final concentrations of 0.3, 3.0, and 30.0 #M. Butrizol, cyprodinil, and azoxystrobin provided nearly 100% growth inhibition for all of the Botryis isolates. Four isolates were determined to be benomyl resistant, and two isolates showed intermediate sensitivity. Two of the isolates were sensitive to dicarboximide fungicides, vinclozolin and iprodione. Three isolates were rated as possessing intermediate sensitivity to the dicarboximides, and one was resistant to vinclozolin with intermediate sensitivity to iprodione. This preliminary testing indicated that these isolates appeared to be benzimidazole resistant and are becoming dicarboximide resistant. Butrizol, azoxystrobin, and cyprodinil should be considered for future disease control of Botrytis fruit rot of strawberry.

Last Modified: 4/19/2014
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