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Title: A MICROTITER ASSAY DEMONSTRATES SENSITIVITY AND RESISTANCE PROFILES OF BOTRYTIS CINEREA ISOLATES FROM LOUISIANA STRAWBERRY FARMS

Author
item Wedge, David
item CURRY, K - UNIVERSITY OF SOUTHERN MS
item BOUDREAUX, J - LA STATE UNIVERSITY
item PACE, PATRICK - AGROSTAT
item Smith, Barbara

Submitted to: Advances in Strawberry Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/7/2002
Publication Date: 3/3/2003
Citation: WEDGE, D.E., CURRY, K.J., BOUDREAUX, J.E., PACE, P.F., SMITH, B.J. A MICROTITER ASSAY DEMONSTRATES SENSITIVITY AND RESISTANCE PROFILES OF BOTRYTIS CINEREA ISOLATES FROM LOUISIANA STRAWBERRY FARMS. ADVANCES IN STRAWBERRY RESEARCH. 2003. v.20. p. 27-33.

Interpretive Summary: Botrytis fruit rot (gray mold) is one of the most destructive diseases of strawberry. Fungicidal sprays have been widely used for control of Botrytis cinerea, but in many areas this fungal pathogen has become resistant to most antifungal compounds. Few fungicides are now available for effective control of Botrytis diseases. New approaches for control of Botrytis diseases have become necessary as the effectiveness and availability of commercial fungicides decrease. Results from this study corroborate the findings of other researchers that Botrytis sp. has developed resistance to benzimidazole and dicarboximide fungicides. Since Botrytis fruit rot is controlled primarily by chemical applications during the flowering period, butrizol, azoxystrobin, and cyprodinil should be considered for future disease control of Botrytis fruit rot of strawberry. Our data also support the usefulness of these compounds as new Botrytis disease control agents. Evaluation of new fungicides to control Botrytis fruit rot with low mammalian and environmental toxicity will help assure the safety of our food supply and the environmental toxicity will help assure the safety of our food supply and the sustainability of United States agriculture.

Technical Abstract: Botrytis fruit rot (gray mold) is one of the most destructive diseases of strawberry. Fungicidal sprays have been widely used for control of Botrytis cinerea, but in many areas this fungal pathogen has become resistant to most antifungal compounds. New approaches for control of B. cinerea have become necessary as the effectiveness and availability of commercial fungicides decrease. Metalaxyl, fosetyl-Al, and PCNB, known to be inactive against B. cinerea, were used as negative standards. Each fungal isolate was challenged in a dose-response format with final concentrations of 0.3, 3.0 and 30.0 uM. Butrizol (0.3 uM), cyprodinil (3.0 uM), and azoxystrobin (30.0 uM) provided nearly 100% growth inhibition for all of the Botrytis isolates. Four isolates were determined to be benomyl resistant, and two isolates showed intermediate sensitivity to 30 uM benomyl. Two of the isolates were sensitive to 3 uM concentrations of the dicarboximide fungicides, vinclozolin and iprodione. At 30 uM concentration, 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 are benzimidazole resistant and are becoming dicarboximide resistant. Butrizol, azoxystrobin, and cyprodinil should be considered for future disease control of Botrytis fruit rot of strawberry.