Resistance ofBotrytis cinereato Benomyl and Iprodione in Vineyards and Greenhouses After Exposure to the Fungicides Alone or Mixed with Captan

(EC 9o) mycelial inhibition (Y) were ABSTRACT examined by analysis of variance. Northover, J., and Matteoni, J. A. 1986. Resistance of Botrytis cinerea to benomyl and iprodione in Differences between means were evaluated vineyards and greenhouses after exposure to the fungicides alone or mixed with captan. Plant using the Student-Newman-Keuls multiple Disease 70:398-402. range test. A discriminatory concentration of Benomyl-resistant Botrytis cinerea was found in southern Ontario vineyards after seven or fewer i prodione at 10 mg/L was used in 1980 in applications of benomyl. B. cinerea with low-level resistance to iprodione (EC5 0 = 2-4 mg/ L) was apreimna at tem pt to intify detected in vineyards after 10 or more applications of iprodione or vinclozolin over 4 yr. Iprodione a preliminary attempt to iden resistance was detected in greenhouses after use of iprodione for 5 yr. In vineyards, captan used in iprodione-resistant B. cinerea in vineyards. mixtures with either benomyl or iprodione for 1 yr gave protection against Botrytis bunch rot of For the 1983-1984 surveys and vineyard grapes, but it did not prevent an increase in the incidence of B. cinerea resistant to benomyl or experiment, however, iprodione at 2 iprodione, respectively. mg/ L was considered more appropriate on the basis of our prior characterization Additional key words: benzimidazole, bunch rot, dicarboximide, gray mold, Vitis vinifera of local sensitive and imported cultures with low-level resistance to iprodione. Vineyard and greenhouse surveys. In September and October 1979, nine Populations of Botrytis cinerea Pers. rated into sterile, molten PDA at 50 C vineyards planted mainly with Vitis resistant to benzimidazole and dicarand immediately dispensed as 20-ml viniera L. 'Chardonnay,'Johannisberg boximide fungicides developed rapidly aliquots into 100-mm-diameter polyRiesling,' and 'Pinot Noir' ('Gamay after their commercial introduction (2,5). styrene petri dishes. Beaujolais') were surveyed, and 12