Resistance of Botrytis cinerea to Benomyl and Iprodione in Vineyards and Greenhouses After Exposure to the Fungicides Alone or Mixed with Captan. J. Northover, Agriculture Canada, Research Station, Vineland Station, Ontario, Canada L0R 2E0. J. A. Matteoni, Agriculture Canada, Research Station, Vineland Station, Ontario, Canada L0R 2E0. Plant Dis. 70:398-402. Accepted for publication 23 October 1985. Copyright 1986 Department of Agriculture, Government of Canada. DOI: 10.1094/PD-70-398.

Benomyl-resistant Botrytis cinerea was found in southern Ontario vineyards after seven or fewer applications of benomyl. B. cinerea with low-level resistance to iprodione (EC₅₀ = 2–4 mg/L) was detected in vineyards after 10 or more applications of iprodione or vinclozolin over 4 yr. Iprodione resistance was detected in greenhouses after use of iprodione for 5 yr. In vineyards, captan used in mixtures with either benomyl or iprodione for 1 yr gave protection against Botrytis bunch rot of grapes, but it did not prevent an increase in the incidence of B. cinerea resistant to benomyl or iprodione, respectively.

Keyword(s): benzimidazole, bunch rot, dicarboximide, gray mold, Vitis vinifera.