Development in New Zealand of resistance to dicarboximide fungicides inBotrytis cinerea, to acylalinines inPhytophthora infestans, and to guazatine inPenicillium italicum

Abstract

Abstract Strains of Botrytis cinerea resistant to dicarboximide fungicides were isolated from glasshouse vegetable crops in the Auckland region in 1980. The isolates showed cross-resistance to 4 dicarboximide fungicides (dichlozolinate, iprodione, procymidone, and vinclozolin), to dicloran, and to quintozene, and most were also resistant to benzimidazole fungicides. Growth was reduced, but not stopped, on media containing 10-1000 mg/litre of dicarboximide fungicides. The resistant isolates varied in their ability to invade plant tissue. In the glasshouses sampled, presence of dicarboximideresistant strains of B. cinerea appeared to reduce fungicide efficacy slightly. Strains of Phytophthora infestans resistant to metalaxyl were isolated from poroporo and potato crops where blight control based on the use of this fungicide was no longer effective. These isolates attacked poroporo or potato plants sprayed with 500 mg/litre metalaxyl, and a poroporo isolate also attacked plants sprayed with either ofurace or...