New fungicides for suppression of sporulation byMonilinia fructicolafrom overwintering sites in peach trees in spring

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Abstract
Summary Spore production by Monilinia fructicola occurs in spring from overwintering sites on peach peduncles and mummified fruit. Several fungicides were evaluated for suppression of spore production. Production was suppressed by >90% by benomyl (250 ppm), procymidone (500 ppm) and vinclozolin (500 ppm). Iprodione (375 ppm) was moderately effective in two separate tests, suppressing spore production from infected peduncles by 39% and 83% and from mummified fruits by 89% and 98.8%. Etaconazole (500 ppm), triadimefon (500 ppm), fenarimol (250 ppm), fenapanil (500 ppm), bitertanol (250 ppm), propiconazole (60 ppm), imazilil (500–3000 ppm) and prochloraz (500 ppm) were relatively ineffective. Benomyl (250 ppm) did not effectively suppress sporulation of a benomyl-tolerant form of M. fructicola. The use of procymidone and vinclozolin as alternatives to benomyl for the suppression of overwintering inoculum is discussed in relation to the likelihood that forms of the pathogen tolerant to all three fungicides will eventually dominate orchard populations repeatedly exposed to them. Strategies for delaying this eventuality are discussed.