Role of Nitidulid Beetles and Vinegar Flies in the Sexual Cycle of Mucor Piriformis in Tree Fruit Orchards

Abstract

Nitidulid beetles (Carpophilus spp.) and vinegar flies (Drosophila melanogaster) from stone and pome fruit orchards readily acquired propagules of + and - mating types of Mucor piriformis from decayed fruit and transmitted them to healthy fruit on which zygospores developed. Higher numbers of decayed fruits on the orchard floor resulted in increased acquisition of + and - mating types of M. piriformis by vinegar flies and vice versa. In controlled laboratory and field experiments, nitidulid beetles and vinegar flies acquired propagules of + and - mating types of M. piriformis and carried them on healthy peach and nectarine fruits, resulting in fruit infection and development of zygospores of M. piriformis. Propagules of + and - mating types of M. piriformis persisted for at least 11 days on natural populations of vinegar flies after exposure to fruit decayed by M. piriformis. Numbers of zygospores developed on fruit exposed to contaminated nitidulid beetles and vinegar flies varied considerably from fruit to fruit as did numbers of zygospores resulting from contaminated insects plated in dishes containing acidified potato-dextrose agar. Several zygospores of M. piriformis developed on peaches as a result of insect activity germinated in 15% of the fruit placed in the field during the winter.