Factors Affecting Dispersal of Mucor piriformis in Pear Orchards and into the Packinghouse. Themis J. Michailides, Postdoctoral Research Associate, Department of Botany and Plant Pathology, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River, OR 97031. R. A. Spotts, Associate Professor, Department of Botany and Plant Pathology, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River, OR 97031. Plant Dis. 70:1060-1063. Accepted for publication 20 July 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-1060.

Mucor piriformis is one of the major causes of postharvest decay of pear fruit in the Pacific Northwest. Propagules of M. piriformis numbering 6–3,381/ g of dry soil were found in soils collected from five pear orchards 1 mo before harvest; however, M. piriformis was absent in samples of leaf, fruit, and air collected during harvest. At harvest 2.5–5% of decayed fruits on the orchard floor were infected with M. piriformis. Two months later, fallen fruits decayed by M. piriformis increased to 23–50%, and propagules of M. piriformis in the soil increased to 365–6,832/g of dry soil. Soil adhering on the picking bins had 1,042–8,333 fungal propagules per gram of dry soil and may serve as an inoculum source of postharvest infections of pear fruits.