Distribution of Sporangiospores of Mucor piriformis in Pear Orchard Soils. R. L. Dobson, 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, Professor, Department of Botany and Plant Pathology, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River, OR 97031. Plant Dis. 72:702-705. Accepted for publication 15 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0702.

Sporangiospores of Mucor piriformis were found to have a clustered spatial distribution in both vertical and horizontal planes of the soil in pear orchards. Between 76 and 93% of the spores detected were found in the top 2 cm of the soil profile, and spore numbers decreased rapidly with increasing depth. In the horizontal plane, the frequency count data for sporangiospores were described with a negative binomial model. This clustered spatial pattern reflects the colonization of a limited substrate with an irregular distribution as well as a limited spore dispersal.