Populations of Mucor piriformis in Soil of Pear Orchards in the Hood River Valley of Oregon. R. A. Spotts, Associate Professor, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River 97031. L. A. Cervantes, Experimental Biology Technician, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River 97031. Plant Dis. 70:935-937. Accepted for publication 7 May 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-935.

A method for determining populations of Mucor piriformis in soil was evaluated using four textural classes of soil. An average of 85% of the sporangiospores added to the soils were detected. Soil in 97 pear orchards in the Hood River Valley was sampled at depths of 0–5, 5–15, and 15–30 cm. M. piriformis was found in 55, 39, and 15% of the orchards with an average of 535, 103, and 9 propagules per gram of dry soil at the respective depths. No significant relationships were found between populations of M. piriformis and boron, manganese, zinc, soil moisture, pH, or soluble salts at 0–5 cm. However, a significant relationship was found between populations of M. piriformis and boron, manganese, zinc, and soluble salts at 5–15 cm.