VIEW ARTICLE

Ecology and Epidemiology

Population Dynamics of Mucor piriformis in Pear Orchard Soils as Related to Decaying Pear Fruit. R. L. Dobson, Department of Botany and Plant Pathology, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River 97031; T. J. Michailides(2), L. A. Cervantes(3), and R. A. Spotts(4). (2)Department of Plant Pathology, University of California, Kearney Agriculture Center, Parlier 93648; (3)(4)Department of Botany and Plant Pathology, Oregon State University, Mid-Columbia Agricultural Research and Extension Center, Hood River 97031. Phytopathology 79:657-660. Accepted for publication 5 January 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/Phyto-79-657.

The population dynamics of Mucor piriformis in soil in four pear orchards were studied over a 3-yr period. Populations of sporangiospores fluctuated in an annual cyclic pattern, with a sharp increase occurring about 1–3 mo after harvest. Population densities increased from less than 10² to between 10³ and 2 × 10³ sporangiospores per cubic centimeter of dry soil, then rapidly declined between December and February, and usually remained below 10² sporangiospores per cubic centimeter throughout the summer. In soil kept free of vegetation and fruit, the population density of sporangiospores declined rapidly from 1.5 × 10⁵ per cubic centimeter and remained below 10³ per cubic centimeter for more than 2 yr. Addition of pear fruits to this soil resulted in an increase from 14 to 9.6 × 10³ spores per cubic centimeter between September 1986 and January 1987. In controlled plots, soils amended with pear fruit showed a significant increase in propagule population densities. However, in commercial orchards, the relationship between density of fruit on the orchard floor and population densities of sporangiospores in soil was less clear. The importance of additional factors affecting population densities of M. piriformis in pear orchards, including insect and rodent vectors, spread of infected fruits by mowing and birds, and favorable soil temperature, are discussed.