VIEW ARTICLE

Ecology and Epidemiology

Survival of Macrophomina phaseolina in Soil and in Residue of Soybean. G. E. Short, Rural Route 2, Box 213, Archbold, OH 43502; T. D. Wyllie(2), and P. R. Bristow(3). (2)Professor, Department of Plant Pathology, University of Missouri-Columbia, Columbia 65211; (3)Assistant professor of plant pathology, Western Washington Research and Extension Center, Washington State University, Puyallup 98371. Phytopathology 70:13-17. Accepted for publication 14 June 1979. Copyright 1980 The American Phytopathological Society.. DOI: 10.1094/Phyto-70-13.

Survival of sclerotia of Macrophomina phaseolina in soil and in soybean residues was studied under mid-Missouri field conditions from May 1975 to October 1977. Sclerotia produced in soybean tissues survived longer in soil than did sclerotia produced in laboratory culture. Sclerotia from soybean tissues were added to soil to augment the natural infestation level. In fallow soil augmented with sclerotia, populations of germinable sclerotia increased by an average of 11% from January to April and decreased by an average of 3% from April to July. Field populations of sclerotia also increased from January to April, with a decline occurring later each year. Populations of germinable sclerotia in soybean residue on the soil surface increased threefold from October 1975 to July 1976, then declined for 9 mo. Populations of germinable sclerotia in residue pieces buried 10–20 cm below the soil surface were relatively stable. When populations of germinable sclerotia declined in residue pieces, there was a concomitant increase in the number of germinable sclerotia in the contiguous soil. The depth at which sclerotia were buried, either free in soil or within soybean residue, had little effect on their persistence. By October 1977, the populations of germinable sclerotia in fallow soil and in residue pieces were as great, or greater, than the initial infestation levels in 1975. Populations of germinable sclerotia in soil were directly related to the number of consecutive years of planting soybeans and corn in the field and showed a twofold increase from 1975 to 1977. In 1975, 1976, and 1977, severity of charcoal rot of soybean was directly related to the population of germinable sclerotia of M. phaseolina in soils, and soybean yields were inversely related to the severity of charcoal rot.