SURVIVAL OF RHIZOCTONIA SPP AND ROOT DISEASES IN A ROTATION OF CORN, SNAP BEAN, AND PEANUT IN MICROPLOTS

The ability of several basidiomycetous fungi occurring naturally in Ge orgia coastal plain soils to survive and control Rhizoctonia solani an astomosis group 2 (AG-2) and AG-4 in field microplots was determined. Undisturbed profiles of soil in field microplots were fumigated with m etam-sodium and infested with Rhizoctonia solani AG-2-1, AG-2-2, or AG -4, or with binucleate Rhizoctonia spp. CAG-2, CAG-3, CAG-4, or CAG-5. A corn-peanut rotation was then grown for 3 yr. In a second experimen t, microplots were infested with AG-4 and AG-2 alone or in combination with the potential antagonists CAG-2, CAG-4, CAG-5, Laetisaria arvali s, and an unidentified orange basidiomycetous fungus. Two-year rotatio ns of corn-snap bean (double crop)-peanut or peanut-corn-snap bean wer e grown for 3 yr. CAG-4 reduced stunting and leaf chlorosis induced by AG-2-2 in corn in the first year but not in the third year after infe station. In the third year, the orange basidiomycetous fungus and CAG- 5 increased the yield of corn with low levels of crown and brace root rot. Root and hypocotyl rot was not decreased, and yield of peanut and snap bean were not increased by the antagonists. Population densities of all antagonists in infested soil remained at levels greater than i n noninfested soil for 3-10 mo, but populations were variable 19-32 mo after infestation. Antagonists were isolated from 0-10% and AG-2-2 fr om 0-7% of the loose, sound, or decayed peanut pods each year. CAG-4, CAG-5, and the unidentified orange basidiomycetous fungus all show pot ential for surviving in soil and reducing deleterious effects of crown and brace root rot in corn in multiple-cropping systems in rotation w ith peanut.