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Effects of Fungicides, Cultivars, Irrigation, and Environment on Rhizoctonia Limb Rot of Peanut. J. S. Barnes, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton 31793. A. S. Csinos, and J. E. Hook. Department of Plant Pathology, and Department of Agronomy, University of Georgia, Coastal Plain Experiment Station, Tifton 31793. Plant Dis. 74:671-676. Accepted for publication 8 March 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0671.

Diniconazole, flutolanil, and PCNB + ethoprop were evaluated in field tests in Plains and Tifton, Georgia, for control of Rhizoctonia limb rot of peanut caused by Rhizoctonia solani AG-4. Diniconazole applications at 60 + 90 days after planting (DAP) or 60 + 90 + 120 DAP were generally the best treatments for reducing incidence of limb rot in Plains. Based on a visual rating of incidence of Rhizoctonia limb rot after inverting, applications of diniconazole at 60 + 90 DAP significantly reduced disease incidence over applications at 90 + 120 DAP in Florunner, Pronto, and late-planted Florunner peanuts. Flutolanil reduced Rhizoctonia limb rot but was less effective than the two best diniconazole treatments. PCNB + ethoprop generally did not reduce incidence or severity when compared to the control. In Tifton, application of diniconazole every 14 days at 0.28 kg a.i./ha provided the greatest reduction in disease incidence in Florunner and New Mexico Valencia A (NMVA) cultivars. Pronto had significantly less Rhizoctonia limb rot than Florunner, and Florunner had less than NMVA. Irrigation increased disease incidence by as much as 109% over plots that received no irrigation.

Keyword(s): sterol biosynthesis-inhibiting fungicides.