Evaluation of Benomyl and Propiconazole for Controlling Sheath Blight of Rice Caused by Rhizoctonia solani. R. K. Jones, Extension Plant Pathologist, Texas A&M University, College Station 77843. S. B. Belmar, and M. J. Jeger. Graduate Research Assistant, and Associate Professor of Plant Pathology and Microbiology, Texas A&M University, College Station 77843. Plant Dis. 71:222-225. Accepted for publication 18 September 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/PD-71-0222.

Twenty-one isolates of Rhizoctonia solani were sensitive to benomyl (mean EC₅₀ 0.5 µg a.i./ml) and propiconazole (mean EC₅₀ 5.2 × 10^–2 µg a.i./ml) in vitro. Radial growth rates for all isolates on unamended PDA averaged 0.96 mm/hr. In field trials, propiconazole applied twice or propiconazole followed by benomyl significantly reduced disease severity and increased yields in three of six studies during 1984–1985 on the semidwarf rice cultivar Lemont. Yield response was related to incidence of sheath blight at the panicle differentiation growth stage. Benomyl applied twice did not significantly reduce disease or increase yields. An economic return from propiconazole/propiconazole or propiconazole/benomyl could be anticipated when more than 5% diseased tillers were observed at the panicle differentiation growth stage.

Keyword(s): fungicides.