Herbicide effects on Rhizoctonia solani in vitro and Rhizoctonia foliar blight of soybean (Glycine max)

Acifluorfen, alachlor, glufosinate, glyphosate, paraquat, and pendimethalin were evaluated for their effects on mycelial growth and sclerotia/microsclerotia production by Rhizoctonia solani AG-1 IA and IB in culture. All of these herbicides except glufosinate and glyphosate were evaluated for effects on severity of Rhizoctonia foliar blight of soybean in the field, In laboratory studies, all herbicides reduced colony radius of R. solani. Growth reductions for IB were greater than for IA in the presence of pendimethalin, alachlor, and acifluorfen, but glufosinate reduced growth of IA more than IB, Sclerotia production by both isolates was prevented by paraquat, greatly reduced by glufosinate, but markedly less affected by the other herbicides tested. In field studies, all tested herbicides influenced severity of Rhizoctonia foliar blight when disease pressure was low, but only paraquat reduced severity when disease pressure was high.