Field response of glyphosate-tolerant soybean to herbicides and sudden death syndrome

Three-year field experiments were conducted to assess the development of su dden death syndrome (caused by Fusarium solani f. sp. glycines) in three so ybean cultivars, tolerant (P9344 and A3071) and nontolerant (BSR101), to gl yphosate following foliar application of four herbicides (acifluorfen, glyp hosate, imazethapyr, and lactofen) commonly applied to soybeans in the nort h-central region of the United States. Cultivar A3071 is resistant to sudde n death syndrome, whereas cultivars P9344 and BSR101 are susceptible to thi s disease. There was no statistically significant cultivar-herbicide intera ction with respect to the severity of foliar symptoms of the disease and th e frequency of isolation of F. solani f. sp. glycines from roots of soybean plants. Across all herbicide treatments, the level of sudden death syndrom e was lower in the disease-resistant cultivar than in the susceptible ones. There was an increase in the disease levels under application of acifluorf en, glyphosate, and imazethapyr compared with nontreated or lactofen-treate d plants. The results obtained indicate that the response of glyphosate-tol erant soybeans to sudden death syndrome is not different from the response of conventional soybeans to this disease following application of the selec ted herbicides, and the resistance of soybean to sudden death syndrome was not changed with application of glyphosate.