Efficacy of Three Postemergence Grass Herbicides for Soybeans

Abstract

The effects of herbicide concentration, adjuvants, and temperature on the phytotoxicity of CGA-82725 {2-propynyl 2-[4-[3,5-dichloro-2-pyridinyl)oxy] phenoxy] propionate}, RO 13-8895 {acetone- O -[D-2-[ p -(α,α,α-trifluoro- p -tolyl)-oxy] phenoxy] propionyl] oxime}, and BAS 9052 OH {2-[1-(ethoxyimino)-butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexene-1-one} to large crabgrass [ Digitaria sanguinalis (L.) Scop. # DIGSA] were evaluated. The addition of adjuvants increased the toxicity of BAS 9052 OH at herbicide rates below 0.14 kg ai/ha, whereas the adjuvants had little effect on the activity of CGA-82725 or RO 13-8895. There were no differences among the adjuvants in enhancing grass control with any of the herbicides. Control of large crabgrass with CGA-82725 or BAS 9052 OH was not affected by temperature at the time of spraying; RO 13-8895 was slightly more toxic at 16 C than at 32 C. Soybean [ Glycine max (L.) Merr.] had good tolerance to the three herbicides at rates 3 to 10 times those recommended; no differences in tolerance were observed among seven soybean cultivars. Stage of growth and the addition of an emulsifiable oil adjuvant did not affect soybean tolerance to BAS 9052 OH.