Submitted to: Weed Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/20/2003
Publication Date: 1/1/2004
Citation: Burke, I.C., Price, A.J., Wilcut, J.W., Jordan, D. L., Culpepper, S.A., and J. Tredaway-Ducar. Annual grass control in peanut (arachis hypogaia) with clethodim and imazapic. Weed Technology. 2004. v. 18. p. 88-92. Interpretive Summary: Peanut growers can choose between herbicides that are effective against either grass species (graminicides) or broadleaf species when making weed management decisions. However, when herbicides that are specific for either grass or broadleaf weeds are combined, the effectiveness of both herbicides may be reduced due to antagonism. Imazapic is a herbicide registered in peanut to control annual broadleaf weeds and purple nutsedge. Clethodim is registered in peanut to control annual and perennial grasses. Antagonism between clethodim and imazapic is well documented. Ammonium sulfate, a chemical commonly mixed with herbicides, can reduce antagonism. Research was conducted to determine if imazapic reduces annual grass control by clethodim when applied together and to determine if applying these herbicides separately or with ammonium sulfate added minimizes antagonism. Results showed that growers should allow at least three days between treatments of imazapic and clethodim. Ammonium sulfate did not reduce antagonism when imazapic and clethodim were applied within two days or less of each other.
Technical Abstract: Field experiments were conducted to evaluate interactions of clethodim with imazapic applied as mixtures or sequentially for control of broadleaf signalgrass, fall panicum, goosegrass, and large crabgrass. Imazapic at 70 g ai/ha controlled grass weeds inconsistently while clethodim at 140 g ai/ha controlled the same weeds at least 99% when these herbicides were applied alone. Imazapic did not affect broadleaf signalgrass control by clethodim. Reduced control of fall panicum, goosegrass, and large crabgrass was observed when clethodim and imazapic were applied in mixture. Antagonism of clethodim occurred when clethodim was applied 1 d before or up to 3 d after application of imazapic (fall panicum and large crabgrass). Antagonism of goosegrass control was noted when imazapic was applied 3 d before or up to 7 d after application of clethodim. In other experiments, large crabgrass and Texas panicum control by clethodim (70 and 140 g/ha) applied alone or with imazapic (70 g/ha) or bentazon (1.1 kg ai/ha) plus 2,4-DB (0.28 kg ai/ha) either with or without ammonium sulfate (2.8 kg/ha) was evaluated. Texas panicum control by clethodim was reduced by imazapic regardless of ammonium sulfate rate.