Interactions of Clethodim and Sethoxydim with Selected Agrichemicals

Experiments were conducted in North Carolina during 2002 and 2003 to evaluate broadleaf signalgrass and large crabgrass control by clethodim and sethoxydim applied in two-, three-, or four- way mixtures with fungicides, insecticides, and foliar fertilizer-plant growth regulator treatments. Broadleaf signalgrass and large crabgrass control by clethodim and sethoxydim was not reduced by the insecticides esfenvalerate, indoxacarb, or lambda-cyhalothrin. The fungicides azoxystrobin, chlo- rothalonil, pyraclostrobin, and tebuconazole reduced large crabgrass control by clethodim or sethox- ydim in one or more of three experiments for each herbicide. Disodium octaborate and the plant growth regulator prohexadione calcium plus urea ammonium nitrate (UAN) mixed with clethodim and fungicides improved large crabgrass control in some experiments. In contrast, prohexadione calcium plus UAN and disodium octaborate did not affect broadleaf signalgrass or large crabgrass control by sethoxydim. Nomenclature: Azoxystrobin, methyl (E)-2-{2-(6-(2-cyanophenoxy) pyrimidin-4-yloxy)phenyl}-3- methoxyacrylate; chlorothalonil, tetrachloroisophthalonitrile; clethodim; esfenvalerate, (S)-cyano (3- phenoxyphenyl) methyl (S)-4-chloro-x-(l-methylethyl)benzenacetate; indoxacarb, (S)-methyl 7-chlo- ro-2,5-dihydro2- (((methoxy-carbonyl) (4(trifluorometoxy)phenyl) amino)-carbonyl)indeno( 1,2- e) (1,3,4)oxadiazine-4a-(3H)-carboxylate; lambda-cyhalothrin, (1 ,o(S*),3cx(Z))-( + )-cyano-(3-phenox- yphenyl)methyl-3-(2-chloro-3,3,3-tifluoro- 1 -propenyl)-2,2-dimethylcyclopropanecarboxylate; prohexadione calcium, calcium 3-oxido-5-oxo-4-propionylcyclohex-3-enecarboxylate; pyraclostrobin, methyl ester of (2-(((1-(4-chlorophenyl)-lH-pyrazol-3yl)oxy)methyl)phenyl)methoxy-, carbamic acid; sethoxydim; tebuconazole, cx-(2-(4-chlorophenyl)ethyl)-cx-(1,1-dimethylethyl)-lH-1,2,4-tri- azole-l-ethanol; broadleaf signalgrass, Brachiaria platyphylla (Griseb). Nash #3 BRAPP; large crab-