Carrier Volume Effects on the Antagonism of Sethoxydim by Bentazon

The effect of spray carrier volume on the antagonism of sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} by bentazon [3-(1-methylethyl)-(1 H )-2,1,3-benzothiadiazin-4(3 H )-one 2,2-dioxide] was investigated under greenhouse and field conditions. In the laboratory, the spray droplet overlap between components of a sequential spray application increased from 17 to 50% as carrier volume was increased from 94 to 374 L/ha, respectively. Carrier volume had a significant influence on treatments of sethoxydim alone and sethoxydim sequentially applied with bentazon, but not on the tank mixture of the two herbicides. Carrier volumes of 94 and 187 L/ha used to deliver sethoxydim alone and the sethoxydim/bentazon sequential treatment were superior to the use of 374 L/ha for the control of large crabgrass [ Digitaria sanquinalis (L.) Scop. # DIGSA], fall panicum ( Panicum dichotomiflorum Michx. # PANDI), and goosegrass ( Eleusine indica Gaertn. # ELEIN). There was no difference in grass control between sethoxydim alone and the sequential treatment except at carrier volumes of 187 L/ha or more with which the sequential treatment was less effective. Rates of 0.06 and 0.11 kg ai/ha of sethoxydim were influenced more by changes in carrier volume than 0.22 kg/ha in both the alone and sequential treatments.