Influence of Adjuvants on Interactions of Sethoxydim with Selected Broadleaf Herbicides Used in Corn (Zea mays)

Field experiments were conducted during 1996 and 1998 to determine the effect of atra- zine, bentazon, atrazine + bentazon, the amine salt of 2,4-D, and bromoxynil on broadleaf signalgrass and barnyardgrass control when applied in mixture with sethoxydim. Herbicide combinations were applied with crop oil concentrate, crop oil concentrate + ammonium sulfate, or BCH 815. Bentazon and atrazine + bentazon reduced broadleaf signalgrass and barnyardgrass control by sethoxydim. Bromoxynil reduced barnyardgrass control but had no affect on broadleaf signalgrass control. In- cluding ammonium sulfate with crop oil concentrate or substituting BCH 815 for crop oil concentrate increased barnyardgrass and broadleaf signalgrass control by sethoxydim when applied with benta- zon. Ammonium sulfate and BCH 815 increased barnyardgrass control when sethoxydim was applied with bromoxynil but did not affect control when sethoxydim was applied with atrazine + bentazon. Atrazine and the ammonium salt of 2,4-D did not reduce barnyardgrass and broadleaf signalgrass control by sethoxydim regardless of adjuvant. Nomenclature: Atrazine, 6-chloro-N-ethyl-N'-(l-methylethyl)-1,3,5-triazine-2,4-diamine; bentazon, 3-(1-methylethyl)-(lH)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide; bromoxynil, 3,5-dibromo-4-hy- droxybenzonitrile; sethoxydim, 2-(1-(ethoxyimino)butyl)-5-(ethylthio)propyl)-3-hydroxy-2-cycloh- exen-l-one; 2,4-D, (2,4-dichlorophenoxy)acetic acid; barnyardgrass, Echinochloa crus-galli (L.) Beauv. #3 ECHCG; broadleaf signalgrass, Brachiaria platyphylla (Griseb.) Nash #, BRAPP Additional index words: Antagonism. Abbreviations: COC, crop oil concentrate; POST, postemergence.