Control of imazethapyr-resistant common sunflower (Helianthus annuus) in soybean (Glycine max) and corn (Zea mays)

Field experiments were conducted in 1997 and 1998 near Rossville in northea st Kansas to evaluate control of imazethapyr-resistant common sunflower wit h selected herbicides in corn and soybean. In soybean, common sunflower con trol was unacceptable with imazethapyr, chlorimuron, CGA-277476, and cloran sulam applied alone. Lactofen or acifluorfen applied with these herbicides slightly improved control, whereas glyphosate applied with them controlled more than 97% of common sunflower. All herbicides reduced common sunflower populations in the corn. The greatest reductions occurred when atrazine was applied with dicamba, 2,4-D, RPA 201772, or CGA-152005 plus primisulfuron. These herbicide combinations also stunted common sunflower that survived t reatment. Several herbicide alternatives are available to control imazethap yr-resistant common sunflower in corn. However, glyphosate was the only her bicide that gave adequate control in soybean.