Herbicide Timing and Combination Strategies for Woolly Cupgrass Control in Corn

Abstract

Field studies in 1992 and 1993 evaluated woolly cupgrass [Eriochloa villosa (Thunb.) Kunth] control in imidazolinone-resistant field corn (Zea mays L.) hybrids with imazethapyr, nicosulfuron, and dimethenamid. Woolly cupgrass control from combinations of cyanazine and alachlor, metolachlor, or dimethenamid applied preemergence was less than 78%. Postemergence and sequential applications (early-postemergence / late-postemergence) of nicosulfuron controlled more than 87% of woolly cupgrass. Dimethenamid plus cyanazine applied preemergence and followed by nicosulfuron postemergence provided greater than 88% woolly cupgrass control. Woolly cupgrass control from imazethapyr alone averaged only 72%. Sequential applications of pendimethalin followed by imazethapyr controlled 87% or more of woolly cupgrass. Corn grain yields from single applications of soil-applied herbicides preemergence, imazethapyr early-postemergence, or sequential soil-applied herbicides were all less than from sequential treatments that included nicosulfuron postemergence. This research suggests that sequential applications or those that included nicosulfuron were essential to many of the successful treatments and that no one treatment timing is always effective for controlling woolly cupgrass.