Bromoxynil for Control of Common Cocklebur and Wild Common Sunflower in Soybeans

Abstract

In preliminary greenhouse evaluations and then in field studies, common cocklebur (Xanthium pensylvanicum Wallr.) and wild common sunflower (Helianthus annuus L.) were controlled by early postemergence applications of 3,5-dibromo-4-hydroxybenzonitrile (bromoxynil). Bromoxynil on young soybeans [Glycine max (L.) Merr.] caused temporary necrosis, retarded growth, and delayed maturity but did not reduce the stand of soybeans. Subsequent recovery and final yields of treated soybeans were such that selective control of common cocklebur and wild common sunflower appeared feasible. Treatments were applied as aqueous sprays over the tops of both the weeds and the crop. Rates of 140 or 196 g/ha were sufficient to control common cocklebur or wild common sunflower that was in the six true-leaf stage or smaller. In terms of soybean development, the optimum time for treatment appeared to be about the first trifoliolate stage.