Postemergence Weed Control in Onions

Abstract

Oxyfluorfen (Goal®) herbicide at 0.125 to 0.25 lb. a.i./A applied postemergence (POST) to onions at the 3-leaf stage of growth effectively controlled London rocket, yellow sweetclover, and prostrate pigweed with marginal injury to onions. Earlier POST applications on 1- and 2-leaf onions caused injury and some stand reduction. Bromoxynil (Buctril®) herbicide at 0.25 lb. a.i./A applied early POST gave generally good weed control but did not adequately control sweetclover. Buctril® applied in clear weather did not injure 1-leaf onions but caused severe injury on 2- and 3-leaf onions when applied during cloudy weather conditions. Buctril® plus pendimethalin (Prowl®) tank-mix combination applied POST provided good control of London rocket, sweetclover, and prostrate pigweed; however, onion injury was severe due to applying Buctril® in cloudy weather. Buctril® and Goal® effectively controlled weeds present in the onions but timing of POST applications was critical with respect to onion size and weather conditions to minimize injury.