Weed Control in Soybeans with Postemergence-Directed Herbicides

Abstract

Greenhouse studies showed that common cocklebur (Xanthium pensylvanicum Wallr.), green foxtail (Setaria viridis (L.) Beauv.), sunflower (Helianthus annuus L.), and velvetleaf (Abutilon theophrasti Medic.) were selectively controlled with postemergence herbicides in soybeans (Glycine max (L.) Merr. ‘Ford’). In the field the control of velvetleaf in soybeans was obtained by applying a postemergence-directed herbicide when soybeans were 15 cm tall and had the second trifoliolate leaf present. Postemergence-directed herbicides did not adequately control grass weeds. It was necessary to use a preplant or preemergence herbicide for grass control. Mechanical removal of lower leaves of soybean plants grown in the greenhouse significantly decreased yield. However, with field-grown ‘Amsoy’ soybeans mechanical removal of cotyledons, unifoliolate, and the first trifoliolate leaves did not reduce yield.