Herbicide selection and application timing for control of cressleaf groundsel (packera glabella)

Field experiments were conducted from 2004 through 2006 to evaluate cressleaf groundsel control following fall or earlyspring preplant herbicide applications. Glyphosate, glyphosate + imazethapyr, glyphosate + 2,4-D ester, paraquat, paraquat + simazine, chlorimuron + tribenuron, and pendimethalin + glyphosate + 2,4-D ester applied in the fall controlled at least 93% of the cressleaf groundsel. Glyphosate, glyphosate + imazethapyr, glyphosate + 2,4-D ester, chlorimuron + tribenuron, and pendimethalin + glyphosate + 2,4-D ester applied in the spring provided at least 94% control of the cressleaf groundsel. Chlorimuron + tribenuron provided at least 98% control, regardless of application timing. These results indicate that herbicides applied in the fall or early spring can control cressleaf groundsel. However, certain herbicides provide greater control when applied in the fall compared with spring. Nomenclature: Atrazine; chlorimuron; clomazone; dicamba; diflufenzopyr; flumioxazin; glyphosate; imazaquin; imazethapyr; mesotrione; paraquat; pendimethalin; quinclorac; simazine; tribenuron; 2,4-D ester; cressleaf groundsel, Packera glabella (Poir.) C. Jeffrey SENGL.