Herbicide options for glyphosate-resistant kochia (Bassia scoparia) management in the Great Plains

Kochia is one of the most problematic weeds in the United States. Field studies were conducted in five states (Wyoming, Colorado, Kansas, Nebraska, and South Dakota) over 2 yr (2010 and 2011) to evaluate kochia control with selected herbicides registered in five common crop scenarios: winter wheat, fallow, corn, soybean, and sugar beet to provide insight for diversifying kochia management in crop rotations. Kochia control varied by experimental site such that more variation in kochia control and biomass production was explained by experimental site than herbicide choice within a crop. Kochia control with herbicides currently labeled for use in sugar beet averaged 32% across locations. Kochia control was greatest and most consistent from corn herbicide programs (99%), followed by soybean (96%) and fallow (97%) herbicide programs. Kochia control from wheat herbicide programs was 93%. With respect to the availability of effective herbicide options, glyphosate-resistant kochia control was easiest in corn, soybean, and fallow, followed by wheat; and difficult to manage with herbicides in sugar beet. Nomenclature: Glyphosate; kochia, Bassia scoparia (L.) A. J. Scott, KCHSC; corn, Zea mays L. ZEAMX; soybean, Glycine max (L.) Merr. GLXMA; sugar beet, Beta vulgaris L. BEAVX; wheat, Triticum aestivum L. TRZAX