Experiments were conducted in the greenhouse and the field to evaluate the efficacy of various sulfonylurea herbicides applied with mesotrione or mesotrione atrazine. The addition of mesotrione or mesotrione atrazine to sulfonylurea herbicides had no adverse effects on the control of large crabgrass or velvetleaf in a controlled environment. Tank mixing mesotrione or mesotrione atrazine with nicosulfuron or foramsulfuron, however, antagonized nicosulfuron and foramsulfuron control of green foxtail and shattercane. Field experiments conducted in 2004 and 2005 also indicated that addition of mesotrione atrazine to a sulfonylurea herbicide decreased herbicidal efficacy on green foxtail, yellow foxtail, and shattercane, compared with the sulfonylurea herbicide applied alone. In addition, increasing mesotrione application from 53 to 105 g/ha decreased efficacy of sulfonylurea herbicide in the tank mix on selected grass species. This research showed that the addition of mesotrione to sulfonylurea herbicides resulted in decreased efficacy of sulfonylurea herbicides on green foxtail, yellow foxtail, and shattercane. The addition of atrazine to the tank mix or an increased mesotrione rate will further decrease herbicide efficacy of sulfonylurea herbicides on shattercane and foxtail species.

Nomenclature: Atrazine, foramsulfuron, mesotrione, nicosulfuron. rimsulfuron. green foxtail, Setaria viridis (L.) Beauv. SETVI, large crabgrass, Digitaria sanguinalis (L.) Scop. DIGSA, shattercane, Sorghum bicolor (L.) Moench ssp. bicolor SORVU, velvetleaf, Abutilon theophrasti Medicus ABUTH, yellow foxtail, Setaria pumila (Poir.) Roemer & J.A. Schultes SETLU