Field experiments were conducted in 1999 and 2000 to evaluate early POST (EPOST) and late POST (LPOST) control of common ragweed and giant foxtail with mesotrione at 70, 105, and 140 g ai/ha alone and in mixtures with glufosinate at 300 g ai/ha in glufosinate-resistant corn. Glufosinate-resistant corn injury was frequently higher with mixtures of mesotrione plus glufosinate than with mesotrione applied alone. Mixtures of mesotrione with glufosinate applied EPOST injured corn 6 to 21% in 1999, but in 2000, injury from mixtures was 23 to 30% from LPOST applications. Common ragweed control was above 77% with all treatments, which included 105 g/ha mesotrione. Giant foxtail control was higher at 76 to 78% by mixtures of mesotrione with glufosinate applied LPOST than by mesotrione alone. Corn yields were highest when glufosinate was included in treatments at either application timing. In the greenhouse, mixtures of mesotrione with glufosinate-injured glufosinate-resistant corn 11% or less, but corn biomass was reduced by 25% for the mixture of mesotrione at 105 g/ha plus glufosinate at 350 g/ha. Mixtures of mesotrione with glufosinate can be more effective than mesotrione alone but control of common ragweed and giant foxtail might not be commercially acceptable.

Nomenclature: Glufosinate; mesotrione; common ragweed, Ambrosia artemisiifolia L. AMBEL; giant foxtail, Setaria faberi Herrm. SETFA; corn, Zea mays L