Field studies were conducted in 1999, 2000, and 2001 to evaluate mesotrione at 105 and 210 g ai/ha alone and in mixtures with imazethapyr at 70 g ai/ha and the prepackage mixture of imazethapyr at 47 g/ha plus imazapyr at 16 g ai/ha postemergence. Mixtures of mesotrione with imazethapyr and imazethapyr plus imazapyr controlled common ragweed, common lambsquarters, and morningglory species better than imazethapyr or imazethapyr plus imazapyr alone. Similarly, mixtures of mesotrione with these imidazolinone herbicides improved the control of giant foxtail over that by mesotrione alone. Crop injury did not exceed 11% with all treatments and appeared as transient stunting. Yields of corn treated with mixtures of mesotrione plus imidazolinone herbicides were highest in 2000 and 2001, when rainfall was higher than in 1999.
Nomenclature: Imazapyr; imazethapyr; mesotrione; common lambsquarters, Chenopodium album L. #3 CHEAL; common ragweed, Ambrosia artemisiifolia L. # AMBEL; giant foxtail, Setaria faberi Herrm. # SETFA; morningglory species, Ipomoea spp. # IPOSS; corn, Zea mays L. ‘Pioneer 3395 IR’, ‘Pioneer 32Z1B IR’.
Additional index words: Imidazolinone herbicides, Ipomoea hederacea (L.) Jacq., Ipomoea lacunosa L., Ipomoea purpurea (L.) Roth, IPOHE, IPOLA, IPOPU, total postemergence, triketone herbicides.
Abbreviations: DAT, days after treatment; POST, postemergence; WAT, weeks after treatment.