Field studies were conducted in 1999, 2000, and 2001 to evaluate weed control and cotton response from PRE herbicides followed by (fb) trifloxysulfuron POST. In the first study, trifloxysulfuron at 3.8, 7.5, or 15 g ai/ha was applied POST with or without pendimethalin at 690 g ai/ha applied PRE in a factorial treatment arrangement. Visible crop injury occurred after all trifloxysulfuron applications, but injury was not affected by application of pendimethalin PRE. Cotton injury was 19 to 22% 7 d after POST treatment (DAT) from trifloxysulfuron at 3.8 to 15 g/ha but was 5 to 12% 28 DAT. Trifloxysulfuron controlled smooth pigweed, common ragweed, and common cocklebur, but spurred anoda, large crabgrass, goosegrass, and stinkgrass were not controlled by trifloxysulfuron. Morningglory species (tall morningglory, ivyleaf morningglory, and pitted morningglory) control with trifloxysulfuron at 7.5 and 15 g/ha was at least 79%, whereas velvetleaf was controlled 66% over all years. In a second study, clomazone, pendimethalin, pendimethalin plus fluometuron, pyrithiobac, or flumioxazin were applied PRE fb 7.5 g/ha trifloxysulfuron POST. Cotton injury from PRE herbicides fb trifloxysulfuron was 13 to 39% 7 DAT. Spurred anoda control exceeded 54% only with treatments that included flumioxazin or pyrithiobac PRE. Common lambsquarters, common cocklebur, and morningglory species were controlled at least 75% with all treatments that included trifloxysulfuron POST, whereas pendimethalin and clomazone usually controlled annual grasses. In both studies, the application of pendimethalin PRE controlled annual grass species and improved control of smooth pigweed and common lambsquarters over that controlled by trifloxysulfuron POST without a PRE herbicide.
Nomenclature:Clomazone, flumioxazin, fluometuron, pendimethalin, pyrithiobac, trifloxysulfuron, common cocklebur, Xanthium strumarium L. XANST, common lambsquarters, Chenopodium album L. CHEAL, common ragweed, Ambrosia artemisiifolia L AMBEL, goosegrass, Eleusine indica (L.) Gaertn. ELEIN, ivyleaf morningglory, Ipomoea hederacea (L.) Jacq. IPOHE, large crabgrass Digitaria sanguinalis (L.) Scop DIGSA, pitted morningglory, Ipomoea lacunosa L. IPOLA, smooth pigweed, Amaranthus hybridus L. AMACH, spurred anoda, Anoda cristata (L.) Schlecht. ANVCR, stinkgrass, Eragrostis megastachya (Koel.) Link, tall morningglory, Ipomoea purpurea (L.) Roth IPOPU, velvetleaf, Abutilon theophrasti Medicus ABUTH, cotton, Gossypium hirsutum L. ‘SG 125’