Through a cooperative agreement: with Calgene, Inc., Rhone-Poulenc Ag Company is developing bromoxynil for use on cotton that has been genetically engineered to be tolerant to postemergence over-the top applications of bromoxynil, the active ingredient in BUCTRIL^® brand herbicide. Residue trials were conducted in 1991 while efficacy and crop tolerance trials were conducted in 1991 and 1992 to support the registration of BUCTRIL^® on cotton.

BUCTRIL^® has been applied postemergence to cotton up to 15 lb. ai/A with no injury symptoms. The proposed label includes broadcast rates of BUCTRIL^® from 0.375 to 0.50 lb. ai/A. When the broadcast rates of bromoxynil at 0.375 to 0.50 lb. ai/A are used as an over the-row band width that is one-fourth to one third of the width between the cotton rows, respectively, the effective rate of bromoxynil within the bank would be 1.5 lb. ai/A. Weeds that are susceptible to bromoxynil at this rate include morningglory (Ipomea sp.), prickly sida (Sida spinosa), common cocklebur (Xanthium Strumarium), common lambsquarters (Chenopodium album), Florida begarweed (Desmodium tortuosum), spurred anoda (Anoda cristata), and velvetleaf (Abutilon theophrasti). Lower use rates also provide excellent control of many of these species.

Efficacy trails will be continued in 1993 to support the anticipated launch in 1994.