At the Northeast Experiment Station in 1979, several field experiments were conducted to evaluate the efficacy of sethoxydim as a postemergence over-the-top treatment for grass control in cotton. Applied at 0.5 lb/A with 1 qt/A crop oil concentrate, sethoxydim controlled 100% of the seedling johnsongrass up to 12 inches tall, the rhizome johnsongrass up to 18 inches tall and the broadleaf signalgrass up to 3 inches tall. Control ratings were made approximately three weeks after application. One hundred percent control was maintained for all target species throughout the growing season. Sethoxydim caused no cotton injury. In 1980, sethoxydim and CGA-82725 were compared for postemergence over-the-top grass control activity in several experiments. Sethoxydim was applied with 1 qt/ A COC; CGA-82725 was applied without a supplemental surfactant. In one experiment with cotton 3-4 inches tall, 3-6 inch tall broadleaf signalgrass, 4-6 inch tall seedling johnsongrass, and B-20 inch tall rhizome johnsongrass were treated with these two materials. All species were growing under moderate drought stress. Sethoxydim was applied at a minimum rate of 0.5 lb/A and provided complete control of all weed species at three weeks after treatment. Sethoxydim caused no cotton injury at rates as high as 2.0 lb/A. CGA-82725 provided 80% control of broadleaf signalgrass and rhizome johnsongrass and 100% control of seedling johnsongrass at the maximum rate of 1.0 lb/A without causing cotton injury.

In another experiment conducted under more favorable growing conditions, sethoxydim 0.5 lb/A provided 100% control of seedling johnsongrass and 89% control of rhizome johnsongrass two weeks after treatment. This treatment maintained a high level of control throughout the season, giving 96% control until harvest. CGA-82725 0.5 lb/A gave 98% control of seedling johnsongrass and 89% control at harvest.

In 1981, several new herbicides were included in the evaluation. Under near-optimum growing conditions 1218 inch tall johnsongrass was treated with sethoxydim 0.25 lb/A, CGA-82725 0.38 lb/A, Dowco-453 0.13 lb/A, and fluazifop-butyl 0.13 lb/A, and all treatments provided greater than 90% control. Minor cotton injury (necrotic spotting of treated leaves) occurred with some of the CGA-82725 and Dowco-453 treatments.

Additional experiments demonstrated that-retreatment when regrowth appears using a full or partial rate can assure season-long johnsongrass control.

An additional experiment conducted in cotton infested with bermudagrass indicated the potential for bermudagrass control with this group of compounds. A single over-the-top treatment with each material was made when bermudagrass stolons were approximately 5 inches long. Dowco-453 applied at 0.5 lb/A gave 98% control, while fluazifop-butyl 0.5 lb/A gave 84% control. Sethoxydim and CGA-82725 both at 1.0 lb/A, gave approximately 70% control of the bermudagrass.

Two johnsongrass control experiments were conducted in 1982 with postemergence over-the-top herbicides. In a rate and timing of application study, sethoxydim 0.3 lb/A, fluazifop-butyl 0.13 lb/A, CGA-82725 0.38 lb/A, Dowco-453 0.065 lb/A and HOE-00581 0.15 lb/A each gave 90% or greater control of 6-24 inch tall rhizome johnsongrass and complete control of seedling johnsongrass up to 6 inches tall in 4-5 inch tall cotton. When application was delayed until the rhizome johnsongrass was in the boot stage and up to 36 inches tall, the following rates of these herbicides were required for 90% control: sethoxydim 0.3 lb/A, fluazifop-butyl 0.38 lb/A, CGA-82725 0.63 lb/A, Dowco-453 0.13 lb/A. HOE-00581 0.15 lb/A provided 80% control at this timing of application. All herbicides except HOE-00581, which received no supplemental surfactant, received 1 qt/A COC.

In another experiment, fluazifop-butyl, sethoxydim and MSMA were applied over-the-top in cotton that had received trifluralin 1.0 lb/A ppi and in cotton that had received no preplant herbicide. The entire test area received a preemergence surface treatment of fluometuron 1.2 lb/A and postemergence directed treatments of methazole + MSMA (0.6 + 0.8) lb/A and prometryne + MSMA (0.5 + 2.0) lb/A and two mechanical cultivations. Fluazifop-butyl 0.25 lb/A and 0.5 lb/A each provided approximately 90% johnsongrass control. A split application of 0.25 lb/A followed by 0.25 lb/A approximately one month later, resulted in greater than 95% control. Sethoxydim 0.3 lb/A and 0.5 lb/A each provided approximately 85% control. A split application of 0.3 lb/A followed by 0.2 lb/A provided greater than 95% control. There were no apparent differences in overall johnsongrass control at harvest which could be attributed to the preplant herbicide with respect to the fluazifop-butyl and the sethoxydim treatments. However, two applications of MSMA 1.0 lb/A provided 55% johnsongrass control without the benefit of trifluralin and 70% with trifluralin 1.0 lb/A ppi. Seedcotton yields were not significantly affected by the preplant herbicide treatment.