ABSTRACT

One hundred and thirty one insecticide treatments were applied to cotton and evaluated for control of the bollworm, Helicoverpa zea (Boddie) and the tobacco budworm, Heliothis virescens (F.) at Chickasha, OK from 1976 to 1990. Yields as lint were also taken. Yields in insecticide treated plots were 9% greater during the 13 years (they were not taken in 1984 and 1989) compared to untreated plots and were not significantly different. This increase did not provide an economic benefit during these years. When killing frosts occurred before day 312 (the 30 year average first frost date) in five (38%) of the 13 years yields of treated cotton were significantly greater than untreated plots in 40% of those years. When frost occurred on or after day 312 as it did in eight (62%) of the years, yields of treated cotton were equal to or greater than untreated cotton in 50% of those years. Mixtures of two and three insecticides were no more effective than each of the insecticides alone against the two pest species.