Profenofos induces leaf reddening of cotton under some conditions, but little is known about the cause of this effect. Field experiments were conducted in 1988 to evaluate the physiological effects of Curacron^® (profenofos) on cotton grown in different moisture regimes. The objectives of this research were 1) to determine the effect of profenofos treatment and moisture level on selected physiological parameters of cotton, and 2) to examine cotton response to time of application and rate of profenofos under a linear moisture gradient.

Seven treatments, including a control, consisted of two applications of profenofos at 1.12 kg a.i. ha^-1 applied at early, mid, and late season growth stages and various combinations thereof. A line source irrigation system provided a linear moisture gradient across the plot area. High, moderate, and nonirrigated levels were designated for each profenofos treatment.

Leaf reddening was restricted to the most recently expanded leaf and/or the leaf above or below this position. Visual ratings of reddening were made on a scale of 0 to 100 with a 0 indicating no reddening. Irrigation treatments did not affect leaf reddening. However, the first early season application of profenofos caused leaf reddening when averaged across irrigation levels. Though leaf reddening was present, photosynthesis was not significantly decreased. No differences in leaf chlorophyll content were observed in profenofos-treated plants. Consumptive water use data verified the existence of a linear moisture gradient, but no significant differences for water consumption for profenofos treatments were observed within the moisture regimes. Profenofos treatments had no effect on yield. No irrigation by profenofos treatment interaction for lint yield was observed. Micronaire and strength were unaffected by irrigation; however, uniformity ratio and length were significantly greater in the high irrigated level compared to the nonirrigated. Profenofos did not significantly affect any parameter of lint quality compared to the control.