Profenofos can induce various plant responses, ranging from leaf reddening or necrotic spotting to total necrosis and abscission. These responses have often been erratic and difficult to predict. Stage of plant development and moisture stress at time of application are thought to be involved in the expression of these responses. Field experiments were conducted to evaluate the effects of profenofos on the physiology and lint yield of cotton. The objectives of this research were to examine the effect of profenofos treatment and moisture level on selected physiological parameters of cotton, and to determine the impact of these responses to lint yield.

The field experiment was a 3 X 7 factorial arranged as a split-plot design. The main plots were the three irrigation levels:high, moderate, and none. A line source irrigation system was utilized to provide a linear moisture gradient across the entire plot area. Irrigation scheduling and water use was determined by using neutron probe measurements. The subplots were seven profenofos timing treatments consisting of early, mid, late, early + mid, mid + late, early + mid + late applications, and control. Two applications of profenofos at 1.0 pound active ingredient per acre were applied at the early and mid-season timings and one application at the late season timing.

Leaf responses occurred only for the most recently expanded leaf and/or the leaf above or below this position. Leaves were visually rated on a scale of 0 to 100 with a 0 indicating no response. Visual leaf responses were significantly greater for profenofos treatment than for the control at each of the five application dates, with <10% of the leaf being affected at peak response. Moisture level did not influence plant response to profenofos treatment. Water consumption was influenced by irrigation, but not by level profenofos treatment. Water consumption increased with increasing irrigation level, with all three levels differing significantly from one another. Plant growth parameters were recorded prior to and 30 days after initial profenofos treatment at the early and mid-season timing, and 45 days after the late season timing. Of the plant growth parameters recorded (height, leaf area index, net assimilation rate (NAR), crop growth rate), only NAR was affected.A profenofos X irrigation interaction was observed at both the early and mid-season timings. Under high irrigation, NARs were lower for treated plants than for nontreated plants. With no irrigation, NARs were lower for nontreated plants than for treated plants. Profenofos treatment did not influence fruit set or retention at either of the early, mid, or late season mapping timings. Lint yield was not affected by profenafos treatment or irrigation level.