A comprehensive evaluation of cotton responses to profenofos treatment

Abstract

Pesticide use in cotton may trigger plant responses ranging from yield enhancement to delayed maturity and yield reductions. Profenofos, an insecticide/miticide, can result in leaf reddening and necrotic spotting. However, these responses do not always occur and are difficult to predict. The purpose of this research was to evaluate the effects of profenofos used alone or in combination with other insecticides or surfactants applied at different stages of growth, soil moisture levels, or with different deposition characteristics, on various plant factors including visual leaf responses, vegetative and reproductive development, lint yield, and fiber quality of cotton. Three field studies were conducted over a four-year period near College Station, TX on a Ships clay soil that is integrated with a weswood silt loam. Cotton was seeded or thinned to a final population of 129,000 plants ha-'. Standard recommendations for soil fertility and weed control were used. objectives of this research required insect control procedures to deviate from standard recommendations. Other organophosphate insecticides were used under strict conditions to avoid interactions with profenofos. Insect control was accomplished primarily with pyrethroid insecticides to diminish treatment effects other than those related to profenofos use. Profenofos was applied at labeled rates, and at timings ranging from a single timing to full season use under different soil moisture levels. None of these treatments influenced vegetative or reproductive development, lint yield, or fiber quality compared to the control. Slight leaf reddening and necrotic spotting of cotton leaves was observed. The occurrence of these responses was more consistent and predictable with irrigation. Non-irrigated plots exhibited the greatest range of responses consisting of no measurable response to greater than 8.OW leaf reddening or necrotic spotting. The addition of a petroleum-based surfactant to profenofos enhanced leaf response, while the addition of cottonseed oil reduced leaf response, compared to profenofos used alone. A relationship between spray droplet size of profenofos and leaf response was observed. Leaf response generally increased as droplet size increased. The addition of cottonseed oil to profenofos and spray conditions that produce small droplets (35OAm) appear to reduce the risk of severe leaf responses.