Cotton Development and Yield as Affected by Insecticides

Abstract

Four major chemical classes of insecticides are currently used for insect control on cotton. Some of these chemicals are reported to have secondary effects on the cotton plant, which influence development and yield. Representative insecticides from the four chemical classes were evaluated under greenhouse and field conditions for secondary effects on leaf gas-exchange rates and developmental alteration of cotton plants. Insecticide applications were initiated during early phases of floral bud development and at 10-d intervals thereafter for a total of five applications. Physiological measurements made 24 and 48 h after each application indicated that insecticide treatment had no effect on CO2 assimilation rate, stomatal conductance, and intercellular CO2 concentration. Insecticide treatments influenced growth and development of the plant, although differences were not always significant. Trends existed for flucythrinate to increase total plant size and dry weight, whereas chlordimeform increased reproductive growth while decreasing vegetative growth. Malathion significantly increased boll numbers per plant. Final lint yield was not significantly altered by any insecticide treatment, primarily because of the relatively short growing season existing on the Texas High Plains, which did not allow all fruit forms to complete development.