Interaction between insecticides and soil moisture in the control of whitefly and aphid in cotton

Abstract

The objective of this work was to evaluate the control, in cotton plants, of Bemisia tabaci and Aphis gossypii by thiamethoxam and pymetrozine, with foliar or soil drench applications, and to determine the
interaction between application method and soil humidity, in different intervals after insecticide application. Insecticide application consisted of foliar spray and soil drench, using cotton plants submitted to three levels of soil moisture. The insecticides were tested separately, in factorial arrangements, with application methods (thiamethoxam), pest species (pymetrozine) and soil moisture levels, as treatments, with repeated measures on time. Evaluations were carried out after 3 hours, and at 3, 6, 12, 24, and 32 days after application. Foliar spray
of both insecticides provided over 80% control, for both pests, up to 6 days after application. Thiamethoxam applied in soil exhibited control bellow 60%, at the day of application, over 90%, at 3 and 6 days, and over 80%, 12 days after application. Plant water stress levels are important to be considered in selection of most suited insecticides and application methods, for control of the evaluated pests.