Chemical Control of the Fall Armyworm on Cotton, 1986

Abstract

Abstract First and third instar fall armyworm larvae were exposed to cotton structures treated with several insecticides. The insecticides were applied using a motorized spray table calibrated to spray 6.0 gal per acre with a TX-4 hollow cone nozzle mounted above the conveyor belt. Leaf disks cut from untreated cotton leaves and then treated on the spray table were used to determine mortality of first instar larvae. The treated leaf disks were placed on moist filter paper in 100 × 15 mm pitre dishes and 10 neonate larvae were placed on each disc using a small camel's hair brush. The covered dishes were placed in a 30�C temperature chamber and mortality was observed 24 h post-treatment. Each treatment contained 5 dishes and was replicated twice. A "water-pic" bioassay system was used to obtain mortality of third instar larvae due to insecticide treatment. Cotton terminals were obtained from an untreated field by cutting the top ca. 30 cm of the stem using pruning shears. The plant material was washed, trimmed and placed in 30 ml test tubes filled with water. The test tubes were then placed in an upright position in wooden holding boxes (0.5 × 0.8 m). After spraying the material on the spray table, one third instar larva was placed on each terminal and caged using a 472 ml styrofoam cup. The boxes were held at room temperature and mortality was observed 48 h post-treatment. After 48 h survivors were placed in diet cups and held in a 30�C temperature chamber until pupation, at which time mortality was again observed. This was necessary to allow appropriate time for several biological treatments to cause mortality. Each treatment consisted of 20 larvae and was replicated 4 times. All tests included a water control treatment.