Comparative Efficacies of Selected Pyrethroids Against Boll Weevils, 1987

A caged-plant study was conducted in the field at the Texas A&M University Agricultural Research and Extension Center at Corpus Christi. Treatments were applied with a CO2-pressurized backpack sprayer to one-row × 30-ft plots of flowering, 3-ft-tall cotton plants. The sprayer delivered 4.5 gal total spray/acre through size 3X hollow-cone nozzles (2 nozzles/row) at 35 psi. At the time of treatment application, the wind traveled at 2-5 mph from SE (row direction was E to W), RH was 70%, and ambient temperature was 89°F. Three- to five-day-old adult boll weevils were caged on the upper third of randomly chosen plants in each plot at both 5-min (0 h) and 48-h posttreatment. Cages were constructed of organdy cloth, each fastened at the top and bottom with Velcro strips. Forty-eight hours after each boll weevil infestation, the caged plants were brought into the laboratory and inspected for the presence of live or dead/moribund boll weevils. A boll weevil was considered dead if it failed to move when- its snout was squeezed with forceps. A moribund boll weevil moved its legs only slightly when its snout was squeezed with forceps, and it was unable to walk on a flat surface without falling on its side. Numbers of dead and moribund weevils were combined as a measure of percent mortality. Each plant was also scored for boll weevil feeding damage. Treatments were replicated 6 times in a completely randomized design. A replicate consisted of 1 plant infested with 10-12 boll weevils. Boll weevils used in this study were obtained from the Boll Weevil Research Laboratory at Mississippi State University (Gast-strain). Prior to use in the study, adult weevils were maintained in an environmental chamber and fed squares collected from field-grown cotton. The chamber was programmed to deliver a 14:10 (L:D) cycle at constant 78°F and 70% RH.