Control of Boll Weevil, 1988

Abstract

Abstract A caged-plant study was conducted in a commercial cotton field near St. Paul, Tex., to compare the effects of water and nonemulsified cottonseed oil on the efficacy of Asana XL, Karate, and Baythroid for boll weevil control. A cottonseed oil control (without insecticide) and an untreated control were included in the study to measure boll weevil mortality due to exposure to oil or natural causes. Boll weevils used in the study were collected from blooms in an untreated cotton field approximately 20 miles from the test site. Water treatments were applied to cotton with a CO2-pressurized (40 psi) backpack sprayer calibrated to deliver 4.4 gal total spray/acre through 2 size 3X hollow-cone nozzles/row. Oil treatments were applied to cotton with a modified CO2-pressurized backpack sprayer equipped with a controlled droplet atomizer operating at 2,000 revolutions/min. The atomizer produced a droplet size of 130 p.m in volume mean diam based on data from the supplier. The atomizer was powered by a 12 V battery. The flow rate was regulated with a size 4916-16 regulator orifice plate and a pressure of 25 psi. Based on ground speed, this produced a finished spray volume of 1.3 gal/acre. Water treatments were applied to 3-row by 50-ft plots. Oil treatments were applied to one-row by 50 ft plots. Twenty-five untreated buffer rows of cotton were planted between each plot to prevent cross contamination of treatments from spray drift. Adult boll weevils were caged 5-min after application. Cages were constructed of organdy cloth fastened at the top and bottom with Velcro strips. The caged plants were brought into the laboratory and inspected for the presence of live or dead and moribund boll weevils 48 h after infestation. A boll weevil was considered dead if it failed to move when its snout was squeezed with forceps. A boll weevil was considered moribund if it moved its legs only slightly when its snout was squeezed with forceps and if it was unable to walk on a flat surface without falling on its side. Numbers of dead and moribund boll weevils were combined as a measure of percentage of mortality. Each treatment was replicated 6 times in a completely randomized design. A replicate consisted of one plant infested with 10-12 boll weevils.