Efficacy of Carbaryl Applied to Different Life Stages of Rangeland Grasshoppers12

Abstract

The Sevin^®-4 oil formulation of carbaryl was diluted either with diesel oil or water + Triton-X^® 190 and was applied at rates of 0.56 or 1.12 kg AI/ha for control of a mixed population of grasshoppers. Treatments were applied when the insects were predominantly in the 3rd instar, 4th and 5th instar, or adult stages. The 1.12 kg dosages caused 89–96% mortality within 7 days and ultimately reached 94–98%. In contrast, mortality caused by the 0.56-kg dosages increased gradually for 21 days after treatment and ultimately reached levels of 85–97%. In a single test, 0.28-kg dosage ultimately caused 90% mortality. The economic benefits of higher dosages apparently did not justify their additional costs. The earliest treatments were most economical because ca. 20 and 50% of the potential forage loss had already occurred before application of the mid- and late-season treatments, respectively.