Long-term Control of Grasshoppers12

Abstract

The length of protection from grasshoppers beyond the year an insecticide is applied was examined by using published and unpublished reports and the results of actual control programs in Wyoming. Of 9 studies that provided untreated check areas for comparison, only 2 demonstrated protection from grasshoppers lasting beyond the year of application. Failure to demonstrate protection beyond the year of application in 7 comparisons was the result of either reinvasion of treated areas or of natural changes in the population of untreated check areas. Of 1,208,000 acres treated initially between 1952 and 1958 in Wyoming, an average of 3.8% was retreated annually for the next 5 years. The use of retreatment rate as a measure of effectiveness is developed employing standard statistical procedures.