"High Plains IPM Guide, a cooperative effort of the University of Wyoming, University of Nebraska, Colorado State University, and Montana State University."

Economic Thresholds

Economic thresholds for grasshopper densities in rangeland vary from 8 to over 40 grasshoppers per square yard. Thresholds are influenced by several factors, including cost of insecticide treatment, projected forage yield, and the value of the area being considered for treatment. These and other factors are considered in a computer program called ‘Hopper’ that can be used to determine the treatment threshold for individual areas. This decision support software for rangeland grasshopper management can be accessed at http://www.sidney.ars.usda.gov/grasshopper/Support/index.htm.

Recent research at the University of Wyoming has demonstrated the effectiveness of a new grasshopper control strategy in rangeland that can cut per acre treatment costs by as much as 60-75%. The strategy reduces both the amount of insecticide and the area treated, and is termed reduced agent/area treatment (RAATs). This method optimizes treatment application and timing, along with taking advantage of grasshopper movement behavior and the reduced impacts on natural enemies.

RAATs recommendations are available for each of the chemicals listed below and can be applied aerially or with the use of all-terrain vehicles (see http://www.sdvc.uwyo.edu/grasshopper/).

The following table gives a list of the registered products for grasshopper control in rangeland. Grasshopper control in rangeland should be targeted at immature stages of grasshoppers. Adult grasshoppers are difficult to control with any of these products.