According to Laurie Kerzicnik (Montana State University Entomologist), grasshoppers continue to be an issue for several areas in Montana. Grasshopper infestations will continue to extend into the fall. High grasshopper populations this year could be due to a couple of factors including an abundance of a yellow sweet clover in 2019 and a cold, wet spring in 2019 where grass was abundant and rising grasshopper populations were tolerated and mostly not managed.

Most grasshoppers overwinter in the egg stage in the soil. After egg hatch in mid to late spring, immature grasshopper (nymphs) immediately begin feeding. At least five or six stages of nymphs exist before grasshoppers reach adulthood. Adult grasshoppers can live for several months into late summer and early fall.

Once adult grasshoppers have entered the yard and garden, management is extremely challenging. Consider focusing on the most important and vulnerable trees and plants for management. Management options are available, but several applications might be necessary to protect yard and garden landscapes.

Many plants and flowers will be hard to protect. Screen the garden and sensitive areas with metal window-type screening. Grasshoppers will easily chew through fabric. Be prepared early next year for possible grasshopper issues as they are a boom and bust family and will continue to grow in numbers if drought continues during the spring.

Several insecticides are available and labeled for use on grasshoppers. Organic insecticides include Neem oil (AzaGuard) and Pyrethrins ( PyGanic). Non-organic insecticides include Bifenthrin (Ortho Home Defense Insect Killer for Lawn and Landscape) and zeta-cypermethrin (Ortho Bug B Gon Insect Killer for Lawns and Gardens). Other Non-organic options include Cyfluthrin (Bioadvanced Complete Insect Killer) and Carbaryl (Eco Bran bait or Sevin). Please read the label for application rates, application timing, and safety precautions. The pesticide label is the law. The label is also a great reference as it will provide important information such as the pre-harvest interval and the restricted entry interval.

Montana State University, U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.