Grasshoppers
More than 70 species of grasshoppers can be found in Montana the Northern Great Plains Region but only one to two dozen of these species become economic pests of rangeland and crops. Grasshopper populations tend to increase over a 2-4 year period and a few species tend to make up the majority of the outbreak. Species that feed more broadly on a variety of grass and forbs host plants are the ones that tend to move into small grain crops from the surrounding boarders. These include the two-stripped (Melanoplus bivittatus), migratory (M. sanguinipes), clearwinged (Camnula pellucida), differential (M. differentialis) and redlegged (M. femurrubrum) grasshoppers.
Most grasshoppers complete their life cycle (egg, nymph, adult) during a single season. Eggs hatch in the spring and the juveniles go through a series of molts to become adults later in the summer. Grasshoppers develop to adults by incomplete metamorphosis, meaning the juveniles resemble the adults in appearance. Nymphs can be distinguished by their wing buds that increase in size after each molt, only becoming fully developed wings and functional for flying in the adult stage.
In rangeland, 15-20 grasshoppers per square yard is considered to be the economic threshold for treatment. In spring wheat, 8-14 per square yard within the field, or 21-40 along the edge of the field, is considered to be the economic threshold for treatment. Winter wheat can be particularly susceptible to damage since it emerges later in the season when many of the grasshoppers are larger adults. In winter wheat, 3-7 grasshoppers per square yard within the field, or 11-20 along the edge of the field, is considered to be the economic threshold for treatment. When present at very high populations, grasshoppers can be difficult to control since they can continue to migrate into a crop field. In rangeland Reduced Area and Agent Treatment Strategies (RAATs) can be used. Crop protection typically involves boarder protection with an insecticide.
2010 Outlook:
Managment:
Resources:
Brochures:
MSU Extension Brochure: Grasshopper Cropland Note
Archived AgAlerts:
Grasshopper in Cropland (July-5-2009)
Helpful Links:
