Authors: Gary L. Hein & Frank B. Peairs[1]
Four Melanoplus species of grasshoppers are mainly associated with damage to cropland. These include the redlegged, two-striped, migratory, and differential grasshoppers. Damage to dry beans is normally confined to fields planted next to grasshopper hatching areas when the hoppers move out from these areas in mid season. Grasshopper populations are strongly influenced by climate; long, warm fall weather and warm, dry springs favor grasshopper population increase.
The following website provides a comprehensive source of information on grasshopper biology, ecology, identification and management of grasshoppers and crickets in North America. [2]
Identification (and life cycle/seasonal history)
The grasshopper species that invade cropland overwinter in the egg stage. They begin to hatch in late May and early June and continue to hatch for about a month. Populations increase through June as does their damage potential. Extended cool (less than 65°F) and rainy weather during hatching can cause severe mortality of the young nymphs and can substantially reduce the buildup of grasshopper populations. Grasshoppers will develop through five immature stages before they become adults. This development will take about five to six weeks. When the grasshoppers become adults beginning in late June and early July they often move out of the hatching areas and into field crop areas. These infestations are often limited to field margins, but extreme populations can produce serious defoliation well into the field. Egg-laying will begin in mid to late summer and continue until the grasshoppers are killed off by frost in the fall. Grasshopper feeding activity begins during the daytime when temperatures rise above 70°F.
Plant Response and Damage
Grasshopper damage is generally limited to the margins of fields as grasshoppers move out of adjoining hatching areas. In mid-summer, the increased mobility of adult grasshoppers, coupled with the drying down of original food sources increases the damage potential to field crops. If a heavy grasshopper hatch occurs, grasshopper nymphs can move into bean fields and destroy emerging beans by consuming the cotyledons and the growing point of the small plants. If grasshopper densities are great at this time, the damage to these emerging fields can proceed quite rapidly and result in nearly complete stand loss near the borders.
Monitoring
Hazard Maps are developed each year as a cooperative effort of USDA-APHIS-PPQ and are available at the following site. http://www.sidney.ars.usda.gov/grasshopper/http://www.sidney.ars.usda.gov/grasshopper/
Management Approaches
Tillage operations will reduce grasshopper egg survival; therefore, untilled areas are the major hatching areas for grasshoppers. Many of these untilled areas are very attractive to grasshopper because of the mixture of both grasses and broadleaf weeds. The attractiveness of these areas to grasshoppers can be significantly reduced by eliminating the broadleaf weeds and establishing solid grass cover.
Due to constantly changing labels, laws and regulations, the sponsors of this web site assume no liability for the suggested use of any chemicals noted in the management section. Contact your local pest management personnel for current information on labeled pesticides that can be used for the intended plant disease, insect pest or weed.
