Purdue University
Cooperative Extension Service
West Lafayette, Indiana 47907
Publication E-19
March 1979
GRASSHOPPER CONTROL
David L. Matthew and C. Richard Edwards, Extension Entomologists
Many species of grasshoppers occur in Indiana. The most commonly observed are the large yellow, differential grasshopper, and the smaller migratory and redlegged species. All are general feeders. They feed on grasses and weeds and often move from these natural host plants to cultivated crops. Populations vary from year to year.
Crop damage is greatest during dry weather when grasshopper populations are high.
Drought conditions reduce natural vegetation, forcing the insects to move to cultivated crops.
LIFE CYCLE
Grasshoppers lay eggs in pod-like masses, generally deposited in uncultivated soil in field margins, roadsides, ditch banks, fence rows, in pastures, alfalfa and clover fields having thin plant stands. Eggs are laid during 1 August, September, and October. Each egg pod may contain 20 to 100 eggs. A female grasshopper may produce 8 to 25 egg masses. Most grasshoppers overwinter in the egg stage although a few species overwinter as nymphs. Eggs hatch during late May through July, and the tiny grasshoppers (nymphs) may feed for 2 or 3 weeks before being noticed.
When their food source becomes scarce or when their early feeding sites are mowed or otherwise destroyed, the nymphs move to nearby crops or into garden areas. They soon become adults and may do serious damage to crops or ornamental plants.
There is generally one generation each year.
CONTROL MEASURES
Grasshoppers are easiest to control while they are in the nymphal stage and still con-fined to the area where they hatched. Make repeated surveys of these areas to determine population counts. An average of ten (10) or
more adults and/or large nymphs per square yard indicates a problem and potential threat to cultivated crops. Early detection generally means that less total area requires insecticide treatment.
Control to Protect Field Crops
When grasshoppers begin moving to field crops, make repeated examinations of the area to determine need for control applications. Need is determined by number of grasshoppers per square yard and or extent of plant damage. An average of three or more per square yard in a corn field may require control. The economic threshold level to require grasshopper control on soybeans is determined by the percentage of defoliation and/or pod destruction and needs to be determined for each field. Table 1 lists insecticides used for grasshopper control plus harvest, feeding, grazing and pasture restrictions. For safe usage, follow all warnings, precautions, and instructions for proper application, storage and disposal.
Control in Home Gardens
Most of the insecticides listed in Table 1 may be used to protect flowers, other ornamentals and vegetable and fruit plantings. Some that are designated for "Restricted Use Only" can be purchased only by certified applicators. Garden supply stores carry some insecticides in small packages for home use. Always check the label before spraying vegetable or fruit plants to determine on which crops the insecticide may be used and the number of days after application you must wait before you can harvest the crop. (Refer to Publication E-21.)
Cooperative Extension Work in Agriculture and Home Economics, State of Indiana, Purdue University and U. S. Department of Agriculture Cooperating. H. G. Diesslin, Director, West Lafayette, Ind. Issued in furtherance of the Acts of May 8 and June 30,1914. It is the policy of the Cooperative Extension Service of Purdue University that all persons shall have equal opportunity and access to its programs and facilities without regard to race, religion, color, sex or national origin.
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