E-19
DEPARTMENT OF ENTOMOLOGY
field crops insects

GRASSHOPPERS
C. Richard Edwards and Marlin K. Bergman, Extension Entomologists

The three most commonly observed grasshoppers in Indiana are the large, differential grasshopper and the smaller migratory and redlegged species. All are general feeders on grasses and weeds and often move to cultivated crops.
Grasshopper populations vary from year to year. Crop damage is likely to be greatest in years when dry weather accompanies high populations. 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, pastures, and alfalfa and clover fields. The eggs are laid among the roots of grasses from August to October. Each egg mass contains 20-100 eggs, and each female grasshopper may produce 8-25 egg masses. Most grasshoppers overwinter in the egg stage, although a few species overwinter as young, tiny grasshoppers (nymphs).
Eggs hatch from late May through July, and the nymphs may feed for 2-3 weeks near the "egg bed" 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.

SAMPLING TO DETERMINE NEED FOR CONTROL
The need for grasshopper control depends on their population level and/or the extent of plant damage in the infested area. These are determined by making periodic sampling surveys in field borders and cropland.
For Field Crops (Other than Soybeans). Check both the fields and field borders to pinpoint the infested areas. Then in at least five random locations within each infested area, estimate the number of grasshoppers in approximately 1 square yard. Also note whether a majority of the grasshoppers are nymphs (no fully developed wings) or adults (fully winged). Continue to survey fields and field borders until populations are no longer threatening.
For Soybeans. The sampling technique is essentially the same as outlined above. However, in addition, at each location inspect five randomly selected plants to determine average defoliation level, and/or examine the pods of all the plants in 2 linear feet to estimate the percentage of pods damaged (i.e., feeding extending through to the bean). If necessary, continue to monitor the field on a regular basis.
For Home Gardens. No specific sampling technique has been developed for use in home gardens. Gardeners should note grasshopper activity in surrounding vegetation and be aware that threatening populations may move into garden areas.

CONTROL MEASURES
Control in Non-Cropland. Grasshoppers are easiest to control while they are in the nymphal stage and still confined to the area around the egg bed. Thus, make repeated surveys of these areas to determine population levels. An average of 8 or more adults or 15 or more nymphs per square yard in field border areas indicates a population potentially threatening to nearby cultivated crops. Early detection generally means better control and less total area requiring insecticide treatment. If treatment is necessary, apply fenvalerate (Pydrin) 2.4 EC at a rate of 5-1/3 oz/acre. 

Control in Field Crops (Table 1). Need is determined by number of grasshoppers per square yard and/or extent of plant damage. An average of

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