Grasshoppers in the Field and Garden
by Barb Ogg, Ph.D., and Don Janssen, Extension Educators

Grasshoppers can be serious pests of field and garden crops. Biblical accounts of swarming "locusts" described the natural devastation that grasshoppers can inflict on human civilizations. In more modern times, grasshopper outbreaks have occurred in the Great Plains in the 1870's, 1930's and 1950's, coinciding with droughty conditions. 

In North America, there are several grasshopper species that defoliate field crops and garden produce as well as trees and shrubs. Grasshopper injury to plants consists primarily of leaf feeding; however, grasshoppers also feed on stems, blossoms, ripening seeds and fruits. During heavy outbreaks, hoppers may feed down to the crown of perennial plants, damaging them beyond recovery. Four grasshopper species--the migratory, differential, two-striped and red-legged cause about 90 percent of the total damage to cultivated crops. Another 25 species cause extensive damage to rangeland. 

Life Cycle. Grasshoppers have three life stages--egg, nymph and adult. In the most destructive grasshopper species, the egg is the overwintering stage. The female grasshopper lays from 8-25 egg pods, each containing 20-100 eggs. These egg pods are laid in the soil, often in range, pasture or other grassy areas that are not tilled. Because egg pods are susceptible to fungal diseases favored by wet soil, survival of eggs is best during dry years. Outbreaks are often related to periods of drought. 

Most nymphs start feeding within one day after eggs hatch and usually feed on the same plants as adults. Eggs hatch during late May through July and the tiny nymphs may feed for several weeks before they are noticed. The immature stage is vulnerable to weather conditions, disease, predators, parasites and insecticides. 

Most years, climatic conditions and biological controls act together to reduce populations of grasshoppers so they cause minimal damage to crops and garden plants. Many plants will withstand minor grasshopper feeding, but when climatic conditions and biological controls do not control grasshopper populations, severe damage can result and control may be necessary. 

Migration. When the density of grasshoppers is very high, there may be a shortage of food and small grasshoppers will migrate to find food. Likewise, adult grasshoppers are winged and may migrate by flight to find food if it is in short supply. Grasses are thought to be the normal food of grasshoppers; still, migrating grasshoppers feed on nearly any kind of vegetation and may destroy every green plant in their path. 

Natural Enemies. There are several important natural enemies that help control grasshopper populations. These include blister beetles, ground beetles and several parasitic flies. Many species of birds and mammals also feed on grasshoppers. 

Grasshoppers are easiest to control when they are small and confined to weedy areas like grassy terraces, fence rows and roadside ditches. Use insecticide sprays or baits. Economic thresholds have been developed for several crops. 

Economic Threshold: Consider an insecticide treatment when there are 21-40 hoppers per square yard in field margins or waste areas or 8-14 per square yard in the crop. 

Some Insecticides Registered for Grasshopper Control of Field Crops:

Insecticide - crop(s)

carbofuran (Furadan®) - corn, alfalfa, soybeans, wheat

chlorpyrifos (Lorsban®, Dursban®) - alfalfa, corn, soybeans

dimethoate (Cygon®) - alfalfa, corn, soybeans, wheat

esfenvalerate (Asana®) - alfalfa, corn, soybeans 

methylparathion (Penncap-M®) - alfalfa, corn, soybeans, wheat

acephate (Orthene®) - alfalfa, soybeans

carbaryl (Sevin®) - alfalfa, corn, soybeans, wheat

malathion - soybeans, wheat 

fenvalerate (Pydrin®) - soybeans

Grasshoppers can attack ornamentals, and turf and garden crops crops--particularly after field crops have matured. The best management strategy is to control them when they are small in margin and waste areas. The following insecticides are registered for grasshopper control on some ornamental and turf crops. Read the label to make sure the insecticide you have selected can be safely used on any plants you are spraying.