Plant Health Initiative

Scouting for grasshoppers

Black chevron markings on the hind legs are a distinguishing feature of the differential grasshopper. Photo credit: B. Drees, Texas A&M University

Nymph stage - differential grasshopper. Photo credit: University of Nebraska

Grasshopper nymphs feeding on a soybean leaf. Photo credit: Marlin Rice, Iowa State University

Adults of the differential grasshopper, Melanoplus differentalis, are are 1 1/8 to 1 3/4 inches long. The grasshopper's upper surface is dark brown to olive green, the under surface is yellow. It has clear, glossy hindwings. The chevron-like black stripes on the large portion (femur) of the hind legs are very distinct.

Scout for grasshoppers from July to September. Weather is the main factor affecting grasshopper populations. Watch for outbreaks in a year following several years of hot, dry summers and warm autumns. Warm autumns allow grasshoppers more time to feed and lay eggs. Dry weather increases nymph and adult survival.

Scout near grassy areas
Differential grasshoppers move in from weedy borders, so check border rows near weedy or grassy areas first. Alfalfa and clover fields are particularly favored; eggs are often deposited on field margins.

Injury symptoms
Leaf injury from grasshopper nymphs look similar to the small holes caused by Japanese beetle feeding, but are more jagged in shape. Older nymphs and adult grasshoppers will eat the entire leaf, leaving only the major leaf veins.

However, soybeans can tolerate a fair amount of defoliation. Typically, 20-25 percent defoliation of all the leaves of the plant would be necessary to justify an insecticide application in late season, pod-setting soybeans.

Resources
For a description of other major grasshopper species, see Grasshopper Identification Guide for Cropland Grasshoppers (pdf format) - University of Nebraska Extension publication EC1569

What's Eating your Soybean Leaves? - Marlin Rice, Integrated Crop Management, Iowa State University