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Extension > Agriculture > Crops > Soybean Production > Insects & mites > Grasshoppers in Minnesota soybean

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Grasshoppers in Minnesota soybean

Robert Koch, Extension entomologist, and Suzanne Wold-Burkness, Research assistant
2015

Name

Redlegged grasshopper nymph

Photo: Joseph Berger, Bugwood.org

Differential grasshopper adult

Photo: David Riley, University of Georgia, Bugwood.org

Figure 1. Redlegged grasshopper(top) and differential grasshopper adult (bottom).

Common species include the following:
Redlegged (Melanoplus femurrubrum)
Differential (M. differentialis)
Migratory (M. sanguinipes)
Two-striped (M. bivittatus) and
Clearwinged (Camnula pellucida) grasshoppers

Identification

Adults (Figure 1)

For a detailed description of each species, please see the Extension publication, Minnesota Grasshopper Management.

Eggs

Eggs are formed into a pod and laid in soil.

Nymphs

Natural history

Summer phenology of 5 grasshoppers in Minnesota

Reprinted with permission from "Minnesota Grasshopper Management: Corn and Soybeans." Ian MacRae, Bruce Potter, and Ken Ostlie.

Grasshoppers overwinter as eggs in the soil. In early to late spring, depending on the species, eggs hatch and nymphs emerge (see Table 1). Grasshopper nymphs undergo 5 molts. Adult grasshoppers mate, and females deposit eggs in the soil in late summer and early fall. Most species lay their eggs in undisturbed areas outside of fields, such as ditches, pasture, and CRP.

Impacts

Both adults and nymphs feed on leaves, resulting in jagged holes. They can also feed on soybean pods, occasionally injuring the seed or clipping pods from plants (Figure 2).

Scouting and management

Grasshopper damage on soybean pod

Kelly Estes, Illinois Natural History Survey

Figure 2. Grasshopper damage on soybean pod

Because grasshopper populations often build in non-crop areas and later move into soybean, field edges are usually the first areas to show feeding injury, and where sampling efforts can initially be focused.

We recommend focusing early-season sampling efforts on insect counts, and as plants develop, switching to plant sampling to estimate percent defoliation.

Begin scouting for grasshoppers after plants emerge. Concentrate sampling on the field edge and count the number of adults and nymphs in a 1 square foot area. Repeat this for a total of 20 samples. To determine the number of grasshoppers/square yard (which thresholds are defined as), multiply your average number of grasshoppers/square foot by 9.

As plants get larger, visually inspect plants for defoliation. To estimate defoliation, examine a minimum of 10 plants.

To estimate percent defoliation:

defoliation guide

Photo: Robert Koch, University of Minnesota

Figure 3. Percent defoliation of soybean leaves.

Risk for infestation by grasshoppers is greater in years following long, warm autumns and warm, dry springs. Populations tend to build over multiple years, so high populations observed in one year could indicate higher risk the next year.

Thresholds

For defoliation-based thresholds, the following recommendations apply:

Management decisions can also be based on insect counts. To find out more about count-based thresholds, see the NPIPM fact sheet.

Treatment

Labeled rates of insecticides can be used to manage this pest. Follow directions on the product label.

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