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Grasshopper management in Minnesota crops

Quick facts

  • Grasshopper populations are favored by long, warm autumns followed by warm, dry springs.
  • Grasshoppers are an occasional economic pest of Minnesota crops.
  • Five species are  important in Minnesota.
  • Scouting is essential to determine whether or not treatment is warranted.   

Grasshopper populations are heavily influenced by climate. Long, warm autumns, followed by warm, dry springs favor the growth of grasshopper populations. A long, warm autumn favors egg-laying by grasshoppers well into September and even October in some Minnesota locations. In addition, if economically impacting  grasshopper populations occurred the previous year in a variety of cropping systems, autumn populations will likely be high.

In a warm, dry spring, areas in the state that had elevated populations the previous year may face localized outbreaks. However, with early scouting and carefully applied management when necessary, grasshopper populations can be controlled and economic damage to cropping systems can be kept to a minimum.

Grasshopper populations generally do not reach outbreaks in one season, but rather build over years. Grasshopper populations also generally develop outside of cropping systems; grasshoppers prefer to lay eggs in undisturbed ground such as pastures or road ditches. 

When grasshopper populations become very high, the nymphs (immature grasshoppers) eat most of the available food where they hatch. They then disperse into neighboring cropping systems to eat the available food there. Although there are 75–100 species of grasshopper on the northern Great Plains, only 5 are likely to become important crop pests in Minnesota.

Important grasshopper species in Minnesota

Early monitoring of crops for feeding damage provides enough information to make sound control decisions. All 5 economically important grasshopper species overwinter as eggs, move readily and will feed on a variety of crops. They also tend to lay eggs in ‘population production areas’ outside of crops.

Twostriped grasshopper

two-striped grasshopper on soybean
Twostriped grasshopper

The twostriped grasshopper is normally the first grasshopper to hatch in Minnesota. Adults are grayish or brownish green and have two distinct yellow strips extending from the head to the wing tips. They are relatively large grasshoppers (adults are 1¼ – 2 inches long), and have a distinct black band on the top of the femur of the jumping leg. Nymphs will begin hatching in early May and be present through early July.

Migratory grasshopper

migratory grasshopper on stem
Migratory grasshopper. Photo: Joseph Berger, Bugwood.org

The adult migratory grasshopper is about 1 inch long, brown to gray with a distinctive black streak behind its eye. It is a strong flier and disperses readily. It is sometimes confused with the Redlegged Grasshopper but has a slight hump behind the spine on its underside, between the middle pair of legs.

Clearwinged grasshopper

grasshopper on gray background
Clearwinged grasshopper. Photo: Sangmi Lee, USDA APHIS PPQ, Bugwood.org

The smallest of the economically important grasshoppers in Minnesota, the clearwinged grasshopper is about 3/4 inches long. It is light tan to brownish and has clear wings, distinctly marked with large brown spots.

Redlegged grasshopper

redlegged grasshopper
Redlegged grasshopper

A medium-sized grasshopper, the redlegged grasshopper is 3/4 to 1 inch long and is brownish red. It has a pink to red (occasionally blue) tibia on the jumping leg. It also has a line of distinct, black spines on the hind margin of the tibia.

Although they will lay eggs and are often abundant in alfalfa, Redlegged grasshoppers cannot complete development on a diet entirely composed of alfalfa. CRP is a prime breeding and population production habitat for redlegged grasshoppers.

Differential grasshopper

diferential grasshopper on soybean
Differential grasshopper

A large grasshopper, adults are 1 ½ – 1 ¾ inches long and olive green to grey. The femur of the jumping leg is distinctly marked with black chevrons. They are the last economic species to hatch in spring and are most abundant in the southern part of Minnesota.

Grasshopper development during summer

The figure below illustrates emergence and development periods for these economically important grasshopper species. As described above, the twostriped grasshopper is the first to emerge in early May, while the differential grasshopper doesn't show up until mid- to late-June. 

timeline of grasshopper development
Summer phenology of 5 major cropland grasshoppers in Minnesota. Dashed blue line depicts nymph development and solid black line represents adult development.

Scouting for grasshoppers

It's essential to estimate grasshopper densities to see if populations are high enough to warrant treatment before initiating any control techniques.  Scout for nymphs and adult in areas with historically high populations; last year’s ‘hotspots’ may have high populations this year. The edges of cropping systems show the earliest grasshopper feeding. Start scouting for grasshoppers at the edge of fields in late April or early May and continue through late June or early July.

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Grasshopper movement

Grasshoppers move into crops from production areas and between different crops. Small grains and sugarbeet are probably the first crops at risk of grasshopper damage in Minnesota. Then as spring wheat matures and dries, grasshoppers will move to neighboring crops, such as corn. Eventually, grasshoppers will move into corn, alfalfa, and finally soybeans and dry beans as the season goes on. Agronomic practices in one crop can also initiate movement of grasshoppers. When alfalfa is harvested, for example, grasshoppers will move into neighboring crops if they are present.

These grasshoppers generally leave tilled fields to lay eggs, so grasshopper populations the following year arise outside of the field. Occasionally, redlegged grasshoppers will lay eggs in alfalfa or soybean fields. All five economically damaging grasshoppers will lay eggs in soybean and dry bean fields. As a result, it's important to monitor fields that were in soybeans or dry beans the previous season.

Management strategies

Control is generally advisable when populations reach or exceed threatening levels (Table 1). Treat crop borders when nymphs are small and numbers are moderate. Treat crop borders and grasshopper population production areas if nymph numbers are high early in the season. As nymphs get larger, move the treatment to the production site and enlarge the treated areas within cropping systems. When nymph numbers are very high (100+ / yd2), it is easier and safer to treat the production area than to allow the nymphs to enter the crop. 

Timing grasshopper control depends on the potential for crop loss - especially for seedling dicots - size of grasshoppers present, and whether hatching is completed. Grasshopper control is most effective before the insects become large nymphs or adults, these stages are more mobile and harder to kill.

Grasshoppers are slow to develop resistance and so a number of different insecticide modes of action are effective (e.g. synthetic pyrethroids still tend to be effective in most areas of MN & ND). ALWAYS read and follow pesticide labels; registrations may change! 

Table 1. Action thresholds for grasshopper nymphs and adults.
Rating Nymphs in
margin
Nymphs in
field
Adults in
margin
Adults in
field
nymphs/yd2 nymphs/yd2 adults/yd2 adults/yd2
Light 25-35 15-25 10-20 3-7
Threatening 50-70 30-45 21-40 8-14
Severe 100-150 60-90 41-80 15-28
Very severe 200+ 120+ 80+ 29+

Foliar insectide for Minnesota grasshopper management

Tables 2 -10 provide labeled insecticide options for grasshopper control in major crops grown in Minnesota, as well as for roadsides and non-cropland.

Always check the product label for application rates and restrictions!

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Inclusion in or exclusion from this publication does not infer any recommendation or statement of efficacy. No statement of inference of comparative efficacy is included in this document. This information is from current registration labels as available.

ALWAYS check the label for preharvest intervals, re-entry periods, further or changed information.

Ian MacRae, Extension entomologist, and Bruce Potter, Extension IPM specialist

Reviewed in 2023

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