Grasshopper Management in Corn
 Several species of grasshoppers attack corn.
 Grasshopper populations fluctuate widely from year to year, and they may cause serious damage
during periodic outbreaks favored by weather.
 Early scouting and proper management practices can keep grasshopper populations to a minimum.
Biology
Grasshoppers are general feeders on grasses and weeds and
often move to cultivated crops when the vegetation is
consumed or reduced by drought conditions. Grasshoppers
usually cause minor damage every year, but they can become
very destructive during periodic outbreaks. Grasshopper
populations are heavily influenced by weather. Several years of
hot, dry summers and warm autumns contribute to developing
large populations of grasshopper.1 Survival of nymphs and
adults may be higher during dry weather and long warm
autumns give grasshoppers more time to feed and lay eggs.
Migratory Grasshopper (Melanoplus sanguinipes)–The adult
migratory grasshopper is about 1" long, brown to gray with a
distinctive black mark behind its eye. It is a strong flier and may
swarm over long distances (Figure 3).
Identification
There are over 100 species of grasshoppers in the United
States, but only four grasshopper species are likely to become
economically damaging pests of crops including corn.
Red-legged Grasshopper (Melanoplus femurrubrum)– Adults
are about ¾" – 1" long, brownish red in color and have a
pinkish-red tibia on the hind leg (Figure 1A).
Twostriped Grasshopper (Melanoplus bivittatus)– They are
relatively large grasshoppers. Adults are 1¼" – 2" long and are
grayish or brownish green with two distinct light yellow strips
extending from the eyes to the wing tips (Figure 1B).1
A
B
Figure 2. Differential grasshopper.
Figure 3. Migratory grasshopper.
Photo Courtesy of David Riley,
Photo Courtesy of Joseph Berger,
University of Georgia, Bugwood.org.
Bugwood.org.
Life Cycle
In late summer or early fall, female grasshoppers lay eggs 1/2
to 2 inches below the soil surface in an elongated pod. They
prefer firm, uncultivated soil such as CRP, roadsides, pastures.
Each egg pod consists of 20 to over 100 eggs, which are
cemented together. A female can lay up to 25 egg pods. The
eggs will overwinter in the soil and small, wingless nymphs will
emerge in May or June. Grasshopper nymphs go through five
to six stages and require 40 to 60 days to become adults.6
There is usually only one generation produced each year.
Damage
Figure 1. Red-legged grasshopper (A) and twostriped grasshopper (B)
Photos Courtesy of Whitney Cranshaw, Colorado State University,
Bugwood.org.
Differential Grasshopper (Melanoplus differentialis)– A large
grasshopper, adults are 1 ½" – 1 ¾" long and yellowish or olive
green color. The femur of the jumping leg is distinctly marked
with black chevrons (Figure 2).4
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Grasshoppers can feed on aboveground parts of corn plant
including leaves, tassels, green silks, and ears. They feed from
the outer edge of the leaves inward and the damage appears
as round to ragged holes on the leaves. Very large grasshopper
populations can consume an entire leaf leaving only the midrib.
Grasshopper feeding on fresh silks may result in reduced
pollination and often causes the ears to be blank or only partly
filled.7 In severe infestations, the entire corn stand is stripped off
leaves leaving only bare stalks.
Grasshopper Management in Corn
Damage can be severe in dry years when natural vegetation is
limited and grasshoppers migrate to corn fields.
yard.6 Action thresholds for field borders and infested areas in
the field that warrant insecticide treatment are listed in Table 1.
Management
Chemical Control. Grasshopper control is most effective
before they become adults, as adults are highly mobile and are
more difficult to control. Targeting insecticide sprays towards
nymphs in egg laying sites or before they move into the field
greatly reduces the area that must be sprayed and the amount
of insecticide.3 Please contact your local agronomist for
insecticide recommendations and doses.
Cultural Control. As grasshoppers lays eggs in undisturbed
areas, tilling these areas will discourage females from laying
eggs. In CRP lands, where tillage is not an option, plant tissue
can be shredded to reduce food supply to grasshoppers.
Controlling weeds on fallow ground will also prevent adult
females from laying eggs because there will be no food source.
If the eggs are already laid, the nymphs will not have anything to
feed on after emergence.2
Figure 4. Grasshoppers feeding on
corn leaves (left) and on ear (right).
Photo Courtesy of Marlin E. Rice,
Iowa State University.
Scouting and Thresholds
Because grasshoppers often lay eggs in field margins, these
areas should be monitored closely in the spring and early
summer. Scout deeper into the filed for grasshopper activity as
the season progresses. Grasshopper density can be estimated
by using the square-yard method. Count the nymphs and
adults in field borders or infested field areas, at 5 random
locations to get an average number of grasshoppers per square
Table 1. Action Thresholds of Grasshoppers
Rating
Nymphs per Square
Adults per Square
Yard
Yard
Field
Borders
Within
Field
Field
Borders
Within
1
Treatment
Field
25-35
15-25
10-20
3-7
No
Threatening
50-75
30-45
21-40
8-14
Probably
100-150
60-90
41 or
1`5 or
Yes
more
more
Source: University of Nebraska-Lincoln5
Deciding among the management strategies discussed above
depends on field and weather conditions as well as
grasshopper populations. Growers should determine the
location of most of the nymphs, assess the intensity of the
infestation, and act accordingly.
Sources:
Light
Severe
Biological Control. Several biological products are available to
manage grasshoppers. A protozoan microbe, Nosema locustae
causes disease in grasshoppers. Its resting spores are mixed
with bait and then placed in areas with grasshoppers. When the
grasshoppers eat the bait, the spores infect and kill the
grasshoppers. Another microbe is the fungal pathogen,
Entomophaga grylli which often kills late season grasshopper
populations when sprayed on plants and the spores are eaten.8
Unfortunately, the mortality caused by these microbes is slow
and may have little effect on grasshopper outbreaks.
McRae, I. et. al. 2002. Minnesota grasshopper management. University of Minnesota
Extension Service. http://www.nwroc.umn.edu (verified 08/15/2013); 2 Patrick, C. D. and S.
G. Davis. 2004. Grasshoppers and their control. Publication E-2-9. Agrilife Extension. https://
insects.tamu.edu (verified 08/15/2013); 3 Glogoza, P. and Boetel, M. Corn insets of North
Dakota. http://www.nwroc.umn.edu (verified 08/15/2013); 4 O’ Day, M. et. al. Corn insect
pests– A diagnostic guide. Manual 166. University of Missouri Outreach and Extension.
http://extension.missouri.edu (verified 08/15/2013); 5 Insecticide treatment options for
grasshoppers in field corn. 2013. http://entomology.unl.edu (verified 08/15/2013);
6
Grasshoppers. Field Crops IPM, Purdue University. http://extension.entm.purdue.edu
(verified 08/15/2013); 7 Ratcliffe, S. T. et. al. Grasshoppers. Integrated Pest Management,
University of Illinois Extension. http://ipm.illinois.edu (verified 08/15/2013); 8 Royer, T. A. and
E. Rebek. Grasshopper control in gardens and landscapes. Oklahoma State University
Extension Service. http://pods.dasnr.okstate.edu (verified 08/15/2013).
Individual results may vary, and performance may vary from location to location and from year
to year. This result may not be an indicator of results you may obtain as local growing, soil and
weather conditions may vary. Growers should evaluate data from multiple locations and years
whenever possible. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Leaf
Design® is a registered trademark of Monsanto Company. Stewart and Design™ is a trademark of American Seeds, LLC. All other trademarks are the property of their respective owners. ©2013 Monsanto Company. 08162013PLB.
For additional agronomic information, please contact your local representative