Grasshoppers in home gardens
Grasshoppers are present every summer, although their numbers vary from year to year. Of the 75+ different species that occur in Minnesota, there are only a few species that are common in Minnesota gardens. These include two-striped grasshopper (Melanoplus. bivittatus), redlegged grasshopper (M. femurrubrum), migratory grasshopper (M. sanguinipes), and differential grasshopper (M. differentialis), as well as clear-winged grasshopper, (Camnula pellucida).
Grasshoppers are easily distinguished from other insects because of their enlarged hind legs, which are well adapted for jumping. The grasshopper body is thickened, and their antennae are relatively short. Identifying grasshoppers can be challenging, but a few species can be identified based on the markings present on the hind legs (jumping legs), or coloring on the body.
Grasshopper nymphs resemble adults, but lack fully developed wings. Wing pads (developing wings) can be seen on older nymphs (4th and 5th instars).
Two-striped grasshopper, Melanoplus bivittatus, adults are gray-brown, 1 ¼" - 2" long, with two distinct yellow stripes from the head to the wing tips. They also have a black band on the top of the femur of the jumping leg.
Red-legged grasshopper, Melanoplus femurrubrum, is ¾ - 1" long, and is brown-red, with narrow, mottled wings. The hind femur is red and the hind tibia is completely red.
Migratory grasshopper, Melanoplus sanguinipes, adults are 1" long, brown to gray with a black spot behind its eye. Adults are sometimes confused with red-legged grasshoppers, but migratory grasshoppers have a slight hump behind the spine on its underside, between the middle pair of legs.
Differential grasshopper, Melanoplus differentialis, is one of the largest of our grasshopper species, at 1 ½" - 1 ¾" long. They are yellow to green colored and have distinct chevron markings on the femur of its jumping leg.
Clear-winged grasshopper, Camnula pellucida, is a smaller grasshopper, measuring ¾" long. It is a light tan-brown color, and has clear wings with large brown spots.
Grasshoppers are present every year. With the right environmental conditions, grasshoppers can build up their populations to outbreak numbers. Oftentimes, an outbreak population can take 3-5 years to develop. These outbreak populations are favored by long, warm autumns followed by warm, dry springs.
Grasshoppers overwinter as eggs in the soil. The highest mortality (death) occurs during the egg stage. This is particularly true when the spring is unseasonably wet.
In early to late spring, depending on the species, the eggs hatch and nymphs emerge. The first few days are the most critical for survival. Adverse weather conditions (cold, wet springs) and lack of suitable foods can be harmful to the young nymphs' survival. If the nymphs have favorable conditions, they will molt five times before they reach adulthood.
Adult grasshoppers mate, and females deposit eggs in late summer and early fall in the soil in a somewhat intricate manner. Females lay eggs in a "pod" in undisturbed soil in a burrow. The female forms an egg pod by combining a frothy excretion, soil, and the eggs. She then deposits this pod by burying it in the soil. The eggs are cemented together and the burrow is closed with a plug constructed of the frothy excretion and soil.
Adult grasshoppers are typically found from June to September, although in some cases they can be found late into the fall. There is one generation of each species per year. The seasonal occurrence is summarized in Figure 7.
Both adult and nymph stages of grasshoppers damage plants by chewing holes in the leaves. They will also feed on flowers and fruit. They are voracious feeders, consuming approximately one-half of their body weight per day. Eventually they will eat the whole leaf, and in some cases, the entire plant.
Grasshoppers feed on both grasses and broadleaf plants, which includes many edible garden and ornamental plants. Adults usually move into yards and gardens in July and August.
Grasshoppers are extremely mobile, which makes their management very challenging. There are several tactics that can be used to limit grasshoppers in home gardens.
There are a few naturally occurring biological control agents that can help keep grasshopper populations in check. The Gordian worm, or horsehair worm, which can reach 4 inches in length, is a parasite of grasshoppers. This nematode becomes more numerous in outbreak years, but their life cycle requires water, limiting their effectiveness in dry areas.
Entomophthora grylli, a pathogen of grasshoppers, infects grasshoppers and causes them to crawl upwards and cling to plants shortly before they kill the insect host. Stiff, dead grasshoppers can be found stuck to a grass stem, which is indicative of this disease.
Since grasshoppers lay eggs in the soil in early autumn and prefer areas of dry, untilled ground, tilling your garden thoroughly in the fall may help to decrease next year's grasshopper populations. However, this will not prevent grasshoppers from migrating into your garden from adjacent areas.
Row covers are an effective option for protecting valuable plants by preventing grasshoppers from getting near the plants. Row covers can be purchased at many local lawn and garden supply stores and online at suppliers like Burpee and Gardens Alive. It is important to make sure the fabric you choose allows both sunlight and moisture to get to the plants. While row covers are a useful tool, they may not be practical for your entire garden.
Insecticides and baits
Insecticides are an option, although the more numerous grasshoppers are the more difficult it is to manage them. When you treat garden plants, they will still suffer some damage before grasshoppers are killed. Even if you succeed with the grasshoppers in your garden, they are very mobile and more can fly into your yard. If you are finding grasshoppers on many plants, you may need to be selective in which plants you try to protect. There are a variety of garden insecticides available, including products containing bifenthrin, lambda cyhalothrin, permethrin, acetamiprid, acephate, or carbaryl.
Another option is a "bait trap". Using a baited trap can be effective, but in order to work they must be more attractive than the food already available in the immediate surroundings. Baits containing Nosema have to be applied under the right environmental conditions. Nosema baits are most effective against younger stages and in cooler temperatures. This will be a challenge to home gardeners, because in many cases the grasshoppers invading gardens are adults. EcoBran, which contains carbaryl, is another bait option. In general, EcoBran is faster acting than Nosema bait.
The information given herein is supplied with the understanding that no discrimination is intended and no endorsement by the University of Minnesota Extension. Mention of a pesticide or use of a pesticide label is for educational purposes only.
A pesticide label is a legal document. Always follow the pesticide label directions attached to the pesticide container you are using. Pesticide labels may change frequently. Internet labels may not match the label on the container you are using. The site of use or plant to which the pesticide is to be applied must be listed on the label or the pesticide cannot be used. Remember, the label is the law.