Of the roughly 600 species of grasshoppers in the U.S., about 30 of those varieties cause serious damage to landscape plants and are considered garden pests. A large group of insects belonging to the suborder Caelifera, grasshoppers are herbivorous, chewing insects that can wreak considerable damage to plants, especially to cereal grains and vegetables. In large numbers, grasshoppers are a serious problem for farmers as well as a serious annoyance to home gardeners. Most landscapes have occasional issues with damage due to grasshoppers, for which there are both natural, organic solutions, as well as chemical means of controlling the pests.
Before undertaking wholesale eradication, though, be aware that grasshoppers do offer some benefit to the environment. The grasshoppers themselves serve as food for birds, lizards, spiders, and other arthropods and insects, and their excrement provides nutrients to fertilize plants. A handful of grasshoppers in your garden is no cause for alarm and may actually be a sign of helpful diversity. It's not until the plant damage becomes widespread that serious control efforts should be considered.
Because they are herbivores, grasshoppers feed on grasses and the leaves and stems of plants. The symptom of grasshopper damage is much the same as for other gnawing insects: ragged and chewed holes in the leaves, stems, and fruit of plants. When large numbers of certain grasshopper species infest farms or garden areas, they can cause extensive plant damage and loss. In fact, in peak years, grasshopper infestations have been known to destroy or consume entire crop fields. In some areas, up to 25 percent of crops are routinely lost to grasshoppers.
Although grasshoppers will feed on many different plants, they often prefer—and cause the most damage to—small grains, corn, alfalfa, soybeans, cotton, rice, clover, grasses, and tobacco. They may also eat lettuce, carrots, beans, sweet corn, and onions. Grasshoppers are less likely to feed on plants such as squash, peas, and tomatoes leaves. The more grasshoppers there are present, the more likely they are to feed on plant species outside their preferred group.
Grasshoppers are most likely to cause damage in sub-humid, semi-arid areas in the middle of the U.S.—from Montana and Minnesota to New Mexico and Texas.
Young grasshoppers are smaller than adults and are wingless. When first hatched, these nymphs are white. As they grow, they will take on the color of the adults of their species, and wings begin to appear as small pads.
Adult grasshoppers are reddish-brown to olive green, depending on species. They can be as long as 1 3/4 inches, with narrow bodies. Most grasshoppers have distinctively long, angled back legs that allow them to be strong jumpers. They have protruding heads dominated by large eyes and chewing mouthparts. Adult grasshoppers have wings and can fly.
Grasshoppers first appear in early spring, with the greatest numbers generally occurring in mid-summer. Grasshoppers' populations are likely to be highest when the weather is hot and dry.
Grasshoppers are known as hemimetabolous insects, which means they do not undergo metamorphosis, as do butterflies and many other insects. instead, they hatch from eggs into nymphs ("hoppers") that undergo five molts, gradually taking on the adult appearance.
When population densities become very high, environmental conditions may cause some species to change color and form swarms. At this point, they are often known as locusts.
Natural and Organic Controls
Because grasshoppers are very mobile, they are also very difficult to control. The best way to control grasshopper damage is to prevent the growth of populations. A number of natural solutions can help control grasshoppers:
- Till the ground. Till in mid- to late summer to eliminate areas in which females lay their eggs. These eggs overwinter in the soil and hatch in the spring. Till the ground in late fall and early spring to destroy the eggs that were laid the previous summer.
- Eliminate weeds even in areas that don't have garden plants to reduce the availability of food for newly hatched nymphs.
- Encourage natural predators. Many insect-eating birds, such as swallows, are notable grasshopper predators. Other animal species also eat grasshoppers, such as praying mantis insects, small snakes, and toads.
- Cover vulnerable plants with a cheesecloth or crop cover to protect them.
- Apply garlic spray. Blend two cups of garlic with 10 cups of water, boil the mixture and let it sit overnight. Then, mix one part of this solution with 3 parts water in a spray bottle and moisten the leaves of vulnerable plants with the spray. This spray will deter grasshoppers and other feeding insects.
- Dust leaves with flour. The flour will gum up the mouths of grasshoppers as they feed.
- Raise chickens. Chickens can eat vast quantities of grasshoppers, so if your community and circumstances allow it, two or three chickens roaming your garden can control grasshoppers and other insects.
- Apply biological controls. Among the preventive measures that work for grasshoppers are Nosema locustae and Beauveria bassiana, fungi that affect the digestion of grasshoppers; azadirachtin, a natural biological agent that is found in neem oil; and organic pyrethrins.
Mow a Buffer Strip
If your garden abuts a meadow, pasture, or wooded area, mow a closely cropped buffer strip about 6 feet wide all around your garden. The low grass offers no food or cover to the grasshoppers, and it exposes them to birds and other natural predators.
When necessary, chemical bait and spray pesticides that are labeled for grasshopper control can also be used, reading and following all label directions. According to Colorado State University Extension, however, baits and sprays need to be applied to developing stages of grasshoppers and concentrated at sites where egg-laying occurs, as the ability to control grasshoppers declines as they develop and migrate.
Carbaryl is the most effective chemical pesticide on grasshoppers, but unfortunately, this chemical is highly toxic to beneficial insects. Baits containing carbaryl are safer than sprays for bees and other beneficial insects, but even baits should be used very carefully and only in areas where you know grasshoppers are feeding.
When chemical treatments are used to kill grasshoppers, they should be focused on young grasshoppers and breeding sites during spring and early summer, depending on the geographic area.
Adding canola oil to an insecticide spray can improve control by making the treated plants more attractive to the grasshoppers.
Watch for Cycles
Grasshopper infestations tend to run in multi-year cycles, so after a year in which grasshoppers were very prevalent, you should prepare for similar problems the next year. Grasshopper populations will decline gradually, but generally, you can expect a year of heavy infestation to be followed by another.