Grasshoppers belong to the order Orthoptera, found across the globe, especially in dry, open grasslands. While they are a natural part of the ecosystem and serve as a food source for predators, their presence in a cultivated space can quickly become detrimental. Low populations typically cause minimal, scattered damage that plants can easily tolerate. However, when population numbers rise, they pose a significant threat to a gardener’s harvest, confirming their potential as a serious garden pest.
The Specific Damage Grasshoppers Inflict
Grasshoppers cause damage with their chewing mouthparts, leaving distinct, ragged holes in plant foliage. They are generalist feeders, consuming a wide variety of plants, but prefer young, tender, and green growth. Young seedlings are especially vulnerable to being completely severed at the stem, resulting in the total loss of the plant.
The most sought-after garden vegetables include tender leafy greens (lettuce and cabbage), beans, carrots, and sweet corn. They tend to avoid plants with tough leaves or strong odors, such as tomatoes, squash, and peas. When populations are high, grasshoppers become less selective and feed on nearly any vegetation, including shrubs and small fruit trees. They also feed on non-leaf structures, chewing soft bark, immature fruit, and corn silks and kernels, reducing plant vigor and crop yield.
Environmental and Biological Factors Leading to Infestation
Grasshopper populations fluctuate in cycles, linked closely to the insect’s life cycle and local weather patterns. Most pest species overwinter as eggs, laid in protective pods in the top two inches of untilled soil, often in dense, undisturbed areas. The eggs typically hatch into small, wingless nymphs in the spring or early summer, which begin feeding immediately.
Warm, dry summers and mild winters favor grasshopper survival, allowing more eggs to hatch and nymphs to survive to adulthood. Drought conditions stress cultivated plants, making them less able to withstand feeding pressure. As natural food sources like wild grasses and weeds dry out in the summer heat, highly mobile adult grasshoppers migrate into irrigated gardens in search of fresh green foliage.
Management Strategies for Gardeners
Effective grasshopper management relies on a combination of cultural, biological, and chemical strategies, with the most success coming from early intervention.
Physical Controls
One of the simplest physical controls is covering vulnerable plants with fine mesh row covers or metal screening. Grasshoppers have been known to chew through plastic or cloth barriers. Hand-picking is also feasible for small gardens; captured insects can be dropped into a bucket of soapy water for a quick, effective end.
Cultural Controls
Cultural control focuses on disrupting the life cycle and habitat. This includes tilling the soil in late fall or early spring to a shallow depth of about two inches. This process exposes overwintering egg pods to harsh weather, desiccation, and natural predators, significantly reducing the number of hatching nymphs. Maintaining a well-watered, dense border of preferred plants, such as tall grasses or sacrificial lettuce, can serve as a “trap crop,” diverting grasshoppers away from valued vegetables.
Biological Controls
A specialized biological control option uses baits containing Nosema locustae, a naturally occurring protozoan. This microbe is mixed with a wheat bran bait that grasshoppers readily consume. Once ingested, it infects the insect’s gut, leading to reduced feeding, lethargy, and eventual death. While not fast-acting, Nosema locustae is effective because infected grasshoppers pass the pathogen through cannibalism, and infected females have reduced fertility, offering long-term population suppression.
Chemical Controls
Chemical control should be considered a last resort for severe infestations. Products are generally applied as a targeted bait rather than a broad-spectrum spray. Baits containing carbaryl or targeted insecticides like azadirachtin or diflubenzuron are effective when applied early in the season. At this time, grasshoppers are small nymphs concentrated near their hatching grounds. Careful application is necessary to minimize harm to beneficial insects and pollinators.