Grasshoppers are common garden pests that possess powerful chewing mouthparts, resulting in immediate and visible damage to foliage. Their feeding habits leave ragged holes and irregular notches on leaves and stems, and in large numbers, they can rapidly defoliate entire plants. Controlling these pests requires a multi-faceted approach, combining immediate eradication techniques with long-term preventative measures.
Physical Removal and Barrier Methods
For smaller gardens or early-stage infestations, direct physical methods offer an immediate, non-chemical solution for reducing grasshopper numbers. Hand-picking the pests directly from plants is effective, especially when performed early in the morning before the insects become fully active. The collected grasshoppers can be dropped into a container of soapy water, where the detergent breaks the surface tension, causing the insects to sink and drown.
Specialized tools, like small, handheld vacuums, can also be used to remove grasshoppers from plants without direct contact. Preventative physical barriers are effective for protecting individual, high-value plants from migrating grasshoppers. Row covers made of fine mesh netting or metal screening should be placed over plants, ensuring the edges are firmly secured to the ground to block access. Aluminum window screening is recommended over cloth because grasshoppers can chew through thinner fabric materials.
Biological Agents and Natural Predators
Biological controls utilize living organisms to manage pest populations, offering a long-term, environmentally conscious method of suppression. One biological agent is the microsporidian parasite Nosema locustae, often formulated into a wheat bran bait. When grasshoppers consume this bait, the protozoan infects their alimentary tract and fat body, causing a chronic disease.
Infected grasshoppers become lethargic, significantly reduce their feeding, and eventually die, often within several weeks of ingestion. The disease spreads through the population by cannibalism, as uninfected insects will consume the bodies of dead or dying infected grasshoppers. This transmission mechanism makes Nosema locustae effective for long-term population reduction, particularly when applied early in the season to target young nymphs.
Encouraging natural predators also contributes to biological control by establishing a balanced ecosystem. Birds, such as chickens and guinea fowl, feed heavily on grasshoppers, though they must be managed to prevent plant damage. Certain parasitic insects, including tachinid flies and flesh flies, lay their eggs on or near grasshoppers, and the resulting larvae consume the host. Additionally, the entomopathogenic fungus Beauveria bassiana can infect and kill grasshoppers, though its effectiveness can be reduced by hot, dry conditions.
Horticultural and Chemical Treatment Options
Applied substances provide a range of options for immediate control, from low-toxicity horticultural products to targeted chemical insecticides. Diatomaceous earth (DE) is a mechanical killer composed of fossilized remains of diatoms. When grasshoppers crawl through DE, the powder scratches their outer waxy layer, causing them to dehydrate and die from desiccation.
Insecticidal soaps contain potassium salts of fatty acids and work by penetrating the insect’s cuticle, disrupting cell membranes and causing rapid dehydration upon direct contact. These soaps are contact-only, meaning they have no residual effect once dry, which minimizes harm to beneficial insects. Neem oil, derived from the neem tree, contains the active ingredient azadirachtin, which functions as an insect growth regulator and antifeedant, disrupting the grasshopper’s feeding and life cycle.
For widespread or severe infestations, chemical insecticides may be necessary, with carbaryl and pyrethrins being common active ingredients. Carbaryl is often formulated as a bait, combining the insecticide with a grasshopper attractant like wheat bran, which the pests ingest. Pyrethrins are fast-acting, derived from the chrysanthemum flower, and kill grasshoppers through neurotoxicity. Since chemical sprays can harm non-target organisms, including pollinators, apply them late in the evening or early morning when beneficial insects are less active. Insecticides are most effective against young grasshopper nymphs, as larger adults are more mobile and less susceptible to treatment.
Reducing Future Infestations Through Prevention
Effective long-term grasshopper control focuses on disrupting the pest’s life cycle by targeting the egg-laying stage. Female grasshoppers typically deposit their eggs in pods, approximately one to two inches deep in undisturbed, firm soil, often in weedy areas, ditches, or garden borders. A single female can lay hundreds of eggs during the late summer and fall, which then overwinter and hatch the following spring.
Tilling or lightly scratching the soil surface in late fall or early spring in known egg-laying areas can expose these egg pods to freezing temperatures, desiccation, and predators like ground beetles. This habitat modification reduces the number of nymphs that emerge in the spring. Removing tall weeds and dense grasses around the perimeter of the garden also eliminates preferred breeding and refuge sites for adult grasshoppers.
Another preventative tactic is the use of trap crops, which involves planting small borders of plants that grasshoppers prefer away from the main garden. The grasshoppers are attracted to these sacrificial plants, where they can be concentrated and treated, diverting them from more valuable crops. Maintaining the health of the trap crop is important, as a stressed or mowed trap crop may cause the pests to migrate into the protected garden area.