Grasshoppers are voracious, chewing herbivores that can cause significant damage to gardens and agricultural crops. They feed on a wide variety of plants, including grasses, weeds, vegetables, and ornamental species. While resilient, grasshoppers are vulnerable to specific environmental conditions, natural enemies, and chemical compounds. Understanding the elements they actively avoid provides effective strategies for their control.
Scents and Substances That Repel Grasshoppers
Grasshoppers actively avoid certain concentrated botanical compounds and physical irritants. One effective deterrent is Neem oil, which contains the active compound azadirachtin. This substance acts as a potent antifeedant, causing the insect to stop eating, and also functions as an insect growth regulator by disrupting the endocrine system and inhibiting molting.
Pungent sprays derived from garlic or hot peppers also serve as immediate, topical repellents. Grasshoppers find the strong odors and flavors highly disagreeable, which helps to mask the scent of desirable host plants. Hot pepper sprays utilize capsaicin, which leaves an irritating residue on the foliage.
For physical control, Diatomaceous Earth (DE) is a substance grasshoppers cannot tolerate. This fine powder consists of the fossilized remains of diatoms, which are microscopically sharp, abrasive particles of silica. When a grasshopper crawls over the dust, these particles scratch the insect’s waxy outer layer, causing rapid dehydration. The effectiveness of DE relies entirely on it remaining dry, as moisture neutralizes its abrasive properties.
Disrupting Grasshopper Habitat and Breeding
Grasshoppers are sensitive to manipulation of their environment, particularly conditions necessary for shelter and reproduction. Females prefer to lay their eggs in undisturbed, untilled soil, often in weedy areas or field edges. Tilling the soil in late fall or early spring destroys the egg pods, which are typically laid in the top two inches of the ground. This disturbance exposes the eggs to freezing temperatures, desiccation, and predators.
Removing tall weeds and grasses around garden boundaries also eliminates preferred daytime shelter and egg-laying sites. Grasshoppers thrive in hot, dry conditions, and populations are suppressed by prolonged cool, wet weather. Heavy rainfall, especially during the spring when young nymphs have just hatched, can cause high mortality because the young lack fat reserves and are vulnerable to fungal diseases in humid environments.
Natural Enemies That Target Grasshoppers
A wide variety of living organisms prey upon or parasitize grasshoppers. The microbe Nosema locustae is a single-celled protozoan commercially available as a biological control agent mixed with a wheat bran bait. Once ingested, this organism infects the grasshopper’s fat body, causing lethargy, reduced feeding, and eventual death. This disease is slow-acting but spreads through the population because grasshoppers are cannibalistic, consuming infected individuals.
Numerous insects also act as natural enemies, including parasitic flies, such as Sarcophagidae and Tachinidae species. These flies deposit eggs directly on or in the grasshopper’s body, and the larvae develop internally, feeding on the host until they emerge. Birds, including chickens, guinea fowl, and wild species like bluebirds and larks, are effective predators that actively feed on both nymphs and adults.