Grasshoppers are a widespread and highly destructive threat to gardens, capable of inflicting severe damage by consuming foliage, stems, and even flowers. Their voracious appetites can lead to rapid defoliation and significant crop loss, especially during population outbreaks. A female grasshopper can lay an average of 200 eggs in a season, and their young, known as nymphs, feed relentlessly as they grow. Successfully managing these pests requires a varied approach, utilizing methods from immediate physical removal to long-term habitat modification.
Physical Barriers and Manual Removal Techniques
For a small garden or a localized infestation, immediate physical controls offer the fastest solution. Hand-picking is the most direct method, effective in the cool hours of the early morning when the insects are sluggish. Captured grasshoppers can be flicked into a bucket of water mixed with dish soap, which causes the insects to sink quickly.
Physical barriers can protect individual plants or rows. Floating row covers, made from lightweight, porous fabric, exclude pests while allowing sunlight and water penetration. Ensure the edges of the fabric are securely fastened to the ground, as grasshoppers are adept at finding small gaps.
An all-purpose flour dusting can be applied lightly to dry leaves; the flour gums up the grasshoppers’ chewing mouthparts, preventing further consumption. Localized trapping also reduces numbers. A simple molasses trap uses a container sunk into the ground and filled with a 10:1 ratio of water and molasses. The sweet scent attracts grasshoppers, and the sticky solution prevents their escape.
Utilizing Natural Predators and Targeted Pathogens
Biological control leverages natural enemies and diseases specific to the pest. The primary biological agent is Nosema locustae, a naturally occurring protozoan. This pathogen is mixed into a wheat bran bait that grasshoppers consume, damaging their digestive system. It is most effective when applied early in the season, targeting the vulnerable first and second nymph instars.
The bait is highly selective and non-toxic to humans, livestock, and beneficial insects. Infected grasshoppers become lethargic, and the disease spreads through cannibalism, perpetuating the control effect. This method is a long-term tool for population suppression, though it does not provide immediate knockdown.
Encouraging natural predators is another steady strategy. Aggressive aerial hunters like robber flies capture and consume grasshoppers in mid-air, injecting them with paralyzing saliva. Other predators include sphecid wasps and ground beetles, which actively seek out and consume grasshopper egg pods buried in the soil.
Chemical Control Options for Widespread Infestations
When non-chemical methods fail during severe outbreaks, chemical treatments may be necessary, primarily baits and sprays. Baits use an active ingredient like carbaryl mixed with an attractive carrier such as wheat bran. This formulation is more selective because the insect must actively feed on the bait, reducing risk to beneficial insects. Baits must be reapplied frequently, especially after rain, as they lose effectiveness when wet.
Spray applications offer quicker results and include botanical options. Botanical insecticides, such as pyrethrins, provide rapid knockdown but have a very short residual life, breaking down quickly in sunlight and air. Neem oil, another botanical choice, works as an insect growth regulator and antifeedant, offering a slower kill that is more effective against nymphs.
Synthetic insecticides, such as those containing bifenthrin or carbaryl, are broad-spectrum and provide a longer residual effect. Bifenthrin kills by contact and ingestion, making it highly effective against dense populations. Due to the toxicity of broad-spectrum synthetics, application requires strict adherence to safety guidelines listed on the product label. Always target the application to the nymph stage, as smaller grasshoppers are more susceptible than winged adults.
Long-Term Habitat Modification and Prevention
Preventing future infestations requires disrupting the grasshopper lifecycle, which depends on undisturbed soil for egg-laying. Female grasshoppers deposit their egg pods in weedy areas, fencerows, and ditches. Tilling these non-garden areas in late fall or early spring exposes the overwintering egg pods to freezing temperatures, desiccation, and predation. This practice must be balanced against soil health concerns.
Weed control is an important component of habitat modification. Grasshopper nymphs emerge in spring and rely on lush weeds as their first major food source before moving into the cultivated garden. Removing weeds and tall grasses from the garden perimeter eliminates this early-season food supply, forcing the young nymphs to starve or disperse.
Strategic planting can divert pests away from valuable crops. Grasshoppers prefer certain plants while avoiding others like tomato leaves, squash, and peas. Planting a trap crop of highly attractive plants, such as lush tall grasses or kochia, around the garden’s perimeter draws the grasshoppers away from the main growing area. This concentrates the pest population, allowing for more efficient and targeted treatment of the trap crop area.