Grasshoppers are common garden pests that can rapidly devastate plants. These insects often migrate from surrounding weedy areas or dry rangeland into cultivated spaces as outside vegetation dries out during the summer months. An infestation can quickly overwhelm a garden, making a proactive, multi-faceted control strategy necessary to protect vulnerable crops and ornamental plants. Effective management involves disrupting their life cycle, targeting the most vulnerable stages, and employing a range of physical, biological, and chemical interventions.
Prevention and Habitat Modification
The most effective long-term defense against grasshoppers begins with modifying the surrounding environment to make it less attractive for egg-laying. Female grasshoppers deposit their eggs in pods within undisturbed soil, often in weedy areas, ditches, and field margins, usually from late summer through fall. Targeting these egg-laying sites can significantly reduce the population of nymphs that emerge the following spring.
Tilling areas where grasshoppers may have laid eggs, such as fallow fields or garden edges, can destroy the egg pods by mechanical damage or by exposing them to predators and harsh weather conditions. While fall tillage is an option, spring tillage is often preferred to preserve soil moisture and reduce erosion risk. Removing weeds and tall grasses from garden perimeters is also useful since grasshoppers prefer these areas for both shelter and egg deposition.
Preventative physical barriers offer immediate protection for high-value plants before an infestation arrives. Floating row covers or fine mesh screening can be placed over susceptible plants early in the season to physically exclude the pests. These barriers must be securely anchored to the ground to prevent grasshoppers from finding their way underneath.
Early Intervention: Targeting Nymphs
The nymph stage, which are the small, flightless immature grasshoppers that hatch in mid-to-late spring, represents the most vulnerable time for intervention. These young hoppers are concentrated near their hatching beds and are far less mobile than adults, making control efforts highly efficient. They typically pass through five instar stages before maturing, and mobility increases significantly after the third or fourth instar.
Baits are a highly effective intervention method at this stage, as they are consumed by the foraging nymphs. Baits often consist of an attractive carrier, like wheat bran, combined with an active ingredient such as the biological control agent Nosema locustae or carbaryl. Nosema locustae is a naturally occurring protozoan that infects and weakens the grasshoppers, leading to reduced feeding and reproduction, though the effects can take several weeks to fully manifest.
Carbaryl-impregnated bran baits offer a faster-acting solution, killing nymphs who ingest it while foraging. Baits should be broadcast thinly in areas where nymphs are actively feeding, particularly in the surrounding borders and weedy patches, rather than directly on garden plants. The application must be timed before the grasshoppers develop wings and disperse, making early summer the most appropriate window for this type of treatment.
Managing Adult Infestations Non-Chemically
Once grasshoppers mature into winged adults, they become highly mobile and can migrate long distances, making localized control much more challenging. Non-chemical management focuses on continuous reduction and protecting individual plants without relying on synthetic pesticides. Encouraging natural predators can contribute to population reduction, particularly the use of poultry like chickens or guinea fowl, which actively feed on grasshoppers.
Physical trapping devices can be employed for localized control within the garden space. One method involves using deep buckets filled with soapy water or a molasses solution; grasshoppers are attracted, fall in, and drown. This method is labor-intensive but provides a non-toxic way to manage small outbreaks of adult insects.
For individual plants, physical barriers remain an effective defense against adult feeding damage. Since adults can chew through thin fabric, high-value plants may require protection with sturdier materials like metal window screening or solid mesh cages. This targeted exclusion prevents feeding damage on the most susceptible crops while other control strategies are implemented across the wider area.
Applying Chemical Control (When and How)
Synthetic chemical controls are reserved as a last resort for severe grasshopper infestations, particularly when non-chemical methods have failed to prevent migration into the garden. The goal of chemical application is to quickly reduce an overwhelming population to protect plants from irreversible damage. Timing the application is important, usually targeting the early morning or late evening when grasshoppers are less mobile and beneficial insects are less active.
Approved insecticides for grasshopper control often include fast-acting nerve toxicants such as pyrethrins or synthetic pyrethroids. Malathion is another option, though these broad-spectrum products kill a wide array of insects, including pollinators and predators. When applying these sprays, it is necessary to follow all label instructions precisely regarding application rates and pre-harvest intervals for edible crops.
Because grasshoppers are highly mobile, treating the surrounding borders or areas where they are congregating is often more effective than blanket spraying an entire garden. Applying a concentrated band of insecticide on the edge of the cultivated area can intercept migrating grasshoppers before they reach the main garden. This targeted approach minimizes the amount of chemical used while maximizing the protective effect for the most vulnerable plants.