Grasshoppers are generalist herbivores that consume a wide variety of plant material. While they play a role in the natural ecosystem as a food source for birds and other animals, their feeding habits can be destructive to cultivated plants and gardens. Grasshoppers are generally considered pests, especially when their populations grow large enough to cause widespread damage to crops and ornamental plants. The level of harm they inflict ranges from negligible to severe, depending heavily on the insect’s population density and the vulnerability of the surrounding vegetation.
The Mechanism of Plant Damage
Grasshoppers are equipped with strong, chewing mouthparts (mandibles) that allow them to consume plant tissue directly. This feeding mechanism results in easily identifiable physical damage to the leaves and stems of plants. They physically remove and ingest portions of the foliage, unlike pests that suck sap or bore into the plant tissue.
The most common sign of their presence is defoliation, which manifests as irregular, ragged holes chewed into the leaves. Damage often appears scattered, with grasshoppers consuming tissue between the leaf veins, sometimes leaving behind only the tough central veins. In cases of intense feeding, they may also strip the outer layer (epidermis) from stems and pods. This extensive physical damage reduces the plant’s capacity for photosynthesis and overall health.
When Grasshoppers Become a Serious Threat
A small number of grasshoppers rarely poses a significant problem, but they become a serious concern when their population density reaches an “economic threshold.” This threshold is the number of pests per unit area that justifies the cost of control measures to prevent economic loss. For rangeland and certain crops, a density of eight or more grasshoppers per square yard is often cited as a trigger for intervention, though this number varies by crop and local conditions.
Grasshopper outbreaks are often exacerbated by warm, dry climatic conditions, as drought suppresses the natural fungal pathogens that help keep their populations in check. During these dry periods, irrigated gardens and cultivated fields become attractive, green “oases,” drawing grasshoppers from surrounding dried-out rangeland or pastures. The most substantial damage is often inflicted by the juvenile grasshoppers, known as nymphs, as they feed voraciously during their constant growth stages.
Nymphs are wingless and remain concentrated near their hatching grounds, making them easier to target with control measures. Grasshoppers are generalist feeders but prefer young seedlings, tender garden vegetables (like lettuce, beans, and corn), and specific crops (like alfalfa and wheat). When preferred food sources are exhausted, grasshoppers will feed on nearly any plant, including shrubs and trees, and move aggressively into new areas when adjacent fields are harvested or dry up.
Strategies for Controlling Infestations
Managing a grasshopper problem is most effective when combining several strategies focused on early intervention. Cultural controls can disrupt the grasshopper’s life cycle before they become active pests. Tilling the soil in late fall or early spring, for instance, can expose the overwintering egg pods to predators and harsh weather, which significantly reduces the number of nymphs that hatch.
Physical barriers offer a non-chemical method to protect high-value plants from feeding damage. Using floating row covers or fine-mesh screening over vulnerable garden rows can physically exclude the insects. For smaller infestations, hand-picking grasshoppers in the cool early morning when they are less active and dropping them into a container of soapy water is a simple, direct approach.
For larger outbreaks, targeted treatment options are available, but they are most effective when applied early against the young nymphs. Organic dusts like diatomaceous earth can be lightly applied to foliage; the abrasive particles scratch the insect’s exoskeleton, leading to dehydration and death. Insecticide baits, often containing a slow-acting biological agent, can be spread in areas where grasshoppers are concentrated, such as field borders.