Grasshoppers are major agricultural pests that can rapidly shift from a manageable presence to an overwhelming swarm, severely damaging gardens and crops. Understanding the environmental, reproductive, and localized factors that contribute to these population booms is the first step toward effective management. These population surges result from a sequence of favorable conditions aligning for their survival and reproduction.
Environmental Conditions Fueling Swarms
The primary drivers behind regional grasshopper outbreaks are large-scale weather patterns that minimize natural mortality rates. Extended periods of drought create ideal conditions for the survival of grasshopper eggs laid the previous year. Grasshopper eggs are highly protected within a pod in the soil and can survive extremely cold temperatures.
Mild, dry winters are particularly favorable because they prevent the eggs from being exposed to prolonged wet conditions, which can lead to fungal diseases and decay. When a mild winter is followed by a warm, early spring, the eggs hatch earlier and more synchronously. This combination of low egg mortality and early hatching allows a massive population carryover from one season to the next.
Natural checks on the grasshopper population, such as predators, can also decline due to habitat loss or pesticide use in large agricultural areas. When predator populations are suppressed, the grasshopper survival rate increases significantly, compounding the effects of favorable weather conditions.
Lifecycle Dynamics: Understanding the Population Boom
The grasshopper’s reproductive strategy takes advantage of favorable conditions. Female grasshoppers deposit their fertilized eggs in clusters called egg pods, typically burying them in untilled soil during the late summer and fall. Each female can lay up to 25 pods, containing many eggs depending on the species.
A small increase in the overwintering survival rate translates into a massive surge in the spring population due to this high number of eggs per female. The eggs remain dormant throughout the winter before hatching into tiny, wingless nymphs in the spring or early summer. These nymphs immediately begin feeding on soft plant foliage and undergo five to six molts, known as instars, over five to six weeks before reaching full adulthood.
The sudden population increase is usually the result of a large, synchronized hatch of these nymphs in a nearby area. While adult grasshoppers are mobile and cause damage, the highest concentrations and most significant early damage are done by these non-flying nymphs near their hatching grounds. The sheer volume of newly emerged insects overwhelms the local food supply, driving them to search for new feeding areas.
Attractants: What Draws Them to Your Specific Area
While favorable regional conditions trigger the overall population increase, grasshoppers are strongly attracted to areas that provide a combination of undisturbed breeding sites and lush, readily available food sources. Undisturbed ground, such as fence rows, weedy ditches, and rangeland, serve as the primary egg-laying habitats.
The movement into a yard or garden is often an instance of “edge feeding,” where the insects move from dry, depleted hatching areas into irrigated, green vegetation. Gardens and lawns maintain higher moisture levels and offer preferred plants, which become highly attractive targets when surrounding natural vegetation dries out.
The presence of specific weeds or grasses can also initially draw them in and hold them in place. Once the nymphs are established, the availability of high-quality food encourages rapid growth. Your landscape may be targeted simply because it represents a green, moist oasis surrounded by dry, less palatable vegetation.
Managing High Grasshopper Populations
Effective population management involves a strategic, multi-year approach that targets the insects at their most vulnerable stages. Cultural controls focus on eliminating the egg-laying sites. Tilling or disking the soil in late fall or early spring, especially in non-crop areas adjacent to the yard, can destroy the overwintering egg pods by exposing them to weather and predators.
Chemical and Targeted Controls
Targeted chemical or biological controls are most effective when applied early to the young nymphs. Nymphs are more susceptible to treatments because they are concentrated near their hatching sites and have limited fat reserves. Chemical baits or sprays should be applied when the nymphs are still small, ideally during their second or third instar stage.
Biological Controls
The use of Nosema locustae, a naturally occurring protozoan pathogen formulated into a bait, is a biological control option. Grasshoppers consume the bait, which infects them. The most practical approach for small-scale control involves monitoring adjacent weedy areas for nymph emergence and treating these “hot spots” before the grasshoppers develop wings and disperse into the garden.