The high visibility of grasshoppers in Colorado is driven by a specific combination of environmental and biological factors unique to the state’s geography. These insects are a natural component of the high plains ecosystem, but their population dynamics are sensitive to weather patterns, leading to periodic, dramatic outbreaks. Understanding the environmental triggers and the grasshopper’s efficient reproductive cycle explains why the population can explode quickly, often resulting in significant issues for agricultural producers and homeowners.
Climate and Weather Conditions Supporting Outbreaks
Warm, dry weather is the greatest environmental factor driving grasshopper population surges in Colorado. A lack of moisture prevents the mortality of newly hatched grasshoppers, which are vulnerable to heavy rainfall and cool, damp conditions in the spring. Dry soil also favors the survival of overwintering egg pods, as excessive moisture promotes fungal diseases that naturally limit grasshopper populations.
Prolonged drought conditions ensure high survival rates while also accelerating development. Warmer temperatures decrease the time required for eggs to complete development and hatch, pushing the event earlier in the spring. This early emergence gives the grasshoppers a longer season to feed and mature, increasing their reproductive success. When plants are stressed by drought, their nutritional quality can increase for grasshoppers, with elevated concentrations of soluble proteins and amino acids boosting insect performance.
Reproductive Biology and Population Growth
The grasshopper’s life cycle is optimized for rapid multiplication once favorable conditions are established. Most species in Colorado overwinter as eggs, deposited in clusters called egg pods just beneath the soil surface during late summer and autumn. Female grasshoppers exhibit high fecundity, with a single individual capable of producing four to 25 egg pods.
Each pod commonly holds between four and 40 eggs, meaning one female can contribute 100 to 500 offspring to the next generation. Since the life cycle involves only three stages—egg, nymph, and adult—it is a swift process of incomplete metamorphosis. When warm, dry weather boosts the survival of these numerous eggs and accelerates the development of the nymphs, the resulting population increase can be exponential.
Colorado’s Specific Habitats
The geographic layout and land use across Colorado create ideal habitats for grasshopper populations to flourish. Grasshoppers thrive in areas with vast, undisturbed open ground, abundant across the state’s semi-arid plains and rangelands. The eastern half of Colorado features the shortgrass and mixed-grass prairies that are prime locations for egg laying and feeding.
Many grasshopper species prevalent in this region, such as rangeland species and the Plains Lubber, are well-adapted to these dry, open ecosystems. Agricultural areas and pastures contribute to the problem by providing concentrated food sources, especially when the surrounding rangeland becomes dry. This combination of vast, dry, open spaces for reproduction and nearby food-rich environments ensures Colorado remains prone to population surges.
Consequences and Control Measures
High grasshopper populations pose a significant threat due to the insects’ voracious appetites; they can consume up to half their body weight in vegetation daily. This feeding pressure results in the devastation of agricultural crops, defoliation of entire fields, and extensive damage to rangeland forage necessary for livestock. For gardeners, the consequence is the rapid destruction of vegetables and ornamental plants.
Management strategies focus on reducing the population when the insects are most vulnerable. Control measures are most effective when applied early in the season, typically May or June, while the grasshoppers are still small, flightless nymphs. On large rangeland areas, agencies often employ the Reduced Agent and Area Treatment (RAAT) strategy, which involves treating swaths of land with targeted, low-rate insecticides to maximize control while minimizing the impact on beneficial insects.
Biological controls are utilized, including encouraging natural predators like birds and using baits containing the microbial pathogen Nosema locustae, which specifically targets grasshoppers. For farmers and ranchers, the economic threshold is reached when densities exceed 15 to 20 nymphs per square yard, prompting professional intervention. Homeowners rely on physical barriers, such as row covers or netting, to protect individual plants from the mobile adults.