By Lisa Mason, CSU Extension Horticulture Specialist, Entomologist

Hop to It: Consider Grasshopper Management Sooner than Later

It’s almost grasshopper season! Last summer, the large populations were highly visible along the Colorado Front Range and became quite the nuisance for home gardeners. Many rural areas of Colorado have been struggling with high grasshopper populations for several years.

Over 75 species of grasshoppers are found in Colorado. Some species are generalists, feeding on a wide variety of plants. They tend to feed on all parts of the plant, including flowers, leaves and stems. Others have specific plants they feed on and specific geographic habitat ranges. For instance, many species will only feed on sedges and grasses or weeds. Five species are responsible for the most damage to plants and crops.

Impacts and Lifecycle

Grasshoppers create steep, negative impacts on the economy, especially during outbreak years, by feeding on crops and livestock forage. A 2005 study estimated that grasshoppers fed on Western US livestock forage worth about $1.25 billion per year (Branson et al., 2006, Hewitt and Onsager, 1983).

From an ecosystem perspective, grasshoppers play an important role in the grasslands. They contribute to nutrient cycling by eating plant material, essentially turning it into fertilizer for the soil. They also are a major food source for wildlife, including a variety of birds, snakes, lizards, frogs, toads, skunks, foxes, and more. It is a common phenomenon to see grasshoppers falling into the water feeding fish, notably rainbow and brown trout. Swainson’s hawks offer benefits to farmers and ranchers by eating large numbers of grasshoppers. When they migrate to the Western US from Argentina, they will feed their young, small mammals and other prey. In the fall, when the hawks are preparing for migration, they can be observed on the mowed fields of eastern Colorado looking for grasshoppers to eat.

Understanding the lifecycle of grasshoppers is critical to managing them. Grasshoppers typically have a one-year life cycle. Females lay clusters of eggs within 1 to 2 inches of soil. The eggs overwinter and emerge when soil temperatures warm up in the late spring. Once the eggs hatch, grasshoppers will molt about five times before becoming adults with wings. Young grasshoppers tend to stay and feed close to where they hatched since they cannot fly.

Control Options

Grasshopper populations ebb and flow each year. Weather patterns can strongly influence high or low population years. Newly hatched nymphs are the most susceptible to weather events. Dry weather contributing to low numbers of plants, or prolonged cool temperatures and moisture can contribute to high mortality after eggs hatch. Diseases that kill grasshoppers tend to spread easier with cool, moist temperatures. Moisture will also prompt additional plant growth, meaning damage from surviving grasshoppers may not be as visible.

Beneficial Insect Predators

In addition to wildlife preying on grasshoppers, insect predators also prey on grasshoppers, including certain species of flies, solitary hunting wasps, and blister beetles. A genus of flies called Systoechus sp., also known as “woolly bee flies,” prey on their egg clusters. Promoting habitat for beneficial insect predators can be a helpful tool for grasshopper management and increasing overall biodiversity in your garden. Beneficial insect predators are harmless to humans. They prefer to visit small, shallow flowers such as plants in the Apiaceae family like dill, fennel and moon carrot. Sedums, basket-of-gold, thyme, mints, sweet alyssum, yarrow, and plants in the Asteraceae family like fleabanes and sunflowers are also great options. Providing flowers with nectar and pollen also attracts pollinators.

Physical Controls

For home gardeners, covering plants with row covers or any type of insect barrier fabric can protect your plants by excluding grasshoppers. Be mindful if your plants need to be visited by pollinators.

Hand-picking grasshoppers in the early morning or evenings can help minimize damage to your plants. Knock them into a bowl of soapy water.

If egg-laying areas are located, disrupting the soil by raking or tilling can destroy grasshopper eggs before hatching. Eggs are often laid on undisturbed soil, so this may not be possible for home gardeners.

Chemical Controls

Insecticides are available as an option for grasshopper control. Consider the following when deciding to use insecticides:

• Always read the pesticide label carefully​ for maximum effective application and safety. Per federal law, the label must be followed.
• Choose products based on the active ingredient and not the trade name. Visit the National Pesticide Information Center (https://npic.orst.edu/) to learn more about the product.
• If you plan to consume produce from your garden, be sure the product is safe and labeled for use in vegetable gardens.
• Make targeted applications. Insecticide treatments are most effective when the grasshoppers are nymphs in the spring and early summer. Once grasshoppers are adults, insecticides are much less effective and likely not feasible.
• Consider persistence and impacts on beneficial predators that prey on grasshoppers.
• Avoid applications when plants are flowering. Depending on the product, this could be hazardous to bees. Read the label and learn more about the active ingredient to understand the risk.
• Follow best practices if honey bee hives are nearby or if other bees are nesting in the vicinity. Some guidelines are available here.
• Baits and sprays are available. Consider the pros and cons of both when considering insecticides. 
• Consider if insecticides are worth the money and resources for grasshopper management for a home gardener. Applications can be effective in the best-case scenarios, but likely grasshoppers will still be in the area and they may still damage your plants. Insecticide applications are often more feasible for rural landowners. Rural landowners are most successful with insecticide applications when they work together as a community and use a strategy called the Reduced Area Acreage Treatment (RAAT) method.

This is not a comprehensive list of options. Other strategies may be feasible, such as using trap crops or allowing poultry to graze on grasshoppers in the garden. Prioritizing plant health can also help since healthy plants can tolerate more feeding.

For more resources, visit the following:

• “What’s Killing your Plants?” webinar series – Check out the recording on grasshoppers! Upcoming live webinars and other recordings are available. Find the recordings here. 
• Grasshopper Control in Gardens and Small Acreages fact sheet.
• Grasshoppers of Wyoming and the West from the University of Wyoming.
• Contact Arapahoe County Master Gardeners with questions by emailing MasterGardener@arapahoegov.com or calling (303) 730-1920.