Grasshopper invasion is taking a toll on local area gardens

Controlling a grasshopper invasion in your garden is challenging but possible.

Local area gardeners are experiencing a dearth of grasshoppers the likes of which we haven't seen in years. Major outbreaks of large numbers of grasshoppers usually occur every 7 to 10 years. Generally, you can expect a year of heavy infestation to be followed by another. They overwinter in the soil, unaffected by extreme temperatures.

When population densities become very high, environmental conditions may cause some species to change color and form swarms (then known as locusts). Grasshopper populations will decline gradually.

Take heart, with a combination of cultural, mechanical, biological, and chemical methods, you can manage and even reduce their population.

• Cultural Control
  • Keep your garden clean and free of debris where grasshoppers can hide.
  • Remove weeds, tall grasses, and any other vegetation up to 20 feet around the garden to prevent breeding grounds for grasshoppers.
  • Till the garden soil from mid- to late-summer to eliminate areas where females lay their eggs. Till the ground again in late fall and early spring to destroy the eggs laid the previous summer.
  • Tip: if your garden abuts a meadow, pasture, or wooded area, mow a closely cropped buffer strip 6 feet wide all around the garden area. The low grass offers no food or cover and exposes grasshoppers to birds and other natural predators. (Credit: The Spruce).
• Physical Barriers
  • Use row covers, Agribon (we recommend Agribon 30 so it lets in 70% of the sunlight $21) or fine mesh netting to protect vulnerable plants. Ensure the barrier is securely fastened to prevent grasshoppers from getting underneath.
  • Install floating row covers early in the growing season before grasshoppers become a problem (next year).
  • Dust the leaves of plants that grasshoppers are munching on with ordinary white flour. This gums up the insect's mouths and prevents them from eating the leaves.
  • Surround your garden with a fence and then place an impermeable physical barrier around the fence with corrugated galvanized steel or other material such as metal window screening that is at least 30 inches high (in general, a grasshopper can jump 30 inches). Don't use cloth as grasshoppers can chew through it.
• Predators and Parasites
  • Encourage natural predators such as birds, spiders, and predatory insects like praying mantises and assassin bugs by creating a wildlife-friendly garden (read the green box in that article).
  • Use biological insecticides like Nosema locustae (Nolo Bait), a naturally occurring protozoan that infects grasshoppers and reduces their population over time. Nolo Bait is not available this year, unfortunately.
  • Plant nectar-rich flowers to attract beneficial insects like ladybugs, lacewings, and parasitic wasps that prey on grasshoppers.
  • Put up a bat box. Click here for instructions, and also see our article on bats here.
  • Place a bird feeder near your garden. More than 200 species of birds are known to feed on grasshoppers. See informative article here.
• Insecticidal Sprays
  • Use insecticidal sprays labeled for grasshopper control, such as those containing carbaryl, permethrin, or spinosad. Follow the label instructions carefully to avoid harming non-target organisms. If spraying near a vegetable garden or fruit trees, make certain the product you are using is food safe.
  • Apply insecticides in the early morning or late evening when grasshoppers are less active and the wind is calm.
  • Neem Oil can be an effective in deterring and slowing down the activity of grasshoppers. A oil solution that can stunt or fully halt a grasshopper's growth can be made using this recipe:
    • Mix two quarts of warm water with a 1/2 teaspoon castile or other mild liquid soap. While stirring, slowly add 3 teaspoons of pure neem oil to the mixture. Pour into a spray bottle and spray directly on your plants AND the garden's soil.  This is a food safe mixture.
  • Garlic spray: blend 2 cups of garlic with 10 cups of water. Boil the mixture and let sit overnight. Then, mix one part garlic mixture to three parts water in a spray bottle and moisten the leaves of vulnerable plants with the spray.
  • The addition of Canola oil to insecticide sprays can improve control by making treated foliage more attractive to feeding grasshoppers. Mix 1 tablespoon of mild liquid or Castile Soap with 1 cup Canola oil. When you are ready to use, add 2-8 teaspoons of the mixture to 1 quart water and shake well.  Spray the solution on affected plants in the late afternoon or at night.
  • Diatomaceous earth - sprinkle on plants. It is a fine grit that absorbs moisture from the insects bodies. Important note: food-grade diatomaceous earth is safe to consume, but DO NOT inhale it, as it can cause scarring of the lungs. ALWAYS FOLLOW LABEL INSTRUCTIONS. Diatomaceous Earth Fact Sheet from National Pesticide Information Center.
• Crop Rotation and Diversity
  • Rotate crops to disrupt the life cycle of grasshoppers.
  • Plant a variety of crops and use intercropping techniques to make it harder for grasshoppers to find and consume large areas of their preferred food.
  • Plant deterrent plants such as garlic, cilantro, and Calendula around the garden's edges.
• Integrated Pest Management (IPM)
  • Regularly inspect your garden for grasshopper activity and damage. Early detection can help you take timely action before the infestation becomes severe.
  • Keep records of grasshopper populations and the effectiveness of control measures to refine your management strategy.

Additional resource from CSU Extension is here.

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Put up a bat box. More than two-thirds of the world's bat species are insectivores (they eat insects exclusively). In North America, nearly all bat species are insectivores and their diets often include grasshoppers, along with other insects like mosquitoes, moths, beetles, and crickets.