The grasshopper, one of the most damaging insects known to gardeners and farmers, is also one of the most difficult pests to control. They are very mobile and their population numbers vary wildly from year at year. When choosing your grasshopper control strategy, don't cut off your nose to spite your face. Choose organic methods that don't poison your soil or your crops.
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Garlic oil sprays and garlic tea sprays may be effective at repelling grasshoppers. Tipnut.com suggests boiling a pint of water and steeping roughly cut chopped garlic in it until it cools. Strain out garlic pieces and spray on plants.
Another Tipnut.com recipe involving garlic calls for blending two hot peppers, one large onion, one whole bulb of garlic and a quarter cup of water in a food processor, then covering the resulting mash with a gallon of hot water. Let stand for 24 hours then strain. "Good for thrips, aphids, grasshoppers, chewing and sucking insects."
Hot pepper wax and chili sprays make plants taste unpalatable to grasshoppers. Green Harvest suggests blending half a cup of fresh chilies with 2 cups of water and a few drops of dish washing liquid "to improve sticking". You can substitute 2 tbsp. Tabasco sauce for fresh peppers. Thoroughly spray any plant that needs protecting.
Test any pepper spray before use. Spray a small section of a single plant and check back in 24 hours. Proceed only if you can detect no damage. Also, avoid using chili sprays during hot weather, as leaf burn is more likely then.
Neem oil contains broad spectrum insecticides, fungicides and miticides. Some consider it effective for grasshoppers although it is more likely to kill the grasshoppers than repel them. Mix 2 tbsp. of Neem per gallon of water and spray all plant surfaces thoroughly.
Other Store-Bought Repellents and Insecticides
Clean Air Gardening sells an "Organic Lawn and Garden Bug Spray" as an all-purpose insecticide. It contains sesame, clove and thyme oils.
Another repellent in Clean Air Gardening's buyer's guide is Natural Fire Ant Killer with Spinosad. Though intended for ant control, Clean Air Gardening says it also controls grasshoppers.
According to Green Harvest, insecticidal potassium soap sprays work well on small grasshoppers.
According to Colorado State University Extension, repellents are often ineffective at keeping these insects away. Further, they caution that some common materials used in repellents, such as garlic oil and vegetable oils, may actually attract grasshoppers to feed on your plants.
Alternatives to Repellents
Chickens, turkeys and guinea fowl eat grasshoppers. After your plants have grown up a little such that scratching behavior won't damage them, allow your poultry to range free through your garden. Alternatively, build a fenced poultry run adjacent to the your garden. Check local zoning regulations to determine what types of poultry are options for you.
Encourage other grasshopper predators in the area: birds, sugar gliders, lizards, snakes, assassin bugs, frogs, ants, paper wasps and parasitic wasps, tachnid flies and robber flies. Maintain a border of perennial plants and nectar-producing plants as an attraction and refuge for many of these predators.
Purchase mermithid nematodes to parasitize your grasshopper invasion. Apply at cool times of the day when light intensity is low, making sure to water just before and right after applications.
Water plants in grasshopper breeding areas and avoid mowing there. The healthier plants there are, the less likely the hoppers will be to migrate from there to your garden in search of food.