Safe, Natural Insecticides for Strawberries
Many traditional insecticides are toxic to you and your family, and their residual effects -- including an increased risk of some cancers -- can linger on strawberry fruit long after the fruit has been picked. Strawberries are targets for many common pests, however, so don't leave strawberry plants defenseless. Several safe, natural insecticides can protect strawberries, but the right choice depends on which specific pest is causing the problem.
Spittlebugs are one of the most prevalent strawberry pests, warns the University of Kentucky. These 1/2-inch-long bugs create sticky masses of white foam and feed on strawberry stems and foliage. Control becomes necessary when there are five or more spittle foam masses per square foot of strawberry garden space, at which point the bugs begin affecting strawberry plant size and fruit yield.
Keep strawberry gardens free of weeds, which are often the host of spittlebugs. Avoid the use of traditional pesticides, which kill the beneficial insects that typically keep spittlebugs in check. Instead, simply shoot strawberry plants down with a strong blast of water from a garden hose. This washes away the sticky foam and knocks the insects off the plants, killing them and quickly eradicating the problem.
Strawberry Root Weevils
Although you can't see them, strawberry root weevils' grubs in the soil are another major headache of gardeners. The grubs feed on the roots and the base of the strawberry plant and can kill an entire patch of strawberries.
At night, set out a tray or cardboard box under the strawberry plants. Shake the plants to dislodge adult weevils -- the adults are slow moving and cannot fly -- and either crush the weevils or freeze them to kill them. This sufficiently reduces adult weevil populations, which in turn limits grub activity.
Instead of traditional grubicides, try the all-natural parasitic nematode known as Hetero-rhabditis bacteriophora. When applied to the soil around strawberry plants in the spring, the nematodes naturally and safely attack and kill the grubs. Parasitic nematodes are available in many garden stores and nurseries. Follow all labeled guidelines, as application rates vary by product. For most nematode sprays, use approximately 3 gallons of nematode spray for every 500 square feet of soil surface.
Tarnished Plant Bug
The tarnished plant bug has an oval shape and a diamond-pattern on its back. It also ranks high in the list of common strawberry pests, attacking young developing fruit. Keep strawberry beds clean and free of debris and fallen leaves to eradicate hiding spots and keep bug populations from reaching nuisance levels.
Hand-crushing the bugs and their young can sufficiently control this problem in many cases, as does shooting down the strawberry plant with a strong jet of water to dislodge and kill the bugs. For a stronger solution, use a homemade insecticidal soap. Combine a tablespoon of liquid dish soap in a pint of water, shake well and mist the soapy water onto affected strawberry plants to naturally kill the pests.
Snails and Slugs
The strawberry plant's low-hanging profile makes it easy for slugs and snails to reach the plant and feed on its stems, leaves and the fruit itself. If you notice missing foliage and telltale slime trails, these creatures are the problem.
Slugs and snails are sensitive to moisture. Allow the strawberry garden to dry out slightly. This dehydrates and reduces the pest population. Additionally, eliminate hiding spots, such as thick mulch and fallen organic debris. If that doesn't sufficiently control slugs and snails, use food-grade diatomaceous earth. This natural insecticide powder kills slugs and snails on contact. Sprinkle the diatomaceous earth in a circle around each strawberry plant, forcing the slugs or snails to crawl over the powder to reach the plant.
Mites and Aphids
Mites and aphids look tiny, but in sufficient numbers, they can suck the sap out of the strawberry plant's foliage and cause widespread wilting and plant death.
Shooting strawberry plants down with water can rinse away the pests and keep their populations from reaching harmful levels. Or, use a homemade insecticidal soap spray by mixing a tablespoon of soap in a pint of water and spraying it directly on aphid and mite activity.
- North Carolina State University: Pesticide Residues in Food - The Safety Issue
- University of Kentucky Extension: Strawberry Pests
- University of Minnesota Extension: Spittlebugs
- Rodale Organic Gardening: Good Bug, Bad Bug
- South Nevada Water Authority: Pest Control
- Rodale's Organic Life: Strawberry Root Weevil
- University of Vermont Extension: Nematodes for Insect Control
- Ohio State University Extension: Plant Bugs on Perennials and Landscape Shrubs
- Colorado State University Extension: Insect Control - Soaps and Detergents
- Colorado State University Extension: Slugs
Joshua Duvauchelle is a certified personal trainer and health journalist, relationships expert and gardening specialist. His articles and advice have appeared in dozens of magazines, including exercise workouts in Shape, relationship guides for Alive and lifestyle tips for Lifehacker. In his spare time, he enjoys yoga and urban patio gardening.