Basic soap and water can seem like a harmless combination, but beneficial ladybugs may feel differently. The same ingredients common to household staples fortify pesticides known as insecticidal soaps. Whether you're recycling soapy household graywater or whipping up pest-fighting garden remedies, some combinations may be harmful to ladybugs -- and gardens. The risks depend on soap types, ladybug life stages and your garden's conditions.
Soaps and Insecticides
Soaps are active components in many effective insecticides. Gardeners often turn to insecticidal soaps to fight common garden pests. Soaps battle insects in various ways, but they rely on direct contact with their target. Most insecticidal soaps kill soft-bodied insects only by dissolving their soft outer membrane. But some soap-based insecticides attack the bug's nervous system instead. Commercial insecticidal soaps are generally considered safe for adult ladybugs, but the strength of household water and homemade solutions varies widely. Soapy graywater containing laundry detergents or household cleaning residue can strip foliage and damage garden plants. These soapy unknowns may harm ladybugs when regular insecticidal soaps would not.
Ladybug Life Cycle
Adult ladybugs are easy to recognize with their black-spotted, orange-red shells. But ladybugs aren't born with that protective beetle covering. Before they reach this stage, ladybugs hatch from eggs and pass through larval and pupal stages. Soft-bodied ladybug larvae are especially vulnerable to soapy household water and insecticidal soaps. Often mistaken for harmful pests, the black and orange larvae are frequently described as looking like tiny alligators. Harsh soapy solutions may injure ladybugs at all life stages, but even gentle, common soap products kill beneficial ladybug larvae as surely as they kill harmful soft-bodied pests.
Ladybugs specialize in eating aphids. Both adult ladybugs and their larvae have voracious appetites for aphids. Young larvae kill aphids by piercing and sucking the pest's bodily fluids, while adults chew and devour the whole aphid. Ladybug larvae and adults get into curled leaves and other aphid hiding places where insecticidal soaps can't reach, but they only stick around where there's food. Adult ladybugs eat 50 or more aphids per day, and some species feed on aphids exclusively. If soapy water is used to kill aphids, intentionally or accidentally, even unharmed adult ladybugs move on to their next meal.
Graywater Garden Safety
Use household graywater responsibly and wisely. Never use graywater from any source on root crops or other garden edibles -- ladybugs or not -- and never use soapy water on drought-stressed plants. For ornamental plants, only use wastewater from showers and clothes washers. Never recycle soapy water with food debris from kitchens or dishwashers. Common household soaps, detergents and shampoos can contain additives that injure garden plants. Powdered laundry detergents, in particular, have high salt levels that can harm plants and negatively affect garden soil. Beneficial insects, including ladybugs, may not fare well against them.
- University of California Vegetable Research and Information Center: Soap Sprays as Insecticides
- Washington State University Spokane County Extension: Insecticidal Soaps
- UC Statewide IPM Online: Convergent Lady Beetle
- UC Division of Agriculture and Natural Resources Green Blog: Lady Bugs Need Special Care to Control Aphids in the Garden
- University of California Cooperative Extension, Riverside County: Use of Graywater in Urban Landscapes
- Rodney_X/iStock/Getty Images