The Q&A Archives: Residual Pesticides Harmful To Beneficial Insects?

Question: Last year I sprayed my garden with insecticides to rid it of a very bad white fly infestation. This year I would like to tackle the problem with beneficial insects who would feast on white flies instead of spraying. Will the pesticides I used last year harm the good insects I bring into my garden this year?

Answer: I congratulate you for trying this approach. It can be quite rewarding to see the ladybeetles, praying mantis, birds, etc. in the garden, doing this work for you. If there is residue it could be a problem. But over time, if you refrain from spraying insecticides, the beneficial insects will arrive on their own to consume the pests. Whiteflies can be tackled with strong blasts of water from the hose on a daily basis, or with a soapy water spray, which is less toxic to other insects. Also, be aware that there must be pests for the beneficials to consume when you release them, or they will go elsewhere, which is sometimes disappointing to gardeners. Good luck!

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