Using Insecticidal Soap

Q. I have been spraying an insecticidal soap solution on my garden plants and houseplants to control insects. How long does this product last on the plants?

A. Soap solutions are designed to target soft-bodied insects on contact or as the solution begins to dry. Once the product is completely dry, it has very little effectiveness as an insect control. This is why you need to reapply the solution following a rainfall. Some gardeners wash off their houseplants once the soap application has dried.