Question: What, exactly, is insecticidal soap? How is it different from "regular" soap?

Answer: All soaps are long chain fatty acids; however, insecticidal soaps are specifically formulated to have insect-killing properties, while being safe for most plants. Insecticidal soaps kill susceptible insects by washing away the protective coating on the surface of the insect and by disrupting normal membrane functions inside the insect. The insects must come into direct contact with the spray droplets for the material to be effective. Good coverage is essential. The soaps have no residual activity toward insects. Note that repeated applications can sometimes have damaging effects on some types of plants. As with all pesticides, follow label instructions carefully.