What is insecticidal soap? How does it work? Can I make it myself?
Insecticidal soaps are environmentally friendly formulations made from mineral or vegetable oils that kill soft-bodied insects either by suffocation or destroying their cells. Insecticidal soaps do not leave toxic residues. They must contact the insects to be effective.
Here's a quick and easy way to make insecticidal soap. Mix one cup of cheap vegetable oil with one tablespoon of dishwashing liquid. Do NOT use soaps formulated for automatic dishwashers because they may contain chemicals that can harm plants. Do NOT use soaps with bleach added. Add two teaspoons of the soap mixture per cup of warm water in a plastic spray bottle. Stir thoroughly. Test a bit of the mixture on a small part of the plant to assure that the mixture won't do damage to the plant. Spray only on cloudy days or before dusk. Hot sunlight combined with insecticidal soap can damage plants.