Answer: What you use really depends upon which plants you're growing because some are sensitive to specific sprays (be sure to read the label to make sure your plants are listed). I have great results with Safer's Insecticidal Soap. It works immediately on aphids and if I'm spraying on an especially sensitive plant such as hibiscus or fuchsia, I rinse the plant with plain water about 10 minutes after spraying.
Best wishes with your garden!
Q&A Library Searching Tips