There are a number of natural repellant sprays available for use against aphids and many other pest insects. These products both kill and/or repel. Aphids doused with these sprays either die or move. New aphids coming along avoid the area with the repellent spray for several days to a few weeks. In the Natural Insect Repellents section you will find descriptions of Neem Oil Soap, Hot Pepper Wax, and Garlic Barrier.