There's an environmentally sound solution, but it does take just a little determination. Mix about three or four tablespoons full of regular dish soap... not dishwasher soap... into about one gallon of warm (not hot) water. Using a clean spray bottle, thoroughly soak the upper and lower surfaces of the plants with the mixture about every other day for a week or so. The soapy water kills the aphids and their parents quite effectively without harming the plant. After the breeding cycle is broken you should have no more problems.... If so, simply reapply the soap...