Pour 2 tablespoons liquid dish soap into 1 gallon water. Stir the dish soap into the water and transfer the contents into a plastic spray bottle.
Spray the affected plant’s leaves on both sides with the soapy mixture. Pay attention to coat the underside of the leaves with the mixture, as this is where you’ll find the highest concentration of aphids.
Spray the soapy mixture directly onto any aphids you notice falling from the leaves. The aphids are small, and it’s necessary to shoot them with the soapy water to kill the unwanted pests.
Rinse away the soapy residue after one to two hours. Allowing the soap to remain on the leaves for longer than a few hours can cause damage and burning. Use a garden hose or spray bottle filled with plain water to remove the residue.
Reapply the mixture every few days, or as necessary, to keep the aphid infestation under control.
Tip: Add 1 teaspoon vegetable oil to the mixture to increase the mixture’s density and make it stickier, helping it attach to and kill the aphids more effectively.
Warning: Test the soapy mixture on a small leaf before a larger application. If the plant shows sign of wilting or damage, don’t use this mixture.
Reprinted from SFgate online: http://www.sfgate.com/homeandgarden