To make a concentrated garlic spray, puree 1/2 cup of water with 2 bulbs of garlic, pour 1 gallon of boiling water over it, and steep the mixture overnight. Once strained into a spray bottle, apply the garlic mixture to infected plants daily. For heavier infestations, add a tablespoon of crushed hot pepper or hot pepper sauce to the garlic spray together with 1 tablespoon of vegetable oil to smother aphid eggs and larvae.
Control small aphid infestations by wiping the aphids off with your hand or a soft cloth and repeating regularly until there is no longer any evidence. Often, a strong stream of water from a garden hose is enough to remove aphids from garden plants. A tablespoon of liquid soap mixed into a spray bottle of water and sprayed on both sides of the leaves is effective for houseplants when applied daily until aphids disappear; repeat weekly thereafter as a preventative measure.
Tomatoes are members of the nightshade family with foliage that contains toxic compounds called alkaloids. Make an easy tomato leaf spray to control aphids by soaking 2 cups of chopped tomato leaves overnight in 2 cups of water. Strain the liquid through a coffee filter, discard the leaves, and add 2 additional cups of water. The mixture is ready to be sprayed on infected plants -- give particular attention to growing tips, stems and undersides of leaves. Precautions to follow, as with any insecticide, include washing treated produce before eating, wearing appropriate protective clothing, and washing hands after spray application.