Aphids can cause a lot of damage. So if you spot them on your plants, it's best to kill them right away. These tiny pests can be killed in several ways; choose the method that works best for your situation. Concoct a simple homemade solution or apply a commercial product to handle the problem.
Remove the Pests by Hand
Use a strong stream of water to knock aphids off your plants. A stream of water can fatally injure them, and those that live through the experience end up on the ground and aren't very likely to find their way back onto plants. Repeat the process as often as you find aphids.
If the aphids are present in only small numbers, then either pick off the individual aphids and simply squish them or cut off affected leaves and destroy them along with the aphids.
Release Aphid Predators
Many insects eat aphids, and releasing these natural enemies of aphids into your yard or garden will help to kill aphids. Lacewings and lady bugs, or lady beetles, are among the insects that kill aphids. Because aphids reproduce very quickly, however, they may stay ahead of these predatory insects, especially if the aphid population is already well-established.
Make and Use Insecticidal Soap
Make your own insecticidal soap quickly and easily. The mixture will not only kill aphids by interfering with their cell membranes, it also will kill other soft-bodied pests such as whiteflies, mealybugs, citrus black flies and scale. Insecticidal soap must touch an aphid to kill it.
Combine 1 cup of vegetable oil, such as corn, safflower, peanut or soybean oil, with 1 tablespoon of a mild, liquid, dish-washing soap, making an insecticidal soap concentrate. Don't use ultra or concentrated dish-washing formulas.
Place the insecticidal soap concentrate in a jar or bottle that has a lid, and put the lid on the container. This mixture will be the basis of your insecticidal spray.
Shake the concentrate just before you want to use it. Ensure its contents are thoroughly mixed.
Place 1 cup of tap water into a spray bottle, and add 1 to 2 teaspoons of the concentrate. Shake the spray bottle well to mix the ingredients.
Spray aphid-affected plants with the insecticidal soap-water mixture either in early morning or late afternoon, when the sun is not at its peak. Ensure that you spray enough of the solution to wet all the plant surfaces, including the leaves' undersides.
Reapply the insecticidal soap solution weekly for two or three weeks if necessary.
Apply Horticultural Oil
An application of horticultural oil – available from plant nurseries and many home centers – can be used to kill aphids that spend winter on plants and then take over in spring. Put on protective clothing and gear that covers your skin, and mix 2 to 4 tablespoons of a horticultural oil concentrate with 1 gallon of water, and place the mixture in a handheld pump sprayer's tank. Spray the oil-water solution on the plants before their leaves appear in spring. Spray all sides of the trunks and branches until they are completely wet. The solution will smother aphids. It is especially useful on fruit trees. Rinse out the sprayer with clean water when you are done.
Spray with Insecticide
Insecticide with an active ingredient such as acephate kills insects on contact by damaging their nervous systems. Apply an insecticide if you notice aphids on plants. Ensure the product is labeled as safe for use on the plants you intend to spray.
Put on protective clothing and gear that covers all of your skin.
Mix 2 tablespoons of an insecticide that is 9.4 percent acephate with 1 gallon of water in the tank of a pump-type garden sprayer.
Spray the insecticide-water mixture on the leaves of plants on which you have seen aphids. Apply the spray until the leaves are wet on both sides. If not enough of the solution is used, the insecticide may not kill all the aphids.
Rinse the garden sprayer's tank, hose and nozzle with clean water.
Wait seven to 10 days, and then check the treated plants for aphids. Reapply the spray if aphids are present.