Insecticides for Aphids

Aphids are tiny, pear-shaped soft-bodied insects that feed on the fluids of plants by poking holes in leaves and stems. There are many different kinds of aphids, and they come in a variety of different colors, such as black, yellow, red, brown or green. When using insecticides on aphids it is important to get the undersides of leaves as well as the tops, as the insects are often found underneath the leaves.

Neem Oil

• Neem oil is pressed from the seeds of the tropical Neem tree (Azadirachta indica) and is often used in the control of aphids. This insecticide is particularly useful on food crops, as it has not been found to be harmful to humans. It also does not have long-term residual effects, so it will kill aphids when it is applied, but it does not kill honeybees or other beneficial insects when used according to directions. This brown oil, which smells like a combination of garlic and sulfur, is both an insect repellant and a growth inhibitor.

Malathion

• Malathion is a chemical that is used to control many different types of insects, such as mosquitoes, lice and aphids. It is an organophosphate and is used to break the aphids' lifecycle by killing the adults. It is applied to plants as a very fine spray. Any insects that are touched by the droplets are killed, and the amounts used for control are so small that it is not considered harmful to human beings, animals or birds. The main concern with malathion is that it can form a much more toxic compound known as malaoxon if it encounters chlorine, which is what happens when it gets into the water supply. It can also form malaoxon under certain other conditions, but when used in small amounts it is still considered to be safe. Malathion works well to kill aphids but must be used sparingly.

Permethrin

• Permethrin is a chemical that is sold to kill many different kinds of insects. It is used as a topical flea killer for dogs, as a cream for humans to treat scabies and lice and as a spray to kill aphids and other pests on plants. Permethrin is a synthetic insecticide that is made to simulate natural pyrethrin, a compound that is made from the pyrethrum daisy. There are some differences, though, especially the fact that permethrin has a higher level of toxicity than pyrethrin, and the artificial compound will remain on the plant and working for days, whereas the natural pyrethrin lasts only a few hours. Permethrin works well to kill aphids, killing any that it touches for as long as it remains potent.