Natural Insecticides for Tomato Plants

Insects don't always bother tomato plants, but when they do they can cause damage to the foliage or fruit that can reduce your harvest of this succulent summer vegetable. Because your tomatoes are an edible crop, you might be concerned about using chemical insecticides that might end up in your body. Alternatives to poisons exist---and they are safe, effective and easy to use.

Insecticidal Soap

If your tomato plant has signs of aphids, whiteflies, leaf miners or spider mites, insecticidal soap is a safe, easy-to-apply natural insecticide that many organic gardeners have used with success. It is available at garden centers and other stores that stock garden products. You can also make your own. All it takes is 1 tbsp. of non-ultra dish soap in 1 qt. of water. Mix together in a spray bottle and douse your plant every day or two until the insects are gone.

Bacillus Thuringiensis (Bt)

Considered organic, Bt is a soil bacterium deadly to caterpillars and other wormy creatures, including young tomato hornworms. Hornworms are the scourge of many gardens in summertime because they grow large, are ugly and cause widespread damage to green tomatoes. Bt helps to control several other insects, including blister beetles, flea beetles and the Colorado potato beetle. This organic insecticide is sold in powdered form. Hand picking is also a natural control for tomato hornworms---if you can stand to handle and squash them.

Diatomaceous Earth

When you keep ants away from your tomato plant, you will have far fewer aphids, scale insects and others that excrete a sweet substance known as "honeydew." Ants are industrious farmers that bring other insects onto plants and then eat their excretions. Although ants don't harm your tomato plant, their presence should alert you that other destructive insects exist on or around your plant. Diatomaceous earth keeps ants away because when they walk over it, their feet get injured, as if they're walking over broken glass, according to Garden Harvest Supply. Scatter this natural product on the soil around your tomatoes and expect ants, sowbugs, flea beetles, sawflies, coddling moths, certain mites, earwigs and other insects to find another place to live.

Iron Phosphate Granules

Slugs and snails can decimate a tomato that's almost ripe. If the population is large in your garden, you can control them by scattering iron phosphate granules on the soil around your plants. Because it's a natural insecticide, don't expect to find heaps of dead snails or slugs when you search for them the morning after you use this product---the creatures tend to hide and then die where you probably won't see them, which can be a nice advantage over poisonous snail baits. Iron Phosphate Granules are available under the brand name "Sluggo," which is available at nurseries and garden supply centers.

Keywords: tomato plants, insect pests, insecticidal soap, hornworms snails aphids

About this Author

Barbara Fahs lives on Hawaii island, where she has created Hi'iaka's Healing Herb Garden. Fahs wrote "Super Simple Guide to Creating Hawaiian Gardens," and has been a professional writer since 1984. She contributes to Big Island Weekly, Ke Ola magazine, GardenGuides and eHow. She earned her B.A. at UCSB and her M.A. from San Jose State University.