Insect Pests on Tomatoes

From time to time, most gardeners have to deal with some of the more common tomato insect problems. Here's some basic information on several widespread insect pests. For more information on the pests most likely to cause problems in your part of the country and how to control them, contact your local county Extension agent.

Aphids
Aphids can bother tomato plants all season long. These soft-bodied, pear-shaped insects may be green, pink or yellow. They suck the sap from plants, weakening them and spreading diseases. To control, spray with neem, insecticidal soap, or commercially formulated vegetable oil sprays. Ladybeetles and lacewings feed voraciously on aphids. You can purchase these beneficial creatures by mail to introduce to your garden.

Beetle Pests
Blister beetles and Colorado potato beetles both feed on tomato foliage. The 1/2- to 3/4-inch-long, black, gray, brown or yellow blister beetles generally don't do much damage. Just keep an eye out when harvesting tomatoes; if you crush one of these beetles, its juices can cause your skin to blister. The Colorado potato beetle is a more voracious feeder. Adult beetles are orange and black striped; the large, orange humpbacked larvae have two rows of black dots down their sides. Both of these pests can be controlled with diligent hand-picking. For large infestations of Colorado potato beetle larvae, spray B.t. tenebrionis. It is most effective while larvae are small.

Cutworms
Cutworms are gray, brown or black caterpillars that curl up tightly when disturbed. They're 1- to 1-1/2 inches long, hide in the soil during the day and come out at night to feed on young plants. They'll chew tomato transplants right off at the soil surface. There's no need to spray for these pests in the home garden. Simply put a newspaper collar around the tender stem at transplanting time, spanning at least one inch above and two inches below ground.

Flea Beetles
Flea beetles are tiny, 1/16-inch-long black beetles that jump like fleas and chew numerous small holes in the leaves, most often early in the season. Damage on established plants usually isn't serious, but young seedlings can be badly weakened by flea beetle damage. To control, cover young plants with floating row cover. Adult beetles spend the winter in plant debris, so clean up the garden well in the fall.

Hornworms
Hornworms are many gardeners' least favorite pest. These huge, green caterpillars with a "horn" on their back ends eat both leaves and tomatoes. They work fast, too. Handpicking is the best control method-don't be intimidated by that fierce-looking horn-it's harmless. If you prefer to spray, use Bt kurstaki (brand names include Dipel and Thuricide), a natural insecticide that requires no waiting between application and harvest. This form of Bt only infects caterpillars. It is most effective if used when the caterpillars are small.

Stinkbugs
Stinkbugs are a problem for gardeners in the southern part of the country. These 5/8-inch-long, shield-shaped insects may be green, gray, blue or red. Like aphids, they feed by sucking the plants' sap. This causes deformed fruits with hard, whitish spots on them. To control stinkbugs, keep down nearby weeds that may harbor them and spray with an approved insecticide, such as neem or pyrethrum.

Tomato Fruitworm
Tomato fruitworm are a season-long pest that feed on tomato foliage and fruits. These yellow-, green- or brown-striped caterpillars can grow up to two inches long. Spray with an approved insecticide (such as Bt) for control. Destroy infested fruits and clean up all tomato plant debris at the end of the season to reduce the number of overwintering insects.

Whiteflies
Whiteflies feed on many plants in the vegetable garden besides tomatoes, including cucumbers and melons. These tiny (1/16-inch-long) pests fly out in a cloud from infested plants when disturbed. They feed by sucking the plants' sap, causing leaves to become yellow and distorted and weakening plants. Whiteflies excrete a sugary substance called honeydew on which a sooty black mold often grows, making tomato leaves appear dirty. Spray with insecticidal soap for control.

If you use insecticidal sprays, be very careful about following the directions exactly. Read the directions three times: before you make a purchase, so you know what you're getting; before you use it, to make sure you use it correctly; and after you've used it, so that you store it properly, out of risk to people and animals.

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