Gardening Articles: Care :: Pests & Problems

Insect Pests of Tomatoes

by National Gardening Association Editors


It's high summer, your tomato vines are flourishing, and you're eager to pluck the first juicy, ripe orb. But chances are you aren't the only one interested in America's favorite vegetable -- you no doubt have competition in the form of pests! Here's some basic information on several widespread pests that, like you, hanker for tomatoes. 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 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, indirectly, spread diseases. Wash them from plants with a shot from your garden hose every few days, and if they peresist, use insecticidal soap.

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. Approved insecticides, such as B.t. 'san diego' for potato beetles and pyrethrum for blister beetles, also provide control.

Cutworms are gray, brown or black pests that curl up tightly when disturbed. They're one 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 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 feeding. To control, spray or dust with an approved insecticide, such as pyrethrum. Adult beetles spend the winter in plant debris, so clean up the garden well in the fall.

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 bet in the home garden because you often discover the pests at harvesttime when it's unwise to spray with chemical insecticides. (The "horn" is fierce-looking, but harmless.) If you prefer to spray, use Bacillus thuringiensis (known as Bt, and available as Dipel or 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. Bt can kill the larvae of all species of butterfly or moth, so be sure to use care during application to minimize drift.

Stinkbugs are mainly a problem 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, reduce their habitat by keeping weeds under control, both in the garden and surrounding. Cover plants with floating row cover to create a barrier against the pests.

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 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 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 secrete 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 any kid of spray, organic or not, follow 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.
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