Why Are There Black Holes in My Tomatoes?

Pest Identification

• The tomato fruitworm is among the serious pests of the plant and potentially the most damaging, notes the University of Kentucky Extension. Although the pest has other host plants, such as corn during silking time, tomatoes are still its preferred habitat for laying eggs and larvae feeding.

Pest Description

• The tomato fruitworm is the larval stage of a brown-colored moth with 1- to 1-1/3-inch wingspan. The front wings have a dark spot in the center and the back wings are lighter are dull white. The female lays white eggs on the foliage. The eggs darken before hatching. The white-colored larvae with black heads change color to green and then black as they mature. There are fine, white lines along the length of the body.

Damage

• The newly hatched larvae initially feed on foliage and then move to the fruit, preferring feeding on green, unripe, ¾- to 2-inch fruit. The pests enter at the stem end, creating holes that eventually turn dark. A single worm can exit and re-enter several tomatoes as its feeds, creating watery, internal cavities filled with worm frass or waste matter. Damage causes premature ripening. If plants are infested later, the larvae also attack ripe fruit.

Control

• Introduce natural predators for biological control of the pests. Fruitworm predators include bigeyed bug, minute pirate bug and egg parasites from the trichogramma group. Monitor the plants regularly for pests in order to control infestations in the early stages. Recommended pesticides include Bacillus thuringiensis, spinosad, fenpropathrin or carbaryl.