Tomato Fruitworm

Tomato fruitworm adults are medium-sized moths with a wing span of about 1 to 1.3 inch (25-35 mm). They are pale tan to medium brown, or sometimes have a slight greenish tinge. The front wings are variously marked and usually have an obscure dark spot in the center and a lighter band inside a dark band around the tip. The hind wings are drab white and have a dark gray band around their tip. A diffuse light spot is in the center of the dark band.

At hatching, tomato fruitworm larvae are creamy white caterpillars with a black head and conspicuous black tubercles and hairs. Larger larvae vary in color from yellowish green to nearly black and develop fine white lines along the body but retain the black spots at the base of bristlelike hairs. Older larvae also have patches of stubby spines on their body segments that are much shorter than the bristles and can be seen best with the use of a hand lens.

Eggs are tiny, hemispherical, and slightly flattened on top with coarse striations or ribs running from base to tip. They are easy to confuse with looper eggs, but looper eggs have fine striations. Fruitworm eggs are laid singly on both upper and lower surfaces of the leaves usually in the upper part of the plant. When first laid they are creamy white, but develop a reddish brown ring after 24 hours.

Soon after hatching, the larvae burrow into the fruit, usually near the calyx, and remain inside, feeding on the flesh. Infested fruit decay, turn red, and fall off the plant early, reducing yield. Larvae consume very little foliage.

Regular monitoring of pepper fields is important in detecting and managing this pest. Weed control, site location, and biological control are important in reducing the potential for damage. Insecticide treatment may be necessary when monitoring indicates a need.

These insects have a wide host range. Weed control in the area can help to reduce the population; however, the moths can fly great distances. Avoid planting peppers near field corn or garbanzo beans.

Tomato fruitworm eggs can be heavily parasitized by Trichogramma pretiosum. Experimental releases of Trichogramma have resulted in control of fruitworm on pole tomatoes. Parasitized eggs are completely black. When any eggs are found they should be held in vials for several days to determine the level of parasitism. The parasitic wasp, Hyposoter exiguae, attacks fruitworm larvae and can reduce fruitworm populations considerably; however, often the worm will die inside the fruit and the parasite cocoon remains in the fruit as a contaminant.

Cultural and biological control and sprays of Bacillus thuringiensis or the Entrust formulation of spinosad are acceptable for use in an organically certified crop.

Start monitoring for tomato fruitworm at the seedling stage and continue through harvest. Inspect the upper part of the plants for fruitworm eggs. Examine the eggs closely with a hand lens to determine the stage of development of the larvae and check for parasitism. If necessary, treat within 2 to 3 days after the head capsule has formed. There are no treatment thresholds.

Timing of sprays is critical because the worms enter the fruit shortly after hatching and are thus susceptible to the pesticide for only a brief period. In peppers grown for fresh market consumption and where fruit aesthetics are paramount, treatments may be needed when egg laying is documented.