The tomato pinworm, with the scientific name Keiferia lycopersicella, is actually a small caterpillar produced by tiny nocturnal moths. Crop losses can reach up to 80 percent in the warm climates where the disease thrives, notes the University of Hawaii Extension. The pest is most severe on greenhouse-grown plants, according to the University of Florida IFAS Extension.
Pinworm moths lay eggs on the lower surface of bottom leaves of the tomato plant. The caterpillars are about 1/4 inch long and gray or pale red to purple in color. They give leaves a ragged appearance and enter the fruit just below the stem attachment. They spread upward, rolling the leaf around them as they build a cocoon, where they change to the pupae stage. The manner in which the pinworm ties together the leaf tips makes it difficult to target using application of insecticides.
Treatment types include mating disruption using a product such as NoMate TPW, which releases pheromones that confuse tomato pinworm males and make it difficult for them to find females. Place plastic laminate clip-ons or spiral rings containing the pheromone on the tomato stems, recommends North Carolina State University. Bacillus thuringiensis (Dipel, Thuricide), a biological agent that kills caterpillars, can also be used as a dust or spray to kill the pinworms; bT makes the pinworm stop eating and die. Kenneth A. Sorensen, extension entomologist at North Carolina State, also recommends spinosad, an alternative biological agent, as well as insecticides including methomyl, endosulfan, esfenvalerate, abamectin, cyfluthrin, emamectin benzoate, indoxacarb, zeta-cypermethrin or lambda-cyhalothrin to kill the pests.
Apply insecticides based on Bacillus thuringiensis as soon as the young larvae are detected, ideally before they begin boring into fruit, the Oklahoma Cooperative Extension Service advises. Spray bT every seven to 10 days beginning at the end of May or early June in temperate areas. Planting in late winter can also solve the infestation problem, according to the University of California Extension.
The tomato pinworm is a serious pest in California, Texas, Florida, Hawaii and Mexico because of warm winters, permitting populations to establish. The insect doesn’t overwinter north of Florida, according to North Carolina State University, but populations bought into the Carolinas on transplants can increase rapidly.
To monitor pinworms, survey your garden weekly looking for eggs, larva and fruit damage. You can also hang trap kits on your stakes, trellises or cages with pheromone lures to capture and count pinworms. Apply insecticides when counts are above 0.25 per plant.
Clear weedy areas close to your garden, recommends the University of Hawaii. Inspect plants and cut off any leaves displaying pinhole damage, bag them and throw them away. Dispose of the plants after harvest, and if you are a commercial grower, establish crop-free periods and harrow your fields to bury many of the pinworm pupae under 2 inches or more of soil, where they cannot survive. Purchase only pest-free transplants
- University of Hawaii Extension: Field Tomato Production Guidelines for Hawaii
- University of Florida IFAS Extension: Insect Management in the Home Garden
- Oklahoma Cooperative Extension Service: Growing Tomatoes in the Home Garden
- University of California: Tomato Pinworm
- North Carolina State University: Insect Pests Of Vegetable Crops In The Southern United States
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