The Tomato Pinworm (Keiferia lycopersicella) is a pest of tomatoes in tropical and subtropical areas of the world. In the United States, it has been reported in several southern states, especially in the hot agricultural areas of Texas, California, Georgia and Florida and has also been reported from greenhouses in Delaware, Ohio and other northerly states.
Tomato is the preferred host of tomato pinworms. They may also infest other solanaceous crops such as potato and eggplant and solanaceous weeds such as purple nightshade, wild tomato, horsenettle and blue witch nightshade.
The tomato pinworm feeds on both leaves and fruits of tomato. When they feast on leaves, they tunnel or mine through making blotch-type mine patches that feature all over the plant. Tomato pinworm larvae will attack fruit at any stage of maturity. Their favorite point of entry is near the stem of the fruit under the calyx. Abundant pinworm populations can seriously damage foliage and infest nearly 100% of the fruit. When infested fruit is picked, tomato pinworms are hard to detect unless they have been feeding long enough to have left behind piles of brown, granular frass at the edge of the calyx or their tiny entry point holes.
Adult moths are small, reaching a maximum of 8mm in length. The wings have a ground color of brown or silver, with ill-defined black streaks and speckling. The antennae and legs are brown ringed with black. They emerge in spring and females lay eggs on host plants.
Eggs are either laid scattered or in small groups of 3-7, mainly on the upper leaves, on both lower and upper leaf surfaces. Eggs are oval, tiny, pearly white at first, becoming a pale yellow before hatching. They are less than 0.5 mm making them very hard to detect. Eggs take 4-8 days to hatch.
Newly hatched larvae are yellow or cream colored with black or brown head. As the larvae mature they develop dorsal coloration that is usually green or yellowish with an irregular band of red, brown or purple across each body segment. Larvae appear smooth skinned without any prominent bristles or tubercles. The fully grown larva is 6-8 mm long and the larval stage lasts about 10-15 days after which they pupate.
Pupation takes place within a loosely-spun cocoon in several possible locations including leaf-folds, just below soil surface, under debris, on support structures of tomato plants or in the fruits which is rare. Pupa is spindle-shaped; greenish at first but soon matures into a dark chestnut brown color. Pupal stage lasts 8-20 days.
Organic Control and Prevention of Tomato Pinworms
1. Monitoring is key to detecting initial populations and preventing their build-up if any. Monitoring can be done by setting up pheromone traps at the same height as the top of tomato plants so as to check if adult tomato pinworm moths have been in the vicinity. Also, inspecting and scouting your plants manually for signs of eggs and pinworms should be done regularly.
2. Cultural Practices: End of season clean-up is essential for the prevention of future contamination. Garden debris should be cleared off and even burned if infestation occurred and the soil should be tilled to destroy any overwintering pupae. Clear weedy areas close to your garden.
3. Hand Removal: By regularly inspecting your crops for eggs and larvae from the very start, and hand removing and destroying infested leaves, a build-up in population can very much be prevented or at least minimized.
4. Light Traps: Tomato pinworm adult moths are attracted to lights and using a light trap once it gets dark can assist in reducing adult populations.
5. Mating Disruption: Sex pheromones can be applied to foliage as a spray or released into the atmosphere to confuse tomato pinworm male moths and disrupt mating.
6. Biological Control: Wasps, ladybugs and lacewings will feed on the larvae or eggs. Trichogramma wasps are predatory egg parasitoid wasps that have been found to be effective for tomato pinworm control.
7. Companion Planting: It is a good idea to plant plants in the umbelliferae family with your tomatoes as they are great for attracting predatory insects owing to their tiny nectar producing flowers. Carrots, dill, parsley, coriander, celery among many others! Also basil with tomatoes are said to go well.
8. Bacillus thuringiensis is a very effective organic insecticide for all worms that attack tomatoes including tomato pinworms. Spinosad, an alternative biological agent can be used as an insecticide on the tomato pinworm. Consult with a local specialist before going for any of these treatments.
9. Row covers: If you cover your tomato plants with row covers, you can avoid all sorts of pests including tomato pinworm adults from laying eggs on plants.