Tomato pinworms are the larval form of a moth that prefers feeding on members of the nightshade family. This means tomatoes, eggplants, and potatoes are at risk. It also means weeds and native plants in the same family can harbor these pests.
Tomato pinworms (Keiferia lycopersicella) are predominantly found in areas with mild winters. They can also appear in greenhouses, so be sure to put new plants into quarantine until you are sure they are pest free.
Tomato pinworm description
Eggs are pale yellow, at first, but then they turn bright orange, just before hatching. Larvae appear dark with light bands. The moth is very small, and a mottled grey with long antennae.
Tomato pinworm lifecycle
Moths lay eggs singly or in groups on leaves. When the eggs hatch, larvae spin protective webs. Then they burrow into the leaf to begin feeding. As the larvae move through 4 developmental stages, or instars, they may also fold leaves, or pull multiple leaves together, for added protection from predators. Tomato pinworms also move into stems and fruit, where they can make your crop inedible.
After eating their fill, larvae then drop to the ground and form a loose cluster of sand grains around themselves, in a form of pupa. Two to four weeks later, they emerge as adult moths. There can be 7 or 8 generations a year. Because there are so many generations each year, and because generations can overlap, serious infestations can decimate your tomato plants.
How to control tomato pinworms
In areas with mild winters, tomato pinworm eggs and larvae can overwinter in the soil, on tools, or in buckets or baskets. Closely monitoring plants for signs of infestation is your first line of defense. Pheromone traps can be used to monitor for the moth and mating disruptants can make it more difficult for adult males and females to find each other. Be sure to thoroughly compost or remove plant residue at the end of the growing season, and always put new plants into quarantine.
Commercial growers use insecticides on the first and second instars, but later instars are protected by their spun tents and by being inside the plant. This is one pest that is hard to get rid of, once it becomes established. Moderate infestations can be slowed by not planting early and late season tomatoes the same year. To manage badly infested areas, the host crops must not be planted for a year or two, to break the tomato pinworm lifecycle.
Crop rotation is not effective, as the moths simply fly from one part of the garden to another.
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