Tomato pinworm

About

The caterpillar of a tiny gray moth, about a quarter inch long. It feeds only on tomato and its relatives and is mostly a warm-climate pest, though it can hitch a ride north on transplants.

Spotting it

Damage

Young caterpillars make winding or blotchy mines in leaves; older ones fold and web leaves together or bore into fruit, usually under the stem cap. The fruit gets pinholes, dark tunnels and frass, and may rot. UF/IFAS says it can infest 60 to 80% of tomato fruits in a season.

How to find it early

Check transplants and leaves for small winding or blotch mines, folded or webbed leaves, and frass at the stem end of fruit. Pheromone traps catch the moths.

When

Spring through fall, getting worse as the season goes on; year-round in warm areas and greenhouses.

Life cycle

A generation can take as little as about 4 weeks in warm weather, and overlapping generations add up to seven or eight a year in Florida (UF/IFAS). It survives winter outdoors only in warm areas, as pupae at or near the soil surface (Lincoln University).

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Clean transplants and a break between crops Prevent

   Buy locally grown transplants and check them for mines and folded leaves. Keep new plantings away from old tomato, eggplant and potato plantings, and leave a gap with no host plants between crops (UC IPM, UF/IFAS).

2. Remove infested leaves and clean up By hand

   Pick off mined or folded leaves and seal them in plastic bags. After harvest, remove and destroy all plant debris (University of Kentucky, UMD).

3. Protect parasitic wasps Natural enemies

   Several tiny parasitic wasps attack pinworms. Broad-spectrum sprays kill them and can also trigger leafminer outbreaks (UC IPM).

Garden friends that go after it

Trichogramma wasps

Protect these helpers: skip broad sprays when they're around.

Plants it goes after

Eggplant, Potato, Tomato

Pressure by region

It lives year-round in warm parts of California, Texas, Florida and Hawaii (UF/IFAS) and is common throughout southern California (UC IPM). Farther north it cannot survive winter outdoors; it turns up in greenhouses and high tunnels (Delaware, Kentucky, Mississippi, Missouri, Pennsylvania, Virginia) and on infested transplants. Ratings other than California are estimates.

Ratings come from extension sources where available; some are estimates, as noted above.