Gardening Articles: Care :: Seeds & Propagation

Keep on Planting! (page 3 of 3)

by Susan Littlefield

Question of the Month: Holes Chewed in Tomatoes

Q: My ripening tomatoes have deep holes eaten into them but I haven't found any insects feeding on them. Help!

A: This sounds like damage from the tomato fruitworm, a striped yellow, green or brown caterpillar that chews deep holes in the tomato fruits and may also feed on the leaves of the plants. It can attack many other plants besides tomatoes (when it's in corn it's called the corn earworm). The adult is a moth that lays its eggs in the spring on leaves and stems. The caterpillars that hatch out feed on the leaves until they are about 1/2 inch long, then they burrow into the tomato fruits, causing the kind of damage you noticed. After feeding for 2 to 4 weeks, they then exit the fruits and drop to the ground, burrow into the soil and pupate, emerging a few weeks later as adult moths to begin the cycle again. This may be why you didn't see any insects in your tomatoes, just the damage they did. There can be several generations a year.

Once the caterpillars are inside the fruits there is nothing you can do except destroy infested tomatoes; don't put them in your compost pile in case the worms are still inside. Clean up all old plant debris in the garden at the end of the season to reduce the number of overwintering adults. To control the insects during the growing season, spray with the microbial insecticide Bt (Bacillus thuringiensis). This is a very safe and effective insecticide that only affects caterpillars (the larvae of moths and butterflies). You can also use the natural insecticide spinosad. Both of these insecticides are available at garden stores under a variety of trade names; look for the names I gave listed as the active ingredient. Either of these products needs to be applied when the young caterpillars are feeding, before they get inside the tomatoes, and you'll need to make repeat applications during the growing season to control each new generation of pests. Follow the label instructions for timing.

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