I finally have started getting some tomatoes from my garden. Much to my dismay, I found worms coming out of a couple of the tomatoes. What is going on in my garden?
— Erica Peterson, Lincolnshire
It sounds like you have tomato fruitworms to contend with in your garden. I haven’t seen these pests in the tomatoes in my garden at home (our dachshunds eating ripening tomatoes have been a bigger issue for me). Tomato fruitworms are caterpillars that bore into tomatoes and other crops, which in turn causes damage and then leads the fruit to rot. This pest makes neat, round holes in the fruit, and its feeding in the fruit causes damage, leading to internal rot. The feces it leaves in the fruit are very unappetizing. The caterpillars can be green, brown, pink or even black, and generally make entrance holes in the fruit near the stem. You may see light-colored stripes along their sides.
To control them, start by inspecting all the fruit on your plants and disposing of any that are damaged. Then inspect the plants for the eggs, which are small with a creamy white appearance when first laid and develop a reddish-brown ring shortly before the larvae hatch. Tomato fruitworm eggs are small — around 0.5mm — and have a flattened base. The eggs are singly laid, spherical in shape with a ribbed appearance. They are often near flowers. Crush the eggs as you find them.
You can apply sprays containing Bacillus thuringiensis (Bt) to the plants. This is a biological insecticide that is effective against caterpillars. I would suggest that you check your tomatoes carefully before taking a bite out of one for the rest of this gardening season.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.