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Tomato started to rot as it ripened

Q. The first tomato in my crop to ripen was rotted. When I picked it, half was gooey and brown. There were two or three tiny white larvae-looking creatures inside it. There were also a couple tiny black bugs. I've got an organic garden. What happened to my tomato? What do I do to prevent this?

A. Tomato fruitworms attack a tomato by tunneling. The pest consumes the tomato’s interior and leaves a cavity filled with fluid, frass, and droppings. The tomato quickly decays and rots. In a word, they are N-A-S-T-Y. Fruit is inedible after a fruitworm infestation.

It's not uncommon to have your plant's first ripened tomato reveal fruitworms. Larvae (worms) attack tomatoes just after fruit begins to set and grow, but before they ripen. They like green tomatoes!

In fact, one way gardeners find fruitworms is to watch ripening. When one tomato ripens considerably earlier than the others on a plant, or even just first on a plant, check it for a fruitworm hole. If you catch it soon (as you probably did), there may be more than one worm per fruit. But soon, they chase each other out of fruit. Worms are cannibalistic and territorial.

Once pests enter fruit, they are protected and cannot be treated. But you can take these organic precautions on the rest of the plant and nearby tomato plants, too:

  • Apply Bt: Bacillus thuringiensis (Bt), a microbial biological control, is considered to be very effective on fruitworms. Bt doesn't harm a majority of beneficial insects. It’s available in liquid, powder, and granules. Follow manufacturer’s directions for application. Treat plants with Bt in the afternoon or evening, since it breaks down in UV light. Apply Bt at the first sign of worm eggs. Once the pests hatch and ingest the chemical, they are paralyzed, unable to eat, and die.
  • Apply oils. Use neem oil or insecticidal soap once a week and after rain.
  • Apply other controls. Treat plants with Spinosad, a natural, broad-spectrum insecticide made from soil microbes.

Find out more about how to identify and control fruitworms.

Good Luck and Happy Gardening!
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