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My tomato plants have big ugly worms on them. What are they and how can I get rid of them?
- Oakland, OR
These big ugly worms are the infamous tomato hornworm, which develops into a giant, alien-like caterpillar. While they may be quite destructive and shocking to look at, they are quite stunning in their own right and a thing of beauty when the eventually pupate into their adult form, which is a hummingbird-like sphinx moth. But that’s besides the point!
The best and most highly effective methods that are nontoxic to pets, humans and the environment are as follows:
- Hand pick the caterpillars with gloved hands and kill them by tossing them into a bucket of soapy water. But look before you toss: leave caterpillars alone that are studded with small oval cocoons on their backs. These house braconid wasps that will use the hornworms as hosts.
- Encourage parasitic wasps by growing yarrow, parsley, dill or other plants with an umbrella-shaped flower head, and by growing flowers in the daisy family, such as rudbeckia, echinacea, asters, cosmos, zinnias, coreopsis, and marigolds. Two tiny wasps that prey on hornworms are the braconid wasp and the trichogramma wasp; both of which can also be purchased online and then released into your garden.
- Look for a product with bacillus thuringiensis (Bt), an organic, spore forming bacterium that is toxic to caterpillars. You can buy it online or at most any garden center.
Here’s to a healthy harvest of fresh-from-the-garden vine-ripened tomatoes!