The Q&A Archives: Tomato Hornworms

Question: Last friday when I was admiring my garden, I noticed tomato hornworms attacking my beautiful tomato plants. In fact, they made quite a feast of them. I promptly picked off what I could find and sprayed with "Sevin." I also took great pleasure in placing four of the fat, juicy critters in a rusted metal bowl I keep in my garden. (Did you know they dry up to the size of a paperclip?). I was wondering what draws them to my garden, how can I prevent this and what other methods would you recommend for getting rid of the little beasts?

Answer: Tomato hornworms can be 4-5 inches long at maturity, so you may have gotten to them before they were fully grown. Most gardeners react exactly the same way when hornworms are discovered in the garden. Hornworms are the larvae of a large moth (Manduca, with a wingspan of 3 1/2 - 4 1/2 inches). The adult is attracted to tomatoes, eggplant, peppers, potatoes, dill, and various weeds. She lays her eggs on the host plant, the eggs hatch, and the larvae feed and feed. They have voracious appetities and can denude a tomato plant in a day! Handpicking is the best defense. You can use the botanical Bt (Bacillus Thuringiensis), which is a bacterium that acts as a stomach poison, and is quite effective against most caterpillars. The use of Sevin isn't often recommended - it's highly toxic to bees and if you use it on a flowering plant, you'll kill off the good guys as well as the destructive insects. To keep hornworms away from your tomato plants next year, try interplanting dill. (Hornworms like dill and are easier to see and remove on the wispy dill foliage.)

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