Tomato Plant – Where do Hornworms Come From?

Q: My ‘Better Boy’ tomato grew slowly for two weeks, but it is now six feet tall. At one point, green caterpillars appeared, thirteen in a ten day period. How did they know it was here? It’s the only tomato plant around and I didn’t see them marching up my driveway, yet here they are.

A: Hawkmoths, which resemble olive-green hummingbirds, located your tomato by its scent and deposited eggs, which hatched into tomato hornworms. A hornworm can strip a leaf in a day so I’m glad you caught them early. When they are about the size of a green matchstick, they’re difficult to find among the green foliage. They hide near the stem during the day and chew leaves, unseen, at night. I’m told that a college-dorm UV blacklight causes caterpillars to glow brightly in the dark. Try this on your plants and let me know!

hornworm in UV light