Halting Tomato Hornworms with Bacillus thuringiensis

Hornworm - Maureen Gilmer
Hornworm Caterpillar

Tomato hornworms arrive at night as gossamer-winged moths that lay their eggs on your carefully cultivated tomatoes. Hatchlings quickly grow to enormous green caterpillars that can decimate a plant overnight.

Inspect new growth daily for these voracious caterpillars. Hand pick them promptly and discard before they feed on the fruit itself.

Another option is to spray the plants with BT (Bacillus thuringiensis). This safe, non toxic, control is approved for organic gardening. Once BT is on the leaves, worms eat it and get a fatal belly ache. This natural spray is one of the greatest success stories in organic horticulture. You’ll find it in garden centers and home improvement stores wherever Black Gold products are sold.

Hornworm Adult

About Maureen Gilmer

Maureen Gilmer is celebrating her 40th year in California horticulture and photojournalism as the most widely published professional in the state. She is the author of 21 books on gardening, design and the environment, is a widely published photographer, and syndicated with Tribune Content Agency. She is the weekly horticultural columnist for the Desert Sun newspaper in Palm Springs and contributes to Desert Magazine, specializing on arid zone plants and practices for a changing climate. She works and lives in the remote high desert for firsthand observations of native species. Her latest book is The Colorful Dry Garden published by Sasquatch Books. When not writing or photographing she is out exploring the desert on her Arabian horse. She lives in Morongo Valley with her husband Jim and two rescue pit bulls. When not writing or photographing she is usually out riding her quarter horse.

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