Tomato Hornworm Identification & Organic Control

Question: In my container tomato garden, I found a 1½-inch green caterpillar with hard white rice-like spikes on its body. It's sucking leaf juices, turning leaves brown. What is it?

Answer: Tomato Hornworm Parasitized by Braconid Wasps

The "white spikes" are cocoons of braconid wasp larvae—a beneficial parasite. The hornworm is being eaten alive from inside. Leave it alone! The wasps will emerge and parasitize more hornworms.

Hornworm Basics

• Large green caterpillars (up to 4 inches) with white diagonal stripes and a rear "horn"
• Feed on tomatoes, peppers, eggplants, potatoes
• Camouflage makes them hard to spot
• Chew large holes in leaves—not "suck juices"

Organic Controls

• Hand-pick unparasitized hornworms (drop in soapy water)
• Bt (Bacillus thuringiensis)—sold as Dipel, MVP; non-toxic to humans/pets/beneficials; apply up to harvest
• Available at garden centers or Gardens Alive

Prevention

• Rotate tomato crops yearly
• Till soil in fall to destroy pupae
• Encourage wasps by avoiding broad-spectrum insecticides

White-spiked hornworms are already doomed—let nature finish the job.