Green Caterpillars on Petunias: Hornworm Control with Bt

Identifying and Controlling Petunia Hornworms

Bright green caterpillars (tiny to 1 inch) eating buds and flowers on your 'Easy Wave Blue' petunias in Brooklyn—these are tobacco hornworms (Manduca sexta) or related species. They blend perfectly with foliage.

Safe, Effective Control: Bacillus thuringiensis (Bt)

• Bt (sold as Dipel, Thuricide, MVP) is a bacterial spray toxic only to caterpillars.
• Non-toxic to humans, pets, bees, birds.
• Apply to foliage (especially undersides) when caterpillars are small.
• Reapply after rain. Can use up to harvest on edibles.
• Available at garden centers or Gardens Alive.

Supplement with Hand-Picking

Check daily at dusk. Drop caterpillars in soapy water. Combined with Bt, you'll achieve near-perfect petunias.