Braconid Wasp

📐 FIELD GUIDE ILLUSTRATION

Tomato hornworm (Manduca quinquemaculata) identification illustration with labeled anatomical features — PestControlBasics.com

Original illustration by PestControlBasics.com. Use the labeled features above to confirm your identification.

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PestControlBasics Editorial Team

Reviewed by Derek Giordano · Updated 2026

🔍 Identification

Adults: 2-5mm; small, dark, wasp-like; rarely noticed. Larvae: develop inside hornworm body, consuming non-vital tissues. Cocoons: white, oval, rice-grain-sized; emerge through hornworm skin and pupate externally. Parasitized hornworms: alive but sluggish; don't feed; will die. Found on tomato hornworm and tobacco hornworm specifically.

🧬 Biology & Behavior

Female Cotesia wasps detect hornworm feeding by plant volatile compounds and lay eggs in the hornworm's hemolymph. Larvae develop inside the living hornworm, avoiding vital organs to keep the host alive. When larvae are ready to pupate, they chew through the hornworm skin and spin cocoons on the outside. The hornworm is still alive and may twitch but cannot feed or reproduce. Adults emerge from cocoons and seek new hornworms to parasitize.

⚠️ Damage & Health Risk

Zero negative impact — entirely beneficial. Cotesia congregata reduces hornworm populations throughout the growing season without any spray application.

🔧 DIY Treatment

Leave parasitized hornworms in place — they are the next generation of parasitoid wasps. Remove unparasitized hornworms. Never spray Bt or spinosad near parasitized hornworms — the spray will kill the wasp pupae inside and on the caterpillar.

👷 When to Call a Pro

Never warranted for braconid wasps — protect them.

❓ FAQ

If the hornworm is still moving with cocoons on it, is it a threat to my plants?

No — parasitized hornworms are effectively paralyzed from feeding. They may twitch or move slightly but cannot eat. The white cocoons indicate the braconid wasp larvae have pupated — the hornworm will die as the wasps emerge. Leave it in place and it becomes the next generation of braconid wasps that will find and parasitize more hornworms.

Can I encourage more braconid wasps in my garden?

Yes — plant flowering herbs (dill, fennel, parsley in flower, yarrow) near tomato plants. Adult braconid wasps feed on pollen and nectar from small flowers while searching for hornworm hosts. Reducing broad-spectrum insecticide use allows natural braconid populations to build. Many other parasitoid wasps attack other garden pests — supporting diverse flowering plants supports diverse parasitoid populations.

🐝 Braconid Wasp