University of Illinois Extension

University of Illinois Extension

Hort Answers

Insect Damage


3 (1 = rare 5 = annual)
4 (1 = very little damage 5 = plants killed)

Plants Affected

Tomato hornworm are heavy feeders and 1-2 worms can defoliate a five-foot tomato plant in less than three days.

Life Cycle
Tomato hornworms overwinter as pupa in the soil and become more active in July. The adult is a large moth, which lay pale green eggs on the underside of the leaves. The larvae are green with eight white stripes and have a horn on their tail end.


Predatory bugs and parasitic wasps do attack the larvae (Look for white cocoons on the body of the hornworm - do NOT kill the parasitized hornworm as that also reduces the number of future predators on the hornworm.), and helps keep hornworm populations under control. For none parasitized larva, physically remove the larva from the leaves and crush them by stepping on them. Farmers should monitor the moth using blacklight trap and spray with insecticides recommended in your state.

Related Resources
Home, Yard & Garden Pest Guide
Illinois Commercial Landscape and Turfgrass Pest Management Handbook
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic