What are some of the clues that gardeners can use to search and destroy this worm? The easiest sign is to look for their feeding activity. Tomato limbs stick out like a sore thumb with 90% of their leaves missing. The easiest way to locate hornworm feeding activity is to use a piece of white paper held against the plant. The caterpillar can reach lengths of 4 inches and half-inch wide in the last instar. But as they go through their numerous growth stages (instars), the feeding intensity increases. In addition, they perfectly blend into the surrounding foliage with their green bodies with white diagonal stripes on the sides. The damage from their small chewing mouthparts is easily missed. The female moth lays eggs on the underside of the leaves in early summer and small little larvae hatch out and start to feed shortly thereafter. For most gardeners, their activity goes unnoticed at first. While the insect does not have a wide host range (as in the children's story), it does have a huge appetite. It can reach lengths of 4 inches and half-inch wide. The tobacco hornworm is identified by its' red 'horn' on the back end and white diagonal markings on the side. There is also a tomato hornworm, but its 'horn' is black and the white markings are 'V' shaped. Another characteristic ID is the white diagonal markings on the side. The name pertains to the red 'horn' on the back end.

A very similar story occurs in our vegetable gardens as a large caterpillar, the tobacco hornworm, devours sizeable portions of tomato plantings.

Download green horned tomato worm