What is on my tomatoes?

By Stephanie Hughes

OSU Extension Master Gardener Volunteer

One morning, you are surveying your garden. You are the proud parent of this extraordinary group of plantings that will be delicious come harvest.

Then – Bam! You behold skeletonized leaves on those wonderful tomato plants you have been yearning for all winter. There is a pile of black droppings (frass) on the ground.

As you look closer, you finally see at little monster eating your tomato plants.

It is green with white V-shapes, and a horn on one end. You have met the tomato hornworm.

This caterpillar is an eating machine, but what does it turn into? This is the part that excites me so much. This is the larva of one of 1,100 species worldwide of the sphinx moths.

The tomato hornworm as well as the tobacco hornworm can plague the summer garden, stripping plants of all leaves. The adult is a beautiful, interesting moth that is also called the hawk moth and the hummingbird hawk moth. They are pollinators of many important plants – especially in the Southwest – as they dip their tongues (the longest is up to 14 inches long) and cover their scales that resemble fur or feathers with pollen that they transfer to other plant blossoms.

They hover, go backward, and can fly up to 12 miles per hour as they visit plants every evening or night.

Eggs are laid by the females on the host-specific plant to the species, then they hatch and feed. Tomato as well as tobacco hornworms can infest the garden, usually on tomato plants, but other solanaceae plants are vulnerable – eggplant, pepper, tobacco, tomato, potatoes; four o’clocks, moonflower and jimsonweed (datura) are also in their diet.

After about five instar stages, they drop to the ground and burrow a few inches into the soil to pupate. They emerge as adults in two to three weeks, or over winter into soil to begin the cycle in the spring.

Picking them off the plants is one good way to eradicate them. My husband plants a couple of tomato plants off by themselves for their food, as the adult moths are an important source in the pollination cycle.

Read more about this interesting caterpillar and moth at: http://go.osu.edu/tomatosandmoths.