How to Rid Your Garden of Tomato Hornworms
When I was a child, I was not afraid of insects and snakes. It was not uncommon for me to capture specimens and bring them home with the intention of keeping them as pets. In an effort to keep me from bringing home tomato hornworms, my father told me not to touch them because they would sting me, pointing out the large stinger on the rear of their bodies. That stinger looked huge and terrified me. I gave tomato hornworms a wide berth after that.
Know Your Enemy
The tomato hornworm is probably the largest caterpillar that you will find in your vegetable garden, measuring as large as 5 inches long. They are green with markings in white and black and sport a horn on the rear of their bodies. They do not sting, however.
Tomato hornworms are the larval stage of the sphinx moth, commonly referred to as the hummingbird moth because of its resemblance to hummingbirds both in body type and how they fly and sip nectar from flowers. The moths pupate in the soil over the winter, emerging in the spring to lay their eggs on your solanaceous plants, including tomatoes, eggplants, peppers and potatoes. They eggs hatch within 5 days and the resulting larvae, the tomato hornworms, then spend the next 4 to 6 weeks gorging themselves on the foliage of your solanaceous plants before they burrow into the soil and spend the winter inside of a cocoon. In warmer climates, the larvae will stay in the soil for 2 to 3 weeks creating the possibility of a second generation during the growing season.
Pick Your Own
Damage from the tomato hornworm is easy to spot, however finding the larvae themselves is a little more difficult because their coloring and markings act as an excellent camouflage. Look for their green droppings in the tops of the leaves. The hornworms will be on the bottoms of the leaves. Then you can simply pick them off the leaves (remember they don't sting despite the scary horn) and either squish them or if you are squeamish, drop them into a bucket of soapy water.
You can prevent the moths from laying their eggs on your plants by interplanting dill or borage amongst your solanaceous crops. The moths don't like them, and will fly off to your neighbor's garden to lay their eggs.
The Enemy of My Enemy Is My Friend
Beneficial insects are a big help in controlling pests in your garden. Attract them with flowers and herbs that have tiny blossoms. Brachnid wasps will reward you by laying their eggs on the tomato hornworms they find on your plants. Those eggs will hatch and the larvae will feed on the hornworm, killing it. If you see a tomato hornworm sporting what looks like grains of rice, leave him alone. The "rice" is actually the eggs of the brachnid wasp and that hornworm is a "dead man walking".
A deep tilling in the fall and then again in the spring will kill up to 90% of the pupating larvae in your garden. That means many fewer moths laying eggs in the spring.
© 2014 Caren White