What is a Tomato Hornworm?
Anyone who has ever grown tomatoes will have, at some point, encountered the dreaded hornworm. This pest just doesn't care how hard you worked on your prize-winning tomato garden. Able to do incredible damage to your crops before you even spot them, both the tomato hornworm (Manduca quinquemaculata) and the tobacco hornworm (Manduca sexta) will also feed on other plants in the nightshade (Solanaceae) family: eggplants, peppers, tobacco, and potatoes. Despite their large size, hornworms are often difficult to spot because of their protective green coloring (you usually don't see one until you reach in to pick a tomato), and willfeed non-stop, uninterrupted, leaving in their wake a host of frustrated gardeners and a mess of chewed and stripped stems and leaves.
How to Identify a Hornworm
If you have never seen one of these creatures, here is what to look for: Probably the largest caterpillar you will ever see in your vegetable garden, a hornworm can grow to 3-4 inches long. Both types of hornworms are green in color and, for inquiring minds who want to know, the tobacco hornworm has parallel white stripes with black spots and a red horn on the tail, and the tomato hornworm has white v–shaped markings and a black horn ( no worries – neither hornworm stings or bites). Adult hornworms, often called sphinx or hawk moths, are large, heavy-bodied moths with a wingspan from 4-5 inch in width. They are gray or brown in color with white zigzags on the rear wings and orange or brownish spots on the body. These moths can fly quickly and hover like a hummingbird.
The Lifespan of a Hornworm
In late spring, large adult moths lay eggs on the undersides of foliage, which will hatch within a week. Caterpillar larvae will feed for 4–6 weeks before creating a cocoon, overwintering in their pupal state in the soil. If the weather is warm enough, larvae may only burrow for as little as 2–3 weeks. Moths will emerge in the spring, then lay eggs, and the cycle continues. In warmer climates, more than one generation a year may be possible - wonderful news for gardeners in the very warm, humid South.
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Go on Patrol to Protect Your Tomatoes
If you are serious about having a healthy garden, you need to spend time every day checking your plants for signs of hornworm infestation. Hornworms usually start feeding from the top of the plant, so look for chewed or missing leaves. Look at the top of tomato leaves for dark green or black droppings left by the larvae. Look for droopy, wilted leaves or stems that are missing leaves. Tip: If you have seen droppings but can't find the caterpillars on the leaves or ground, spray the foliage with water. The caterpillars will wiggle about and give away their hiding spots. If you have a small garden, handpicking is the best way to remove tomato hornworms. To destroy them, drop them into a bucket of soapy water or feed them to your chickens if you happen to have a flock. If you have a very large tomato garden and can't control hornworms, check with your local extension agent or a trusted nursery to determine the best pesticide to use.
Be Proactive and Plan Ahead
To keep hornworms away from your tomato plants next year, decide to interplant with borage, basil, and marigolds. These plants not only attract bees and other beneficial insects, but their chemical makeup is thought to repel the hornworm. You can also use birds to help with the organic control of pests. While the human eye can't always spot the hornworm, especially when it is small, sharp-eyed birds can find them and pick them off for you. Place small feeders around your tomato plants to attract birds to your garden; the birds will then spot and happily devour any hornworms or other harmful pests munching on your vegetables.