What’s Eating My Tomato Plants?

What’s Eating My Tomato Plants?

Is the foliage of your tomato plant disappearing at an alarming rate? If the plants are small it might be woodchuck or deer damage, but if the plants are taller, an insect may be responsible. When the leaves at the top of the plant are being stripped but the stems left in place, you probably have tomato or tobacco hornworms. These large larvae consume tomato, pepper, potato and eggplant leaves quickly and they can grow up to 4″ long. They can also be hard to spot because they are bright green, so blend in well with tomato foliage.

One telltale sign that you do indeed have a hornworm is the presence of dots that look like course, black pepper on the foliage underneath the damaged leaves. This is frass, or hornworm droppings. If you see this, look for the hornworms underneath leaves above…don’t bother looking on the stems that are already stripped as the worm has finished feeding in that area and moved on.

The tobacco hornworm (Manduca sexta) looks similar to the tomato hornworm but this larvae has seven stripes and a slightly curved horn that is reddish in color. The tomato hornworm (Manduca quinquemaculata) has eight stripes and a straight horn that is almost black. Both are quite beautiful but very destructive in the vegetable garden.

Although a spinosad-based product such as Captain Jack’s Deadbug Brew works on the hornworm, it’s usually faster to hand pick this pest whenever possible. Some people smash them with a garden tool, others put them on the bird feeder for the crows, and many toss them into the woods. If you see a hornworm that has what appears to be tiny grains of white rice on its back, leave it in the garden. Those are the eggs of a parasitic wasp, nature’s way of keeping the hornworm in check!

This group of tobacco hornworms were stripping the leaves on tomato plants in a Cape Cod garden. They were fed to Cape Cod crows.

Here is a plant that was almost completely stripped by the hornworms. If this happens to you, find and destroy the larvae and feed the plant with a mild application of organic fertilizer to jump-start the production of new foliage.

If you see a hornworm that has these parasitic wasp eggs on it, leave the worm and eggs in the garden. This is nature's way of keeping pests in balance.

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