Are Your Tomato Plants Safe from Pests?

Growing your own vegetables is fun, and much safer than chancing buying a product with Salmonella, which seems to be happening more and more often these days. However, there are certain insects that can make all your hard work disappear in the blink of an eye. If you like tomatoes and have planted some vines, anxiously counting the days until you have your own organic, homegrown ripe tomatoes, you might want to be aware of the tomato hornworm caterpillar. This green monster will eat your plants down to the stems overnight.

The hornworm, Manduca quinquemaculata, is the larval stage of the five-spotted hawkmoth, sometimes called the hummingbird moth. The caterpillars can be as large as four or five inches long! They are very distinctive because they have a curved 'horn' on their back end and are a bright green color with eight v-shaped marks running along its body. They certainly look imposing, but they're not harmful to humans. They have no poisons on their skin and no teeth or stingers. You can pluck them off your plants without any problem. In fact, that's one of the best ways to get them off your tomato vines.

You'll know if you have the hornworms because you can easily see their black, squareish droppings beneath the plant. If you find the droppings, carefully look around the plants and you will see these caterpillars hiding within the foliage. Since they are green, they blend in very well with the leaves, so you might have to look carefully. They eat an awful lot, which means they can strip the leaves extremely fast. And the more there are, the faster you'll lose your crop.
The hornworms can be found in most states in the United States, in parts of northern Mexico and even in Canada. The eggs of the hornworm can be green or white and more or less oval, usually found on the underneath of leaves. The eggs hatch quickly, in about a week, give or take a couple of days. During the winter months, the hornworms go into a pupal stage where they rest in underground burrows until the spring.

Even though they common name is tomato hornworm, they will eat other plants such as potatoes or eggplant. There are natural enemies of the hornworm. The best and most efficient is the braconid wasp. These wasps lay their eggs on the backs of the hornworms. It's an awful thing, but the eggs hatch and eat the hornworm from the inside. If you see a hornworm with the white wasp eggs all over it, leave it alone because you'll want the wasps to hatch and stay close to your garden.

One interesting thing that I personally noticed with these hornworms is that they can emit a very high pitched alert when they are injured. Apparently not everyone can hear this sound because I could never prove it to my father who insisted he heard nothing. I wouldn't do this now because I'm more humane these days, but in my youth I would shoot the large hornworms with a BB gun. Once struck the caterpillar would curl its head down and freeze, emitting the high pitched sound. I noticed that this sound alerted the others nearby. Each caterpillar would stop moving and curl its own head down.

This is a sort of altruistic response that I find very, very interesting. Of course, it makes it harder to find the rest of the caterpillars when they stop moving, the whole point of the response.

You can always use pesticides to get rid of the caterpillars, but it's never good to overdo it around food. Therefore, taking off the caterpillars and disposing of them in some method is probably the best way. Just keep on eye out for stripped leaves and black droppings if you want a healthy crop of tomatoes!