Tomato Hornworms and Parasitic Wasps
After squirrels and deer, the tomato hornworm may be the bane of a tomato grower’s existence. Fortunately, tomato hornworms and parasitic wasps go together like tomatoes and basil. Finding a tomato hornworm in your garden is not the end of the world if you catch them early, and if you employ natural gardening techniques, they garden is brought into balance by bracondid wasps.
Here’s a tomato hornworm in my urban garden happily munching away on the foliage of one of my tomato plants. This caterpillar get’s its name from the vicious-looking horn at one end of the body. In this photo of the hornworm, you can see the horn on right side. This caterpillar, should it be allowed to live, pupates into the five-spotted hawkmoth–a brown and gray hawk moth–in the Sphingidae family.
Identifying Tomato Hornworms
It took years of gardening before I ever spotted a tomato hornworm in my garden. And when I finally did see them growing on my tomato plants I wasn’t upset. On the contrary, I was rather excited to see this garden pest in my garden. I like bugs, and bugs happen when you garden. If you’re hunting hornworms on your plants the first sign you may see is the caterpillar’s poop. For a rather small bug the hornworm leaves behind some rather large poop trails. They look a little like mouse droppings and you’ll see them on the leaves of your tomato plants, or if you grow tomatoes in containers, you’ll see a lot of them on the ground around your pots. Tomato hornworm poop is really hard to miss.
A parasitized tomato hornworm in my garden this year. Notice the the tomato hornworm is covered with cocoons of pupating braconid wasps. The braconid wasp is a parasitoid of the hornworm because it kills the hornworm as it pupates. If you look closely, you’ll see a drop of something emerging from the left side of the caterpillar and from among the cocoons. I’m not sure if the secretion is something the caterpillar does normally, or if it’s occurring because of the wasp eggs. But this year I noticed a high presence of wasps on my tomato plants and after observing them, they seemed to be drawn to the sticky secretion. So a high number of wasps and bees on your tomato plants is another sign to look for when identifying and locating tomato hornworms on your tomatoes.
Eliminate and Control Tomato Hornworms
Don’t go with your instinct and reach for any bug sprays or synthetic chemicals if you spot tomato hornworm damage on your plants. You are, after all, going eat those tomatoes at some point. Instead, pluck off the hornworm by hand and dump them into a bucket, pail or glass of soapy water. Alternately, you cut them into pieces and feed them to birds that visit your garden, or see if your backyard chickens would like a fat, juicy treat. Some chicken growers I’ve talked to said their hens turn their nose up at the hornworm, but the chickens and roosters that live in the parking lot of the laundromat I use seem to love them.
My absolute favorite method of controlling hornworms on my tomato plants is to save a few of these caterpillars and let nature take its course. Pull the hornworm from your plants and place it inside a jar or plastic bottle without a lid to allow for ventilation. Every couple of days add a few tomato cuttings to the container to allow the caterpillar to continue to eat. And then sit back and watch as the hornworm is eaten from the inside by the pupating parasitic wasps. It’s so disgusting, but it’s so much fun to watch. This has the added benefit of ensuring that there will be parasitic wasps around your garden the next season to help you eliminate and control tomato hornworms on your plants.
How do you handle the tomato hornworms in your garden? Do you pluck them, or do you leave them for the parasitic wasps to devour?