If you can get past that "yuck" factor, they're actually quite fascinating. Next year, we will try to raise ours inside in a butterfly house inside – away from the braconid wasp. I'll keep you posted.
Research and Photos by Renee C. Brannigan
THE GOOD: Hummingbird Moth
Hummingbird Moths are smaller even than tiny hummingbirds. A joy to watch, they have similar mobility and proboscis as a hummingbird. One buzzed past me in the garden. It's larger than a Carpenter Bee, but smaller than a Hummingbird. Sphinx moths (Sphingidae and aka hawkmoth or hummingbird moth). Like Hummingbirds, their long proboscises are key pollinators of deep-throated flowers. They can also hover, and hum like hummingbirds. Strangely, their fanned tail strongly resembles a lobster tail.
THE BAD: Hornworm or Braconid Wasp?
A few clicks later, we had a visual of the suspect who had stripped the leaves on the branches above the scat.The next morning, we fully understood why Hornworms evoke shudders from most gardeners – their insatiable appetite for our beloved tomato plants.
We clipped the branch they were on (often half eaten) and filled a giant jar with tomato branches (mostly suckers).
You may be thinking like we did, “Get those things off my tomato plants.” Until I learned that hornworms grow up to be Hummingbird Moths!
Okay, they are really bad if you LOVE your tomato plants, and don't want to share. They have voracious appetites. During my research, I came across a brilliant suggestion to create a Hornworm Haven, ideally located next to the compost bin. In this spot you will toss inedible tomatoes and all plants in the Solanaceae family that are great hosts for Hornworms: tomatoes, peppers, potatoes, and eggplants and flowers like petunias and Nicotiana. Next year, whenever you find a hornworm, clip the leaf or branch they are attached to (they have a good grip and squish easily) and relocate it to Hornworm Haven, a foster home for hungry Hornworms.
Hornworms are one of the biggest caterpillars I've seen, up to four inches long. By the way, this variety of hornworm is called “tobacco hornworms” (Mancuda sexta). Many New England gardeners call these creatures “tomato hornworms” (Manduca quinquemacula). It is confusing, since we find them on tomato plants, and we don't grow much tobacco in these parts. The physical differences are slight, but only the Tobacco Hornworm lives East of the Mississippi and has diagonal white stripes (versus the tomato hornworms v-shaped white markings on its sides) and its red "horn" (the others' are black or dark green).
One of the most common parasites in home gardens is a small, parasitic braconid wasp. It lays eggs on the Hornworm, the wasp larvae feed inside the hornworm, eventually killing it. The cocoons containing the wasp pupae looks like grains of white rice. When you find a hornworm in this condition, putting it into warm soapy water to put it out of its misery.
Most of the tobacco worms we observed had been victimized by the parasitic Braconid Wasp. Within a day or two, they developed what looked like a coat of grains of rice. A wasp lays eggs on the hornworm. When the eggs hatch, the larvae will make a meal of the hornworm. Each Braconid Wasp can make a huge impact in the local hornworm population.