Hornworm

The hornworm gets its name from the spike on its tail end. The red “horn” indicates a tobacco hornworm, which likes tomato plants just as much as tobacco plants.

Leaving the mid-summer forest to the hungry, biting deerflies, I spend more time mowing fields or watering and weeding the vegetable garden. Like the forest, the garden provides a miniature ecosystem to study, tend and from which to learn.

Dave Anderson Forest Journal sig

As a naturalist, I try to appreciate and understand ecological niches filled by all plant and animal life. Even slimy or creepy-crawly critters have some redeeming purpose. Spiders, snapping turtles, snakes, bats, black flies, mosquitos — even parasites like ticks — are all animals with bad reputations but they surely serve a purpose in nature.

Noxious plants — poison ivy, for example — have evolved camouflage, spines, thorns or clever chemical defenses to colonize challenging habitats, repel grazing animals or attract specific pollinators.

So it becomes difficult for me to explain why a few particular creatures make me squeamish and even queasy.

Here’s my list of things I hate to handle: huge hairy spiders, snakes that tend to coil and strike, and large writhing green worms.

That’s it. Just three. But each is capable of making me wobbly in the knees, particularly if I am not prepared for an encounter. I try not to show it, but then my voice cracks.

Cue the sci-fi theme music for this annual garden “harvest” in the midst of summer weeding and watering. Picking hornworms from our tomato plants takes me from shudder to shrieks if they latch on. I know it’s irrational, but they are gross!

Tomato hornworm caterpillars and their closely related cousins, tobacco hornworms, are huge, ornate, beautifully patterned — and repulsive. Most gardeners agree: Picking bloated green worms off the tomato plants takes grit.

Failure to remove hornworm caterpillars guarantees the plants will be completely defoliated in days. But picking caterpillars is not optional if you want delicious, sun-ripened backyard tomatoes.

Hornworm

A tobacco hornworm makes its way to a leaf on a tomato vine, preparing to tuck into one of its favorite meals.

The two related hornworm caterpillars are the larval stages of two different hawkmoths. Tomato hornworms mature to become five-spotted hawkmoths. Tobacco hornworms (also called “goliath worms”) become tobacco hawk moths, aka “Carolina sphinx moths.”

These larval hornworm caterpillars feed exclusively on tomatoes, eggplants, peppers, tobacco and potato plants — members of the “nightshade” plant family that includes other plants that produce toxic alkaloids including “deadly nightshade.”

Research suggests tobacco hornworms are more common in the South, not surprisingly, while the tomato hornworms are more prevalent in the north. But a colleague who has trapped and released more than 800 moth species this summer using an UV light and funnel trap shares that “looking at where people have reported seeing tobacco hornworm moths, there are plenty of sightings in New Hampshire and into Canada. The moth field guide range maps make it seem like they are occasional or even uncommon in northern New England but clearly that is not the case.”

I collected 30 fat green caterpillars from our tomato plants over two days. All of them were tobacco hornworms.

Both hornworm species feed on tobacco or tomato plants, so the host plant isn’t an indicator of which caterpillar it is. Both have a prominent horn on their rear end, hence their name. Tobacco hornworms have red horns and tomato hornworms have dark blue or black horns. Tomato hornworms have eight V-shaped white markings. Tobacco hornworms have seven white diagonal stripes with a black border. An internet source suggests remembering parallel white stripes look like tobacco cigarettes and the “V-” is for “vine-ripened.”

The caterpillar life cycle takes 30 to 50 days. Larvae hatch from eggs laid by adult moths in early summer and develop through five different body stages called “instars.” They continue to feed until late summer, when they drop off plants to burrow into the soil to form a pupa that overwinters underground. Large, ornate gray moths emerge the following spring to sip nectar, mate and lay eggs one at a time on the leaves of their preferred host plants.

I interrupted that life cycle. My photo collection of fat, finger-size wriggling caterpillars amused or horrified Facebook friends. I made a video showing how to remove them from a tomato plant starting with the posterior “horn” end. When the squiggly tiny front legs and mouth parts clasped at my finger, I squealed. Intrepid naturalist?

Online friends suggested caterpillar disposal strategies — put them in a zipper plastic bag and leave in the sun or place in the freezer, squish them or even obtain a military flame-thrower? Memes appeared ranging from “Game of Thrones” dragons to William Hurt in the movie “Aliens.” One friend provided a recipe for “fried green tomato (hornworms).” Appetizer anyone? No thanks.

I used to feed the caterpillars to our backyard chickens, which wasted no time consuming them. It was very satisfying to convert pests to fresh eggs. But there are no more chickens on our farm; the myriad predators made it impractical. So I added the bumper hornworm harvest to the lily pond — a water feature complete with a solar-powered fountain, an elegant setting.

Most of the hornworms drowned, but a few wriggled onto the lily pads and drew the attention of resident frogs. One frog made a huge meal of a hornworm nearly its own size! I figure at least there is virtue in recycling. No word on psychoactive frogs, but if I start finding more frogs in the vegetable garden, I’ll know why.

Naturalist Dave Anderson is senior director of education for the Society for the Protection of New Hampshire Forests. Contact him at danderson@forestsociety.org.