If you’ve ever been outside in your garden, coffee in hand, excited to look over your rapidly-growing tomato plants, only to find them appearing as if they just got hit with a swarm of locusts—welcome to the world of the tomato hornworm. They are green, they are plump, and they will completely decimate your tomatoes if you allow them to.
The hornworms start small, but don’t let that fool you. They can grow to be the length of your finger and devour your plant’s leaves quicker than you think. One day your tomato plant is lush and green, the next day it’s a sad row of naked stems. They are the garden version of an identity theft—quiet, sneaky, and pretty darn destructive.
What In The World Are Hornworms?
First and foremost, hornworms are not actually worms. They are also not even an adult worm. These pests are the larval stage of sphinx moths (or hawk moths) and are surprisingly dignified-looking considering they started life as a tomato plant-based carnivore. The hornworms get their name from a little horn-like protrusion at the posterior end of their bodies. It looks intimidating but it doesn’t sting or puncture. It’s just there to creep you out a little.
Hornworms are not aggressive, so they are not going to bite you. They are not even that fast. But they do not need to be. Give them a few hours and they will consume leaves like they are at a buffet. If you are growing tomatoes, they are the worst kind of dinner guest.
Meet the Two Most Wanted: Tomato Hornworm vs. Tobacco Hornworm:
If you live in North America, there’s a good chance you have one—or even both—of these pestering your plants right now. They look similar enough that most people can’t tell them apart at a glance, but there are a few ways to differentiate them.
Tomato Hornworm:
Color: Bright green
Stripes: White, diagonal
Horn color: Reddish or orange
Favorite meal: Tomato plants (but will also eat eggplant and peppers if they are adventurous)
Where: All over the US
Tobacco Hornworm:
Color: Bright green (again)
Stripes: Similarly diagonal, but sometimes nicer and cleaner
Horn color: Black instead of red
Favorite meal: Tobacco plants (but loves tomatoes, peppers, and potatoes)
Where: Again, pretty much everywhere
At the end of the day, it doesn’t make a difference which one you have—both are perfectly capable of ruining your hard work as a gardener.
How to actually spot them
The frustrating part? They are ridiculously good at hiding. You would think a four inch green caterpillar would be a giveaway, but nope, they have the camouflage down. Often you won’t see them at all until you start noticing the damage. So what should you be looking out for?
Leaves disappearing. Entire branches are stripped clean, sometimes overnight.
Droppings. Little dark pellets you find on leaves, or on the ground below—they’re disgusting, but helpful for locating them.
Them. If you look carefully (and squint a little), you will start to see their pudgy green bodies extending along a stem or upside down on a leaf.
They like to eat in the shade during the hottest part of the day, so the best time for detecting hornworms is early morning or late afternoon.
How to Get Rid of Them (Without Burning Down All Trials Gardens)
So you have seen one. Or five. Now what?
Hand-Picking:
Yup, that’s exactly what it says. Put on some gloves, get a little container, and go full hunter-gatherer. Grab them gently (they won’t fight back, just hold on tight with their little feet) and toss them into a bucket of soapy water or take them far from your tomatoes. If you don’t have a total infestation, this is actually the quickest and most reliable way to deal with them!
Get Help: The True Insect Friends
Braconid Wasps: There are little, parasitic wasps which lay their eggs on the hornworms. Do you see hornworms with little rice (sort of) looking shapes on its back? Leave it! That hornworm is dead and they are doing your dirty work.
Ladybugs & Green Lacewings: They go after the eggs and smaller caterpillars. You can encourage them with planting some of the following herbs close by: dill, fennel, yarrow.
Birds: Chickadees, sparrows, and robins love to snack on hornworms. Get a bird feeder or add a birdhouse to your garden to get some feather friends interested in potential hornworm brunch.
Tilling
A little less dramatic but just as effective. Tilling your garden at the end of the season, or really, even in the early part of spring can kill hornworm pupae waiting to unleash themselves from the ground and unrelentingly destroy the leaves above them. While not ideal, disturbing the hornworm lifecycle and killing a bunch will lower their population levels before they dominate the growing season.
What’s the Best Management? Be Constantly Vigilant (and maybe at night)
Tomato hornworms don’t want to be seen. But if you make it a habit to check your plants every day, you usually spot these pests early on. And when you recognize the signs—chewed leaves, little poop pellets, sudden lack of tomatoes—you will get better at spotting these nasty bugs more quickly.
If you want to get really into it, there are gardeners who claim to do a night time inspection with a UV flashlight. Hornworms glow under uv light slightly, which is either cool or horrendous depending on your target perception of glowing bugs.
Let’s face it, hornworms are disgusting, invasive, and oddly good at hiding—and not invincible. If you catch them sooner rather than later, their damage is significantly less. Hand-picking, surrounded by helpful bug friends, and some bird recruitment can keep hornworms off your tomato plants and ensure a productive harvest.
Just don’t ever turn your back on them. Ever.
