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A Complete Guide to Tomato Hornworm Caterpillars

A Complete Guide to Tomato Hornworm Caterpillars

You’ve worked hard on your tomato patch. The plants are staked, the soil watered and suckers pruned. Now you sit back and wait for the fruits of your labour to produce summer’s favourite bounty. A juicy and delicious tomato!

However, the scenario isn’t always this perfect.

If you’ve noticed your plants looking chewed on, stems stripped and fruit damaged, you may have a predator on the loose. In the case of your tomato patch, that predator may be the ghastly Tomato Hornworm Caterpillar!

Read more to help you identify this shocking predator and learn how to get rid of it.

A Complete Guide to Tomato Hornworm Caterpillars

Potato bed – I thought it was ready for harvesting, then I took a closer look and found 5 more Tomato Hornworm Caterpillars!!

The other day in the garden was a beautiful day! The sky was clear, the birds were chirping, I could hear the owls hooting in the background. It was nice and warm. The perfect day to spend some time in the garden.

I hadn’t watered the garden in a while, so I started on the carrots. As I moved along the garden, through the zucchini and squash, I turned towards the potatoes. What I saw next almost knocked me over!

Gardening Tip: For more information on proper watering techniques, please read my post “10 Ways to Properly Water Your Garden“.

It was thick, green and stripy, with a pointy blue horn on one end! I recognized it immediately. It was a TOMATO HORNWORM CATERPILLAR! I almost fell over in surprise!

I’d heard the nightmare stories about these creatures, but I’d never really experienced one in person. This one was four inches long and about half an inch thick! It was huge and it was eating my potato plant!

A Complete Guide to Tomato Hornworm Caterpillars

First tomato hornworm found and branch ripped off potato plant! About to take this caterpillar to the chickens.

Earlier that day, I noticed half the potato bed had died back and turned yellow, but I hadn’t thought anything of it. I just figured that the potatoes were ready for harvesting. So this tomato hornworm really surprised me.

My next thought was, “How many more are there??

I ripped off the first branch, with tomato hornworm in tow. There was no way I was touching it! I decided to bring this creepy crawly to my chickens. I was sure they would attack it! However, only one of them responded.

I then headed back to the garden and proceeded to look for more. Grabbing a basket, I looked over the dying side of the potato bed. I quickly found five more large-sized tomato hornworm caterpillars! My skin was crawling! Upon further inspection, I collected 10 more!

What are Tomato Hornworm Caterpillars?

A  Complete Guide to Tomato Hornworm Caterpillars

A younger and smaller Tomato Hornworm Caterpillar.

The tomato hornworm caterpillar is the larvae of the Five-Spotted Hawk Moth. The largest moth in the garden! This moth has a two generation life cycle in one season. In the spring, moths emerge from overwintered locations in the soil. Female moths mate and deposit their eggs singly, on the lower and upper leaf surfaces of different plants. After two days, these eggs hatch and baby caterpillars begin to feed on the plant foliage. The larger they get, the more vigorously they eat. As they grow, they develop eight, white ‘v-shaped’ markings on the sides of their body. These markings assist them in camouflaging into the tomato foliage. They also develop a spike or “horn” on the tail end. For tomato hornworm caterpillars, this horn is dark blue in colour.

Within 3 to 4 weeks, the caterpillar will have reached its full size of four inches and will drop off the plant and burrow into the soil to pupate. Two weeks later, a moth will emerge from the soil and begin its second generation. This is typically around mid-summer. By early fall, caterpillars are fully grown and will pupate in the soil until the following spring.

What to look for on your plants?

A Complete Guide to Tomato Hornworm Caterpillars

Tomato Hornworm Caterpillar poop on the leaves.

This is what I’ve learned in my experience:

  1. Caterpillar poop on the plant leaves and soil below. The poop is a small dark green or black chunk, a few millimetres in size. As the caterpillar grows, their poop grows with them and becomes wider and longer.
  2. If you listen carefully, you can hear a faint clicking sound. I noticed this noise with the first caterpillar I picked off. It was chewing on the leaf as I was making my way to the chicken coop. It’s very faint, but if you hear it, you will know there are hornworms on your plant.
  3. Hornworm caterpillars dislike the sun and heat of the day and will typically hide on the lower leaves of the plant. I have found it easier to spot them in the early evening when they emerge to the upper parts of the plant. However if you can’t wait (and I can’t and want them off ASAP!) look a little lower into the plant and on the underside of the leaves.
  4. Look for signs of destruction. It’s harder to find damage when the caterpillars are small. However, once they grow, they will have chewed off the tops of the plant. Look for plant damage and you will know there are hornworms living on that plant.

* If you follow these steps and in this order, starting with trails of poop, you will have a better chance of finding them.

What do Tomato Hornworm Caterpillars eat?

Tomato hornworm caterpillars feed on tomato and other Solanaceous plants, such as potato, eggplant, pepper and deadly nightshade. However, I found two on my grape vine and callaloo weeds. I’ve read that they may even eat collard greens.

What to do to get rid of them?

Your first line of defence is to be vigilant daily and search through your garden. Once tomato hornworm caterpillars are present, they are difficult to get rid of. You need to keep a close eye on all your Solanaceous plants for any of the above mentioned 4 signs.

If you do find them, here’s what you can do with them:

  • Remove hornworms from leaves, or cut the leaf off with the hornworm.
  • Either step on the hornworm, cut it in half or feed it to your chickens.

*On a positive note:
If you find a hornworm caterpillar with white eggs on its back, resembling grains of rice, leave it alone. These are the eggs of the Braconid wasp. The larvae that hatch from these eggs will feed on the inside of the hornworm caterpillar, until they are ready to pupate. These wasps are beneficial for the garden and will seek out and feed on other hornworm caterpillars.

A Complete Guide to Tomato Hornworm Caterpillars

Tomato Hornworm Caterpillar poop on the plastic mulch beneath the tomato plants.

How to Prevent Tomato Hornworm Caterpillars in your Garden?

Since tomato hornworm caterpillars pupate and overwinter in garden soil at the end of the season, clean up all garden debris and turn over your soil at the end of the season and again in the very early spring.

Any pupated moths are hidden in the top 2-3 inches of the soil. Once they pop up, remove and destroy them.

This method removes a majority of any overwintering cocoons.

I hope this information will help you in your vegetable garden. Although a lot of work, diligence is best. Check your garden every day, and carefully scan through your plants. Evening is the easiest time to find them. Use a flashlight for help. They can be caught and your plants will recover. Patience will bring you success and a delicious bounty at the end.

If you’ve dealt with tomato hornworm caterpillars and have additional tips, I’d love to hear from you. Please leave me a comment below.

Good luck and happy gardening!


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Julia Dimakos

Hi, I'm Julia from Mono, Ontario, Canada. I began my gardening adventure after having children. Since then, my interest grew into a passion. I love growing vegetables, herbs, flowers, fruit and medicinal herbs. I'm here to show you that growing your own food is not difficult and in fact can be simple.