Tomato Horn Worms

The Tomato Horn Worm and/or Tobacco Horn Worm are very similar in appearance. Tomato hornworms have eight V-shaped marks on each side and a blue-black color “horn”. Tobacco hornworms have diagonal white stripes and a red “horn.” These hornworm caterpillars are pretty small at first and hard to see because of their pale green color, but they become huge – 3 1/2 to 4 inches (7-10cm) in 3-4 weeks. You can’t miss them then!

tomato hornworm larva tobacco hornworm larva
Tomato Hornworm-(left) Paul M. Choate – University of Florida, Tobacco Hornworm-(right) Colorado State University,

Tomato/Tobacco hornworms are the larval stage of a huge moth called five-spotted hawkmoth, sphinx moth, also known as hummingbird moths. Approximate size of the moth is around the size of a hummingbird so you can’t miss them. The hawkmoth is gray-brown with yellow spots on the sides of their body. Hornworm eggs are green and are laid on the underside of leaves.

Five-spotted hawkmoth Tomato Hornworm Pupa (Cocoon) hornwormegg_1.jpg
Five-spotted hawkmoth (left)-Floridagardening.com, Hornworm Pupa (cocoon), Hornworm Egg (right)-Colorado State University

Hornworm Lifecycle
The five-spotted hawkmoths lay their eggs as soon as they mate after hatching. They appear in late June to August. Full grown larva (3-4 weeks feeding) wander around the garden digging themselves in where they form a pupa (brown and about 3cm long) that overwinters and hatches in the spring.

hornworm4_1.jpg
Hornworm Damage-Floridagardening.com

Hornworm Damage
Tomato Hornworms feed on leaves and stems of tomato plants. Ocassionally they will also eat the fruits later in the summer months. They also feed on peppers, eggplant and potatoes. They can defoliate a plant in just a few days. There can be two generations of tomato hornworms every year. A bunch of them can spell disaster in your garden!

How To Control Tomato Hornworms

  1. Use a liquid Bt spray like Green Steps Caterpillar Control
    Bt (Bacillus thuringiensis) does not harm animals, people or the environment. It paralyzes the horn worms and they die from starvation. Spray the top and bottom of the tomato plant leaves. Repeat every 5 to 7 days until you don’t see anymore worms. Bt is safe to use right up to the time of picking your tomatoes.
  2. Another all-natural environmentally friendly pesticide that is safe for use around kids and pets is Plant Guardians Houseplant Insecticidal Soap
    Spraying the undersides of the leaves with an insecticidal soap mixture kills the eggs at the first sign of seeing the moths. A hard spray of water will also help if your plants are strong enough. Wiping the eggs off with alcohol on a q-tip is also effective.
  3. Introduce Parasitic Wasps into your garden
    Parasitc Wasps (Braconid and Trichogramma) lay their eggs on the larva. If you see little white things on the worm don’t kill the worm, place it in a jar with a fresh leaf and keep feeding it until the wasps do their job. These are the cocoons of the wasp and their larva feed inside the host and will kill it. This guy below has just met his maker!

    hornworm3_1.jpg hornworm5.jpg
    Hornworm with parasite eggs (left)-Joe Boggs, Braconid Wasp (right)-Perdue University
  4. Hand Pick
    Tomato Hornworms are so big you cannot miss these guys. If you don’t want to touch them I recommend cutting them in half with the kitchen scissors. In the fall when you turn your garden pick out any pupae (cocoons) you might find and destroy them.
  5. Companion Planting
    Plant marigolds as a deterrent around or between your tomatoes. Marigolds stink to a lot of different bugs and they avoid them.

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Comments

  1. Jennifer says

    If you’ll pick or cut leaf worm is on and place in jar, keeping it alive til your ready to go.fishing fir bass, you should catch yourself a pretty nice size bass cuz they love tomato worms AND baby frogs!! JS

  2. Thomas says

    I live in central Florida. Just yesterday, I found a tobacco hornworm chewing on my hummingbird bush in my front yard. It caught me by surprise, since I’ve never before found them on any of my 4 hummingbird bushes, and my tomato plants are in the backyard. Where I’ve found one, there were always more chewing nearby. It was easily dispatched with my hedge trimmers.

  3. debbie says

    I have a trapped one…after picking about a dozen off my plants…lol…I have him in an insect habitat…hoping he will caccon soon…is there anything I can do to get him to burrow faster? Keeping him fed takes a lot of foliage…little pig…lol…and what do I need to do to the habitat once he has burrowed? add water or anything? Or just keep it sheltered till spring? (I just want to film it coming out)

  4. Paula says

    These horn worms are destroying my tomato and pepper plants… I leave out in the Palm Springs area of California, so my plants have been in the ground since March 1st. I thought it was grasshoppers but then I saw this huge caterpillar… The reason I noticed them was the poop they leave behind and of course all the leaves were gone….I just killed 8 on one plant – all different sizes and 3 on another…. They creep me out!!!

  5. Sami says

    melissa luque… if you want to make sure the worm is dead… smash it with a brick. Some people like those destructive critters, and while the Moths they turn into are beautiful, the WORM Destroys gardens. I don’t know about you, but the food from my garden is more important to me that a worm or moth. Good Luck with your garden.

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