First Hornworm on a Tomato

While watering my tomatoes this morning I noticed a few roundish black droppings on a tomato leaf. I know, from many years of tomato growing, to suspect a leaf-eating caterpillar in the presence of such droppings. I had to look closely, just above the leaf where the droppings rested, and there it was.


The first hornworm of the season. (I removed the leaf, hornworm and droppings included, for the sake of this photo.)

It had only done minimal damage, but left unchecked it could have defoliated the entire upper branch structure of the potted tomato. Hornworms voraciously munch on tomato leaves. They are so well camouflaged, assuming the same color of a tomato leaf, that it’s difficult to locate them until they are much larger.

The only time to leave a hornworm in place on a tomato leaf is when it is covered by tiny, white, oval egg casings … the sign of a parasitic wasp that uses a hornworm body as a breeding/gestation ground for the next generation of wasps. Youngsters hatch out of the casings and feed on the guts of the hornworm before transforming into parasitic wasps like their parents.

I know, this sounds gross. But it’s not nearly as appalling as the sight of mature tomato plants with leaves munched to their veins by adult hornworms. Left unchecked, hornworms will totally defoliate a mature tomato in just a couple of days.

It takes a sharp eye to find them, though. When young and small, they are often at the edges of tomato leaves. When more mature, that is more full of your tomato leaves, they often rest along stems, like in the photo below from my 2010 garden.


Always look for hornworms when you see tiny roundish droppings, like those on the leaf surface in the photo at the top of this page, on or just below a tomato leaf.

If you cannot tolerate leaving a hornworm in place, munching away while waiting for parasitic wasps to find it as a host for egg laying, then hand-pick any hornworms you find and drown them in a jar of water, lightly soaped (dish detergent). Or, if you’re not the squeamish type, squish them.

But, before destroying any hornworm, take a moment or two to admire their coloring. They can be truly beautiful, intricately-patterned, almost other-worldly creatures.

Macro Horned Tomato 9D86DB

Chomp, chomp.

Hornworm hunting is an annual event in joene’s garden. Just read posts from 2011 and 2010.

Garden thoughtfully.

Digiprove sealCopyright secured by Digiprove © 2012 Joene Hendry

9 comments for “First Hornworm on a Tomato

  1. July 14, 2012 at 12:23 am

    Joene, good eye–I will definitely start checking my tomatoes! Here’s a little something I learned about these guys last year–just because they do not have the cocoons on their backs when you see them does not mean they aren’t already parasitized by the wasp. I would bring these guys to work for a “show and tell” on a stalk in a jar and let them continue eating and we could all watch. Sometimes 2-3 days later (you need to keep feeding them fresh stalks) the cocoons would appear! We saw the tiny white larvae “hatching” out of the hornworm-then they turn into the cocoons-it was a real science experiment to watch! Then in a few days the wasps hatch!

    • July 14, 2012 at 8:36 am

      Diane, this is great information to know. Thanks for sharing. I’ve not had a large outbreak of hornworms in years so I usually remove the leaf or short stalk one is feeding on and watch it for a day or so … they are such interesting creatures. Now I have even more reason to observe hornworms. I’ll definitely use your trick in the future.

  2. July 14, 2012 at 3:22 pm

    I don’t grow tomatoes, so I can admire your hornworm’s beauty and camouflage with gusto! How fascinating, and your close up pictures are incredible. Nature is so weird and wonderful.

    • July 14, 2012 at 5:26 pm

      Laurrie, hornworms certainly are intriguing creatures eventhough they would/could destroy a tomato crop if left unchecked. Glad you like the close-up but the credit for that photo goes to my favorite photographer, Ralph Chappell. The link to his photo sites is in my sidebar.

  3. July 15, 2012 at 9:11 pm

    I have found these pests before, and it is always shocking. Because tomato plants are so full of foliage, I often miss these until I notice missing and eaten foliage. They do have somewhat of a B-movie horror film kind of appearance.

    • July 15, 2012 at 10:00 pm

      So true, Sage Butterfly. You want to look away but the unique characteristics draw you to watch these strange creatures.

  4. July 18, 2012 at 3:27 am

    Wow the information and photograph are great. I have to share this with colleague who is in his 2nd year of serious vegetable gardening.

    • July 18, 2012 at 12:56 pm

      Thanks, Margaret. I’ll pass your kind words on to my favorite photographer … he took the striking close up.

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