Tomato Hornworms and the Awesome Braconid Wasp Super Hero

We were in the garden Sunday morning, and while I was glancing at my in-ground tomato plants, I noticed what looked like white spikey roots growing out of a tomato leaf. Mind you, my eyesight is not great, but I immediately thought about how weeks before, I noticed low branches were beginning to develop roots where they were touching the ground.

I took a closer look, and yuck! I was mortified to see a big fat icky green worm with rice-like eggs on it’s back. I wasn’t wearing my garden gloves, so I called DH to come and grab it off. Luckily, he broke off the whole leaf (more on that later) and kept the bugger intact.

I was fascinated by this little pest, so I took it into our workroom, grabbed the camera and took some photos.

Then I googled, and learned that we had a Tobacco Hornworm (with a menacing-looking horn on its back-end, that actually isn’t menacing or harmful at all!) and those weren’t eggs on its back. They are Braconid Wasp larvae cocoons.

(click for larger view)
hornworm with wasp parasite cocoons attached

The more I learned, the more grossed out but fascinated I became. It’s literally the movie “Alien” come to life!

What happens is the female braconid wasp lays eggs under the skin of the hornworm, and the baby larvae feed on the worm, as he sits, paralyzed on a leaf. They eat their way out of the layer of skin and spin themselves into a cocoon, where they continue to eat their “host” until they eventually emerge from their cocoons as adult braconid wasps.

hornworm with wasp parasite cocoons attached

I have had the worst case of heebie jeebies all day thinking about it, especially after seeing all the youtube videos and photos. Yuck. Just thinking about the wasps eggs hatching inside a living host and popping out is enough to give me nightmares!

But I was a good doobie, and I put the hornworm, complete with leaf, back over near our tomatoes. I’m hoping that all the wasps will hatch and feast on any hornworm pest population left in my garden.

Nature is wonderful, isn’t it? And I have discovered so much about nature in just a few short months, it’s amazing and thrilling!

It also makes me sad because so many home gardeners don’t think twice about using toxic pesticides instead of allowing Mother Nature a chance to handle it herself!

UPDATE 2012-08-19 ~ This morning, I noticed TWO more icky hornworms covered with the Braconid wasp cocoons, and I let them be on the plant. Exciting. I hope the wasps hatch and attack any future hornworms on my tomato plants.

Horned worm vs. Braconid Wasp – CTnaturalist Online
Tomato Hornworm covered with white cocoons of Braconid Wasp
Tobacco Hornworm Parasitoids Emerge from their cocoons