Skeletonized catalpa weed/treeSkeletonized catalpa weed/tree
So many caterpillars!So many caterpillars!
A very suspicious-looking wasp that wasn't interested in flying away even when we got close. I'm going to guess this is the female that laid the eggs.A very suspicious-looking wasp that wasn't interested in flying away even when we got close. I'm going to guess this is the female that laid the eggs.
These suckers get big!These suckers get big!
Parasitized catalpa wormParasitized catalpa worm
  • Skeletonized catalpa weed/tree
  • So many caterpillars!
  • A very suspicious-looking wasp that wasn't interested in flying away even when we got close. I'm going to guess this is the female that laid the eggs.
  • These suckers get big!
  • Parasitized catalpa worm

When we bought our house nearly two years ago, there was one curious little stick sticking out of the ground in the backyard. It was about 3-4 feet tall, and being distracted by demolishing our house, we left it alone.

The next summer, the thing exploded with growth. Our neighbour asked if we were going to keep it, and when we responded that we didn’t know what it was, she told us it was a catalpa tree – or, more correctly, a catalpa weed/tree. And so it has been the weed/tree to us ever since.

The second summer it exploded with even more growth. It even got to the point that it was casting afternoon shade on garden bed #2. Un-ac-ceptable. I’d been wanting to get rid of it for a long time (and Charlie had spent an equally long time trying to convince me of its merits), but when it finally came down to weed/tree vs. garden, the garden won. Charlie got out his sawzall and that was the end of the weed/tree.

Or so we thought.

Because, you see, there are certain plants in this world that you just can’t kill. We have several dieffenbachia plants in our house that are several generations down from a dying leaf that Charlie raised back to life when he was young. Not only have they survived years (decades?) of houseplant neglect, but when we moved out of Charlie’s college apartment we were forced to transport the dieffenbachia in the back of the truck in 7 degree temperatures (F), and the plant was not impressed. (And this was after we’d driven it in the back of the truck all the way from Springfield to Columbia on Thanksgiving two years earlier.) All the leaves froze and died, but about a year later, having spent a year forgotten in the open closet at my office, it came back to life. You just can’t kill these things.

And so it is with the weed/tree. We chopped it down, but now, a few months later, the stump has put out 4 foot shoots.

Needless to say, we were surprised when we went out to visit the garden and discovered that the leaves of the weed/tree were skeletonized. What in the world? Where did they go? A quick look under the leaves revealed the answer: catalpa worms. Hundreds of them.

These are black hornworm caterpillars, much smaller than a tomato hornworm but equally destructive – at least to catalpa trees. They are the caterpillar stage of a brown common hawk or sphinx moth. Apparently they exclusively feed on catalpa leaves, which was a relief to me when I saw that they were hornworms and just feet from my tomato plants. I also learned that they are prized by fishermen and even hoped to get them up on Craigslist to sell, but they moved too fast through the weed/tree and within a few days they were gone.

Interestingly, catalpa worms are often parasitized by a female braconid wasp. Check this out:

The female wasp deposits eggs through the skin of the caterpillar.   Wasp larvae feed and develop inside, then emerge to the outside and spin conspicuous white, silken cocooons on the caterpillar skin. Parasitized catalpa worms do not survive to adulthood.

Barf. That’s pretty brutal.

Even though the weed/tree looks like it’s had the life eaten out of it (and it has), it will grow back. sigh.

6 Responses to “When catalpa worms attack”

  1. Chris
    6 June 2013 at 10:51 am #

    Please let me know if the worms come back. I would be more than happy to remove the by hand for free.

  2. jean
    11 June 2013 at 6:47 pm #

    I understand the worms are highly desirable as fishing bait. We have catalpa trees and no catalpa worms last year … perhaps the drought didn’t suit them.

  3. renee
    2 July 2013 at 9:26 am #

    i really wish i knew how to prevent the worms cause they make an all full mess and eat my shade trees up

  4. Deborah
    6 September 2013 at 6:22 pm #

    I have 3 Catalpa tree full of worms, they have all but destroyed the leaves on our trees. If anyone want them feel free to come and get them. Our trees are very tall so you better bring a ladder. Is there anyway to keep them from attaching the trees.

  5. Jerry
    18 October 2014 at 12:21 pm #

    I am looking for live catalpa worms in the Toledo bend La. area if anyone has any I would sure appreciate a response

  6. jenn
    6 August 2015 at 10:22 pm #

    I love my have catalpa tree but the catalpa worms always attack my poor tree leaving it dead looking. I have about a thousand of them on my tree right now, I pick them off everyday but they just come back. If someone wants them for fishing please contact me. I’m in the Pitt. Pa area.