Monday, October 25, 2010

Orange Coneflower Stem Borer

This is the last of the Orange Coneflower blooms. Growing right beside the house caused it to be spared from the killing frost. I’ll have to wait until next summer to see the blooms in profusion again.

The rest of the plants display dried seed heads and brown stalks. Beneath the mass of dead stalks are spring blooming plants that will begin growing as soon as the rain returns. I’ll remove the coneflower stalks so the spring flowers can develop unimpeded.

Each year, I find that the flower stalks have been invaded by some type of stem borer. Almost every stalk has a hole at the base that is surrounded by some powdery residue. The base of each stem is also surrounded by clusters of basal leaves that will generate the flowering stalks for next year.

Holes also appear at intervals higher up on the stalk.

Each hole indicates a weakness in the stalk. This doesn’t seem to bother the plant while it’s flowering, but at the end of the season, any pressure on the stalk makes it snap.

This is what makes the holes. I’m not sure what this larva will develop into. Years ago I wondered if my cutting the stalks and throwing them out into the field would have a negative impact on this population of stem borers. Since the infestation returns every year, I would say not. It’s funny that my flower bed population, which was started from seed I collected in the field, hosts a borer in almost every stem, while the population in the field is rarely infested.


  1. Fascinating! Sounds like a good topic for me to investigate. I'll see what I can turn up. :)

  2. ...interesting! Love the photo of the little guy too...

  3. Hi Steve...I am here..
    I have battled borers in my roses for years!!
    The reason there in your garden plants is to bug you..; }

  4. Let me know what you learn, Janet. I'm thinking it's a beetle larva, but I'm willing to change my mind as soon as someone points out that I'm wrong.

    Hi, Kelly. I've been noticing how many insects spend their lives inside plants. There's a bunch of them.

    Hi, grammie g. It's nice to know why those bugs are there. It's interesting that I'm often bugged by people, but I've never been peopled by bugs.

  5. Definitely not a beetle - looks lepidopteran to me. I'd be willing to bet it is one of the crambids, a large family of moths whose cateripillars bore in the stems of herbaceous plants. European corn borer is in the same group.

  6. Thanks, Ted. I'll research that group a little bit.

  7. Hi there, I'm an amateur entomologist who came across this post while doing a Google search. Though there are many many things this could be, the appearance and activity of the larva look to me to be consistent with the sunflower bud moth, which in spite of its name is known to tunnel in sunflower stalks and flower/seed heads as well as buds.
    Nice extension publication from Kansas State:

    Sunflower bud moth reared by a field of mine from stalk of sawtooth sunflower:

    Similar looking larva (but who knows) in a coneflower:

    Would you consider joining Bugguide (if you are not already a member) and posting this series of images there? This would make a nice contribution to the guide.

    John v., Iowa, USA

    1. Thanks for the information, John. It might be best if I wait and see if I can photograph some adult specimens, so those can be posted along side the larvae. I'll try to get some photos this summer.