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.