Caterpillar inside meadow rue cane - eh what??

Perham, MN(Zone 3b)

A week or two ago, a storm bent and broke the top of the largest cane/stem of my thalictrum, so I went and cut it off at the broken point. In the last week, still more of that particular cane appeared to be dying off, with all the leaves and flower buds drying up further down the cane. So I went out to cut away the dead material. I cut away only a little at a time, to prevent damage to other delicate leaves and so on. As I went down the stem, I noticed it was quite hollow, like a reed; no wonder it couldn't support foliage. I had been thinking it was environmental damage, perhaps something I harmed during the staking process. But about a couple feet from the ground, there were healthy new offshoots, growing well. I trimmed the cane closer and closer to this point, and noticed this little devil in there. Anyone ever get a caterpillar *inside* a cane like this? I theorize it got in through the original storm damage point, but -- not sure! Can it have arrived by any other means? Can anyone identify this? Should I consider some control method? Thalictrum is supposed to be pretty much pest-free, and I've never seen anything like this in any other plant around here.

Thumbnail by joanlc
Hummelstown, PA(Zone 6b)

looks like european corn borrer to me. They get in corn stalks all the time and can cause them to lodge over.

Perham, MN(Zone 3b)

Thanks for the ID. I'll do some research on habits. Odd that a corn borer moth would have chosen thalictrum to lay eggs on. I've gone out to check that garden, and note that while the rest of the canes on that thalictrum look ok for now, one of three castor beans - also a plant with a big, cane-like stem - is wilting. This gives me concern that there will be more deaths out there. I don't suppose there is any point in spraying, since the pests are certainly protected inside the canes. I can either let things happen as they're going to happen, or perhaps use a systemic, since this isn't a food crop. What do you think?

Hummelstown, PA(Zone 6b)

Corn borrers infest all sorts or ornamentals.

In terms of deciding whether to control or not...I guess its all up to you how acceptable some losses are. You could use imidacloprid liquid or buy a granule with a systemic.

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