Herbicides can cause that also, perhaps drifted from the neighbors. Some residual herbicides can remain in a plant or in the ground around the plant for a couple of years or more.

Kt

Is that on new culms only? Is it on every culm? Does it eventually branch out? Do you see any evidence of insects there? Do those growths come off? If so, if you break one open do you see insects inside it?

I don't have any ideas what it may be right now, but trying to get more info.

Need more info, what zone? what winter temps? It looks to me like winter kill, especially if it puts out new branches and leaves each year.