On my last post I found what I thought was some kind of pseudo-flower on Canada goldenrod. Actually, I found out a little more about what was going on, but still ended up with a mystery.
What I found was called a goldenrod bunch gall, or goldenrod rosette gall. It is caused by a tiny fly, Rhopalomyin solidaginis. There are a number of different kinds of galls found on the many species of goldenrod, and each have a number of insects associated with them. This is a more typical bunch gall:
I walked around in the prairie and by the edges of the road. All of the vegetation is very dry. I was able to find a few more bunch galls. Most did not have the white center, although I did find one other plant that had one bunch gall with a white center.
So the gall itself is caused by the fly. But what causes the white center? I am still thinking fungus spores.