do wasps eat the stem of a sunflower?

This is the sixth occasion I've heard of this this year alone, and in one case, it was the older stems of a dahlia. It would seem the wasps do like the stems of sunflowers, possibly for the cellulose content, and in theory to build their nests with, but its getting a bit late for nest building I'd have thought, so I'm not really convinced that's why they do it.

I think Bamboo is right. I have also found wasps eating the thatch off my bird table. I was sitting in the garden and I could hear this annoying little noise. I eventually found about five wasps on the thatch and they were making the noise as they chewed the straw!

i too have had this on three of my 9 sunflowers with wasps on them. I found it odd as they would sit just ahead of the leaf, and not really do anything, just walking around, though sometimes they looked like they were eating the lil hairs off the plant. On the "problem child", the worse sunflower infestation, which is right next to my pole beans, i could see that where they congregated the most on the back of the flower, that part of the flower was less developed or stunted. They also would buzz me when I went to pick the beans so I had to spray them with an insecticide. I plan on doing a biopsy later after the flower dies just to see what they were doing on it.