Canton, Norfolk County, Massachusetts, USA August 1, 2010
Rosettes of this form are reportedly caused by the gall midge Rhopalomyia capitata Felt. Dorchin et al, Revision of the goldenrod-galling Rhopalomyia species (Diptera: Cecidomyiidae) in North America, Zootaxa 2152: 1–35 (2009). Larger image.