Your research proved correct, in that this looks like Crown Gall. It is caused by the soil inhabiting bacterium " Agrobacterium tumefaciens "  that infect the plant through wounds in the roots, crown , stem, contaminated tools and soil water.  The bacterium survives and persists in the soil for many years and removing the galls will not cure your infected dahlia's , because bacterial genes already inserted into the plant cells will continue to transform additional cells throughout the plant and produce galls in other locations. You would be correct in "not wanting to store them" and the removal of them will lower the bacterial populations in your soil, however, low populations of soil bacteria will still persist as surface colonies on many plant species regardless of their susceptibility to crown gall.Hope this helps!  Karl,  MG Lycoming County.

Carol.  Thank you very much for the confirmation. 

You are welcome!
Carol