Hi all, I've searched the forum and couldn't find my answer - but apologies if I missed it. Does anyone know what is causing this cluster of tiny eyes to grow on this tuber? A virus? Will this be a viable tuber? Should I do anything - like slice off the majority of the small ones and hope a "normal" eye grows? Thanks!

It looks like it might be leafy gall. I don't know where you live but if your state has an extension program for Master Gardeners, you might want to contact them. They usually have a laboratory so that you can submit pictures of the plant or bring the plant itself to them to confirm and guide you in your options as to the future of the plant.

That definitely looks like gall. You can follow Laura's instructions, but if that were my tuber, I would toss it in the garbage (not the compost bin) and get rid of the soil, too. It's become an unfortunate plague with dahlias the past few years.