We haven't had a lot of rain, but I have had many small stunted distorted dahlias, many took an extra 2-3 weeks to come up and they are tiny and unhealthy. Some never came up. So the last two days I have dug up the no-shows. Most were just stringy husks, others were full of gelatinous goo. Those with the goo often contained the tiny white worms I am showing in the picture. What are these awful things? Are they doing this? Or are they just scavengers eating already rotten tubers? I had many tubers looking like husks last year, but I thought it was rot from the rain, there has been almost none, and for two weeks I had them covered with row covers keeping them dry.
Well, I think I answered my own question, they do seem to be cabbage root maggots, or at least some kind of root maggot (develops into fly). I found a picture of a pupae, and I did find something exactly like that. And the adult cabbage root flies are probably one of two or three kinds of flies intensely interested in my dahlias as long as I can remember. They seem very difficult to control. I bought more nematodes specifically mentioning them, next year I will probably start all my tubers in pots, maybe use the extra light row covers I found at Gardens Alive to keep the flies from laying eggs at the plant bases. Though this year I found row covers get in the way. Its very irritating... :(
Thanks everyone for the kind thoughts, I am potting up all the intact tubers with sprouts and/or leaves that are looking the worst, I have a bunch of extra tubers on hand but its kind of late to start them. All is not lost, I have a bunch growing and will see how they do. I like to save my debugging for computers, not plants. :)