looks like it to me. I had it happen last year. I applied beneficial nematodes this earlier in the season, so hopefully that will fight them.

Wow, that's interesting. I do have root knot nematode problems on my tomatoes and peppers, but haven't had it affect my chard like that.

I removed the chard. For now I think I'll dig in plenty of organic matter, and plant mustards and rapeseed in the area, and dig them in before they flower. I'll probably eat some of the mustard greens along the way. Not too much of a sacrifice as I was probably going to plant some mustard greens there anyway.

I am in Southern California and I have them too. Around my swiss chard. I wasn't sure if it was nematodes but it must be.