Ick! They aren't thrips. Thrips are so tiny as to make a flea look huge- like a thin little black ~1/8 inch long streak happily munching up and down your Gladiolas. And they like dahlias too.

I would carefully divide any tubers you think are worth saving, dip them in a 10% bleach/water solution for up to half an hour, then go on to dry well and inspect for more bugs. The other part of the clump I would tie up in a garbage bag or dip in soapy water bucket ( use the old bleach water) to kill the bugs, then discard.

It could be your lucky day: I've never found any underground bugs- just worms.

Thanks, maybe they really are ants. They actually look a bit like termites, but that doesn't make much sense. They really don't seem to have done a lot of damage, I think they just got into some of the older tubers that may have been rotten already. I thought that soaking in bleach would be the thing to do, but wasn't sure about the ratio bleach solution. Thanks again for quick response!

If you didn't separate in the fall, then you most likely have the old tuber which has rotted. This is normal. We plant only the new ones. Poochella has a good idea though about a bleach solution, although I would be tempted to dip and run. Also, if the new tubers are firm, plant them up and see what happens. Nothing ventured....nothing gained.

Did as suggested & planted yesterday. Frankly, these are probably my best looking tubers after I divided them up. I hope I didn't divid too much, I wanted to be sure to get all the bad tubers out. I had never divided before & I think this was on its 4th year, huge. I'm sure I will never miss the 3 or 4 bad ones.