greta, I don't know about worms but I had a tree killed by termites. They entered the trunk through an unhealed scar from pruning at ground level.
"gene"

Hi Greta, good to see another Texan on the forum. Figs an be bothered by Termites, Canker, Cotton Root Rot, borers and others. My M-I-L lost a huge celeste tree probably 45 years old this summer to canker. It did, as yours did---four huge 10" trunks just fell down from the base. There was a black looking fungus there. I cut them all out and left 1 sucker there to grow. Tim

Dare I dig up the root and check things out???

I really hate to cause any more damage. I know this area is subject to cotton root rot, but I saw no outward signs indicating this. I did not see any black fungus at the break either. I'm puzzled.

How big of a pot would I need if I chose to pot a fig tree up, plant it (pot and all) in the ground with outside soil, incase it is cotton root rot? Any ideas?

These figs have spoiled me, I loved them. I will want more.