Rhubarb Crown Rot?

I started splitting my rhubarb crowns the other day - and found that the long-neglected roots (large) were hollow! The inside of the hollow is black, but not sticky. Is this Crown Rot? Or is it just the result of not having split the crowns for years? (i.e. they're just old). If it is Crown Rot, do I really need to go as far as bagging up and disposing of the soil - or could I just plant some virus-resistant plants in the same place?

 

I would say that it's age, Crown Rot causes the top of the root to go black and soft, in the picture the top appears to be like an expected rhubarb crown.
You can either buy new crowns, or split the existing ones, if they have good buds on them anywhere. I would also dig a lot of manure/compost into the patch as rhubarb plants are need plenty of food.