Excessive moisture can sometimes lead to outbreaks of bacterial rot. It is imperative that you remove the rotting tissue as soon as possible. Remove the soil from around the rhizome, leaving the roots anchoring the plant. Using an old spoon, carefully scoop out all the mushy tissue. If necessary, dig up the entire plant and remove the rotten tissue. After removing the tissue, drench the wounds with a 10% bleach solution (1 part bleach to 9 parts water) and allow them to dry for several days before covering with soil again.