Copper sulfate to treat a partially rotten corm?
 

A friend has dug up all of her banana plants a few weeks ago. She gave me one pup that was abandoned ever since. It had a decent sized corm but many mushy spots. I cut down the stem almost to the corm but did not find any promising green. The corm itself had lots of mushy spots which I generously cut off. I left only the roots that looked promising to me and dusted them with mycorrhizae before planting in a pot with coarse well draining soil/sand/perlite mix of what was left of the "gift" . I only watered it lightly once on day one to get rid of air pockets.
Forwarding two weeks later today:
no new growth above soil level. That was expected. I carefully dug out whatever I had planted two weeks ago to inspect the corm and found new white roots. Great.
But unfortunately there were also some spots that were not mushy yet but definitely a little softer. I scraped those spots and dusted it with copper sulfate before planting it back in the pot, no water this time.
Anybody else using copper sulfate for similar problems? Any additional suggestions? I do not really want to dig out the corm every other week and disturb the new root growth, but of course I don't want it to rot away either.

On a different note: I normally do not grow in pots here in Southern California, but this little challenge I am facing here gives me a whole lot of more respect of all you people growing bananas in pots and in more marginal climates.

Re: Copper sulfate to treat a partially rotten corm?
 

I use bleach water after scraping off the rotten parts of the corm. I treat a couple of time and rinse, then re-pot. The bleach will kill any infection on contact. I think the copper sulfate would be helpful to prevent a new infection from the soil.

I use copper sulfate in my garden and on my young bananas.