All succulents can run into problems as houseplants. Long dark winters and over watering can cause beautiful jade plants to rot seemingly overnight. The water isn’t the problem so much as the bacteria that thrives under those conditions.
First make sure your jade plant gets plenty of light. Supplement it in the winter. Second don’t over water jades, especially in the winter. Let the soil get dry a inch down before watering.
If that all fails try this method:
. . . Noting a large patch of rot on her plant, the lady got the idea of injecting common 2% aqueous mercurochrome from her medecine cabinet into the patch with a hypodermic syringe. The fluid quickly diffused throughout the rotten tissue, arresting its further development and it dried up. The plant survived in good condition, albeit with a dried-out cavity.
Later attempts by others with the same solution did not always succeed and, thinking that this was due to the histological differences between plants and animals, one experimenter, faced with a potentially serious loss of plants after a storm, tried a solution of 5% mercurochrome in 45% ethyl alcohol . He excised the rot from affected plants and he painted the exposed tissue with the 5%/45% solution. All of the plants so treated survived while nearly all of those untreated did not. Several Euphorbias healed themselves. . . [ read more A unique method of combating rot ]