Can lime sulfur be applied to live wood?

[Perrywinkle]

I have a bougainvillea with a robust trunk whose bark is getting a bit mush from our humid summers. The tree is perfectly healthy, it's only the outtermost bark that has gotten soft with all the rain, the inner cambium and actual deadwood are fine. Can lime sulfur be applied to this bark to keep it from rotting? I know you apply to deadwood, but I can't find much information general application to the trunk.

 

[Shibui]

Lime sulfur is used traditionally as a fungicide and pesticide when diluted. Some Japanese nurseries dip the entire dormant tree in dilute lime sulfur in winter.
Strong lime sulfur is used as a wood bleach and preservative. it is applied to wood after the bark has been removed or to dead sections of the tree.
Not sure why you want to preserve dead bark? If the bark is dead get rid of it and show off the dead wood underneath.
Bougie is a tropical plant. It should be able to cope with warm and humid and rain so I would be looking for some other cause if sections of trunk are dying.

 

[Maiden69]

I thought all bark is dead? If the bark is getting "mush" I don't think the lime sulfur would do any good.

 

[Perrywinkle]

The live wood is fine, but knots in the trunk as well as any bark are getting mushy. I guess my main concern is rot getting into the center of the trunk through knots where branches were pruned off. Bougies are tropical but they’re not native to wet regions, so their wood isn’t meant to resist constant rain and high humidity.

 

[Wires_Guy_wires]

I've used LS on open wounds and on fresh cuts, on herbaceous plants. Their health wasn't affected by it but it's a delay of the inevitable.
Maybe a hardener would provide a better seal and prevent rotting all together. It's also easier on the eye compared to lime sulphur.