Reading this entire document on Rot and Repair Procedures, from start to finish. Don't think you can skip to the 'guts' of your question w/o reading the entire text. If you miss the 'point', you'll be writing us again in the near future! It's important to understand the causes and mitigation procedures in this situation.
That's all I've got to say 'bout that. My best to ya and hope this helps.
Teacher Jay J
PS: Yes, 'sistering' is in there, among other things ...