Will destroying the strands that form from dry rot from the source save the dry wood?

Lets suppose the wooden joist in the wall is the area where the dry rot started from is cut off at a point where the wood is still firm and there are no dry rot strands left.The remainder of the wood and all other masonry past this point is dry.From what I gather,the dry rot will not be able grow again as it needs damp wood to start.Thank you,help appreciated.