[Cynthia, Prescott, AZ]

I think the fear of 'rot' running thru the plant, when you see roots at repotting time that have dead portions, is totally over blown. Rot can run thru the roots, but it happens so fast that the problem is over by the time you see the damage at repotting. Roots dying of old age is a fact of life and depends on the genetics of the plants. Some plants will have all roots alive, even those that are 6 and 7 years old, but more often, the roots last about 3 years give or take a bit. When you repot and find portions of a root dead, it has probably been that way for a while and is not a thing that needs immediate attention (or you lose the plant). I don't believe in my 45 years of growing orchids that I have ever seen root rot move into the base of the plant. Fusarium will move from the roots into the plant, but it does so before it kills the roots and it causes wilting in the plant, not rot. Currently at repotting time, I use Thiophanate methyl (OHP6672, Cleary's 3336) to spray the roots and then drench the new mix to avoid fusarium wilt. I have used Phyton 27, but it is useless for fusarium, a fungus, which is the bigger issue for me.

Often, the roots below a break that occurred when putting the new mix into the pot on a previous repot are dead because of the break, but often a break does not even kill the roots below.

Updated 6-19

Something I have been meaning to mention. When I cut off partially dead roots, I almost always cut below the living portion, into the dead part of the roots. I do this because I am not opening any fresh wounds and this way I avoid more opportunities for fungi and bacteria to invade. As I mentioned above, I believe the rot is not active at the time of repotting, so I feel there is no advantage to cutting into living root.