How to avoid disease when topworking or making large cuts

Starting to plan for pruning and then grafting season.
I have a major problem. Over the last few years, when I have attempted to top work an apple tree to another variety, the whole tree seems to become infected and die in a few years. Also, large pruning cuts seem to get infected. What to do about this?


What kind of infection- like fire blight?

Beware fatal sun damage to bark after you remove part of the canopy in topworking.

I learned the hard way to whitewash way up the trunk and lower scaffolds before removing canopy.


I think it’s fireblight but not totally sure

What apple varieties have you grafted and what variety is the base tree? If your varieties are very bllight susceptible that might explain it. I’ve had a handful of topwork grafts get blight the first year but never introduce that blight into the host tree. I’ve also not seen the host tree get blight from big stump cuts. I think fire blight has a very hard time penetrating old wood.

Did the host tree bark show significant damage, flaking off, decay? If so that could be sun damage that can kill bark. Beyond that I’m not much help.

Any photos of damage?