Tree surgery - wasps in plum tree

[fd3]

Our plum tree has lost a large branch a while back.  We left it as was but then a wasp's nest set up in the jagged end of the branch (powder down killed them) and then some fungus started to grow on the remains of the branch.  Advised to make a clean cut of the branch to remove fungus - but now we have wasps setting up shop again and the branch is cut very close to the trunk of the tree (really don't want it to die).

1. If I put powder down will it harm the tree?
2. Wasps have dug a good couple inches down the centre of the branch.  Should I make a clean cut at this depth?  Should I then treat the cut with something to harden it (varnish? Danish oil?) Or should I put some sort of wood filler into the hole to harden it and prevent return of wasps?

[Aunt Maud]

What's wrong with having wasps in the tree?

And applying anything like wood filler or danish oil would be a waste of time and danish oil may harm the tree if it is in contact with the cambium.

If the branch is cut close to the swelling where it comes from the stem, it should callus over in time, but may also create a hollow where wasps or birds will nest.

[L CC]

What's wrong with having wasps in the tree?

I can't speak for fd3 but for me, I like to pick my plums¹ wasp-free.


1: Not a euphemism.

[fd3]

Wasps:
1 - I like them not to sting me as I pick plums
2 - I like them not to sting my kids when they play in the garden or climb the three
3 - I like them not to dig into the tree and make it die

other than that

4 - I don't like them making a nest in the bike shed!