|Top two feet died so we trimmed off. Now another two feet is dying.|
|It doesn't sound good for your birch tree. What you describe is symptomatic of Bronze Birch Borer damage. Initial damage is usually discovered when the top part of a birch tree suddenly wilts and dies. This happens when a larva girdles one of the upper branches. Careful examination of branches and the trunk usually reveals raised ridges or bumps, commonly referred to as "gouting" of the branches. These are ridges formed when a larval tunnel is closed in by callous tissue of the tree.
Often, D-shaped holes are found in the bark and these may be stained with rust colored sap. These holes are emergence holes made by adult beetles.
Heavy attacks and continued reinfestation results in most of the trees dying from the top down. Eventually the trunk is girdled and the entire tree dies.
As with most wood boring insects, the bronze birch borer is extremely difficult to control, especially if an infestation is established.
I hope I'm wrong! To confirm the presence of bronze birch borers, look for the signs and symptoms as described above.
Best wishes with your tree!