The first and most devastating thing it might be is rodent damage; voles or
mice.
Have your trees been nibbled at the soil level, or at the roots?
The second thing is Borers, but less likely.
The third thing is too much fertilizer in the fall.
The fourth is too much Round up.
The fifth is the Winter Moth worms that have gotten in the buds and eaten
them.
Isn't this fun?
Murph
[NAFEX] Mr. Wagner's trees,
Richard MURPHY, 04/30/2011