Dieback in birch tree
This year our Birch trees have smaller leaves and tip dieback in the entire crown. There are catkins but not nearly as many as we usually see. I see no evidence of bronze birch borer and the neighbors birch look great and healthy. Any thoughts?
Since you have looked for evidence of bronze birch borer I am going to assume that you have a white birch or paper birch. Die back can be caused by root problems, planting too deep, roots that get too hot in summer, lack of water and unrecognized birch borer damage. One has to check near the crown for exit holes as well as lower on the trunk and the exit holes can be hard to see. Birch are not well adapted to the hot summers in the metro. Removing turf (without tilling or digging), mulching under the tree and making sure it gets an inch of water per week and on very hot and dry weeks water if the top 6 inches of soil are dry will help.