Answer: According the the University of Massachusetts, the bronze birch borer is active in your gardening region. This pest tunnels into the wood and you can sometimes see faint outlines of tunnels that are beneath the bark by looking for raised areas along the trunk. An infestation will stress the tree and it can lose its leaves early in the season. Initial symptoms may be chlorotic foliage and a thinning canopy. Attacked trees that survive will form callous tissue in the mines that become raised areas visible through the bark. Adult emergence holes, through the bark, are "D"-shaped.
You may want to contact the U Mass Ag Dept. and fill out a diagnostics request form:(http://www.umass.edu/agland/diagnostics/tree_shrub.htm)
Someone there should be able to help diagnose the problem and recommend control strategies.
Best wishes with your birch trees!
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