A Technical Report from The Bartlett Tree Research Laboratories 401
Mining by birch leafminers causes birch leaves to dry out and turn brown. When viewed from a distance, heavily infested birches appear scorched as if burned by fire. Severe damage can result in stress, reduction in growth, and dieback. The first indication of a birch leafminer infestation is distinct gray spots that develop around eggs deposited in succulent leaf tissue. Often, the foliage on the upper branches of trees is most severely infested.