Melanconium betulinum (fungus)
All birch are suseptable.
Found throughout United States and Canada.
Borer infestation, drought, poor soil drainage, adverse temperatures (over 95o F.), exposed locations, and sandy soils all contribute.
There is a Progressive browning of foliage and dieback of twigs and branches from flattened, sunken, swollen and discolored cankers. Diseased bark on branches red-brown, dotted with cupped, black fruiting bodies.
Acervulus are embedded in outer bark, hyphae extending into cambium. Conidia are released to invade bark through natural openings (lenticels), where new acervuli develop. Infection continuous during growing season.