During the early stages of infestation there iare often moist areas on the bark, many times accompanied by sawdust. When trees are chronically infested they may have a black varnish-like stain on the bark below points of the borer attack. The developing larvae push stringy sawdust out of holes in the bark and the sawdust often piles up around the base of trees. Weakened branches and trunks may break off in high winds and trees may be invaded by wood rot. Rough growths at the wound spots often harden and split the bark.