Tunnels of the Bronze birch borer meander throughout the wood. White, cutleaf and yellow birch are preferred but other birches are also attacked. Look for top dieback, with first symptoms including sparse, chlorotic foliage. Larvae are flat-headed borers with two spines at the posterior end. It takes one to two years to complete development.
Winter is spent in the larval stage in tunnels beneath the bark.
Depending on location, adults emerge from early spring through August. They feed on leaves for several weeks before laying eggs on unshaded bark. Weakened or injured trees are preferred by this pest, but healthy trees are also attacked. Trees which have been recently transplanted or those on stress-prone sites are especially susceptible. Numerous galleries can girdle the tree, causing branch dieback.