Many of the birches are susceptible to damage from two
insect pests. The
birch leaf miner will eat between the layers of
the leaves causing the leaves to turn brown and, in
severe cases, defoliate the tree early in the
growing season.
In itself, leaf miner
damage stresses the tree but rarely kills it.
However, the weakened tree is then more attractive
to a much more serious pest called the
bronze birch borer. This critter will bore into
the wood and kill the tree starting from the top and
working its way down the trunk.
These are trees with alternate, simple, toothed
leaves and are most prized for their bark which
may be in some shade of white and may also be
exfoliating. Most birches fall into the group
called "bleeders" which means that sap will flow
from pruning wounds made in the spring. So, they
are best pruned any time after the first flush
of growth or during the dormant season when the
leaves are absent.
