on image for larger version
Figure 2. Flat-Headed Apple Tree Borer Adult
The borer will attack many species of trees and shrubs including
maple, oak, sycamore, tulip, poplar, willow, rose, and cotoneaster.
Newly transplanted trees and shrubs or plants that are stressed
are particularly susceptible to attack. The adult female lays
her eggs in bark crevices and the legless larva enters the
bark at that point. If the plant is healthy, the larva may
be killed by heavy sap flow. If not, it bores in to the inner
phloem, forming irregular tunnels and partially filling them
with powder-like frass. When nearly mature, in either spring
or fall, the larva bores into the heartwood and pupates. Adults
feed at the base of twigs, on partially defoliated trees.
There is one generation per year.