Borers have been attacking my two birch trees this year. Our arborist says this problem is pretty wide spread in the Portland/Vancouver areas this year. How can I control this pest?
Attacks of the bronze birch borer on white bark birch trees have increased this year due to our hot, dry summer weather. Water stressed trees are especially susceptible to borer attack.
The bronze birch borer is a slender, dark bronze beetle about 1/2 inches long. The adult female lays eggs in the cracks and crevices of susceptible birch trees in May. The light brown 3/4 -inch larvae bore into the wood and begin feeding on the interior tissue of the bark. They mine intricate tunnels, feeding actively until fall, where they overwinter. Larvae pupate the following spring and emerge through D-shaped holes cut into the bark. Winged adult beetles feed on tender young foliage for about a week and then move around trees laying their eggs.
Other borers can attack other tree species.
Spring and early summer warning signs are yellowing and thinning of foliage in the upper part of trees. Tunnels made by the larvae inside the bark girdle the trunk and branches reducing the flow of sap within trees. These tunnels appear as a raised or rippled bumpy surface of the bark.
In late summer and fall, the foliage turns brown and falls to the ground. Symptoms begin in the younger and smaller branches and progress downward to the larger branches and trunk and will kill the tree in about three years.