Home News Local News Insect attacking Baker's birch trees
Insect attacking Baker's birch trees
By Joshua Dillen
Parasites are invading Baker City and they are targeting some of the more spectacular trees in town.
The bronze birch borer (Agrilus anxius) is responsible for the browning and die off of several weeping birch trees in the area. The tree, also known as the silver birch, is particularly susceptible to the insect.
Besides ruining some of the city’s most attractive trees — birch leaves turn a brilliant yellow in autumn — the insects leave behind dead branches that can be a hazard.
Katie Lompa, a community assistance forester for the Oregon Department of Forestry and a certified arborist, has some troubling information about this pest and its effect on birch trees.
“If you see dead branches, it may too late to do anything,” she said.
Lompa said a good rule of thumb is that if more than one-third of a tree’s canopy is affected by the parasite and has turned brown, the tree probably cannot be saved.
Lompa has practical advice for those who have birches on their property.
“Make sure your tree is well taken care of — that will help the tree fight it (the birch borer) off — but it’s not a guarantee,” she said.
Jim Watt of Bingham, Bingham and Watt CPAs has a weeping birch in front of his house that corroborates Lompa’s advice. The tree shows no signs of damage.
“It’s a beautiful tree. It’s been here for a long, long time,” he said. “I take care of it pretty well.”
Watt waters the tree adequately and has treated it for aphids in the past.
Although not as attractive as the weeping birch, the river birch (Betula nigra) is the most resistant of birch species.
The tree in front of Watt’s house at 1385 Fifth St. shows no apparent signs of damage from the birch borer.
But just a few blocks away on Third Street the city required an infested tree to be removed.
A block south of that are two birch trees that appear to be infested with the destructive insect.
According to Baker City Ordinance 94.07 (A) the city’s Tree Board may remove or cause to be removed any tree or part thereof which is infected with any injurious fungus, insect or pest. This ordinance applies to trees and shrubs in the public right of way. Ordinance 94.10 (A-C) pertains to hazard trees that are on private property or public rights of way. Property owners will be notified that they must take remedial action and abate potential hazards that the tree might cause, according to Jennifer Murphy, engineering technician with Baker City Public works. The complete ordinance can be accessed at http://www.bakercity.com/government/ordinances. More information is available by calling Murphy at 541- 524-2063.
Adult birch borers lay their eggs in cracks in the bark of the trees. In about two weeks, the eggs hatch into larvae that burrow through and feed on the inner bark of the tree. At this stage of infestation, look for raised ridges or bumps on the branches or trunks. At this point the pests can be eliminated by treating with a systemic insecticide. Lompa said residents of Prineville, where they have a fairly severe infestation, have had good luck with pesticides that have imidacloprid as an ingredient. She said to be sure to follow completely the instructions on the label of any insecticide.
Signs of severe infestation by the birch borer include D-shaped emergent holes (adults exit from these after transforming from the larval stage) about the size of the D in this newspaper. Look for them on the dead branches. Regretfully, if you find these emergent holes, the tree is more than likely too far gone to save.
The adults and larval birch borers are active throughout the warm months of the year. Adults will emerge in the spring and females will lay as many as 75 eggs over their 3-week lifespan.