City says Birch Disease Affecting Upper Snoqualmie Valley Trees, Down Goes the Backyard tree

So it appears there is a good reason that pesky woodpecker won’t stop drilling into what once was a pretty birch tree we planted five years ago in our backyard – it’s diseased and the woodpecker is hungry.

The City of Snoqualmie, which employees an arborist to help maintain hundreds of city trees, stated on May 10, 2016 that an insect pest, bronze birch borer, is affecting certain kinds of non-native birch trees in the upper Snoqualmie Valley.

According to a city press release, affected city-owned trees owned will be removed over the next couple of years and replaced as funding becomes available.

Property owners are asked to check their own trees for signs of possible infestation. Susceptible birches are European (weeping) white birch, Himalayan birch, and paper birch.

Signs of infestation include brown wilted leaves at the top of the tree in the summer, and dead twigs falling from the upper part of the tree. Birches that are drought-stressed are even more susceptible. Birch trees typically need an abundance of water to thrive.

River birch is not susceptible to the borer and would be a good replacement option for diseased trees that need to be removed.

“Improving tree health through proactive maintenance can help with preventing infestation,” said Phil Bennett, City of Snoqualmie Arborist.

Good prevention practices include keeping a 4-6 inch thick layer of wood mulch at the base of the tree and giving additional water through the summer months. Bennett recommends “arborist chips” rather than beauty bark. Arborist chips are available through local tree companies and from landscape supply yards. Extra water can be dispensed slowly and effectively with a “Gator Bag”, which can be filled once a week. Gator bags are available at hardware and home improvement stores.

Pesticide treatment is possible, but treatments can affect pollinators such as honeybees, should be done by licensed operators, and may be expensive long-term.

More information about the bronze birch borer is available at

As for us, seems we’ll be looking for a tree as we sadly say bye-bye birch tree.  I won’t miss the woodpecker, though.

Birch tree is its healthier days, 4th of July 2013.
Birch tree is its healthier days, 4th of July 2013.

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  • The birch borer also affects other trees beyond birches though usually with less damage. The borers cut holes in the bark that makes it look like a tree has been punctuated by a hole punch in a horizontal lines around the trunk. These usually appear at shoulder height or higher on a tree trunk or limb 4″ wide or larger. It might be just a partial line of little dots or entire rings of these holes two feet high. My first observation of a severe case looked like the trunk had been shot by a shotgun – except the ring of damage went all the way around the trunk.

    The borer cuts through the outer layers of bark which is where the roots of the trees send nutrients to feed the upper branches and leaves. With the food supply cut off, limbs or even the entire leaf structure can die.

    In Sammamish, more than half the white birches are affected and many of those will die. Bellevue is removing them from city properties. Still, I’ve seen trees this spring with significant damage to the trunk that seem to be warding off wilt or columns of dead branches. Healthy, non-parched trees may be able to shrug off this otherwise fatal situation. Arborists may recommend pesticides or pruning but be aware that these may not salvage your tree(s).

    Much as I love the stunning color and form of white birches, until you are certain that this pest is in remission, stay away from new plantings of the betulas.

  • Living Snoqualmie