Anchorage birch trees dying off

Posted: Monday, July 15, 2002

ANCHORAGE (AP) -- Birch trees are ailing all over Anchorage.

Experts disagree on the cause of the problem, which has prompted hundreds of calls to the University of Alaska Cooperative Extension Service.

''It's citywide,'' said extension service technician Michael Rasy.

Siri Moss, a downtown resident, said her birches have been dying this summer from the ground up despite a heavy regimen of watering and basic tree care.

''We're noticing that a number of our trees are just weakening over time, and last summer, our trees down here were hit really hard with the (birch) leaf miner,'' Moss said.

Sorting out the root cause of the tree problem has sparked some disagreement among local experts. One theory is that it is the work of the birch leaf miner, an alien sawfly species whose larva has been eating the inner layer of leaves each summer since it showed locally about six years ago. Some believe several factors that can include leaf miners and other pests are to blame.

Rasy has found no ''telltale sign'' of a single cause.

''It's basically several environmental and biotic factors working together over the course of multiple years that have prevented normal growth and defensive processes,'' Rasy told the Anchorage Daily News.

A dry spring, poor watering practices, compacted soils and a winter warm spell that dried out trees compounded the damage done to many trees last summer by insects, including the leaf miner and aphids, Rasy said.

Matt Tyrala, an arborist who has worked in Anchorage for 25 years, believes the leaf miner has played a much larger role than people realize. He likens Anchorage to a sort of ''ground zero'' for a spreading infestation.

''It's everywhere,'' he said. ''You can drive down any street in Anchorage, and you can see this stuff. By this time next year, it will be ubiquitous. . . . This has the potential to eclipse the spruce bark beetle.''

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