New anti-beetle device shows promise after recent Peninsula tests

Posted: Friday, September 22, 2000

SEWARD (AP) -- What could be bad news for the spruce bark beetle could be good news for Alaska's environment, according to scientists who are trying out a new experimental device that could keep the voracious pest from further destruction.

From recent tests in the Kenai Peninsula, researchers with the U.S. Forest Service are optimistic about the small plastic devices that pump out pheromone excreted from beetles. The compound presumably tricks the insects into believing the targeted trees are already occupied.

Ed Holsten, a Forest Service entomologist, and two colleagues hiked into research plots in the Snow River area last week to collect test data. In May, researchers attached timed-release devices to trees.

Testing was done on eight treated and eight untreated plots containing about 100 unattacked spruce trees per plot.

Holsten said it's too soon for conclusions. However, he pointed out, untreated areas had about 4.7 attacked-trees per half-acre plot while treated plots averaged one attacked tree.

Since the time-release device works as a deterrent and not a repellent, plots already heavily infested with the beetle could not be used, Holsten said.

So to make sure the beetles were attracted to test plots, small vials of a attractant were attached to trees in the center of the plot, Holsten said.

''At first glance, it appears there was a treatment effect,'' he told the Seward Phoenix-LOG. ''The release devices greatly reduced the number of attacks. But that's not to say we kept every beetle out.''

More than 300,000 acres of trees on the Kenai Peninsula are in various stages of infestation by the beetles, according to Bill Shuster, a biologist with the U.S. Forest Service. About 8,000 acres are affected in the Moose Pass and Crown Point area.

Adult beetles, having a two-year life-cycle, fly and attack standing trees usually in the spring or early summer, Holsten said. Adults lay eggs under the bark, and the resulting larvae consume the tissue around the tree that supports its food transportation system, virtually starving the tree to death. By the end of the second season, the new adults bore out of the tree, fall to the base and burrow under the bark for a second winter. In the spring, the beetles bore out and attack a new tree, repeating the cycle.

Similar deterrent studies have been done for about the past five years using a different type of release device that bases the amount of compound released on outdoor temperature, with little luck.

Varying temperatures mean varying amounts of pheromone released, with hotter days causing more of the compound to be released, Holsten said. But Alaska summers tend to be much cooler than in other states, where the so-called bubble caps appear to work on other types of bark beetles.

''We were kind of giving up on them,'' said Holsten. Then he agreed to test the new time-release devices used on the Snow River plots.

Key is a small electric pump about the size of a pencil eraser developed by Med-E-Cel in San Diego. Similar pumps are used by cancer patients and veterinarians treating horses, Holsten said.

The prototype devices Holsten used for his project are manufactured by Columbia Analytical in Anchorage.

Holsten hopes to have the statistical data compiled in the next two weeks. The information will be passed on to Med-E-Cel, which is expected to request a second year of funding for the project from the Alaska Science and Technology Foundation.

While it wouldn't be practical to cover entire forests with the devices, this alternative to pesticide use or harvesting trees could be used to deter spruce bark beetles from campgrounds, around homes or other sites needing protection, Holsten said.



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