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CORVALLIS - Forestry researchers at Oregon State University have tested and proven a strategy to control Douglas-fir bark beetles using one or more "pheromones" to attract or repel this serious forest pest.

The most useful of these chemicals, a repellant pheromone called MCH, now awaits only approval by the Environmental Protection Agency to gain widespread field use, scientists say.

The new techniques were developed in cooperation with scientists from the Pacific Northwest Research Station of the U.S. Forest Service. They may play a vital role in combatting a major insect pest that often is the actual killer of Douglas-fir trees, finishing the job that drought, other plant diseases or the spruce budworm may have begun.

And it may be particularly necessary to meet some goals of ecosystem management, said Darrell Ross, an OSU associate professor of forest science.

"These bark beetles breed and thrive in stressed trees or those that have recently died," Ross said. "One of the ways we managed them in the past was by removing much of that material. But the new approaches to forest management and ecology call for leaving more debris that may actually worsen the bark beetle problem."

But after years of research, Ross said, it now appears that the use of pheromones can successfully "push" the beetles away from vulnerable areas or, if desired, "pull" them into traps. In recent studies, OSU scientists have learned the exact and minimal amounts of these natural chemicals that can be used for optimal control.

The most recent findings were published in the Journal of Economic Entomology, and confirmed that even the lowest dose of chemicals the researchers tried could reduce mass beetle attacks on Douglas-fir trees, while having no impact on the predatory insects that also helped control the beetle.

New approaches such as this, Ross said, might be used in any situation where bark beetles pose an epidemic risk, or especially to protect small, high value stands such as those near parks, campgrounds or riparian zones.