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Why I Do Science: David Wood

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David Wood, professor emeritus of entomology, has had a strong influence on a generation of land and resource managers as well as on the pest control industry. He continues to run an active research laboratory in the College of Natural Resources.

I love trees.

I love trees because they form forests, which bring so much beauty and serenity to a crowded and fast-paced urban world. My parents exposed me to the beauty of the eastern hardwood forest as they fished, watched birds, and collected wild berries on weekends.

How do insects find and colonize trees? This question has provided me with endless fascination and challenges for a professional lifetime and beyond. The integrating discipline is insect behavior. Some forest insects, such as the spruce budworm, gypsy moth and bark beetle, develop epidemic populations which result in the death of trees over vast areas. For example, in the largest epidemic ever recorded, the mountain pine beetle is estimated to have killed trees over 130,000 square km range in British Columbia at the end of 2006. Global warming has been implicated in this particular outbreak.

I began work on bark beetles during my dissertation research. Bark beetles must aggregate on trees in order to overcome tree defenses. In collaboration with organic chemists we isolated these aggregation pheromones (chemicals which attract the opposite sex). In collaboration with plant pathologists we isolated the blue-staining fungi that are carried by these beetles, and through dye studies, demonstrated that they interrupt the flow of water in the sapwood. We also showed that ponderosa pines weakened by photo-chemical air pollutants and by black-stain root disease were more likely to be killed by bark beetles than trees without these problems.

Although students and postdoctoral scholars in our lab have worked on other forest insects, such as carpenter ants that tunnel in giant sequoias, subterranean termites in wildland and urban forests, spittlebugs, and weevils, bark beetles have been our primary focus. Bark beetle biology is endlessly fascinating and stimulates research questions at the molecular, species, tritrophic, guild, community, and landscape levels of biological organization. And the results contribute to both the applied and basic research worlds.

Our recent studies have uncovered new relationships between native bark beetles and the recently introduced "pitch canker" and "sudden oak death" pathogens. They introduce the pitch canker pathogen into twigs, cones, and the main stem, and then kill the weakened trees. Ambrosia beetles are attracted to the SOD-bleeding cankers and tunnel into the sapwood, thereby reducing the the flow of water in the sapwood and weakening the main stem, resulting in tree failure. Bark beetles are also associated with tree failures that result in wildland fires. The lack of thinning in much of our western forests has lead to bark beetle outbreaks and subsequent wildland fires. The beetles also exploit trees injured by both prescribed and wildland fires.

Humans interact with forests in many ways that favor bark beetle activity—through our management practices, by producing smog, and by introducing exotic species. I’m proud that my lab’s work has lead to new understandings about these ecological processes—that will help sustain our forests for future generations.

-David Wood


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