Pheromone trackers

It’s in the news everywhere -— predictions for another bad wildfire season in the western United States. According to a local report, the Washington State Department of Natural Resources had already fought 70 small fires by the end of May, well above the usual 20, and finds that forests are as dry as they normally are in late July or August.

There is no doubt the trees are stressed these days. One of the culprits is the lower-than-average rainfall the western states have been experiencing for a number of years. Another is the lowly bark beetle, which among other things, has been blamed for heightened devastation in recent California forest fires. Bark beetles, which are normally present in all healthy coniferous forests, bore into trunks causing the trees to defend themselves by producing sap. But during a drought, there may not be enough water to produce sap and the beetles can do more damage, leading to infestations that can kill the tree.

Over time, this leads to great economic losses and increased risk of catastrophic fire. As beetles kill off trees, more dry, flammable debris accumulates on forest floors. During the Smokey Bear era, for example, when all forest fires were prohibited, much of this fuel built up, allowing beetle populations to increase. The results were fires that could destroy whole forests such as the one in 1988 in Yellowstone Park.

Up until the mid 1920s, fires in the west kept forest floors cleaner, allowing many trees to survive a blaze. Realizing the benefits fire provided, forest management agencies in the early 1980s changed their approach, increasing the removal of understory fuels and use of prescribed burns, to begin returning the forests to a more natural state.

Researchers focus on pheromones

Searching for better ways to deter bark beetle devastation and resultant wild fires are Washington State University’s Brian Lamb, civil engineering professor, and Tara Strand, Ph.D. student, in the Department of Civil and Environmental Engineering’s Laboratory for Atmospheric Research, http://www.ce.wsu.edu/LAR. Lamb and Strand are studying the use of artificial pheromones.

Pheromones are chemicals produced by insects and mammals that are used for communication or signaling purposes within the same species.

“For example, when a beetle finds an acceptable tree,” said Strand, “it lays eggs while releasing pheromones to signal other beetles to come to that tree.” In effect, the pheromone is saying, “come and help us overtake this tree,” which can lead to a massive attack or infestation.

Slash and burn not effective

In the past, various methods of beetle control have been tried, such as salvage or slash-and-burn techniques together with pesticide applications, but most were only marginally effective. Recent studies have shown that insects rely on extremely sensitive chemical communication methods that can be disrupted by use of artificial pheromones. Hoping to capitalize on these discoveries, Harold Thistle, program manager for the Forest Health Technology Team in West Virginia, issued a request in 1999 for proposals to study the dispersion of pheromones in forests. Lamb responded from WSU and began a collaboration that led to atmospheric studies in Virginia, Montana, Oregon and, most recently, Louisiana.