Current Events 7: Pheromone That Could Save Pine Forests

In the last 15 years, the number of bark beetles has grown exponentially, leaving a devastating amount of pines stripped of their bark in the beetles' wake. These beetles have the ability to wipe out entire forests and have done so at an unprecedented pace; in 2010, 9.2 million acres of forest in the western United States were destroyed by bark beetles. In the last few years, scientists have come up with a way to combat bark beetles by confusing their sense of smell via pheromones. One pheromone they release, called verbenone, acts as a warning sign to other beetles to avoid certain trees. Verbenone is secreted from the beetles at the end of their reproductive cycle, after adults have carved out tunnels, or galleries, into the bark so females could lay eggs. The larvae emerge and feed on the tree's phloem tissues, disrupting the transfer of its nutrients, and at this point, verbenone is secreted to signify that the tree is already taken and other beetles must find another one. The pheromone acts as a safe, natural repellent of the beetles, as opposed to the failed approaches previously taken, such as chopping down the infected trees and spraying large amounts of harmful pesticides. Older, dense forests were most susceptible to infestation, and adverse effects of climate change have enabled the beetles to survive longer seasons, not helping the problem. However, with the invention of a pheromone releasing plastic an opportunity to fix the problem has been presented. The flake consists of plastic parts at the top and bottom with verbenone in the middle, which is secreted along the edges. The flakes have been able to cut tree mortality rates by up to 90%, however they do still have a few setbacks. They must be placed on trees or in forests before adult beetles start their reproductive cycles and young larvae emerge, but it is impossible to determine when exactly this occurs. Additionally, the dispersal of the flakes is expensive; the cost of treatment is about $150 an acre and even more expensive if done by helicopter. Because costs are so high, scientists are looking into an alternative way or distributing the pheromone by genetically engineering microbes that could secrete it, and this avenue of dispersal would be significantly cheaper.

http://discovermagazine.com/2012/jul-aug/06-pheromone-save-pine-forests-oblivion/article_view?b_start:int=1&-C=