Female polyphagous shot hole borer. Shot hole borers have spread to 280 different plant species in Southern California. Photo: Gevork Arakelian / LA County Agricultural Commissioner7 June 2014 (CBS News) – Southern California is already plagued by a crippling drought and wildfires.

Now you can add a legion of seemingly unstoppable beetles to the list of threats facing the region’s forests. They’ve already invaded hundreds of tree species, and they are showing no signs of slowing down. “We have lost numerous trees,” said Jim Folsom, director of the Huntington Botanical Gardens outside of Pasadena, Calif. “On the property, in these 200 acres, we have over 700 species of large tree, woody tree. Of those, fully one-third, over 200 different kinds, different species of tree have proven to be invaded or impacted by this borer,” Folsom said. The polyphagous shot hole borer is a tiny, grain-sized beetle first discovered in the area two years ago. It drills a hole into the heart of the tree and deposits a fungus that it carries in its mouth. That blocks water and nutrients and in many cases kills the tree. “We have no known treatment,” Folsom said. “We have no capacity to fend it off.” University of California, Riverside, plant pathologist Akif Eskalen first discovered the pests in avocado trees. They have since spread to 280 different species in Southern California, and he fears they could be unstoppable. [more]

Tree-killing beetles attacking California’s forests