Tree mortality following severe defoliation by the pine butterfly (Neophasia menapia) in eastern Oregon

The pine butterfly (Neophasia menapia) is a native insect that is commonly observed at endemic levels in forests of the Pacific Northwest. Pine butterfly outbreaks appear to occur at widely-spaced, irregular intervals with each lasting approximately 3-5 years. During outbreaks in pine-dominated forests, large areas can be completely defoliated over several consecutive years, commonly resulting in tree mortality in association with attacks by pine bark beetles, drought, and other factors. The current outbreak in eastern Oregon, which began in 2008, has affected over 250,000 acres and is the largest ever documented in the state.  As previous outbreaks have not been well-described, a cooperative research effort has begun to examine infestation characteristics and assess the effects of severe defoliation within pine-dominated stands in the Malheur National Forest.  In 2012, 48 permanent plots were established in 16 stands, with additional plots to be installed in 2013.  Each will be re-assessed annually over 5 years to examine the extent of tree mortality and describe the contributing agents.  Stand structures are being characterized and will be examined in relation to defoliation severity.  Findings will be used to refine silvicultural recommendations for increasing forest resilience to the effects of pine butterfly and further elucidate aspects of their biology and ecology in the Pacific Northwest.