The fir engraver beetle ( Scolytus ventralis) occurs from British Columbia south to California and as far west as Colorado and New Mexico. Within that range, it is a noted killer of white fir, grand fir, and red fir and occasionally kills other true fir species as well as Douglas-fir, hemlock, and spruce. Like many other bark beetles, large outbreaks often occur during and after droughts (fig 1). Root-diseased firs, especially those infected by Heterobasidion occidentale ("annosus root rot"), are always susceptible to attacks.

	Figure 2. Fir engraver-caused dead cambium. Photo by Chris Lee, CalFire

Fir engraver beetles attack a tree at multiple sites along the trunk. Often the tree's resistance limits the success of the attacks, resulting in scattered patches of dead  cambium or individual branch kill (fig 2). Female beetles attack initially, with males following to mate. The females lay eggs in niches along the distinctive egg gallery which runs perpendicular to the wood grain (fig 3). Developing larvae mine away from the egg gallery, parallel to the grain. There is generally 1 generation per year, with each generation taking 2 years to develop in colder parts of the beetle's range.

California's recent extreme drought initiated widespread true fir mortality, especially in the southern Sierra Nevada range. In 2016 alone, the USDA Forest Service, State and Private Forestry, Forest Health Monitoring aerial detection survey mapped over 1.3 million acres of true fir or mixed conifer mortality for which fir engraver beetle was found to play a primary role.

Figure 3. Fir engraver galleries run perpendicular to wood grain. Photo by Chris Lee, CalFire