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December 14, 2016
Vol. 3, Issue 5
December 2016
Know Your Pest - Fir Engraver Beetle
Figure 1. Fir engraver-caused fir mortality. Photo by Don Owen, CalFire 

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 
   
Tree Mortality Levels Continue to Rise
The US Forest Service (FS) announced in November that 2016 aerial detection surveys identified an additional 62 million trees that died from drought-related causes in 2016 - 100% increase from 2015, when 29 million trees were estimated to have died. Since 2010, over 102 million trees have died in California over 7.7 million acres. Millions more drought-stressed trees that are not yet dead are expected to die in the coming months and years as a result of 5 consecutive years of severe drought, epidemic-levels of bark beetle infestations, and warmer temperatures.
Tree Mortality, Mariposa Co., 2016. Photo by CalFire. 
 
The majority of the dead trees are located in 10 counties in the southern and central Sierra Nevada region. The FS also identified increasing mortality in the northern part of the state, including Siskiyou, Modoc, Plumas, and Lassen Counties. Over $10 million in state funds have been earmarked in grants for local projects to help combat tree mortality, focusing on the removal of dead and dying trees around homes. Another $6 million of state funds have been used to buy equipment for removing dead and dying trees in high-hazard zones.  For more information on tree mortality and management efforts in affected communities, visit the Tree Mortality Task Force website. 
Newsletter feedback and ideas are welcome.  Please submit comments to caforestpestcouncil@gmail.com

When buying firewood for home heating this winter, remember to buy it from local sources, helping to minimize the spread of pests and diseases - Buy It Where You Burn It.  For a list of local firewood dealers, go to firewoodscout.org.

Sincerely,

Katie Harrell
Communications Director  
California Forest Pest Council
California Forest Pest Council | (510) 847-5482 | caforestpestcouncil@gmail.com |

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