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  September 8, 2014
Vol. 1, Issue 4
September 2014
September 30 - CFPC South Bay Arborist Training, San Mateo County. ISA and DPR credits available.  For more information, or to register, go to  


November 12 - 13 - 2014 CFPC Annual Meeting, McClellan (near Sacramento). More information will be available soon at

Douglas-fir Tussock Moth Outbreak

A Douglas-fir tussock moth outbreak is impacting over 28,660 acres of white fir in Tehama, Butte, Lassen, Plumas, and Sierra Counties, with areas on the Plumas National Forest being the most severe. As caterpillars feed on fir needles, the foliage turns brown and shrivels. Defoliated trees appear to be dying, but unless a tree is nearly stripped of its foliage (90% or more defoliation), full to partial recovery is likely. It is possible, however, that current drought conditions could reduce recovery rates for some severely defoliated trees.

Tussock Moth Larvae. Photo by USFS SPF Pacific Southwest Region
Douglas-fir tussock moth larvae. 

Outbreaks of this native insect are cyclical throughout the state in areas with high concentrations of white fir, the preferred host in California. Historically outbreaks last for 3 years, ending with a population collapse caused by natural enemies such as parasitic flies and a naturally occurring virus. Due to the short timeframe of outbreaks and the limited number of trees that are ultimately killed, control options are seldom employed.


Areas with the most severe white fir defoliation are typically drier sites, such as upper slopes and ridge tops that were historically dominated by pine species. White fir has become more abundant in these areas in the absence of fire, leading to greater potential for damage during Douglas-fir tussock moth outbreaks. For more information, go to

Burn It and They Will Come

Many wood boring insects such as wood boring beetles and wood wasps migrate into  

Roundheaded wood boring beetle larvae in fire-killed tree, 2012 Reading Fire, Lassen NF. D. Cluck, USFS.

burned areas to exploit fire-injured and fire-killed trees.  They find scorched areas and individual trees by following smoke or, in some cases, by using infrared receptors on their bodies. These pyrophilous (or fire loving) insects seek out burned trees in order to mate and lay eggs. Larvae of different species feed solely within the inner bark, in the sapwood, or a combination of both. Feeding activity is the first step in the decomposition of a fire-killed tree. The tunnels created by the larvae serve as entry points for fungi and other insects that hasten decay. Wood boring insect larvae are also a major food source for other insects, birds, and mammals. Wildfires in California support numerous wood boring insect species (e.g., over 40 species were collected from one location of the 2012 Reading Fire, Lassen National Forest). 


Beetle galleries in fire-killed tree, 2012 Chips Fire, Lassen NF. D. Cluck, USFS.

While these wood boring insects are simply fulfilling their ecological role in the forest, they can create problems if infested trees are to be used for lumber. Wood boring insects can cause a significant loss of value by creating large tunnels in the sapwood, facilitating the spread of decay fungi or introducing wood staining fungi. Fire-killed trees that are not processed within the first 2 to 3 years after a fire can lose all of their value. Smaller diameter trees can lose all of their value within 1 year.  

Beetle tunnels and bluestain fungi in sapwood, 2012 Reading Fire, Lassen NF. D. Cluck, USFS.

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Have a safe and happy fall, and remember when buying wood for home heating this winter to buy from a local source - Buy It Where You Burn It.




Katie Harrell (formerly Palmieri)

Communications Director

California Forest Pest Council

California Forest Pest Council | (510) 847-5482 | |

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