USDA Forest Service

Pacific Southwest Research Station

Pacific Southwest
Research Station

800 Buchanan Street
Albany, CA 94710-0011
(510) 883-8830
United States Department of Agriculture Forest Service. USDA logo which links to the department's national site. Forest Service logo which links to the agency's national site.

Research Topics: Insects and Disease

The walnut twig beetle excavates under bark to inoculate a tree with the Geosmithia morbida fungus, resulting in Thousand Cankers Disease.
An aerial survey of dead trees on the Sierra National Forest.
(U.S. Forest Service)

2017 Bark Beetle Forecast for California

California experienced extremely high levels of tree mortality in 2016 because of the combined effects of drought and bark beetles. Images like the one to the right were common in the southern Sierra Nevada Range, and aerial surveys conducted by the U.S. Forest Service estimated that 102 million trees have died in California since 2010.

To help land managers anticipate the risk of tree loss ahead of these surveys, PSW and collaborators created a forecast of the intensity and location of bark beetle-caused mortality, by analyzing historical aerial survey data and variables known to influence bark beetle success, such as precipitation and stand density.

The 2017 Bark Beetle Forecast for California is based on history of drought and bark beetle attacks from 1993 to 2016. Areas with similar histories of bark beetle activity and precipitation were grouped together into ten risk groups. These risk groups forecast a range of the likely number of trees expected to die from bark beetles by the end of summer 2017.


Invasive Insects: PSW has one of the world's leading authorities on termite taxonomy and has developed and evaluated numerous methods for assessment, taxonomy clarification, and control.

Pitch Canker: This fungus causes several serious diseases of pines. The pathogen infects a variety of vegetative and reproductive pine structures at different stages of maturity and produces a diversity of symptoms.

Response to Climate Change: Extreme weather can kill large expanses of trees directly by overwhelming tree physiological and structural strength. Patterns and rates of wood decay, caused by forest fungi, are also expected to change in response to climate changes which will influence forest carbon cycles.

Related Research

Sudden Oak Death
Research Partnerships:
Sudden Oak Death
White Pine Blister Rust
White Pine Blister Rust
in Western North America