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Jul 27

Western Spruce Budworm

Posted on July 27, 2019 at 5:04 PM by Alicia Doran

We are seeing an outbreak of Western Spruce Budworm in the southern part of the county in the Foxton area.

Western Spruce Budworm (WSBW) is a native moth with one generation a year.  In recent years, Colorado has seen an increase in WSBW outbreaks.  In 2018, CSFS had seen about 150 acres affected in Jeffco.  WSBW defoliates the branch tips of Douglas-fir, true fir (e.g., subalpine fir and white fir) and spruce trees.

Repeated defoliations may kill the tree or make it more susceptible to other insects.  High value trees may be treated with insecticide early when the larva first emerge (mid-May) but forest-wide treatment is usually not a recommended option.  Link to Fact Sheet


Western_spruce_budworm_larva  Western_spruce_budworm_damage