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