Douglas-fir ring width data for reconstructing past periods of western spruce budworm outbreak

The western spruce budworm (Choristoneura occidentalis; "WSB") is one of the most widely distributed native defoliators of coniferous forests in North America, where it plays an important role in shaping ecosystem function. Here we provide tree-ring data used to reconstruct periods of past WSB outbreak at 12 sites across central to northern Colorado over the past 300 years.