What Is the Douglas-fir Tussock Moth and What Is It Doing?
The Douglas-fir tussock moth is a native insect of Yosemite and the rest of the Sierra Nevada. It is during the larvae or caterpillar phase of this insect’s life cycle when it eats the needles from the trees. The distinctive caterpillar can be readily identified by its four “tussocks,” the line of buff-colored tufts that runs along its back. It feeds primarily on white fir in the Sierra forests. Historically, Douglas-fir tussock moths have had wildly fluctuating populations punctuated by irruptions (sudden upsurges in numbers) and massive die-offs from natural causes—particularly a virus that is always present in the soil and that affects only them. Recently, Yosemite foresters detected an increase in 2002 that lasted until 2006. Visitors in the Chinquapin and Crane Flat areas of Yosemite may notice thin foliage, snag tops, and dead white fir trees in the forest. This is evidence of a recent outbreak of Douglas-fir tussock moth caterpillars. Over the course of about three years, tussoc
