Douglas-firtussockmoth (Orgyia pseudotsugata) is a native defoliator of spruce, Douglas-fir (Pseudotsuga menziesii) and true firs (Abies spp.), though will rarely feed on planted Colorado blue spruce in urban areas. The moth is a native species found throughout... The Douglas-firtussockmoth is a destructive native defoliator of Douglas-fir. This moth kills trees, and the caterpillars' hairs are a serious human health risk.Damage. Douglas-firtussockmoth outbreaks can cause extensive mortality of interior Douglas-fir. Douglas-firtussockmoth spends the winter as an egg within the egg mass. Eggs hatch in the spring, often in late May, typically following bud break. The small, hairy caterpillars migrate, moving to the new growth but also often dispersing upwards in the trees. The Douglasfirtussockmoth 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. Figure 9. Adult female Douglas-firtussockmoth on egg mass. Note that female moth is wingless. Biology: Eggs hatch from mid-May to early June and caterpillars feed on the current year's developing foliage. Main Host(s): Douglas-Fir (Pseudotsuga menziesii), Grand Fir (Abies grandis), Subalpine Fir (Abies lasiocarpa), White Fir (Abies concolor), and less frequently on Ponderosa pine (Pinus ponderosa), Eastern Larch (Larix occidentalis). Life Cycle. The TussockMoth is native to the forests... Douglas-firtussockmoth is a native defoliator of conifers in North America west of the Rocky Mountains. Periodic outbreaks occur at about 10-year intervals and last up to four years. Douglasfirtussockmoth larvae start at branch tips at the top of the tree and work down, feeding mainly on the new foliage and causing severe defoliation. They may be found under webbing on the branches. Douglasfirtussockmoths primarily attach Douglasfir, grand fir, subalpine fir and spruce trees, but will also feed on larch, shrubs and even pines. Tussockmoths can be seen every year in Idaho, but a population boom can be expected every 8-10 years. Doiuglas FirTussockMoth. Orgyia pseudotsugata (McDunnough) Lepidoptera: Lymantriidae.The Douglas-firtussockmoth: a synthesis. USDA Forest Service Technical Bulletin 1585: 331 pages.
