Leucoma salicis L. (Lepidoptera: Erebidae: Lymantriinae)
Multiple pesticides are available to control satin moth populations that are occasional pests of nursery plants (Rinehold 2015). However, integrated pest management (IPM) practitioners have limited pesticides that can be used to protect poplars grown for Forest Stewardship Council (FSC) certified pulp and wood products east and west of the Cascade Mountains in Oregon and Washington. This publication contributes additional information regarding identification, life history, monitoring, and FSC-approved management strategies to control Leucoma salicis.
Erebidae is one of the largest families of macro-moths and includes the satin moth as a member of the Tussock moth subfamily, Lymantriinae. Tussock moths are notorious pests of forests in the US. Included in this group are the gypsy moths, Lymantria dispar L., and the Douglas-fir tussock moths, Orgyia pseudotsugata McDunnough. Other members of the Erebidae feeding on poplar in the Pacific Northwest include: the fall webworm, Hyphantria cunea Drury subfamily Arctiinae; black/white underwing moths, Catocala relicta Walker; and the spotted tussock moth Lophocampa maculata Harris subfamily Erebinae (Crabo et al. 2016). Adult satin moths and adult fall webworm are very similar in appearance.
Leucoma salicis larvae feed mostly on poplar, willow, and aspen (Wagner and Leonard 1979; 1980). Humphries (1984) reported satin moths feeding on Saskatoon (Amelanchier spp.), oak (Quercus spp.), and crabapple (Malus spp.).
Satin moths are an invasive species from Eurasia. They caused the first severe defoliation of eastern cottonwood in the early
20th century (~1920). They were found in New Brunswick, Nova Scotia, Quebec, Ontario, and Maine in the east, and Alberta, British Columbia, California, Idaho, Nevada, Montana, Oregon, Utah, Washington, and Wyoming in the west (Latchininsky 2016; USDA Forest Service 2016).
In mid-summer the first instar hatches and feeds on foliage for a month (Figure 1) before seeking an overwintering site in a crack or crevice, where it spins a silken hibernaculum, molts to a second instar, and survives winter conditions. Dormancy is broken in May and by mid-June when notable, even significant, defoliation becomes apparent. Development from the overwintering second instar through the ultimate seventh instar takes place within 90 days (Ferguson 1978). The most damaging larval stages are 3rd through 7th instars (Zurek and Keddle 2000) in June. Full-grown larvae are conspicuously colored with 10–11 (intersegmental) white spots on their dorsal surface (Figure 2), and they wander down the trunk of their host tree in search of a pupation site (Figure 3). Adult moths emerge in July (Figure 4). They are poor fliers and are mostly active at night, when they mate. Females lay egg masses on the undersurface of leaves. The first egg mass is generally the largest, but females average 4.6 egg masses and can total 650 eggs oviposited and covered with frothy secretions (Wagner and Leonard 1979).