The non-native white satin moth is causing medium to heavy defoliation in the North Canyon and Marlette Lake areas at Lake Tahoe Nevada State Park.

Nevada Division of Forestry has recently mapped approximately 200 acres of defoliation in this area. Sightings in the Carson Valley, Spooner Summit, USA Parkway area and Paradise Valley have also been confirmed.

White satin moth

The white satin moth (Leucoma salicis) is a non-native defoliator of aspen, cottonwoods, willows and other deciduous species and is native to Europe and Asia.

It was first introduced into North America in British Columbia in 1920. It is currently distributed from BC to Northern California, and has been present in Nevada since the 1980s. Moths overwinter as larvae, and hibernate on trunks or branches in silken coverings, which are very hard to see because they are covered by bark, mosses and other debris. They emerge from May to early June and feed on the new young leaves. Feeding continues through July as the larvae grow until they are approximately 3.5-4.5 cm long caterpillars. This stage is the most often seen and the caterpillar is grayish brown with a dark head and back. Unique markings for identification include a row of large oblong white to pale-yellow patches down the back. The caterpillars spin cocoons and emerge as adult moths from late July through August. The white adult moth is 2-4 cm long and has no markings on the wings.

Damage done by the white satin moth larvae is directly related to their population size. Defoliated trees can produce new leaves the same season and will have a ragged appearance. However, continued, repeated defoliation can weaken trees, causing long term damage and tree death.

Current damage is medium to severe with damage ranging from 40 to 70 percent canopy loss. The most significant areas of defoliation known are on the east side of Marlette Lake at the campground and in aspen stands immediately south of the lake in north canyon. Other damage has not been estimated but will be monitored for the remainder of the summer season.

The Nevada Division of Forestry will also investigate the possibility of a control program in the future to minimize damage to the aspen forest.

NDF is requesting if the public has observed the white satin moth or the damage caused by this insect to call Gene Phillips at 775.849.2500, ext 241.