The Nevada Division of Forestry conducted trapping and aerial surveys this season, focusing on the White Satin Moth outbreak in Lake Tahoe Nevada State Park.
The survey revealed 226 acres of infestation, ranging from minimal to heavy defoliation. Minimal defoliation was mapped on 52 acres, with moderate areas mapped on 107 acres, and heavy areas mapped on 67 acres.
Results of trapping indicate populations are trending higher; freezing weather in the higher elevations is triggering the insects’ transition to its over-wintering stage which results in lower trap numbers.
In late August, the second hatch of larvae occurred and sampling found high caterpillar numbers feeding in upper North Canyon, Marlette Lake, and west of Hobart Lake. Bark and leaf samples found 10-15 caterpillars per leaf, which is extremely high. It’s anticipated fall color will be diminished this year, and populations will likely increase next year causing more defoliation, tree stress, and tree mortality.
Moths in the more urban areas shouldn’t lead to any major defoliation since the insect requires more than individual landscape trees to flourish. Defoliation may still occur, but it should be minimal.
“NDF would like to extend our thanks to the general public who called us to report sightings. It provided valuable tracking and movement information and helped us to develop and focus surveys in priority areas,” said NDF Forest Health Specialist Gene Phillips.
The Nevada Division of Forestry is researching the possibility of conducting a biological insecticide spray project next year to control the insect population within the park to minimize the infestation. Since this is a non-native invasive insect, native predators aren’t present in sufficient numbers to control the population. This type of project will require inter-agency cooperation and planning.
For information about the defoliation, infestation and future plans to control White Satin Moth populations, call 775-849-2500, ext. 241.