Leaf-eating moths causing problems at Lake Tahoe Nevada State Park

STATELINE —The non-native white satin moth has eaten its way through 200 acres of aspen and cottonwood leaves in Lake Tahoe Nevada State Park this summer, forcing the Nevada Division of Forestry to issue a “Forest Pest Alert” on Thursday.

The moth is responsible for 40-70 percent canopy loss in the North Canyon and Marlette Lake areas at Lake Tahoe Nevada State Park, according to the Nevada Division of Forestry. Sightings have also been confirmed in the Carson Valley, Spooner Summit, USA Parkway area and Paradise Valley.

Native to Europe and Asia, the white satin moth was first introduced to North America in British Columbia in 1920. It has been present in Nevada since the 1980s.

The moths overwinter as larvae and hibernate on trunks or branches in silken coverings masked by other natural debris. They emerge between May and early June and begin to feed on the leaves of aspens, cottonwoods, willows and other deciduous trees. Feeding continues into July as they grow into caterpillars, which then spin cocoons and emerge as moths during late July and August.

The increase in defoliation this year is due to a surge in the moth’s population.

“Their populations are really a boom and bust cycle,” said Gene Phillips, NDF forest health specialist. “About 2010, 2011 they reared their head through about 2013 in some of the same areas of Lake Tahoe.”

The reason for the population surge this year is unclear.

“Being an invasive, those predators aren’t there,” said Phillips. “I can’t really tell what caused this population increase other than they may have just found the habitat with the right species composition, enough trees per acres, to take off and get established in some larger stands and have a bigger impact this year.”

Though the defoliated trees can produce new leaves in the same season, continued defoliation can weaken trees and lead to long-term damage or death.

Phillips said NDF is also looking at the possibility of a control program using a “natural parasitic bacteria.”

“We’re just starting to look at this. Something like that requires a lot of coordination with a lot of agencies,” noted Phillips.

Over the next four weeks NDF will conduct aerial surveys to determine the extent of the moth infestation. The agency is also asking the public to come forward if they have observed any areas with white satin moths or defoliation damage that the insects may have caused. Phillips can be reached at 775-849-2500 ext. 241.