Placer issues Gypsy moth warning 

Published on August 4, 2020  

Placer County is issuing a gypsy moth warning in response to finding a moth in the Foresthill area last Thursday. 

Gypsy moths are an invasive species whose caterpillars feed on tree leaves, threatening forested areas especially. Though findings are extremely rare in Northern California, Placer successfully prevented a gypsy moth infestation several years ago in the Dutch Flat area. 

Gypsy moth introductions typically occur when outdoor equipment, patio furniture or vehicles are moved from locations in the eastern United States, where gypsy moths are common. The moths lay egg masses on the undersides of these items, and then the eggs hatch after the item is moved to California.

“We take this invasive species very seriously and are pursuing the necessary precautions,” said  Placer County Agriculture Commissioner Josh Huntsinger. “Our department put out additional traps around the area where the one moth was found, which we believe will eradicate the species in the region for this season. Pesticide treatments are not part of the eradication protocol for gypsy moth. The traps themselves are so effective, they can be used to eradicate any latent populations. Our team has not found any moths since setting out the additional traps and plan to continue monitoring the traps closely.” 

Placer County maintains over 1,000 invasive species traps and monitors the traps bi-weekly. Residents in the Foresthill area may notice additional bright green gypsy moth traps placed on the trunks of trees. These traps contain a pheromone lure that entices the male moths into the trap, where they become stuck on its sticky insides.  

Gypsy moth young larvae feed primarily on oaks, aspen, birch, willows and alder, and older larvae feed on a broader range of trees including cedar, pine, spruce and fir. Common California species such as manzanita, western hemlock, Douglas fir and live oak are also prone to damage by this pest. A single gypsy moth caterpillar can eat up to 1 square foot of leaves per day. 

In the northeastern United States, where this pest arrived from Europe in the late 1800s, millions of these caterpillars emerge each spring and devour large swaths of forest and foliage. When trees are repeatedly defoliated, they are more susceptible to other pests and diseases, possibly leading to tree death and an increased potential for fire and erosion.

Residents can learn more about gypsy moths at