The Asian spongy moth is a greater threat to Washington's forests than the European spongy moth. Also an aggressive defoliator, the Asian spongy moth female can fly up to 20 miles. European females are flightless. The Asian spongy moth feeds on a greater number of host trees (over 500 species) including many conifers.
Washington has had more Asian spongy moth introductions than any state in the US. They arrive as egg masses attached to ships carrying cargo from Asian ports. The Asian and the European spongy moths are different varieties or sub-species of the same moth (Lymantria dispar). The two varieties look very similar and only through DNA testing can the identity of the Asian variety be confirmed.
In 2019, a new variety of Asian spongy moth was detected in Washington State. This was the first-ever detection of the Hokkaido spongy moth (Lymantria umbrosa) in the United States. In May of 2020, WSDA conducted an eradication where the Hokkaido spongy moth was detected.
2016 APHIS Asian Spongy Moth Fact Sheet
USDA APHIS Asian spongy moth web page