Parks & Recreation

Spongy Moth

Female spongy moth with egg casing. The moth is a creamy white color with brown and black markings. The egg casing is a brown, yellow color that appears to have a spongy texture.

The spongy moth (Lymantria dispar) is an invasive insect that was introduced to North America from Europe. Spongy moth is a destructive pest that feeds on more than 300 species of deciduous, hardwood trees and shows a strong preference for oak and aspen. 

The Minnesota Department of Agriculture (MDA) has monitored spongy moth populations in our state through a trapping program. The traps are a green, triangular box baited with a pheromone specific to spongy moths. In the summer these traps can be seen hung in trees around Duluth and throughout the State. The number of spongy moths caught in an area help determine future control efforts.

The MDA has taken proactive measures to control the spread of spongy moth. When populations become high enough, counties are quarantined. Currently, only Cook and Lake Counties are quarantined in Minnesota. Prior to establishing a quarantine, efforts are made to control the population through pheromone disruption or applying Btk, an organic pesticide specific to moths.

Results from spongy moth trapping last year in Duluth showed elevated populations in the Lakeside neighborhood. The MDA has decided to spray Btk in Lakeside to prevent that population from growing

Btk is a naturally occurring bacterium that is found in soils throughout the world, is organic and safe to humans and pets. The MDA has a question and answer page concerning Btk and its application. Learn more about Btk HERE.

Visit the Minnesota Department of Natural Resources for more information on identification and management.