The Entomological Society of America approved “spongy moth” as the new common name for Lymantria dispar. This name replaces the old common name, “gypsy moth,” which was removed in 2021 due to its use of a derogatory term for Romani people. The new name—derived from the common name used in France and French-speaking Canada, “spongieuse”—refers to the moth’s sponge-like egg mass, an important target for management efforts to slow the spread of the insect.
The spongy moth is an invasive forest pest that feeds on more than 300 species of deciduous trees and shrubs, including aspen, oak, and birch. Repeated removal of leaves, or defoliation, stresses trees and can leave them vulnerable to disease or other pest infestations that can kill trees. Once it becomes established in a location, the spongy moth has cycles of large population outbreaks every eight to 12 years, leading to widespread defoliation and nuisance from caterpillars.
Spongy moth egg masses are well-camouflaged and easily transported on firewood and other items, such as camping equipment stored outdoors in summer.
The spongy moth has expanded from its initial introduction in Massachusetts south to Virginia, north to the Canadian Maritime Provinces, and west to the eastern edge of Minnesota. In Minnesota, the spongy moth is found most frequently in the southeast and northeast corners of the state because the invasion front is moving in from the east.
The Minnesota Department of Agriculture Spongy Moth Program has conducted annual detection trapping surveys for spongy moths since 1973. They have successfully eradicated all small, isolated infestations that have been found throughout the state eradication area. They have also conducted dozens of successful mating disruption treatments along the eastern border of the state over the years to slow the spread of spongy moth.