A Brief History of the Spongy Moth
"Spongy moth" has been formally adopted as the new common name for the moth species Lymantria dispar (formerly known as the gypsy moth) by the Entomological Society of America. The new name comes from a translation of a French name based on the destructive forest pest's sponge-like egg masses. You can learn more about the name change from the Entomological Society of America.
Originally native to Eurasia, the spongy moth is an invader to North America. By the 1600s, it was already being noted to cause problems. By the 1800s, it was a prominent pest in Europe; one that had spread widely and was causing the same sort of damage there as it is now known for on this side of the Atlantic.
Unlike most invasive insect pests, we know where and how the spongy moth was brought to North America. In the 1860s, several entrepreneurial individuals had a keen interest in developing a silk industry in the United States. Disease had hit the traditional silk moth (Bombyx mori) and the Civil War was affecting the availability of cotton. These young men, well skilled in entomology, were experimenting with various species of moths that might work as a source of silk fiber. Among the places where people sharing this interest congregated was in greater Boston.
In 1868 or 1869, one of these young moth-enthusiasts in Medford, MA - Etienne L. Trouvelot - received a shipment of potential silk moth candidates from a colleague in France. The shipment, whether by accident or on purpose, included some spongy moth eggs. Mr. Trouvelot began rearing these spongy moths in his backyard and some escaped. That is where the story of the spongy moth begins in the United States.
Since then, the spongy moth has woven its way into many different narratives. Early efforts to control this insect were notable for their aggressiveness as well as their ultimate failure. These efforts encouraged a reliance on the use of pesticides that, in turn, influenced early approaches to the practice of arboriculture in this country. This historic pesticide use here stands in contrast to use in other places, such as Europe. Perhaps this is most notable in the use of DDT. Following World War II, DDT was used widely in the effort to restrict the spread of the spongy moth. The goal was to "hold the line" at the Hudson River, to keep it from spreading westward across the river and on through to New Jersey and Pennsylvania.
In the years following the halt in the use of DDT, the spongy moth reached some of its greatest population numbers, culminating in Connecticut with the extensive outbreaks of 1971 and 1981. Those outbreaks are legendary in both forestry and arboricultural circles. A wide range of tree species were stripped clean and the woods were turned bare due to the extensive feeding of these insects. Arborists were hard-pressed to meet the demands of an increasingly frantic public, as the caterpillars covered houses, roads, and sidewalks. The spongy moth caterpillars were even blamed for traffic accidents, as people would skid on their massed numbers in the roadways.
The role of the maimaiga fungus in controlling the insect is critically important. In the end, it is somewhat ironic that, after all of the efforts in chemical control, it is a biological control that has proven most effective. The maimaiga fungus was deliberately introduced in North America in order to control the spongy moth, even though its effectiveness only became apparent after a gap in time.
The limited precipitation that occurred in Connecticut in 2015 and 2016 allowed the numbers of the spongy moth to begin increasing again. 2017 turned out to be another difficult year for trees attacked by the spongy moth, particularly in the eastern half of Connecticut. In 2018, the extent of the outbreak declined significantly, but the secondary pests that follow the spongy moth and further damage or kill stressed trees, showed themselves to be a problem. Chief among these secondary pests are the two lined chestnut borer and the honey fungus (also known as armillaria or the shoestring root rot).
The History and Impact of Gypsy Moth in North American and Comparison to Recent Outbreak in Europe, 2007, Michael McManus and Gyorgy Csoka
The Great Gypsy Moth War - A History of the First Campaign in Massachusetts to Eradicate the Gypsy Moth, 1890-1901, by Robert J. Spear, published by the University of Massachusetts Press
Legends of Arboriculture - a video produced by the International Society of Arboriculture
Spongy Moth Fact Sheet, CT Agricultural Experiment Station, Dr. Kirby Stafford
Content last updated in March 2022.