DEEP anticipates heavy moth activity

Connecticut’s Agricultural Experiment Station and Department of Energy and Environmental Protection are cautioning residents in northern portions of Litchfield County to anticipate a heavy presence of spongy moth (formerly named gypsy moth) caterpillars this spring along with significant defoliation of hardwood trees. Spongy moth populations rose substantially in 2021 particularly in the Sharon-Cornwall area last year, and spongy moth caterpillars have begun to emerge, DEEP representatives said.

“Our 2021 statewide gypsy moth egg mass survey, especially in northwestern Connecticut, showed large amounts of spongy moth egg masses, which leads us to believe there will be a continued hatch and extensive caterpillar activity in 2022,” said Dr. Victoria Smith, CAES deputy state entomologist.

Residents, arborists, and foresters have also reported large amounts of spongy moth egg masses.

“2021 was the first year of widespread defoliation in northwest Connecticut and most healthy trees refoliated in part due to sufficient summer rains. The energy required to refoliate places significant stress on trees increasing the risk of tree mortality in 2022,” said DEEP Director of Forestry Chris Martin.

Wet spring conditions should activate a naturally occurring soil borne fungus, Entomophaga maimaiga, which is lethal to only spongy moth caterpillars and normally keeps their populations in check. Connecticut has experienced similar cyclical outbreaks, most recently in eastern Connecticut that resulted in widespread tree mortality after several dry springs and corresponding consecutive years of defoliation. Wet spring weather eventually returned favoring growth and effectiveness of the Entomophaga maimaiga fungus and ending the infestation.

Annual forest pest and disease aerial surveys conducted by CAES documented spongy moth caterpillars defoliated 156,000 acres in 2020 (mostly in the eastern half of Connecticut) and 45,548 acres in (mostly in Litchfield County) in 2021.

“While most trees will refoliate initially, repeated attacks from spongy moths can weaken a tree’s natural ability to ward off secondary stressors such as drought or other insects and disease. Oaks are most preferred tree species,” said Martin. “Under heavy infestation spongy moths will eat just about everything with green leaves and even needles. Some people may remember that nearly 1.5 million acres were defoliated by the spongy moth in 1981, and while we lost trees, our forests recovered.”