Science Beat: Gypsy moth invasion sees improvement from 2017


The gypsy moth invasion has improved vastly from 2017's numbers.  (Washington State Department of Agriculture/Flickr, Creative Commons)

The gypsy moth invasion has improved vastly from 2017’s numbers. (Washington State Department of Agriculture/Flickr, Creative Commons)

Last year’s gypsy moth invasion left over one million acres of Connecticut land defoliated. University of Connecticut Extension Professor of Entomology Ana Legrand said this year has seen significant improvement.

“Last year [we saw] some infestations here and in neighboring towns,” Legrand said.  “[This year] wasn’t as widespread as in 2017.”

The Connecticut Department of Energy and Environmental Protection noted that the insects have made a home in the Nutmeg State over the past century.

“The gypsy moth has been in Connecticut since 1905 and is now established in the forests of southern New England,” the DEEP website said. 

In order to combat the issue, Legrand said scientists have turned to using fungi such as Entomophaga maimaiga, the leading natural method of controlling the gypsy moth population.  Scientists have released the fungus into devastated areas since 1910. As the fungus is dispersed, it decomposes existing caterpillars and then reproduces inside of the hanging cadavers.  This then spreads to the base and all around the tree, preventing any further gypsy moth developments.

“Entomophaga maimaiga attacks the caterpillars,” Legrand said.  “The dry conditions are not very good for this particular fungus, so that lets the gypsy moths control the escape from the fungus.”

According to Legrand, because Entomophaga maimaiga was used last year, the gypsy moths were unable to lay as many eggs, leading to a smaller invasion in 2018.  Rain levels also increased, aiding in the process of controlling the insects.

“This fungus needs rain to become activated,” the DEEP website said. “With 2015 and 2016 being so dry, the fungus did not get enough moisture to become fully activated.  As a result, the gypsy moth population has grown substantially…”

UConn associate extension professor of forestry Thomas Worthley released a paper entitled “The Slow Storm: Tree Mortality in CT from Invasive Insect Pests” on Aug. 29, 2018. 

In the paper, Worthley details the damage insects like gypsy moths can do.

“During the early summer of 2018 it became apparent that numerous trees throughout eastern and southern Connecticut did not produce leaves this spring, having died sometime during the winter,” Worthley wrote. “While it is not unusual to lose a tree or two to natural causes here and there at any time of year…the combination of recent gypsy moth infestations and associated drought conditions is notable and concerning.”

Worthley recalled defoliation due to gypsy moth invasions in the 1980s in his paper.  Legrand said the same effects can be seen today.

“You can see it right here on campus, parts of the trees from over the summer just have no foliage,” Legrand said. “In 2017, the gypsy moth caused defoliation in 1,175,000 acres around the state.”  

Luke Hajdasz is a campus correspondent for The Daily Campus. He can be reached via email at

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