DEEP: The Gypsy Moth in Connecticut - An Overview

The Gypsy Moth in Connecticut - An Overview

{Female laying eggs}
female gypsy moth laying eggs
{Gypsy Moth Larva}
gypsy moth larva (late instar)
{Male Gypsy Moth}
male gypsy moth
The gypsy moth (Lymantria dispar) is well-known for the damage it does to trees.  Though not native to North America, it has been here since about 1868. The gypsy moth has been in Connecticut since 1905 and is now established in the forests of southern New England. 
Outside the forest, it can be a pest of landscape trees. In its larval stage, it consumes foliage voraciously.  It will feed on most species of trees in Connecticut, with oaks being its favorite.
Normally, the gypsy moth population is low and the damage it does is fairly restricted.  However, when it enters into outbreak status, it is a significant problem. 
In outbreaks, the larvae, or caterpillars, emerge in great numbers.  By the end of June, they will have stripped bare a majority of the trees in an area.  Forest and yard trees look more like they do in January than in July.  In outbreaks, people find the presence of the insect to be highly objectionable.  Besides the harm done to the trees, the caterpillars seem inescapable.  They descend from trees and crawl on lawns.  Their droppings fill gutters and cover outdoor spaces.  They are, in a word, obnoxious.  People look to do what they can to be rid of them.
In the 1960's through the end of the 1980's, several major gypsy moth outbreaks occurred in Connecticut. Since then, the state has been spared the worst of this insect.  Starting in 1989, a fungus has re-appeared annually that specifically attacks the gypsy moth caterpillars.  This fungus has kept the gypsy moth population in check, to the extent that, in recent years, the moth has been little more than a local and occasional problem.  (See the CAES Gypsy Moth Fact Sheet for further details).
This fungus needs rain to become activated.  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 in parts of Connecticut, reaching outbreak status locally in areas of south-central and eastern Connecticut (map). 
If the dry weather continues into the spring of 2017, these outbreaks will also continue to grow and spread.  The gypsy moth will then become a problem in even more areas of the state.  Additionally, the more often an outbreak is repeated and the more intense an individual outbreak is, the more likely it is that the activities of the gypsy moth will affect the health of individual trees.  They may also impact the health of the forest as a whole. 
Among the concerns associated with drought and gypsy moths is an increased risk of woodland fires, as defoliated trees lead to even drier forest floor conditions. 
Additional Information:
Content last updated April 26, 2018