The wetter than normal spring and summer has been dampening gypsy moth populations, and the colder than normal winter froze most of the hemlock wooly adelgids.
Andrea Hille, Forest silvaculturist, said, "Gypsy moth populations appeared to have dramatically dropped off as of our egg mass surveys conducted last fall. One of the natural controls for gypsy moths is the Entomophaga maimaiga fungal infection. I suspect the abundant rainfall and moist conditions this spring and early summer have benefited fungal infections, to the detriment of gypsy moths."
Cecile Stelter, district forester for the Department of Conservation and Natural Resources noted, "In other cases however, warm, humid, wet conditions provide the opportunity for harmful pathogens, especially fungus and molds, to develop."
"This can especially be true in forests with closed, tight canopies or even in individual trees that have very dense foliage which does not allow the air to circulate throughout the tree. Thinning branches or trees to encourage better air circulation is an option for dealing with those types of situations."
As far as the hemlock wooly adelgid, Hille said, "The cold this past winter did result in fairly high hemlock woolly adelgid mortality- over 90 to 95 percent of hemlock woolly adelgid in samples taken on the ANF and in Cook Forest State Park as of early May had died. However, sample sizes were limited in number and scope, and some adelgids did survive."
"Overall, the cold snap did help reduce hemlock woolly adelgid populations in the short term. However, hemlock woolly adelgid only needs female insects to produce offspring, thus a few surviving individuals will mean we still have adelgid infestations,"Hille said.
"I have noticed, however, that the optimal conditions we have had this growing season have resulted in much new growth on eastern hemlock trees in our area, meaning an abundance of new growth for hemlock woolly adelgids to feed on, and help rebuild their numbers. In reality, another mild winter or two will allow populations to build right back up."
She added that the wet weather probably did not affect the emerald ash borer, as the insect is protected by the bark of ash trees.
"The rainfall and optimal growing conditions this year have certainly benefited ash and other hardwoods, but likely not in any manner sufficient to reduce impacts of emerald ash borer," she said.