Caterpillars invade many tree species

FINGER LAKES--Oak trees, apple trees and many others throughout the region are under threat if not an outright attack from the voracious appetite of the European gypsy moth caterpillar. Not satisfied with stripping many trees completely barren, these invasives also have a foul tendency to accumulate en masse and leave cars, roofs, decks and anything underneath them completely covered in waste.
"It's an invasive species, it's a problem here," said Ann Hajek, Entomology Professor at Cornell University. "It's a kind of species that can increase to big densities which we call outbreak species. And right now its outbreak is in our region. And it's a problem because when it's in outbreak it is a nuisance. Big caterpillars poop a lot, and they can eat all the leaves off all the trees."
Already there have been reports of properties in Schuyler County losing every leaf on every one of their shade trees, and Hajek said she has gotten reports that the Oak trees on the southern shore of Canandaigua Lake are under heavy attack.
The state department of environmental conservation has also acknowledged the issue many New Yorkers are facing and hosted a question and answer session Wednesday, June 16 to educate the public and if possible help stymie their spread.
"The DEC does not have a widespread treatment program for gypsy moths," said Rob Cole, forester for the DEC during the virtual presentation.
The reason for that, Cole said, is because after more than 100 years in the area, gypsy moths have become too prevalent in the environment and there are also a number of natural factors that help to kill them. However, Cole did caution people that it can be easy to help their spread by allowing them to hitch rides on anything from cars to backpacks to boats.
"Healthy trees can actually have all the leaves eaten off them and survive," said Hajek. "They will actually start to grow new ones relatively soon, within a month. But when they infest young or old trees that are not completely healthy or not doing very well, it can be the death knell for those trees."
Caterpillars are the larval stage for either moths or butterflies and in order to store up enough energy to engage in such a drastic transformation have nearly endless appetites. Gypsy moths are especially notorious in this regard and have a long history of tormenting New York after being brought to the states in 1869.
"It takes them two months to get really big and then they pupate to become moths, and when that happens (in early July) you won't have caterpillars anymore," Hajek said.
Gypsy moths are not always in an outbreak, and mostly remain in manageable numbers that do little damage to the region's shade trees. The reason why they end up in an outbreak remains a mystery, one that Hajek said she is working with a graduate student to try to deduce.
"The biggest predator of these caterpillars are not birds or other insects, it's actually a fungus, and (we) are working on a theory that the outbreak of gypsy moths coincide with dry seasons, because during those dry seasons the fungus that kills the caterpillars can't thrive," stated Hajek.
Hajek openly admits however that other theories remain, including drastically increasing population as a method of predatory saturation to ensure a large breeding population. In the end, it could be some time before an answer is found.
Laura Bailey, Cornell Cooperative Extension Natural Resources Educator recently updated an article that was published earlier this year on gypsy moths. The article mentions for this year it is too late to spray tree leaves with Btk or Bt insecticides as it is only effective on small, young caterpillars. However, when the caterpillars go into cocoons, it recommends crushing or burning them. When the moths emerge, swat the females which are cream-whitish colored and cannot fly. In the winter and fall scrape egg masses that are tan in color and velvety into a container with soapy water and leave for two days. Gloves, protective clothing and a dust mask are recommended whenever interacting with the caterpillars.