Pa. foresters turn to landowners in fight against oak-killing spongy moth

This story is part of our series, Wild Pennsylvania. Check out all of our stories here. 

Pennsylvania’s Department of Conservation and Natural Resources wants forest owners to help fight spongy moths — formerly known as gypsy moths.

Spongy moths pose a serious threat to oaks, as well as witch hazel, aspen, willows and a slew of other species across the commonwealth. The nonnative forest pest was accidentally introduced to North America in the 1860s, has been plaguing Pennsylvania forests since the 1970s, and is responsible for killing millions of oak. There was a bad outbreak in the north east 2013-2019 and another that began in 2021.

Last year, DCNR treated some 227,000 acres of state forest and parklands and the Pennsylvania Game Commission treated another 120,000 acres, resulting in population crashes.

But 70% of the state’s forests are privately owned, so foresters are now turning to forest and woodlot owners for help.

The spongy moth caterpillar has a yellow and black head, a hairy body with pairs of blue spots, followed by pairs of red spots. State foresters say the problem requires aerial treatment and the time to spray is spring.

DCNR experts say spongy moth egg mass surveys are the best way to determine the need for treatment.

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“Private landowners play a critical role in protecting Pennsylvania’s forests,” state forester Seth Cassell said in a news release. “Early action against spongy moth caterpillars can help prevent widespread tree loss.”

DCNR provides a list of aerial applicators, a suppression guide, and expert foresters in each county to help landowners plan treatment.

• Preparing for the arrival of the invasive spongy moth