Spongy Moth (fka Gypsy Moth) Information

Spongy Moth Outlook 2023

To assess the likelihood of future spongy moth (formerly known as gypsy moth) outbreaks in our county this year and onward, the Pennsylvania Department of Conservation and Natural Resources (PA DCNR) typically has given annual regional briefings every June. However, the last PA DCNR briefing that Centre County was invited to attend was in 2019.

At that time, the DCNR Bureau of Forestry specialists were unanimous in their opinion that because there were minimal spongy moth populations in adjacent counties, we were likely to be clear of spongy moths in 2020.

Three years have passed since that briefing. This summer, the Centre County Planning and Community Development office has received many calls from residents concerned about spongy moth infestations in their communities. 

This year, PA DCNR advised that only State Parks, State Forest Lands, and some forest lands in the Allegheny National Forest were being sprayed this summer -- a total of 209,838 acres on 220 sites. No private lands have been sprayed in 2022. Learn more...

View PA DCNR Spraying Map

Are We Protected from Spongy Moths in Centre County?

Short answer: No. A series of two or three dry springs could tamp down the activity of pathogenic fungus and allow the low background gypsy moth population (which is always present in low numbers) to expand exponentially, increasing its numbers a hundredfold each season until it becomes a major outbreak.

What Should I Do If I See A Spongy Moth?

First, positively identify the caterpillar as a spongy moth. Search online for images of "spongy moths." If the caterpillars are forming webs on the tips of branches, they are not spongy moths. 

Spongy moths are always present in Centre County at low levels, so you should expect to see the occasional caterpillar. However, if you see many spongy moth caterpillars and observe that they are defoliating foliage, please report this by filling out the Centre County Spongy Moth Survey.

Health Facts:  Control Agent 

Only one Spongy moth control agent is used in the state suppression program, a biological insecticide called B.t. or B.t.k.. B.t. is an abbreviation for Bacillus thuringiensis var kurstaki. A soil bacterium, it produces a protein that binds to specific receptors found only in the guts of Lepidoptera (butterflies and moths), and eventually ruptures the gut walls, causing septicemia and death.

The Pennsylvania Department of Conservation and Natural Resources (DCNR) states that "B.t. has the highest known degree of safety to human health and the environment of any insecticide currently on the Market." The US Department of Agriculture (USDA) has published extensive information on B.t. in its Spongy Moth Environmental Impact Statement (EIS), which is available in a book (but not in PDF) format from the USDA.

The USDA concluded that based on "both the available epidemiological studies as well as a long history of use, no hazard has been identified for members of the general public exposed to B.t.k. formulations."

The USDA ranks relative risks to the public in all of its activities by an index called the Hazard Quotient (HQ). The HQ is measured on a logarithmic scale, from 0.0001 to 10,000. A value greater than 1 means an effect may be observed after exposure. B.t. is given a value of 1 (2 in cases of extreme exposure). By contrast, an infestation of spongy moth is given an HQ of 100, with an extreme exposure being given an HQ of 7,000. This is a result of skin lesions and respiratory tract effects, as well as the psychological stress associated with living with large numbers of caterpillars in a homeowner's vicinity.

Spongy Moth Links

How Homeowners Can Prepare for 2023
Start looking for egg masses in October 2022

Pennsylvania Department of Conservation & Natural Resources: Spongy Moth

Penn State Extension: Spongy Moth Update