USDA Forest Service officials call attention to spongy moth increases in the Chequamegon-Nicolet National Forest

Release Date: Jul 14, 2023

Contact(s): Veronica Hinke

Active quarantines currently in 10 counties in the Forest

RHINELANDER, Wis., July 14, 2023 – Large areas of the Chequamegon-Nicolet National Forest (CNNF) are being impacted by spongy moth caterpillars. Spongy moth caterpillars have a voracious appetite for deciduous tree leaves and have left many areas nearly leafless, especially on the Washburn and Lakewood-Laona ranger districts. In some places, there are great lengths of leafless trees in areas that are typically lush with green tree leaves this time of year.

A single spongy moth caterpillar will eat a square yard of foliage of green leaves in its lifetime of just a few weeks, causing trees to have to regrow leaves to convert carbon dioxide and water into sugars and oxygen. The trees will re-flush new leaves, however some mortality may result in trees of lower vigor from the stresses of defoliation, as well as the recent drier-than-usual conditions in Northern Wisconsin. Most of this mortality will be seen in oak trees, especially in sandy, drought-prone areas. Spongy moth caterpillars also feed on aspen, birch and nearly 300 other species of trees and shrubs.

The following 10 counties in the CNNF are under quarantine for spongy moths (datcp.wi.gov/Pages/Programs_Services/SMQuarantineRegs.aspx): Ashland, Bayfield, Florence, Forest, Langlade, Oconto, Oneida, Price, Taylor, and Vilas. The quarantine aims to help reduce the spread of the spongy moth.

Landowners can help in the fight against the spongy moth by, while wearing gloves, collecting caterpillars, pupae, and egg masses on their property. They should drop them into soapy water or a bleach solution. Spongy moth caterpillars search out places to pupate underneath loose tree bark flaps or under the eaves of a cabin or shed; or under a picnic table.

“This will help to reduce next year’s caterpillar hatch,” said USDA Silviculturist John Lampereur.

More information about how landowners can help reduce spongy moth outbreaks is online.

“Please, do your part in helping to reduce the risk of spreading the spongy moth by adhering to quarantine guidance and following USDA Forest Service firewood rules,” urged CNNF Forest Supervisor Jenn Youngblood. “It is so important that we each do all that we can to help slow the spread of threats to the health of our Forest and all that is dependent upon it.”

Pathogens that are naturally present in the Forest are a key factor in the fight against the spongy moth.

“Many of the natural pathogens that can help reduce the numbers of spongy moth caterpillars grow best in moist weather conditions, and right now we are experiencing drier-than-usual conditions.” Lampereur said. “It is hoped that, next spring, spongy moth caterpillar populations will be greatly reduced as they ingest these pathogens.”

Spongy moth caterpillars have already started turning to pupae that will become moths, which do not cause serious health risk to people.

In the coming days, visitors to the Forest will encounter less and less spongy moth caterpillars. However, those who find a spongy moth caterpillar should avoid touching them as the hairs can cause a skin rash, welts, or other irritation. Rubbing alcohol can help to remove the hairs and chemical irritants from skin that is exposed to the hairs.

Since 1869 when the spongy moth was first spotted in Massachusetts, the moth has spread to 20 Eastern and Midwest states. There is potential for the moth to spread across the entire continental United States.

Noticeable increases in spongy moths occur approximately once every 10 years. Outbreaks tend to run for two years, which means that it is possible that there will be heavy populations again in spring of 2024.

 

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