WISCONSIN — A new invasive insect has been found in Wisconsin, according to the Department of Natural Resources.

The elm zigzag sawfly was first discovered in Portage County on July 4. As of Aug. 12, the pest has now been detected in 17 Wisconsin counties.

The pest, native to parts of East Asia, feeds only on elm trees and causes minor damage. That’s because elm trees have lots of leaves and can tolerate some insect feeding.

This pest can be spotted by a distinctive “zigzag pattern” on elm leaves caused by young larvae chewing on them or by large notches in the leaves from older larvae.

Officials said there is the potential for the insect to cause “significant defoliation” and have long-term effects on the health of trees. The DNR said this is possible if there is repeated severe damage, which will weaken trees and cause branches to die.

DNR officials did say that in many cases, you may not need to do anything for an infestation.

If needed, the larvae can be blasted off elm leaves from a garden hose; they can also be squashed, hand-picked or scraped into a container of soapy water. The DNR said this is best for small landscape trees.

However, the DNR did say it may be best to contact a professional for infestations.

“…it may be best to consult a certified arborist to assess tree health and discuss management options,” officials said.

Elm zigzag sawfly populations are entirely female and reproduce without mating. Officials said the pest can create multiple generations in a year and that adults in the species can endure long-distance dispersal, with some having moved up to 56 miles per year. The small cocoons are sticky, meaning they can attach to many man-made items.

The insect was first detected in North America in 2020 in Quebec, Canada. It was found in the U.S. in 2021 and has been moving westward ever since.