Invasive Insects in Wisconsin: What You Need to Know

Wisconsin is home to a diverse range of insects, but some of them are not native to the state and can cause significant harm to the environment and local ecosystems.

The Emerald Ash Borer, for example, is a highly invasive insect that has already caused widespread damage to Wisconsin's ash tree population.

In fact, it's estimated that over 50 million ash trees have been killed by the Emerald Ash Borer in Wisconsin alone.

Native to Asia, this insect was first detected in the United States in 2002 and has since spread to many states, including Wisconsin.

The elm zigzag sawfly has been found in 17 Wisconsin counties, including Portage County where it was first discovered on July 4. This invasive insect is native to parts of East Asia and feeds only on elm trees.

It's worth noting that elm trees have lots of leaves and can tolerate some insect feeding, which is why the damage caused by the elm zigzag sawfly is considered minor. However, repeated severe damage can weaken trees and cause branches to die.

The elm zigzag sawfly 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. This is a key way to identify the pest.

If you have an elm tree and notice any of these signs, you may not need to do anything, especially if it's a small landscape tree. However, if the infestation is severe, it's best to contact a professional for help.

The elm zigzag sawfly has some unique characteristics, including entirely female populations that reproduce without mating and the ability to create multiple generations in a year. Adults in the species can also endure long-distance dispersal, with some having moved up to 56 miles per year.

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A new invasive insect has been found in Wisconsin, specifically the elm zigzag sawfly, which was first discovered in Portage County on July 4.

The elm zigzag sawfly is native to parts of East Asia and feeds only on elm trees, causing minor damage due to the abundance of leaves on the trees.

Elm trees can tolerate some insect feeding, but repeated severe damage can weaken trees and cause branches to die.

The elm zigzag sawfly 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.

If you have an infestation, you may not need to do anything, but if needed, you can blast the larvae off elm leaves from a garden hose, or squish, hand-pick, or scrape them into a container of soapy water.

However, for larger trees or more severe infestations, it's best to contact a certified arborist to assess tree health and discuss management options.

Elm zigzag sawfly populations are entirely female and reproduce without mating, and the pest can create multiple generations in a year.

Adults in the species can endure long-distance dispersal, with some having moved up to 56 miles per year, and the small cocoons are sticky, meaning they can attach to many man-made items.

As the fall season arrives in Wisconsin, the changing foliage and cooler temperatures can make for a beautiful time of year. The state's forests, which are home to many invasive insect species, are particularly vibrant during this time.

The Emerald Ash Borer, a highly destructive invasive insect, is most active during the fall months. It's during this time that the beetle's larvae are feeding on the ash tree's bark, causing further damage.

Wisconsin's fall season typically runs from September to November, with the peak foliage season usually occurring in mid-October. This is a great time to get outdoors and enjoy the state's natural beauty.

The Asian Longhorned Beetle, another invasive insect species, can be found in Wisconsin's forests during the fall. Its distinctive sound and bright colors make it easy to spot.

Fall is also a great time to take action against invasive insects in Wisconsin, as the cooler temperatures can help slow their spread.

For another approach, see: Invasive Weeds in New York State