Traps collect information on tree-killing pest

The Douglas County Forestry Department teamed up with the USDA to monitor emerald ash borer.

Green funnel traps, left, and purple prism traps are being deployed throughout Douglas County to monitor the spread of emerald ash borer. (Courtesy of Douglas County Forestry Department)

In an effort to increase monitoring of emerald ash borer movement in the county, as well as supporting research on the effectiveness of various treatments, the Douglas County Forestry Department has partnered with the United States Department of Agriculture, Animal and Plant Health Inspection Service on a long-term study.

As a result, clusters of green funnel traps will be placed at selected sites within the forest to monitor the presence of the insects. Douglas County will also be continuing other monitoring for emerald ash borer using purple prism traps around the forest.

The forestry department has been trapping for the tree-killing pest for the past four years, according to inventory forester and GIS specialist Keb Guralski.

“This year we have 10 trap locations around the county, but in the past we have done up to 20 trap locations,” he said.

The number of traps was reduced this year because of the partnership with the USDA on trapping, and research projects they are conducting in the Nemadji River area along County Highway W and in the Lake Nebagamon area.


Traps can be found across the county in highly visible areas such as Lucius Woods and Mooney Dam county parks, along busy highways and in areas with little traffic. All have an informational sign posted nearby.

Emerald ash borer was initially detected in the city of Superior in 2013 and led to the preemptive removal of 3,000 trees. Additional infestations have been found in Amnicon Falls State Park in 2017 and the town of Highland in 2019. Guralski said it is likely that there are other areas of the county with infestations that haven’t been discovered. In March 2018, all of Wisconsin was put on quarantine for emerald ash borer.

The Douglas County forest has roughly 23,000 acres of black ash, and monitoring for emerald ash borer goes well beyond trapping. Foresters are in the field looking for signs of unhealthy ash trees. The department is also partnering with the Wisconsin Department of Natural Resources on research to determine alternative native tree species in areas of infestation.

The spread of emerald ash borer has been shown to slow in colder regions because a larger percentage of larvae do not survive winter temperatures, and larvae can take two years to mature in colder climates compared to a one-year cycle in warmer regions.

“These factors allow us additional time to respond and plan for the spread of emerald ash borer, but will not stop the spread,” Guralski said.

Members of the public can help by identifying and reporting any signs of emerald ash borer they find on public or private lands. Another key is the responsible handling of firewood. On average, an adult beetle will travel less than half a mile per year naturally.

“But a person can transfer them through firewood movement much quicker,” Guralski said.

Visit the DNR website ,, for more information on emerald ash borer, or call the Douglas County Forestry Department, 715-378-2219.

Maria Lockwood covers news in Douglas County, Wisconsin, for the Superior Telegram.
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