When it was discovered in 2013 that emerald ash borer found its way to Superior, that was cause for concern for Douglas County officials.
After all, Douglas County owns the state’s largest county forest with 28,000 acres of ash trees alone.
The emerald ash borer, a native of Asian countries and far east Russia, has killed millions of ash trees; infestations have been discovered in 35 states and the District of Columbia, according to the Animal and Plant Health Inspection Service (APHIS), a division of the U.S. Department of Agriculture.
The discovery in 2013 prompted city officials to remove about 3,000 of Superior’s public ash trees from boulevards, and county officials to develop a plan. That plan will be implemented for the first time since Douglas County was placed in quarantine eight years ago because of the find in Superior.
“One of the reasons they said it hasn’t spread here is because of the cold,” said Jon Harris, Douglas County director of natural resources and forestry. “I’m not sure of the temperature threshold, but if you have so many days or hours at 30 below or worse, 95% plus are killed. They’re saying that’s one of the biggest deterrents — why it hasn’t spread here as fast as it could have.”
County forest officials have been monitoring for emerald ash borer since at least 2015 using traps provided by the APHIS, Harris said.
“We’ve never found one in a trap until a month ago,” Harris said. “We found one in a trap off the Cleveland Road.”
Seven or eight of the green metallic beetles were found in the trap, which is indicative of a pretty active site, said Kevin Guralski, GIS specialist and inventory forester for Douglas County.
As the first find on Douglas County Forest land, Harris said the beetles were sent to the state’s forest health specialist, Paul Cigan, who confirmed the county was dealing with emerald ash borer in a location near the Brule River State Forest.
Harris said county officials will now implement the plan developed after the invasive beetle was first discovered in Superior.
A second discovery was made about four miles from the site where county officials trapped the beetles, Guralski said. The affected area includes about 3,500 acres of Douglas County’s ash resources.
Douglas County's five-year average ash sales is $11 per cord and one-year average is about $5 per cord because of market conditions, Harris said. Poor market conditions and the wetter conditions ash grows in limit when the trees can be cut and removed from the forest and are concerns for salvage operations.
"If they don't sell, there's not much we can do," Harris said.
Guralski identified the size classes of ash within a five-mile radius of the find to identify the area where abatement will occur.
Douglas County is planning to hold a salvage timber sale as part of its quarterly timber sale in October to take out the mature trees that can be salvaged.
“One of the biggest challenges I foresee is that we can’t market them and sell them, and the stand of dead ash, you have brush that comes up underneath it, which really prevents any other regeneration from coming in there,” said Craig Golembiewski, forestry operations manager. “There is some grant money available, but we can’t apply for the grants unless it gets harvested.”
He said ideally, the county could replace the ash with taller shade species like tamarack and yellow birch.
The smaller trees in the area are likely to be used as a test site to determine how to best control the spread of emerald ash borer.
“APHIS is doing some scouting now to kind of look at how they can proceed with the next state of their study site,” Guralski said.
Officials are looking for three sites to set up a study that will include using wasps in one area, injecting trees with a pesticide in another area and a control site to see if any of the control measures are effective.
Guralski said when the site is identified, APHIS staff will come back to get county approval. The trees of interest to APHIS are five to eight inches in diameter.
“Paul Cigan has been scouting the area, and indications I’ve gotten from him is that it’s widespread in the area,” Guralski said.