The Scoop on Emerald Ash Borer

By Maria DeLaundreau, Minnesota GreenCorps

Ash trees are valued for their beauty, shade, and value to wildlife. They are very popular as a street tree, but you might recognize them from a path you like to tread at Coldwater Spring. Near the trail from the parking lot to the spring house there is a small grove of ash trees that provide refreshing shade in the heat of summer. These trees and other ash trees in the national park are threatened by the emerald ash borer, a small green invasive insect native to Asia.

Ash trees near the trail to the spring house at Coldwater Spring. 

There’s been a lot of buzz  about the emerald ash borer this winter. Many hope that an upside to the extreme cold we faced in January and February is that emerald ash borer larvae will freeze and die, potentially saving ash trees like those found at Coldwater Spring. Evidence shows it is unlikely we will get a long reprieve from this pest, even with the cold, because emerald ash borer larvae don’t start to freeze until the air temperature drops between -20 and -30° F, and wind chill does not count because the larvae are shielded from wind by bark. But perhaps the cold will set their populations back by a year or two. From a practical standpoint, this means that emerald ash borer are still here–we might just get a little more time to prepare for them.

The emerald ash borer is a green insect that is smaller than a penny.
This extra time is valuable because there is still much planning and defensive action to be taken against the invasion of emerald ash borer in our national park. There are, of course, several ash trees, like those shown above, that are along the trails and roads on the fringes of the park, but there are also many ash trees growing in the floodplains and bluffs of the Mississippi River. These trees are common in the forested areas around Coldwater Spring, but we don’t yet know how common.

This summer, I will be working with National Park Service staff and volunteers to inventory the trees at Coldwater Spring. The inventory will give us a better idea of how many ash trees are at Coldwater Spring and what the potential impact of this pest may be. This information will help guide management decisions concerning emerald ash borer. This insect is not known to be at Coldwater Spring yet, but it is present in the Fort Snelling area, so we anticipate that if it is not there now it will be within a few years.

Emerald ash borer has been found near Coldwater Spring at Fort Snelling.
Many people around the state are working to limit the spread emerald ash borer. The Minnesota Department of Agriculture is tracking the known locations of this pest on their website. They also have a helpful flow chart  to help you determine if a tree has been infected with emerald ash borer, and from there they provide information on contacting the Department of Agriculture about your find. For more information about emerald ash borer, or to learn what to do about ash trees at your home or on your street, check out the Minnesota DNR website.