This invasive pest has come to Minnesota, and it may well affect the ash trees in your neighborhood. Right now, there is an ash tree quarantine in effect throughout the Twin Cities, and people are getting pretty worried. As always, though, it is important to take a measured view of the situation. First, the Minnesota Department of Agriculture has information on their website to help you figure out if your trees are infested. If you do have infested trees, they recommend that the trees be removed. Here at Giving Tree Gardens, though, we see tree removal as a last resort, and decided to look around to find out if there were any other options.
After doing some research, we found Vineland Tree Care, a local company that has lots of experience with all things tree related. I spoke with Jim Walsh, and he did a good job of clarifying the emerald ash borer problem, as well as options for dealing with it.
It's a tricky problem for a number of reasons. First, early detection of infestation is extremely difficult, because emerald ash borers are really small when they're young and first starting to do their damage. They can spend a year or two chewing tunnels through a tree's vascular system before ever becoming visible. This vascular structure is what moves water and nutrients throughout the tree's trunk and branches, and needs to be intact for any treatment to be possible.
The only time treatment is effective, then, is during this early-stage infestation, and diagnosing the problem involves wounding the tree by removing some bark and wood. If the tree is infested, and you want to try and save it, Vineland Tree Care offers a treatment that consists of drilling holes in the trunk and injecting a systemic insecticide. This must be done a couple of times over a period of a few years.
Normally Giving Tree Gardens doesn't advocate the use of any type of chemical insecticides, and this case is no different. It has been found that chemical treatment of ash trees kill not only ash borer, but also kills bees and other foraging insects. If the price of keeping an ash tree alive is killing off bees and butterflies, then it can't be justified.
A final point that Mr. Walsh raised, and one that bears mentioning, was that these types of issues are great reminders of the need to always plant more trees. By maintaing a healthy urban forest with many types of trees at all life-cycle stages, we can ensure that any pest or disease that comes through is merely a nuisance, and not a disaster.