Some of you may remember the devastation that Dutch elm disease wrought on elm trees across the country. Well, something similar is happening now with ash trees and the emerald ash borer.
The insect can kill a tree in as little as three years
The emerald ash borer is an exotic insect. It was first documented in the United States in Michigan in 2002, and has been spreading since. Our native ash trees are very susceptible to this insect pest, which can kill a green ash in as little as three years. I have not seen any statistics on the mortality rate, but it appears to be comparable to that of Dutch elm disease.
Although I have not heard about any documentation of it in North Dakota, no doubt some of you have heard the news that it was recently documented in Moorhead, Minnesota.
Green Ash trees are common in North Dakota
Green Ash is perhaps the most abundant in North Dakota. It can be found from the banks of the Red River to the woody draws in the badlands. Because it does so well in our region, it has been a preferred species for boulevards, yards, farmsteads, and shelterbelts — particularly after Dutch elm disease devastated the elms.
The first symptom is often the dieback of branches
The rate of spread of the emerald ash borer is about a half mile a year, with a maximum of perhaps 10 miles. The first noticeable symptom is often the dieback of branches. But that is often not observed until the tree has been infected for three years or more. Woodpecker damage may also be conspicuous. A “D” shaped hole in damaged bark is a good indication of emerald ash borer activity.
Curbing the spread of the emerald ash borer will take a concerted effort. The larvae can hide in firewood, so that needs careful attention. The health of ash trees also needs careful monitoring.
Now may be a good time to plant a replacement
Treatments are available to save ash trees (e.g., trunk-injected systemic insecticide) but they can be expensive. If you have some green ash in your yard or farmstead, now might be a good time to consider planting something to replace them, especially when you consider how long it takes to grow a good shade tree. If you do, select a species that is not so abundant in your area, and if you need to plant several trees, please do not plant all the same species.
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