Tree variety diversity important
North Dakota has had a history of planting only a few varieties of hardy trees due to climate and availability of species. Because of this history, we are vulnerable to a disease or insect causing wide spread problems across the state. Dutch elm disease is a good example of this. DED moved rapidly across the state killing almost all of the American elms. The large number of spruce trees suffering from a few serious diseases is another example.
The emerald ash borer will be the next of these serious problems to attack our native and planted trees. Green ash are by far our most abundant tree in North Dakota. This is in our native forests as well as our home yards, field shelter belts and farmstead shelter belts. When the emerald ash borer arrives in our state, it will be a huge disaster! And it is WHEN, not IF, this insect arrives here. It is in Winnipeg, Manitoba, to the north, Sioux Falls in South Dakota, and was just discovered April 19, 2019, in Sauk Center, Minn. This is less than 100 miles from North Dakota.
There is not a cure for emerald ash borer. The damage is extensive and complete. In southeast Michigan it is estimated that several million ash trees have been killed. One only needs to see photos of southern Michigan to see the amount of damage. With this in mind, we will need to stop planting green ash and plant more different tree varieties when planting trees. There are a large number of available trees to select from. The key is to always plant a variety of species, not just one. This will help prevent a repeat of what we saw with Dutch elm disease and are seeing in 25 other states, and will too soon to be seen in ours.
There are a number of beautiful, adapted trees in a large number of cultivars to make planting selections easy. Some of these include honey locust, bur oak, American elm (there are new varieties that are resistant to Dutch elm disease), American linden (basswood), little leaf linden, hackberry, silver maple, hybrid maples, black walnut, golden and weeping willow, Meyer spruce (not Colorado or Black Hills spruce), ponderosa and Scotch pine, paper birch and many more. In all instances, there are a number of different cultivars. Not all are adapted for North Dakota. An example would be paper birch. The bronze birch borer insect kills susceptible paper birch varieties. Prairie Dream and Dakota Pinnacle are two North Dakota releases that are resistant to the borer and thrive in a wide variety of soils and growing conditions. Consult with your Extension agents, nursery staff, North Dakota Forestry Department staff and city foresters for advice and suggestions on the best cultivars for your needs.