I usually begin our weekly gardening chats with a little humor, because most of us are in a pretty good mood talking about our yards, vegetable gardens, houseplants and flowerbeds.
It’s difficult to be lighthearted, though, about an invasive insect that has killed millions of trees while marching across 34 states, and is well-established in the Upper Midwest, including Wisconsin, Minnesota and South Dakota. In recent breaking news, emerald ash borer is now at North Dakota’s doorstep, discovered across the river in Moorhead in recent weeks.
According to Michigan state, where emerald ash borer was first detected in 2002, over 99% of ash trees attacked by the insect have died. That’s alarming, because in many regional communities, 25% to 80% of all trees are ash.
If the insect sweeps through our region as it has in other areas, the plague will cause wide swaths of dead trees up and down our streets, in homeyards, farmsteads, field windbreaks, and native tree stands along lakes and rivers.
Emerald ash borer, abbreviated EAB, attacks only ash trees. Unfortunately, ash trees were the most commonly planted tree for decades to replace elms devasted by Dutch elm disease, which explains why our communities are so heavily planted with ash. Unfortunately, no ash types are immune to this imported insect.
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Larvae of EAB likely arrived in this country in the wood of a packing crate or pallet on a cargo ship from Asia. These wormlike larvae are the insects’ destructive stage, tunneling under tree bark and creating serpentine channels that cut off a tree’s uptake of food and water. The adult beetles are metallic green, longer than wide, and several can easily fit on a penny.
Given the probability that EAB will likely continue its devastation as it moves through the region, what can homeowners do? A logical first step, of course, is to identify whether your trees are ash. North Dakota State University has a helpful site that can be found by Googling " NDSU ash tree identification ."
For homeowners with ash trees, there are at least three options. First, doing nothing is an option, in a wait-and-see-what-happens approach.
A second option is to remove ash proactively, and get a head start on planting a replacement tree.
“It’s not an easy choice whether to keep your trees for the future, or is it time to remove and replace them?” says NDSU Extension Forestry Specialist Joe Zeleznik.
“For trees that have poor structure or are in declining health, it’s pretty easy to justify removal and replacement," he says. "That’s actually been the main approach of city foresters working towards tree diversification. Remove the trees that don’t provide much benefits, but keep those in good health and are structurally sound.”
A third option for homeowners is treating ash trees with insecticides.
“Retaining larger, healthier ash trees comes at a cost. There are several effective chemical treatments available for controlling EAB. While many of these are available to homeowners, the treatments that professionals offer are usually more effective, as the professional-grade chemicals are at higher concentrations," Zeleznik says.
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“These chemical insecticides must be reapplied every one to two years, and the annual cost has to be factored into decision making. In any given area, EAB is likely to take at least 10 years to work its way through the local population of ash trees. Do you want to continue treating your ash tree — or trees — for that long? The decision isn’t always easy,” he continues.
A readily available example of an insecticide that homeowners can use to treat ash trees is BioAdvanced Tree and Shrub Insect Control. Along with other brands, these systemic insecticides are applied at the base of the tree and are taken up internally within the tree’s system. Label instructions must be followed carefully, and results will vary.
If you suspect your ash tree is infested with EAB, contact the North Dakota Department of Agriculture at their website http://www.ndda.nd.gov/eab or by emailing them at reportapest@nd.gov.
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