On her way to work one morning this past summer, Kama Ross noticed some sick-looking oak trees near a recently cleared right-of-way in Bingham County. Luckily, Ross knew what she was looking at: the first confirmed case of oak wilt disease in Leelanau County.
As the forester for three conservation districts, Ross regularly provides help and advice to forest owners all over Benzie, Grand Traverse and Leelanau Counties. She’s both an energetic advocate for healthy forests and a gentle teacher. She explained that Oak wilt is a tree-killing fungus that is spread by beetles as well as through tree roots.
“Oak tree roots graft. So a tree that has the fungus in it will graft with a healthy tree and the fungus will go into the system of the healthy tree,” Ross said. “Also, a little beetle active in Michigan loves the fungus that’s in the sap of the infected oak tree. So any pruning or any cutting of an oak tree that allows sap to open, will attract this beetle.” The beetle can then spread the fungus to other trees up to a mile away.
To contain this infestation, Ross said all the infected oaks and some of the surrounding trees will need to be cut and either buried on right site or disposed of very carefully to prevent further infection. Then, the roots at the edge of the area must be cut and separated.
“We’ll take a vibratory plow and encircle all the diseased trees,” she said, cutting “five foot down into the ground. And we try to go two times around.” Additionally, insecticide spraying may be needed outside of the encircled area.
Planned for next spring, this will be a big effort requiring the cooperation of the Michigan Department of Natural Resources, Michigan State University, the Leelanau County Conservation District and the Cherry Electric Cooperative.
Ross encourages people who may be concerned about unhealthy red oaks in their woods or forests to get in touch with the Conservation District or contact an arborist to help identify the problem. There are a number of much-less threatening reasons that red oaks may appear stressed, but oak wilt disease is very aggressive. So, rapid detection and response is critical to combating the spread of this disease. She encourages owners to avoid cutting or wounding red oaks during the beetles’ active period from mid-April through July.
Ross hopes that this outbreak will help raise awareness in Leelanau County. “I’m actually very optimistic that we can use this outbreak to maybe minimize where oak wilt is going to go,” she said. “Maybe we won’t repeat what we’ve seen in some of the other counties.”
Unfortunately, this is only one of the challenges facing Leelanau’s forests. As most residents know, the Emerald Ash Borer invaded the area about 10 years ago. Having hitched a ride with some goods imported from Asia, this pest has been killing trees across the upper Midwest ever since. The results are quite visible from almost any roadway in the county. Over 90 percent of all Leelanau’s ash trees will die within a few years, Ross said.
And even more trouble is coming to the woods. A tiny, soft-bodied insect called beech scale is also invading Leelanau’s forests, drilling little holes in the bark of American Beech trees. The holes allow another tree-killing fungus to weaken and kill beech trees. Ultimately, this “beech bark disease” may kill most of the county’s beech trees.
“I don’t know where this is going to end up,” Ross said, “but our experience in the Upper Peninsula is very devastating.”
Clearly, Leelanau County’s forests are changing. These invasive pests and diseases are removing whole species from the community of trees that make up our forests. Brian Price, executive director of the Leelanau Conservancy says there are actually several factors at work.
“There are three major things or factors that we’re dealing with that are extremely disruptive in our forests,” Price said. “First, the pests and diseases are a huge factor and extremely troubling.”
Second, with the on-going loss of ash and beech trees, large openings are being created in the forests. These openings allow sunlight in that encourages new tree growth. But that’s when another “huge” influence on forest composition takes over. Price puts it this way.
“The only thing coming us is what the deer won’t eat. We have so many deer to over-browse the young trees that come back up to replace the ones that are dying, we’re going to only get the trees that the deer won’t eat.”
The third big factor influencing the composition of our future forests, Price said, is climate change. “Certainly, climate change is having an impact. But it’s hard to see the direct impact.”
Apparently, the US Forest Service is also concerned about the impact of climate change on the forests of northern forests. The Michigan Forest Ecosystem Vulnerability Assessment and Synthesis, a report issued by the Northern Research Station in March discusses a number of changes underway and anticipated.
According to Stephen Handler, the report’s lead author, the interaction of climate and forests is complicated. There are many forest stressors at work, including diseases, suburban development, fire and a large deer herd. But some climate-related changes have been observed.
For instance, he said, “the red maple, typically a southern or temperate species, is all of the sudden regenerating more successfully up in northern Minnesota, where it wouldn’t have previously been.”
Handler and the Forest Service see climate change as presenting new risks to forest managers. Like an approaching storm, it’s difficult to predict exactly what the results will be, but to stay safe, people need to be cautious. Forest owners should not bother waiting around for a crystal ball that shows what the future’s going to look like. “We know enough now to begin taking action,” he said.
Handler points out that all the climate models predict an increase in average temperatures for Northern Michigan over the coming decades. Additionally, precipitation is more likely to come in the form of large downpours, resulting in a lot of runoff. That combination of higher temperatures and less water staying in the soils may stress many of the region’s tree species.
“We’ve got some potential for pests and diseases and other stress agents to become more damaging,” Handler said. For example, “as winters become shorter and growing seasons extend, beetles are likely to become active earlier and may become active later into the season as well. Some of these pests and these disease agents may become even more damaging if they interact with trees that are already stressed from weather or climate.”
While all this change can be overwhelming, even frightening, there are lots of things people can do to help forests and woodlots adapt to climate change. Handler said he’s even optimistic because most of the recommended actions will encourage healthy forests, whether climate changes are severe or not. He calls them “no-regrets” strategies.
“The first thing is to focus on diversity,” Handler said. “That’s a diversity of species, age classes and a diversity of genetics.” For instance, forest owners should maintain and plant a variety of native tree species. Some landowners may want to plant trees that may have been more common in the southern part of Michigan such as hackberry or white oak to hedge their bets. Additionally, tree plantings should be tried in different locations such as slopes facing different directions.
Landowners interested in learning more about tree health and forestry can contact the Leelanau County Conservation District. Additionally the Forestry Division of the Department of Natural Resources offers direct assistance to promote vigorous forests throughout the state.