Overview

• As fall colors peak across Washtenaw County, leaf drop offers a timely moment for tree health assessments and strategic planning, especially before spring’s renewed growth. Michigan’s Department of Natural Resources recommends that oak pruning be done during dormant months and avoided between April 15 and July 15 to limit spread of oak wilt. (michigan.gov)

• Oak wilt, caused by the fungus Bretziella fagacearum, remains a leading pathogen threat in the region. It moves underground via root grafts and aboveground via sap-feeding beetles that land on fresh wounds. In Michigan, red oaks infected by oak wilt typically die rapidly. Control strategies include severing root grafts, promptly removing and disposing of infected wood, and applying fungicides to nearby healthy oaks. The state provides a comprehensive overview and detailed pruning advisory. (michigan.gov)

• In June 2023, beech leaf disease (BLD) was confirmed in Washtenaw County at Legacy Land Conservancy’s Creekshead Preserve in Salem Township. Researchers observed dark interveinal banding, leaf thickening, and canopy thinning in beech specimens, and laboratory testing confirmed the disease’s presence. There is currently no cure for BLD, so management practices center on early detection, monitoring, and preventing the movement of beech logs or nursery stock. The Michigan invasive species division maintains a detection map and guidance. (legacylandconservancy.org), (michigan.gov)

• Hemlock woolly adelgid was verified at the University of Michigan’s Nichols Arboretum in Ann Arbor on May 9, 2023, marking a local detection in Washtenaw County. Homeowners and land managers may treat infested hemlocks using systemic insecticides such as imidacloprid (which provides multi-year protection) or dinotefuran (which gives quicker protection for one to two years). Guidance is available in the state’s MDARD/DNR pest bulletins. (content.govdelivery.com)

• Spongy moth outbreaks reached a peak in Michigan during 2021 and have declined in 2025; in Washtenaw County, control tactics include manually scraping egg masses and, when necessary and timed properly, applying Bacillus thuringiensis kurstaki (Btk) to vulnerable early-stage larvae. The Michigan DNR’s invasive species news notes that spongy moth populations are waning for 2025. (michigan.gov) Meanwhile, the box tree moth (Cydalima perspectalis) triggered a state quarantine in December 2023 that includes Washtenaw County, restricting movement of boxwood plants and plant parts to prevent spread. Additionally, spotted lanternfly infestations have been confirmed in adjacent counties—Lenawee, Macomb, Monroe, Oakland, and Wayne—but not yet in Washtenaw; residents are advised to report any suspect sightings. (michigan.gov), (content.govdelivery.com)

• Scientific studies and forest health reports suggest that climate change is playing a growing role in worsening the effects of forest pathogens and pests. The U.S. Forest Service states that oak wilt’s range is expected to expand northward under warmer conditions, and that changes in insect vector behavior may accelerate disease spread. Similarly, peer-reviewed reviews of beech leaf disease warn that climate stressors such as drought and temperature extremes can amplify disease progression in affected trees. These findings imply that Washtenaw County may see higher pressure from these diseases moving forward. (fs.usda.gov)

• The Washtenaw County Conservation District plays a coordinating role in local forest health efforts. It helps with early detection, public education, invasive species reporting, and connects landowners to arborists and foresters through its partnership with the Jackson–Lenawee–Washtenaw CISMA. The District also runs native tree and shrub distribution programs aimed at enhancing canopy resilience and supports municipalities via its Community Trees initiative, which helps integrate tree health considerations into planning policies. (washtenawcd.org), (washtenawcd.org)

Transcription

David Fair: This is 89.1 WEMU, and the change of seasons is upon us! I’m David Fair, and on today’s edition of Issues of the Environment, we’re going to talk about the challenges of keeping all of our beautiful trees healthy and the challenges we have in doing so. Matt DeJonge is a community forester with the Washtenaw County Conservation District and is on the other end of the WEMU phone line. And nice to talk with you again today, Matt!

Matt DeJonge: Thanks for having me on, David! And, yeah, I certainly agree with that. You know, this time of year, we are having some tree disease issues, and I’m excited to discuss what I know with members of the community today.

David Fair: [00:00:39] Well, before we get into the bugs and the disease, as a forester in the fall, is change of color kind of your favorite part of the year?

Matt DeJonge: It really is. And I’m aware of some foresters who actually do work in this regard. I met someone who kind of tracks these color changes throughout his state, which was North Carolina. And, yeah, it’s really one of my favorite times of year is watching the trees turn their different colors and really get that full expressivity of the natural landscape.

David Fair: Well, you are certainly not alone in that sentiment. Unfortunately, we’ve had a very dry end of the summer and start of the fall, and a lot of leaves didn’t wait to change color to fall off. Should we be concerned about that?

Matt DeJonge: We have had some drier weather, and this is one of those environmental variables that changes year to year. And the variability has gotten a lot more volatile over the last 10 to 15, even 20 years and will, year to year, cause some stresses on our community’s trees.

David Fair: How else is climate change impacting our forest canopy and even the trees that line our yards and streets?

Matt DeJonge: That’s a great question, David. And, again, I think it gets back to that volatility. You know, in Michigan, we’re relatively blessed with a a temperate climate, but as the years go by, we can expect maybe shorter shoulder seasons in the spring and in the fall, or even longer shoulder seasons with increased drought pressure where we go longer time periods with no rain, or even, especially in the last couple of years here, effects from Canadian wildfire. That’s impacting trees and plants’ ability to photosynthesize. All of these things really add up to that increase in volatility, like I mentioned.

David Fair: What are some of the methods of helping nature adapt while we figure out as humans how to adapt?

Matt DeJonge: That’s another really good question. I think it comes down to interacting more with the natural world. One thing that, as a forester, I really strive to discuss with people in my day-to-day is getting closer and actually interacting with the natural world, and that could just be taking some time to enjoy some morning sunlight for five to ten minutes or even learning more about the habitat that’s around us, maybe in our local parks or natural areas. I think that’s a good first step. And there are other ways too. Eating locally is a great option. You get the chance to interact with people who are growing food in your local area, and that’s one of our closest connections to the natural world is the food that’s on our plate every day.

David Fair: And it just kind of tastes better too, doesn’t it?

Matt DeJonge: It does. It does.

David Fair: Our Issues of the Environment conversation with Matt DeJonge continues on 89.1 WEMU. He is a forester with the Washtenaw County Conservation District. At the outset, I mentioned bugs and disease, and that is an issue for trees. Let’s start with the bugs. Is the emerald ash borer still a problem?

Matt DeJonge: You know, it’s a really good question. I can tell an anecdote going back to 2007 where it’s probably my first known interaction with a tree pest. And this was when my parents moved into their new house and had to get some ash trees removed and was really questioning why half of these trees have to get removed all of a sudden. And this was right around the height or the growing of the EAB. And unfortunately, still in 2025, the EAB is present in in Michigan and will likely be here for quite some time. And I would say it’s still a risk to the ash resource in Michigan and in the southeast.

David Fair: What about the hemlock wooly adelgid?

Matt DeJonge: It is. Recently, I believe it was in 2023, what was a tree pest that was only on the west coast of Michigan was unfortunately spotted. I believe it was in the Nichols Arboretum. Yeah, I think it was the summer of 2023, and this is a tree pest that affects eastern hemlock. And it can be tricky to spot, but if you have that eye, you can see the wooly pattern on like the bottom of the hemlock needles. And it is unfortunately here in Washtenaw County.

David Fair: There have been some areas outside of Washtenaw County struggling with spongy moths. How are we doing locally with that problem?

Matt DeJonge: Last I heard, the issue was really at its height in 2021, and spongy moth has been around in Michigan since about the 1950s. And it’s one of these pests that actually has like an ebb and a flow with the population. So, if you imagine the population getting to such a large amount, that it actually begins to get affected by this virus. And as recently as 2021, I think there was one of these large populations that was affected by this virus. And luckily, we’re on the other side of that now. And unfortunately, it’s again only a matter of time before spongy moth does wind up coming back to our area in southeast Michigan. So, I would just encourage residents to stay on the lookout for this because this pest does tend to cause mass defoliation. And it’s quite disgusting if you ask me.

David Fair: This is Issues of the Environment on 89.1 WEMU, and we’re talking with Washtenaw County Conservation District Community forester Matt Dejonge. What are the most prevalent tree diseases impacting the canopy in Washtenaw County at present day?

Matt DeJonge: Well, that’s a good question, David. And I think the trends I’m seeing and most concerned about right now are the presence of spotted lantern fly in our area of the state. And this was a pest that, I believe, was first identified in Pennsylvania and has slowly been making its way through the northeast and now into the Midwest. It’s a really big risk on Michigan’s fruit production. And so, that’s been one thing that’s been developing recently, and another one is the incidence of beech leaf disease, which is another very important tree–very important, functional group dominant tree–in Michigan’s canopies. And beech leaf disease is another new forest disease that we just don’t know a lot about. So, those are two things that I’m really seeing are trending and are concerning for me.

David Fair: It’s hard to protect trees when you’re not exactly sure what is coming, when it will arrive and what impact it will have. How much of the work you do is reactionary and how much is predictive?

Matt DeJonge: Some of the reactionary work that we tend to do is in the form of technical assistance. I get phone calls from residents and landowners who maybe are looking to identify a particular repester disease, and I do my best. I really do. There’s so much variability out there, but I really do my best to try to help identify what may be going on in that particular case. And in terms of proactive work, Washtenaw County Conservation District is a part of the Jackson, Lenawee Washtenaw Cooperative Invasive Species Management Area. And that’s a big word salad, but, essentially, what it means is it’s a organization or group of us natural resource professionals that are out here trying to influence management through outreach for some of these pests and diseases, especially when it comes to things like invasive species that may be really impacting our resources. So, there is work being done on both sides of the coin.

David Fair: I think it’s quite amazing how healthy the trees in Washtenaw and surrounding counties have remained. Given all of the challenges of different bug species and different diseases, are you confident we’ll be in an even better place a decade from now?

Matt DeJonge: I am. I think that, over time for humans, our interaction with the natural environment has really, really improved in my lifetime, and I’m very hopeful that that will continue to grow because it’s really essential for, I think, the continued success of not only our natural areas but ourselves as a society. That’s something that’s very important to me is is our connection to our trees, our food and the green spaces that we enjoy.

David Fair: I’d like to thank you so much for taking time and talking with me today! I certainly appreciate the information, Matt!

Matt DeJonge: Yeah! Thank you so much, David!

David Fair: That is Washtenaw County Conservation District Community forester Matt DeJonge, our guest on Issues of the Environment. For more information on our conversation today, stop by our website at WEMU.org. Issues of the Environment is produced in partnership with the office of the Washtenaw County Water Resources Commissioner. You get to hear it every Wednesday. I’m David Fair, and this is your community NPR station, 89.1 WEMU-FM Ypsilanti. Celebrating 60 years of broadcasting from the campus of Eastern Michigan University!

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