Emerald Ash Borer Threatens Vermont Forests
Emerald Ash Borer Threatens Vermont Forests
By Tessa Lightfoot, Intervale Center Intern
Have you heard of the Emerald Ash Borer? If you live in Vermont, chances are you have. The Emerald Ash Borer is an invasive beetle that was inadvertently brought to the U.S. through human transport of lumber. Infestations first began in the Detroit area in 2002 and have spread throughout the eastern United States and Canada. It is currently found in 35 states, including Vermont. These beetles are worrisome because they kill ash trees, a species that comprises 5% of forests in Vermont.
I had the chance to chat with Duncan Murdoch, our Natural Areas Stewardship Coordinator and he gave me the lowdown.
How do the beetles kill trees?
“The beetles lay eggs in the cambium (the bark). Then the larvae hatch and eat their way out of the tree, creating an S pattern around the inside of the bark. As they munch on the cambium tissue, it girdles the tree. The cambium layer is the outside layer, where nutrients are transported up and down the tree. Once you cut off that flow, the tree will die.”
How do you know when a tree has been infected?
“If you see woodpeckers pecking a tree all over then it could be infested with emerald ash borer. Other early detection signs are crown die-off and bark splitting.”
How does the Ash Borer issue impact the Intervale specifically?
“It’s something we’re thinking about because we have ash trees as ornamentals and in the forest. It’s on our radar more because of the immediate aesthetic value that the ash trees have, like those in the Summervale area. It’s also something for us to think about in relation to invasive plant species. When an ash tree dies it opens up a hole in the canopy and that will let in a lot more light. If we don’t have invasive species under control in the understory, then they will proliferate and fill in that gap. Right now we’re in the risk area, so we haven’t had any confirmed infestations in the Intervale, but it’s growing pretty rapidly so we will soon. Within a year I bet we will be in the infected area and in 5 years we will see things start to die.”
What will be some of the socio-cultural, economic, or ecological impacts of the Ash Borer’s infestation?
“It’s going to impact us in all of those areas. The economic impact can be measured and is a little more straightforward in urban areas. One economic impact we will face is the heating and cooling costs associated with the trees. The tree canopy provides shade and blocks cold wind so if large swaths of trees die, energy costs will be affected. Storm water runoff will also be affected. It’s something like every 5% canopy cover provides a 2% reduction in storm runoff. So with its roots, each tree is capable of capturing hundreds of thousands of gallons of water. Without those trees, water will run off and need to be treated and mitigated in some other way.
Carbon sequestration is an issue. The mass of a tree is carbon, so the larger the tree, the more carbon is stored. A big part of the issue is that all the carbon stored in these trees will be released all at once, or in a relatively short amount of time. Five percent of our forest is going to die and will be releasing carbon into the atmosphere. That is not good. Trees in general filter particulates out of the air and effectively reduce pollution and are constantly producing oxygen. We are losing a lot of beneficial, naturally occurring services as these trees die off.
It is also just going to be sad to see a whole species decimated. There will be areas with concentrations of ash stands that will be visually striking when they die.”
Do these beetles have any predators?
“Yes, woodpeckers! They eat the larvae in the trees so they could slow the spread. There have also been experiments of introducing a biological control—I think some fungus or something that kills the beetles. In my view that’s kind of dangerous because you don’t know what kind of impact that introduction might have. But I think they have had some promising reports with this new “predator” being introduced to eat the emerald ash borer.”
What are the options going forward? Can we stop the Ash Borer from coming to the Intervale Center? If it does come, what is next?
“It’s spreading. We can’t stop it, but we can try to slow it down. There are areas that have been infected where trees have been decimated, but there are some new growth of ash, which signifies that the ash trees have some sort of resistance to it, so that’s hopeful.
We don’t want to be premature and try to kill the ash trees before the ash borer kills them. I think nature is incredibly resilient and surprising. For us to be able to predict with 100% certainty that the ash borer is going to kill every ash here wouldn’t be a fair assumption. We can’t stop the spread of the ash borer. There have been efforts to slow it down by limiting transportation of firewood. There have also been efforts to quarantine areas that have been infested, but the beetles fly so they will just fly over to the next tree.
The Intervale Conservation Nursery will be involved too. They will try to capture the resistant strains of ash and grow those. This involves identifying ash trees that were lucky or resistant somehow and then starting to cross breed/hybridize those resistant strains to create an ash tree that is able to resist the Emerald Ash Borer. Then the conservation nursery can grow those resistant trees so they have a better chance of survival.”
Tell me about the inoculation of the ash tree at Picnic Grove.
“There is a very old ash tree (likely over 100 years old) that has a big canopy covering most of picnic grove. The option came up to inoculate ash trees with a type of pesticide that will prevent the ash from being infected. We decided to use the ash tree at picnic grove as an experiment and we partnered with Burlington Parks and Recreation. Each inoculation is supposed to last up to three years and then it needs to be re-upped. So it’s not permanent, we’re just experimenting with it. We drilled holes in the flare of the tree and then attached compressed canisters of fluid to push the pesticide into the tree. Over time the tree sucks up the fluid through the cambium.”
Why are you inoculating this large tree by the Picnic Grove?
“We decided to do this because we thought that if we see a future with no ash trees (or very few ash trees) it would be really special to have an ash for people to visit or to use for an educational experience or for a spiritual experience. We wanted to have an ash in a public space for people to enjoy.”
Are there any worries or potential side effects of the inoculation?
“From everything I’ve read it’s really localized. It’s not a spray application so it stays in the tree. But I’m a little hesitant because the Intervale Center has a policy where we don’t use herbicides or pesticides in invasive species management or in agricultural fields. The Intervale is an organic landscape, but this is an exceptional circumstance and is a temporary experiment. Like I said, it’s a 2-3 year period and we will re-evaluate afterwards. With time, I do believe there will be more biological treatments that we can look into instead of the chemical treatment. Maybe we will let that tree go in the future, but we wanted to buy our time with that one tree in particular because it’s so beautiful.”
Anything else?
“I’m aware that we are looking at invasive species through our lens as humans and their impact on us specifically, mostly through an economic and resource lens. That is very human-centric view. In reality, we are not the only species on this planet and the whole ecological system doesn’t revolve around us. Nature is bigger than us. In my view nature is highly resilient. There are so many things we don’t know about nature. For us to assume that we have the answers or know what is good or bad is highly presumptuous of us. I try to be humbled by the intricacies and subtleties and the mystery of nature and careful not to be so absolute about “this is the right way, this is good, this is bad.”
Want to know more? Visit https://vtinvasives.org/land/emerald-ash-borer-vermont for more information on the Emerald Ash Borer in Vermont.