The relentless creep of the emerald ash borer into Maine is depressing, and it seems likely that the devastating green beetle eventually will invade the entire state, decimating the state’s population of the native trees.
But a June presentation at Maine Audubon Society’s Gilsland Farm in Falmouth by a University of Maine team working to save the trees gave me hope that at least some of them may survive.
The EAB, as it is known, is a native of Asia. It was first discovered in the United States in 2002, showing up in Michigan. It was thought to have travelled there in packing crates. The beetles quickly spread across the country, arriving in Maine in 2018. The invasive insect is now in northern Aroostook County with separate populations in York, Cumberland and parts of Oxford County.
Maine is home to three types of ash trees: white, green and black ash. Mainers, somewhat confusingly, call the third the brown ash. Brown ash is the most susceptible to the EAB, while green ash has shown the most resistance.
Forestry doctoral student Suzanne Greenlaw at Maine Audubon’s Gilsland Farm. Maine’s native tribes use wood from the brown ash to make baskets. The tree is threatened by the emerald ash borer. Photo by Madeline Reaume/courtesy of Maine Audubon
Of the three types of ash trees here, brown ash is the most important to Maine’s Wabanaki tribes. Not only is it key to the Wabanaki’s creation story, Maliseet basketmaker and forestry doctoral student Suzanne Greenlaw said during the Audubon event, it also is the best wood to use in their traditional baskets.
A Mik’maq doctoral student in forestry at UMaine, Tyler Everett, some fellow forestry students and Professor John Daigle are working to protect Maine’s ash trees from the emerald ash borer. Photo by Madeline Rheaume/ courtesy of Maine Audubon
Tyler Everett, a Mik’maq doctoral student in forestry, said that brown ash is also important because it controls flooding. It likes to keep its roots damp, and it has high levels of hydro-evaporation, meaning it pulls up water from its roots to disperse through the leaves in an especially efficient way.
So, why am I hopeful that some of the ash trees, even the most vulnerable brown ash, can be saved? Because the state has a plan, with University of Maine professor John Daigle and his students playing a major part.
First, they are trying to slow the spread of EAB. The pests’ natural spread would be about half a mile a year, but they can spread much more quickly if people move infected firewood into areas that don’t have the pest. Hence the state’s education campaign urging people not to move firewood from area to area. The hope is that slowing the spread of the beetle will keep trees safe until more permanent remedies can be found.
Several signs indicate an infected tree, including curved galleries or trail markers that show where the emerald ash borer larvae have crawled through the bark; and D-shaped holes in the bark, where the pupae have emerged from the tree after hatching. Also, if woodpeckers are spending a lot of time feeding on ash trees, chances are good they are feasting on the beetle larvae.
People with ash trees on their property should keep an eye out for those signs, and report any findings to bugwatch@maine.gov. People willing to monitor for the pest, and perhaps even have a trap tree set up on their property, should contact Colleen Teerling at the Maine Forest Service, Daigle said.
Another thing people can do is to collect seeds from the ash trees, which can be saved until we come up with a solution to the EAB infestation. UMaine is working on organizing such a seed-saving program.
Some trees have shown resistance to the beetle, Daigle noted. The mortality rate of the infestation is 95 to 99 percent, which sounds terrible. But keep in mind that conversely, the numbers mean that 1 to 5 percent of the trees can survive.
Another way to slow the spread of EAB is to remove trees that aren’t doing well, Everett said. The reason he gave surprised me. “There is a scent that a low-vigor tree emits that actually attracts the emerald ash borer,” he said.
The state is also releasing parasitic wasps in an attempt to control the EAB. These tiny wasps, by the way, don’t sting people. In Asia, the wasps keep the emerald ash borer under control. The theory is if we import the wasps to Maine, they can assist the woodpeckers in keeping the EAB population in check.
When a person in the audience asked how we can be sure these introduced wasps won’t cause a problem, state horticulturist Gary Fish, who was in the audience, said that all of these released bio-controls undergo long, strict testing at the federal level and have been shown to cause no problems. Similar insects have been released in Maine to control such pests as winter moth and lily-leaf beetle.
Another method to control the EAB is to inoculate trees with pesticide. Although expensive, it might work. (When you spray a tree, much of the pesticide runs off, potentially contaminating soil, water and other creatures. Inoculation gives more targeted control.)
The UMaine group said that Mohawk tribes in New York have been a helpful source of information. These tribes have been dealing with the pest for longer than Maine has. The two groups are sharing information about their trials and errors in an effort to eradicate the beetle from places it does not belong.
Tom Atwell is a freelance writer gardening in Cape Elizabeth. He can be contacted at: tomatwell@me.com.
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