Thursday August 16, 2018
Seven-hundred and sixty ash trees grace the streets and the parks of South Burlington. Upwards of 80 percent of those trees are located off of Dorset Street in the Dorset Farms, Brand Farm, and golf course neighborhoods. These numbers are courtesy of South Burlington City Arborist Craig Lambert, who has been responsible for tree maintenance in the city since the spring of 1998. During Lambert’s tenure, the ash tree has become a hot topic for arborists, foresters, and community members alike. Once popular for its attributes of fast growth, nice shade, and ability to adapt to a range of soil conditions, the ash tree has been pulled into the limelight due to an invasive insect known as the Emerald Ash Borer (EAB). This metallic green bullet-shaped beetle is credited with what might lead to the end of ash trees as we know them in both our forests and urban landscapes. Along with city staff, Lambert is working on a plan to protect and care for South Burlington’s trees, including the endangered ash.
“There are roughly 6,000 street and park trees in South Burlington,” says Lambert, adding, “So the percentage of ash is roughly 13 percent. That is a little higher than a recommended maximum of any one species, but the real problem is the concentration of ash trees in a few neighborhoods.”
It is important to begin with the current state of affairs in regard to the invasive insect. To date, according to Chittenden County Forester Ethan Tapper, “There is no EAB in Chittenden County as far as we know.” However, EAB has been found in Vermont. Up until recently, the current infestation in the state was centered in the north central area and includes the towns of Orange, Groton, Marshfield, Barre, and Montpelier. As recently as July 31, the Vermont Agency of Natural Resources (VANR) reported the USDA Animal and Plant Health Inspection Service alerted state officials that EAB was captured on a purple detection trap in the town of Stamford, in Bennington County. VANR noted, “This location is within five miles of another recent EAB detection in the town of North Adams, Massachusetts.”
This advancement of EAB is not unexpected. According to Tapper, EAB naturally spreads up to two miles per year, which makes planning a perfect antidote to the developing problem, which first began in the United States in 2002, when it was first discovered in Michigan, believed to have been transported on wood shipping materials like crates and pallets. Native to China, eastern Russia, Japan, and Korea, the beetle is now found in 33 states, including neighboring New Hampshire, New York, and Massachusetts, as well has three Canadian provinces. The spread of EAB is attributed to humans moving firewood. Lambert describes the beetle as “a prolific hitchhiker.” Tapper adds, “One person moving firewood from an infected area can spread EAB hundreds of miles in one day.” Vermont currently has a firewood quarantine which prohibits the importation of untreated firewood into the state. Tapper warns, “Never, ever, move firewood more than a few miles, even in an un-infested area.”
According to the VANR, some infestations have also been traced to shipments of nursery trees and logs, noting, “All stages of the insect can travel 65 miles per hour down the interstate inside infested wood.” In addition, climate does not hinder the EAB. Just as it does in northern China, the insect survives Vermont winters.
The invasive beetle kills ash trees by girdling. Adults lay eggs in the tree’s bark and the eggs hatch into larvae, which feed on the inner-bark of the tree, carving tunnels, and cutting off the tree’s ability to transport water and nutrients. Eventually, this causes the tree to starve. Lambert reports, “EAB generally will kill trees in three to five years.”
Foresters like Tapper explain that the answer to this growing problem is not removing all ash trees. Although EAB infestation has caused 99 percent mortality of ash trees in infected areas, according to Tapper, this has happened regardless of cutting or quarantining. Noting that approximately five percent of Vermont’s forest is comprised of ash trees, he says, “Cutting every ash tree will not slow the spread of the borer, nor will it necessarily benefit the health of the forest.” He adds, “Proactively removing ash trees gives landowners a chance to capitalize on any value in those trees before they die but doesn’t make the forest any healthier. In an urban or suburban setting, proactively removing ash trees is a way for communities to spread out the cost of replacing those trees, rather than removing and replacing them all at once when EAB arrives. [Communities] can spread the expense and effort over a number of years. Again, this does nothing to stop EAB, it just softens its effect on us.”
This is exactly what Lambert and the City of South Burlington is working towards, proactively removing trees in some of the neighborhoods with high concentrations of ash. Lambert says, “We are planting a variety of species to replace the ash tree in South Burlington to increase diversity and lessen the impact of another insect or disease problem that affects particular tree species.” London Planetree, Accolade Elm, Swamp White Oak, Red Oak, River Birch, and Freeman Maple are some of the species that Lambert says may be planted. He adds, “We are in the very early stages of planning and have not yet designated areas where we hope to start removals. Funding at this point will have to originate in next year’s municipal budget.”
Interplanting trees is another plan of action in the city, according to Lambert, which consists of planting trees from the TREEage Community Nursery between existing ash trees in order to establish new trees before the removal of the ash becomes necessary. He reports, “This has been started on a limited basis on Midland Avenue, Nowland Farm Road, Four Sisters Road, and Brand Farm Road.”
Besides eventual removal of ash trees, there are some who tout preventative treatment programs. Trapper says, “I think that for scattered, high-value trees, the stem-injection of non-noenicitinoid insecticide is a good option. This protects individual trees but requires re-application every two to three years and is probably not a feasible solution for a large number of ash trees, such as those in our forests.”
Lambert concurs with Trapper’s assessment, adding, “Preventative treatments are an option that require fairly intensive and costly management of trees. To prevent attack by EAB, trees will need to be treated on annual or biannual basis for the life of the tree. The most recent pricing I’ve received from a local arborist is $10-12 per inch of diameter.”
It is the strength of the ash tree that caused it to be planted in so many new developments over recent years. South Burlington is not alone is this distinction, with many Vermont towns having a much higher percentage of ash trees gracing their streets and newer developments. Trapper says, “I’ve talked to arborists and urban foresters about this, and it sounds like green ash is a common street tree due to their resilience. The urban and suburban environment is a tricky place for trees to grow, and green ash tend to deal with it well.”
Lambert explains that when the neighborhoods around the golf course were developed, “Ash was a popular street tree selection due to its hardiness and ability to stand up to the stresses of urban/suburban conditions. Unfortunately no one seemed to be considering that they should be diversifying the number of species to guard against insect and disease infestation.” He notes that while the vast majority of ash trees in the city are green ash, “There are some white ash, and black ash is also native to Vermont. All true ash species, not mountain Ash, are affected by EAB.”
There are a number of things residents of South Burlington can do to assist in the management of EAB. First and foremost, do not move firewood from other potentially infested areas. Lambert recommends notifying public works if you suspect an ash tree may be infested. Some of the signs and symptoms include woodpecker activity in ash trees, dieback and thinning of the upper crown of a tree, bark splitting, profuse sprouting along the trunk of a tree, tiny D shaped holes in the trunk of a tree, and S shaped feeding galleries under the bark of a tree.
The Vermont Invasive website, which is a joint effort between the University of Vermont Extension; the Vermont Department of Forests, Parks and Recreation; the Vermont Department of Environmental Conservation; and the Vermont Chapter of the Nature Conservancy, has helpful information, pictures, and videos for those who would like to learn how to identify an ash tree and the EAB, including pictures of other native insects that can be misidentified as the invasive beetle. Visit the website at vtinvasives.org.
While the depletion of ash trees presents a significant loss to communities and forests in Vermont, Tapper says it is important to regenerate ash seedlings and saplings, including retaining ash seed trees as long as possible. “If the EAB dies off after running out of larger ash trees to infest, there is a chance that these young trees could save ash as a species. Finally, continuing to encourage a diversity of tree species and conditions is the best way to ensure that our forests remain healthy and resilient.”
Although Tapper remarks, “Once EAB reaches Chittenden County, it is unlikely that ash will ever play an important role in our forests and urban landscapes again,” he advocates for seeing the problem as an opportunity for thoughtful planning. “With increasing fragmentation, parcelization, urbanization, the increased presence of invasive exotic species and the uncertain future effects of climate change, it is critical that we hold the management of our forests to a high standard, so that they are best equipped to weather this storm.”
Meanwhile, closer to home, Lambert has made presentations about the EAB to city council and members of the Natural Resources Committee. He adds, “It would be helpful for concerned residents to contact their representatives to express their concerns. I’d also ask residents to contact me if they believe they are seeing evidence of ash borer.”
SOURCE: Carole Vasta Folley, The Other Paper