A canopy of majestic trees, one of North America’s most significant remaining cultivated stands of American Elms, provides shade for the thousands of New Yorkers who walk, bike and play in Riverside Park along Manhattan’s Hudson River shoreline. These historic elms, most of which were planted between 1890 and 1930, are threatened by the spread of Dutch Elm Disease, a fungus that kills trees by preventing water from reaching leaves and limbs.
Almstead Tree & Shrub Care Company of New Rochelle has been hired by the Parks Department of the City of New York to help prevent the spread of Dutch Elm Disease in Riverside Park. If not properly managed, the disease can wipe out a large population of elms in a few years.
“Parks & Recreation is committed to controlling the spread of Dutch Elm Disease (DED) in Riverside Park and elsewhere throughout the City,” said Parks Commissioner Adrian Benepe. “Thanks to funding from the Greenacre Foundation and the Riverside Park Fund, we are able to work with Almstead Tree Company to take proactive measures to remove infected trees and inoculate our healthy trees in the fight against DED.”
Dutch Elm Disease was first identified in Holland in 1921, and has been in the U.S. for almost 80 years. The disease is usually spread from infected to healthy trees by the elm bark beetle, which crawls into the vascular tissue of a tree and lays its eggs there. Many cities lose between 3-8% of their elms, commonly located in parks and on streets, to the disease each year.
According to Ken Almstead of Almstead Tree, American Elms can grow as much as 80 feet high with a canopy that can spread as much as 60 feet across. “These are big shade trees that do well in compacted urban soil, which is why you find so many of them in city parks,” he said. “We are delighted to be working with the Parks Department on trying to save these wonderful trees throughout Manhattan.”
In Riverside Park, there are two big groves of mature American Elms, one between 85th and 92nd Streets and another be tween 104th and 125th Streets. Of the 80 total trees, 14 have been removed this year. Another 30-40 healthy trees are being inoculated by Almstead’s crews to prevent the spread of the disease.
During the inoculation, several holes are drilled into the base of the tree, and water carrying the inoculant is injected via a pump, explains Almstead arborist Justin Rawson, who is managing the Riverside Park project. The procedure, called macro-infusion, uses a product called Arbotect 20-S. The inoculant protects a tree for three years and has been proven to be more than 99% effective.“Dutch Elm Disease shuts down a tree’s vascular system, similar to a heart attack in a human,” said Rawson. Although diseased trees cannot be saved, the key to keeping Dutch Elm Disease from spreading is the prompt removal of diseased trees or limbs, which reduces the number of disease-carrying beetles.