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Deadly, incurable & fast spreading oak wilt disease detected in Brooklyn trees

DEC issues emergency orders for protective zones

December 30, 2016 By Mary Frost Brooklyn Daily Eagle
To the horror of urban tree lovers, a quickly-spreading disease that kills oak trees has been discovered in Brooklyn. Photo by Mary Frost
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A disease that kills oak trees and spreads like wildfire has been detected in Brooklyn.

The news has sent shock waves through the borough’s tree experts and arbor groups. Many of the borough’s oaks are massive and more than a century old, providing shade and character to streets and parks and a habitat for birds and other animals.

The NYS Department of Environmental Conservation (DEC) sent out a bulletin on Thursday saying that the disease, oak wilt, which is caused by a fungus, was identified by the Cornell Plant Disease Diagnostic Clinic after samples from oak trees showing symptoms were collected by DEC technicians. Symptoms include leaves wilting, turning brown and dropping off, followed by the death of the tree. Infected trees were also detected in Long Island.

There is no known treatment for oak wilt other than to remove and destroy the infected trees, as well as any surrounding host oak trees. Healthy oaks growing next to infected ones can become infected through their roots or from beetles that spread the fungus.

DEC is issuing emergency orders to establish a protective zone encompassing the entirety of Brooklyn, and another zone around Suffolk County. The emergency orders prohibit the removal of any standing, cut or fallen oak trees, living or dead. Removing tree parts, including branches, logs, stumps or roots, is also forbidden. 

“It is important that these emergency orders are taken seriously,” DEC Commissioner Basil Seggos said in a statement. “Moving contaminated wood without taking precautions will spread this serious tree-killing disease to additional areas.”

“I’m very shocked to hear this,” said Brooklyn tree activist Nancy Wolf, a member of the planning committee of NY ReLeaf, the urban forestry program of the state of New York.

Wolf, a resident of Brooklyn Heights, said the neighborhood was full of wonderful oak specimens, including white, red and willow oaks.

“It’s really tragic. Oaks are among the best of all trees,” she said. “They live a long time and provide a shady canopy,” especially important in light of global warming, she said. “Mature oaks provide so much shade.”

“Oak trees contribute enormously to the character of the Heights’ tree-lined streets. Any disease that diminishes their health is of great concern,” Peter Bray, president of the Brooklyn Heights Association (BHA), told the Brooklyn Eagle. “The BHA will closely monitor this situation and will work with the community and the city to seek ways to ameliorate it.”

Red oaks hit the hardest

City Parks Department spokesperson Maeri Ferguson told the Brooklyn Eagle that the affected trees were discovered in Greenwood Cemetery.

“Oak wilt was only very recently discovered in Brooklyn, and the infected trees are not under Parks’ jurisdiction,” Ferguson said. “To limit the potential spread of the disease, Parks is collaborating with NYSDEC to monitor Brooklyn’s trees and test suspected cases.”

Ferguson said that this particular oak wilt pathogen affects species from the red oak family more severely than those in the white oak family. It typically kills those in the red oak family within one to two years, while some species in the white oak family have a moderate degree of resistance and can live for some time longer with the disease.

According to the Park Department’s latest tree censes, Brooklyn has 19,721 street trees that belong to the red oak family. (Parks does not currently have a complete census of trees in parks and natural areas in the borough.)

Previous tree surveys have shown that oaks make up roughly 7.5 percent of Brooklyn’s street trees, but have more than a 7.5 percent impact on Brooklyn neighborhoods. Oaks have a “higher importance value” in the city due to their larger stature and leaf size. While 7.5 percent of sidewalk trees are oaks, they provide 10.9 percent of the canopy.

More testing to come in the spring

DEC is removing and destroying oaks that have tested positive for oak wilt, but further testing can only be done during the growing season when the fungus is active. Intensive sampling across Brooklyn, Nassau and Suffolk counties will take place in the spring. The Parks Department will begin testing trees near Greenwood Cemetery at that time. Aerial surveys will be conducted beginning in July when signs of oak wilt will be most apparent.

DEC said it will schedule public meetings to address concerns once the extent of the disease is determined and a plan is made to control the disease.

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DEC asks the public to be on the lookout next summer for oak trees that suddenly lose leaves during the months of July and August and to report these occurrences to the Forest Health Information Line toll-free at 1-866-640-0652.

More on this topic  from the U.S. Department of Agriculture.


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