NEW YORK (CBSNewYork) — Another tree-killing fungus has been found in the Tri-State Area.

As CBS2’s Elise Finch reported Monday, the oak wilt fungus until recently was only impacting trees in upstate New York. But now, trees on Long Island and in Brooklyn are dying.

First it was ash trees and then pine, but now with the oak wilt fungus, the mighty oak is under attack.

“Oak wilt is a fungal pathogen that gets into the vascular system of oak trees — specifically red oak trees,” said plant pathologist Karen Snover-Clift, “and it doesn’t allow nutrients to move back and forth within the tree.”

Snover-Clift is the director of the plant disease diagnostic clinic at Cornell University. She said dozens of oak trees in the New York City area were tested, and at least five oak wilt cases were confirmed.

Among the trees affected was one at the Green-Wood Cemetery in Park Slope, Brooklyn. The tree had to come down.

Oak wilt is so devastating it can kill a tree in just three weeks. At that point, the only thing to be done with the infected tree is to cut it down — and in most cases, neighboring trees have to be cut down too.

“Trees around here make this neighborhood what it is, so to find out that there’s a fungus killing trees – it’s crazy,” said Ellison Antonsanti of Park Slope.

“Humans have become a little too disconnected from nature — especially in big cities like this,” said Emma Johnson of Yonkers. “I think it’s like almost something you need.”

The fungus is typically spread by beetles. But it can also spread underground through tree roots.

The signs of oak wilt are leaves that wilt, turn brown and fall off when they are still green. Branches that turn yellow and blue-gray streaks that develop under the bark are also among the symptoms.

Snover-Clift said it is important to stop the spread of the disease, because oak trees are so important.

“A lot of things are made from oak trees — furniture, flooring,” she said, “and then the environmental factor of the acorns feed a lot of animals.”

Oak trees are the largest group of forest trees native to New York. The goal is to stop oak wilt from spreading like it has in other states.

Scientists think drastic swings in temperatures weaken trees and make them susceptible to oak wilt. Pruning and trenching can prevent the disease from spreading, but when that does not work, infected trees must be removed.

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