Last fall, the New York State Department of Environmental Conservation announced that an oak tree in the town of Canandaigua had been infected with oak wilt disease, and an update was published recently in the Rochester Democrat & Chronicle.
The DEC has established a “Protective Zone” (quarantine) around the infected tree. This severely restricts the movement of fresh wood into or out of the zone. Obeying this, and other quarantines, is important. This disease, like most fungal diseases cannot be controlled easily with a fungicide. Propiconazole, a fungicide that, if applied on a regular basis, will keep this fungus under control. Once use of the fungicide is started, it must be continued or the fungus will become active again, making diseases like this much more serious in the long term than insects. Off hand, I can’t think of an insect for which an effective chemical or natural predator was not found eventually.
The fungus that causes oak wilt is Ceratocystis fagacearum, which develops in an oak tree’s water-carrying cells, called xylem. The water carried by the xylem contains life sustaining nutrients. These nutrients are essential to photosynthesis. Lacking water and nutrients, the leaves wilt and fall. Oak wilt kills red oaks in six month or less, while it takes much longer, often years, for the disease to claim white oaks.
Insect carriers and root contact are the most common natural ways for oak wilt to spread, but the movement of wood and wood products like firewood have become become an increasing concern. This is why quarantines carry stiff penalties. It is believed that bringing infected wood into Canandaigua caused this outbreak.
If you see oak trees with wilting and falling leaves or the top branches are defoliated, report them to the local DEC office so that action can be taken to keep the disease from spreading. Let’s not let it get a foothold in our area. Remember what fungal diseases did to the American chestnut and the American elm.
Birchcrest arborists are working with the DEC to contain and eradicate the oak wilt in Canandaigua. Believe me, it’s painful to take down a majestic oak tree that has been growing so long that it witnessed much of the rich history of the Finger Lakes.