Leaf tips will bronze in the middle of the growing season when a tree is infested.
Oak wilt resurfaced in Glenville this year. After battles with this invasive tree pest in the town in 2009 and 2013, DEC flyovers revealed another site in Sanders Preserve, and a neighbor’s vigilance brought to light another site in a residential neighborhood. Considered one of the worst forest pests that New York is currently battling, oak wilt is a huge concern for the forestry community and could have devastating impacts on all species of oak found in the state.
Oak wilt was first identified in Wisconsin in the 1940s, but may have been present in the U. S. before that. Currently its affects are most strongly felt in the Midwest and Texas, though the range expands upwards north into PA. It is currently reported in New York in Brooklyn, Long Island, Glenville, and Canandaigua. Fortunately there are few enough locations that the DEC has been running an extermination campaign, working to eradicate this fungal disease when it appears in upstate areas. The door-to-door outreach took place on two cold mornings in January, notifying homeowners within a half mile area of the two sites about the pest and its symptoms. The public meeting (attended by 49 Glenville residents) to announce the eradication plans was on January 31st, and the goal is to have the infected trees removed by April 1st.
Now at this point you may be asking, what exactly is oak wilt? It is a fungal infection of all species of oak trees, though its effect is most visible in the red oak family, where it can kill a tree in a matter of weeks. It is most visible through the leaves of the tree, which start to bronze uniformly at the tips like they were dipped in paint. These leaves often start to fall off the tree, still green, around the fourth of July. The symptoms have been described as a “tree heart attack,” clogging the transport mechanisms through the tree with the fungus. Species in the white oak family are not immune either, though they exhibit less symptoms they can be passive carriers of the fungus.
One of the reasons that this is such a difficult pest to manage is that there are a few ways that the disease spreads. Locally, the fungus can spread through the root connections between trees, most present in trees of the same species, though links between different kinds of oak species are also common. This is the reason a buffer zone of trees is often cut when treating for oak wilt, there can be asymptomatic trees within root-reach of obviously infected trees. The disease can also ‘jump’ up to five mile through a common species of beetle, which after feeding at a fungal tree, go to a fresh wound (often caused by pruning or construction) on a healthy tree. For this reason, it is recommended that trees be pruned in the winter, and not in the months of March-September. The DEC diagnostic laboratory is preparing for a monitoring project later this year to determine the most active time of year for this beetle to make more exact pruning recommendations to both homeowners and arborists.
PRISM staff have been working to help the DEC with outreach efforts regarding oak wilt. If you think that you have a tree that is infected on your own property, the DEC runs a hotline at (866) 640-0652 which you can call to have a DEC technician come take a sample of the tree in question that will be tested at the labs at Cornell. Community involvement is huge when taking on a tree disease of this magnitude. The oak is one of the most ecologically important trees in our state, providing animals with food throughout the winter through its acorns, supporting a vast number of insect herbivores with nutrients, which then in turn feed our birds. While it is hoped that the efforts in Glenville puts a stop to the northern movement of the fungus, it is important that all forest owners keep an eye out for the symptoms in their woodlots in order to protect oaks on their property, and statewide.
An infested tree showing heavy bronzing during the summer.