Although oak tree blight has been reported in other states as early as 1944, it did not reach New York until 2008 when it was discovered in Schenectady New York. This caused concern because the Adirondack Preserve in northern New York has the largest group of red oak in the United States. Oak tree blight has the scientific name of Ceratocystis fagacearum and is only found in the continental United States.
According to Cornell University all of the native oak species in New York State are susceptible to blight at some degree with the northern red oak, black oak and pin oak being the most likely to die after infection. White or bur oak can survive for years after infection but are not immune to blight. Individual trees react differently to infection making prognosis concerning lifespan after infection difficult.
Oak tree blight is a fungus that has two methods of travel. The most documented method according to Cornell is between trees through roots growing within 50 feet of each other; these roots can intermingle and eventually graft together forming combined root systems sharing water, nutrients and the fungus. Oak trees of the red oak group (northern red oak, black oak, pin oak) found in clusters can form an infection center for the fungus; red oaks used as treelines on city streets can also spread the blight if they are spaced close enough together for the roots to graft into a root system. A secondary method of development is by spores; these spores are created by a mycelial mat that forms under pressure pads formed by the fungus. These spores can be carried overland by beetles and bugs to infect healthy oak.
Oak tree blight has identifiable symptoms according to the USDA Forestry Service. Initial signs include subtle color shifts in leaves at the upper crown of the tree. Discoloration begins at the end of June or the beginning of July in the northern area of the state. Wilted leaves will appear from the crown downward; individual leaves quickly discolor around the leaf margins from tip to base; the discoloration takes a bronze hue. Red oaks can become defoliated within weeks of infection; Texas live oak can take up to six months to succumb to the blight while white oaks can take a year or longer to show significant defoliation. Groups of oak trees showing symptoms are a sure sign of root infection. Cornell University states that infected trees near death create a sweet rotton fruit smell.
There is no chemical treatment for oak tree blight. Removing infected trees is the best method of treatment to save the remaining stand surrounding the tree; this includes the root system. Root systems should be cut first before treating any infected tree to avoid the fungus from spreading.
Management programs are the best method of prevention against oak tree blight. There are various strategies and practiced management combinations according to the USDA Forestry Service and Cornell University. Prevention measures include avoiding wounding oaks during high periods of infection mainly June through July. Use tree dressings or paints on wounded trees to prevent the fungus from entering. Graft root disruption is used to stop cross-contamination via root systems by breaking up root systems. Trenches dug through tree groups is how disruption occurs. Dead oaks must be removed before the following spring. Debarking, chipping and drying infected wood must be completed before removing the wood as the fungus can spread to healthy trees nearby if not treated first.
USDA Forestry Service