Prune in fall and winter, not spring
In an effort to control oak wilt, which can kill a tree in four to six weeks, the state Department of Environmental Conservation recommends pruning oaks in the fall and winter rather than the spring and summer because the beetles that spread the disease are now active and are attracted to the cuts in the wood.
Oak wilt was first seen in New York in 2008 in Glenville and last year was discovered on Long Island and in Brooklyn and Ontario County. See dec.ny.gov.