Bacterial leaf scorch (BLS) of amenity trees is caused by the bacterium Xylella fastidiosa, a xylem-limited pathogen that causes water stress resulting in leaf scorch, decline, and eventual death of affected trees. Recent surveys indicate that BLS is widespread throughout the eastern United States. In New Jersey, BLS primarily affects red and pin oak landscape and street trees. Until recently, the disease was limited to southern and central New Jersey, but is now found throughout the State. As many as 30% of oaks may be affected in some municipalities. Not only is BLS considered a threat to northern red oak, the state tree, it has potential to devastate other oak species, such as pin and scarlet. In spite of its widespread distribution, little is known of the biology of BLS. Without basic information, development of effective management strategies is difficult.