Bacterial Leaf Scorch: Northern red oaks in New Jersey are being attacked by this bacterium. It “clogs” the tree’s water conducting tissues or xylem. Water transport becomes disrupted in roots, branches, and leaves due to large amounts of multiplying bacteria and their by-products. It may also trigger a reaction in the tree that plugs the xylem, further impeding water transport. It can be diagnosed based on time of symptom developments, leaf color change and the annual progression of the symptoms throughout the crown. Symptoms start to appear in mid-summer and continue until fall. Leaves on diseased tress begin to dry along leaf margins and death of the leaf progresses slowly downward toward the midrib and petiole. The leaf color changes to a dull pale green and finally, the entire leaf dies and turns brown. This happens during the height of summer not during the fall.