Vein Pocket Gall is an enlargement of the mid and sometimes lateral veins of pin oak and scrub oak leaves (fig 1). Recently, we have been receiving calls from concerned customers who noticed the leaves of their pin oaks are twisted and deformed (fig 2).
This year many pin oak trees in the area have been affected by vein pocket gall. The gall is caused by a tiny fly (Macrodiplosis quercusoruca) known as a midge or gnat. The midge lays its eggs in the spring as leaves are emerging. As the eggs hatch, maggots (larvae) begin to feed on veins, causing gall formation, which protect the maggots from predators and chemical control. When finished feeding the larvae will drop to the ground to pupate, and remain there until the next spring. Then the pupa will hatch as an adult and lay eggs completing the life cycle. While causing unsightly leaves on the tree, the galls usually do not harm the host plant, therefore control is not necessary or practical. However, if this condition persists year after year please contact our plant health care technician for possible treatment options.
For more information on Vein Pocket Galls check out these sites: