Vein Pocket Gall
Vein pocket galls are caused by the larval stage of small flies called gall midges (gnats), family Cecidomyiidae. The tiny maggots cause elongate, pocket-like swellings to occur along midribs and lateral veins on pin oak leaves.
The infestation begins in early spring when the newly unfolding leaves begin to flatten out , which coincides with egg laying by the gall midge female. The tiny maggots move to the leaf veins where they begin to feed. Within a few days gall tissue forms about and covers the feeding larvae. Development is usually complete by mid-spring, when mature larvae emerge, drop to the ground, and remain there until the cycle repeats next spring. There is usually one generation per year.
Adult gall midges are minute flies that rarely exceed 3mm in length. Mature larva are about 2mm long, whitish, and usually have a sclerotized plate on the ventral surface of the mesothorax.
Please contact your local county extension office for current information.