81 Records

“The Petiole Gall of Black Walnut, caused by the Eriophyid mite, Aceria caulis, is an interesting and beautiful gall that passes through several color changes as it matures. The galls start as enlarged greenish to white galls on the petiole and main leaf rib. They are covered with a mass of erineum-like hairs that give the galls a felted appearance. As they mature, they become pink and crimson to reddish brown. Large petiole galls grow to cover most of the leaf and stem, causing leaflets to fail to develop, and affected leaflets to be distorted and twisted. No control is generally necessary for Walnut Petiole Gall. The galls may be handpicked and destroyed if there are only a few and can be reached” (Sherrie Smith, 2015).

Galls form on Black Walnut leaves.