These beetles are also attracted to the bleeding sap of an oak tree, which leads the insects to transfer the disease from one location to the next.
Root graft transmission is the most common way for an oak tree to develop the disease. It is possible for trees within 50 feet of each other to be infected. The disease is simply transferred through roots that become interconnected, called root grafts. Spores have already been produced and they move through the vascular system of the tree, which in the end leads to attacking the healthy tree.