chlorosis, shade treee, leaves
Oak, maple and birch, and other trees may exhibit yellowish leaves by early summer. A closer examination of these leaves may show that while most of each leaf is yellowish-green, the veins are still green. This condition is known as chlorosis. Chlorosis is a common problem with the above mentioned trees growing on the Great Plains. These tree species, growing on our typically alkaline soils, may exhibit chlorotic leaves by early summer. By late summer, the leaves also may have brownish patches of dead tissue. In extreme cases, the leaves may die, shoot growth becomes reduced, and eventually the tree dies.
Ball, John and Graper, David, "Chlorosis (Yellowing) of Shade Tree Leaves" (1993). SDSU Extension Extra Archives. 228.