Why Is My Oak Tree Shedding Leaves Now?

Oak WIlt

• The condition known as oak wilt, caused by the pathogen Ceratocystis fagacearum, is a serious disease that can cause an oak tree to shed its leaves early. Oak wilt is often transmitted via the root system of an infected tree interacting with the roots of other trees. Animals, insects and garden tools also spread the infection. There is no cure for this lethal contagion and the majority of affected trees will die within one year, while others may linger up to two years before dying.

Oak Wilt Symptoms

• A tree infected with oak wilt will display the first symptoms in its crown as leaves begin to wilt and droop while turning a bronze or tan color. The disease progresses down the tree and masses of oak leaves are likely to fall early. If the bark of the tree is peeled back, brown streaks will be visible in the sapwood. Trees in the red oak group are the most susceptible, while those in the white oak family show some resistance and live longer before dying.

Iron Chlorosis

• In severe cases of iron chlorosis, the oak tree may be damaged enough to shed its leaves early. This is particularly true if chlorosis has existed untreated in the tree through several growing season. Iron chlorosis is distinguished by oak leaves that prematurely turn yellow but maintain a green color along their veins. It is the result of the tree being unable to absorb a sufficient amount of iron from the earth. Remedy the problem by applying iron or sulfur additives to the soil or oak foliage.

Oak Leaf Blister

• The fungus Taphrina caerulescens causes oak leaf blister and affects all species of oak, but especially pin oaks and the white oak group of trees. Patches of what look like blisters pop up on the leaves and hold a lighter green color than the surrounding tissue. As the disease progresses, those spots turn brown. Little damage is done when the infection is minor, but serious attacks can result in the defoliation of the tree as early as halfway through the summer.