Curved Damage to Oak Leaves

Oak Leaf Blister

• Curved oak tree leaves occur when they are suffering from oak leaf blister, a disease caused by the pathogen Taphrina caerulescens. Leaves infected with this fungus will begin to curl inward and otherwise become distorted when the disease has reached a severe point. Upon curling and becoming nearly completely brown, they will often fall from the tree prematurely. All species of oak can develop leaf blister, but red and black oaks are particularly susceptible.

Symptoms

• Before the curve damage takes place, other symptoms of the disease will have already appeared. Newer leaves are typically first affected in the spring, especially if cool and wet weather has been dominant. Bulges and blisters will begin to pop up on the upper surface of the leaves, with alternately placed, light green or yellow depressions appearing on the underside of the foliage. The blisters eventually take on a shade of gray and become fuzzy.

Management

• These fuzzy patches are the fruiting bodies of the fungus and contain massive amounts of spores that serve to distribute the disease to other leaves. Oak leaf blister is primarily a cosmetic problem and rarely seriously damages the overall health of an oak tree. However, if the disease repeats year after year, it will eventually sap the vigor of the oak. Fungicide can be used to help manage this disorder, but it must be applied as soon as the buds of the oak begin to break.

Iron Chlorosis

• Iron chlorosis, indicated by leaves that turn prematurely yellow but maintain their green veins, is caused by a lack of iron in the leaf. As the problem progresses, brown spots also develop, giving the leaf a scorched appearance. They are likely to eventually show curved damage as they curl up, dry and fall to the ground. If the problem persists over several years, the entire tree can die. The problem is rectified by correcting the alkalinity and acidity of the soil. A correct pH level will allow the tree to receive the appropriate amount of iron.