What is Oak Leaf Blister? Oak Leaf Blister, a fungus caused by Taphrina Caerulescens, is a disease that attacks oak trees. It occurs most often in spring, when the cool, moist conditions are ideal for the fungus. It is most common on red oaks but can also affect other species. This disease usually affects newly emerging leaves and causes them to blister, curl, or distort.

Recognizing the symptoms
Oak Leaf Blister can be identified by the presence of bubble-like, raised blisters that appear on the surface. The blisters may be pale green initially, but they turn brown as the disease advances. Infected leaves can become twisted or curled and may drop prematurely. However, complete defoliation of the plant is rare. The disease can appear to be very serious, but it usually only causes cosmetic damage.

How it Spreads
Early spring, when temperatures are mild and conditions are moist, the fungus becomes active. Fungal spores begin to infect tender tissue as leaves emerge. As the leaves mature they become resistant to fungus. This is why spring outbreaks tend to be seasonal.

Oak Leaf Blister: How to Manage and Prevent it
Oak Leaf Blister is rarely a threat to the health of trees. The majority of trees recover and produce healthy leaves in the following years. Repeated infections can cause the tree to become stressed over time.

Manage the disease:

• To reduce the spread and growth of fungi, rake up fallen leaves.
• Pruning overcrowded branches will allow air to circulate around the tree.
• Avoid overhead watering as this creates conditions that are favorable for fungus.

If the infection is severe or repeated, a fungicide for Taphrina can be applied in late winter or spring, right before buds break.

Final Thoughts

Oak Leaf Blister may look alarming, but is usually a minor issue for healthy trees. Your oak tree can thrive for many years with the right cultural practices, and occasional preventative treatments.

This post was written a professional arborist from Arbor Wise Professional Tree Service . Arbor Wise Professional Tree Care is owned by Robert Miller, an arborist with years of experience. Arborwise Tree Services, a tree service company, offers tree removal, tree trimming, stump grinding and fertilization. Our lawn care business is well-known in the Pinellas County area.