Florida Oak Tree Diseases

Several factors, known as causal agents, can cause tree diseases. The Florida oak is affected by these agents, both biotic (living) and abiotic (non-living). Living agents are pathogen-disease-producing organisms. They are not the disease themselves, but the pathogens that cause the disease. Pruning and using fungicides can control several diseases. Check with your nursery for the right fungicide for the disease that affects your Florida oaks.

Anthracnose

Anthracnose infects white oak leaves, leaving dead, brown areas along the veins. As the disease progresses and begins to severely affect the leaves, leaves curl, and fall off during the rainy season. Anthracnose affect the lower branches more severely than the upper branches. It eventually spreads to twigs and forms cankers. It is caused by the fungus, Gnomonia quercina. Anthracnose overwinters on the leaves and is spread by rain or sprinkler water. The fungi germinate on new growth, and enter the leaves and new twigs. During the moist, humid rainy season, another generation of spores occur in the previously infected parts of the leaves.

Leaf Blister

The fungus Taphrina coerulescens causes leaf blister. This disease infects the leaves of Florida oaks. It causes yellowish-white spots up to a half-inch in diameter on the leaves. The spots are generally circular, raised and wrinkled. The affected leaves do not fall and function as normal leaves. Wind and rain spread spores to new buds. The spores lodge themselves under the bud scales and overwinter there. They germinate in the spring and cause new infections.

Large Leaf Spot

Large leaf spot is caused by a casual fungus, Monochaetia desmazierii, and infects the leaves of red and white oaks. The disease causes 2-inch circular spot with yellowish centers and reddish-brown margins to form on leaves. When the disease progresses, rings form around the spots.

Common Oak Tree Diseases

Oak is part of the common name of about 400 species of trees and shrubs in the genus Quercus. Oak trees are beloved for their grand, beautiful appearance and their lovely foliage in fall. These groups include red oaks, live oaks and white oaks. You can easily identify an oak tree by its leaf shape because the shape determines the species of oak. Trees in the white oak group have fan-shaped leaves with blunt or rounded tips; trees in the live oak group have oval leaves with pointed to rounded tips; and trees in the red oak group have fan-shaped leaves with blunt or rounded tips. The cap of the mushroom is typically about 1/2 to 6 inches in diameter with a slightly depressed center. Leaf symptoms typically include brown spots or patches that expand outward to the leaf margins. You may need a magnifying glass to see these spots.) * Oak wilt is a fast-spreading and fatal disease that’s caused by the fungus Ceratocystis facacearum. This disease affects the vascular system of the tree. Here are some tried-and-true ways to manage diseases and save your oak tree from dying off (or prevent other trees from being affected), organized by disease type: Luckily, leaf blister is rarely severe enough to require control measures (and fungicide treatments are generally ineffective).  * Armillaria Root Rot. Remove the diseased tree(s) along with as much of the root system as possible. Any tree with fungal fruiting structures, such as those with ganoderma root rot, should be removed immediately.  * Powdery Mildew. Avoid injury to the trunk and never apply fill soil around the trees.  * Oak Anthracnose. ** Prune and destroy dead twigs and branches during dormancy; apply a fungicide to protect new leaves and branches. ( Fortunately, little damage results from this disease; no control action is recommended.  If you care for your oak tree by properly pruning it, using oak tree fertilizer and watering it the correct amount, this will help your tree remain healthy and better able to stave off infections or have diseased acorns and experience other environmental stressors. Depending on the type of oak, a little goes a long way (and you may not even need to water at all).  * Avoid -injury to your oaks during favorable conditions for infection (typically in spring and early summer) in the form of damage from construction, severe storms or pruning.