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 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.
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.