Florida Oak Tree Diseases

Diseases that affect trees can have a variety of impacts, ranging from subtle and barely noticeable symptoms to incredibly debilitating and obtrusive ones. In Florida, many oak trees are at risk of infection, or are already infected, which threatens their ability to thrive in the state. Some common Florida oak tree diseases include armillaria, ganoderma, phytophthora, chlorosis, oak leaf blisters and hypoxylon.

Armillaria and ganoderma (Armillaria mellea and Ganoderma zonatum, respectively) are both root-rotting diseases caused by mushroom-forming fungi . According to the Florida Department of Agriculture and Consumer Services, both fungi are known to colonize and deteriorate the stumps of Florida's oak trees, specifically those trees that have been damaged by construction work or weather phenomena, such as floods and droughts. Oaks commonly contract the fungi from decaying roots or stumps that they come in contact with.

The soil-born fungi Phytophthora cinnamomi are responsible for causing the root disease known as phytophthora. According to the Florida Department of Agriculture and Consumer Services, the fungi feed on the roots of a number of different trees and plants in Florida (including oaks), and can eventually debilitate roots to the point that they become nonfunctional (and the tree or plant dies). Oak trees growing in waterlogged or otherwise poorly drained soils are particularly susceptible to contracting phytophthora.

Chlorosis is a condition wherein a plant loses its usual green coloration caused by the pigment chlorophyll. According to the Florida Department of Agriculture and Consumer Services, oak trees in Florida usually become infected with chlorosis due to poor soil conditions, such as high soil pH levels, an abundance of disease-causing fungi and herbicide damage. Chlorosis typically causes oak leaves to turn yellow (either along veins or all over).

The fungus Taphrina caerulescens is largely responsible for producing oak leaf blisters on Florida oaks. According to the Florida Department of Agriculture and Consumer Services, the blisters appear as irregular, wrinkled or raised blotches on otherwise healthy-looking leaves.

According to the Florida Department of Agriculture and Consumer Services, hypoxylon is a fungal pathogen that attacks oak trees after they have already been infected by other diseases. Florida is home to a number of species of hypoxylon, most of which appear on infected trees as irregular patches of grayish, blackish or brownish crust-like or powder-like substances. According to the above source, hypoxylon fungi live in the bark of healthy oaks, but only penetrate deeper and cause rotting once other stresses have occurred and the tree is unable to maintain a high-enough water content.