Little can be done about the severest of common diseases that plague trees worldwide, though awareness of all such dangers would be wisest of any gardener that cares for these towering living beings. In the United States, there are roughly twenty major diseases related to fungi, bacteria and viruses that befall large portions of this country’s trees.
Nearly every species of tree must be weary of what is known as “Powdery Mildew.” Spotted as ominous white coverings that spread from leaf to leaf, the fungus responsible for this disease travels airborne and will flourish in areas of intense humidity. Though powdery mildew is among the less harmful of tree diseases, it may still incur enough damage to call for chemical control, which varies by tree type but generally entails sulfur treatment.
Only a small batch of trees is naturally resistant to the next culprit: Verticillium Wilt. Caused by another type of fungus, this naturally occurring disease may be spotted by observing normally bright colored leaves turn grayish and less vivid. This signifies the onset of Verticillium Wilt, and if not controlled, will spread throughout entire branches of the tree and cause unmanageable decay. Unfortunately, the only measure that may be taken to rid one’s yard of this destruction is elimination of the infected tree. Then, be sure not to plant in the infected area’s vicinity to ensure complete elimination.
When caring for tree wounds, it is highly advisable not to expose excessively large areas of the tree’s wood to avoid what is known as Heart Rot. Fungi use this opening as an opportunity to infect the tree’s weakened spot, and unless the entire tree is in full health, the fungi will spread throughout other wounds in the tree and eventually become its downfall.