Most Common Tree Diseases and How to Treat Them

There are several tree diseases that affect trees across the United States. These diseases can lead to severe tree health problems and in some cases even death. No tree is insusceptible to disease. Whether it is a tree in a front yard or a tree in a dense forest, every tree is at risk. Here are the top five tree diseases:

1. American Chestnut Blight

The American chestnut is a commercial species of tree located in eastern hardwood forests. These trees have been ravaged and practically obliterated by a type of fungus that destroys these trees just as they reach the sapling stage. Unfortunately, there is no cure or known treatment for the disease. The fungus is widespread and while it is lethal to the American chestnut, it is nonlethal to many other trees including Spanish chestnut and post oak.

2. Armillaria Root Disease

This tree disease, which is also caused by a fungus, is found in temperate and tropical regions around the world. Softwood and hardwood trees are affected as well as shrubs, vines, and forbs. It has spread throughout North America and has been proven to be destructive commercially. This disease is responsible for a serious decline in oak trees. This fungus kills trees that are already weakened from other factors including bug infestation and climate changes. This fungus also infects healthy trees and will kill them immediately or leave them weakened enough to be killed off by other factors.

Unfortunately, since fungus is everywhere and spreads rapidly, there is no way to completely destroy it. All one can do is help limit the growth of the fungus. Several chemicals including chloropicrin, methyl bromide, and carbon disulfide can be used to reduce the amount of infection.

3. Anthracnose and Leaf Spot Diseases

This tree disease affects hardwood trees in the Eastern United States. The most prevalent symptom from this disease is dead areas or large blotches on the leaves. Trees that are hit hard by this disease include the American sycamore, the white oak group, black walnut, and dogwood. Anthracnose occurs most commonly in urban locations. When trees die from this disease, it can cause a drop in property values.

4. Annosus Root Rot

This disease, also caused by a fungus, rots a number of conifers in the Eastern and Southern United States. The fungus infects trees by entering though freshly cut stump surfaces. Essentially, they look like white mushrooms surrounding the bases of trees.

5. Aspen Canker

Aspens are the most common of tree species seen in the mountains of the Western United States. The fungus infects these trees by going through wounds. The taxonomy of the fungi has changed over the years so there are a lot of scientific and common names.

Treatments

Unfortunately, there is no way to cure these trees of these diseases. The best way to treat them is by applying chemical fumigants. By chemical fumigants we are talking about a release of gas that penetrates a pest and kills it. It can be especially helpful with trees because it severs the roots connections between diseased and healthy trees. Chemical fumigants can be purchased in granule, liquid, or compressed gas form. Common fumigants include Chloropicrin, Dazomet, Formaldehyde, Metam Sodium, Methyl bromide, and Vorlex.

Sources:

Steve Nix, "An Index of Common Tree Diseases." About.com.

R.E. Williams, C.G. Shaw, III, P.M. Wargo, W.H. Sites, "Armillaria mellea Root Disease." U.S. Department of Agriculture Forest Service.

G.L. Worf, "Selecting and Using Chemical Fumigants and Soil Sterilants for Ornamental Disease Control." http://learningstore.uwex.edu/pdf/A2612.PDF