Diseases that affect tree trunks usually occur on the lower trunks or bases of trees. The symptoms include cankers – dead areas of bark – and oozing patches. Insects and other diseases frequently invade the cankers causing additional damage.
There are few effective chemical treatments for diseases that affect tree trunks. Infected trees often decline or die. A laboratory analysis of diseased and healthy tissues from an infected tree can determine the causal agent. A local county extension office can provide assistance with identifying a disease and taking a sample for analysis.
Annosus Root and Butt Rot
Pine trees are affected by annosus root and butt rot, which is caused by the fungus Heterobasidion annosum. Fruiting bodies (mushrooms) grow on and around the base of the infected tree. The disease causes root rot, reddening of needles and reduced growth of foliage. Eventually the tree dies.
Often a ring of trees will be infected around the remaining stump of a diseased tree. Infected or dead trees should be removed and destroyed. Pine trees should not be planted within 20 feet of a tree that has died or been infected by annosus root and butt rot, although it is safe to plant hardwood trees in that area.
A species of Phytophthora fungus attacks maple trees and causes basal cankers. The bark in the affected areas peels off easily to reveal dead wood underneath. The disease kills the plant tissue that transports water and nutrients, resulting in the death of the tree.
It is probable that the disease enters a tree through wounds caused by a mower, weed eater or some other object striking the trunk. A tree located in wet soil is more prone to Phytophthora diseases.
Sudden Oak Death
Another species of Phytophthora fungus causes sudden oak death, which affects numerous shrubs and trees besides oak trees. Cankers that ooze a dark-colored substance form on the lower trunks of infected trees. The foliage turns brown and the tree dies in one to two years.
Sudden oak death is difficult to control because the fungus produces thousands of microscopic spores several times each season. The spores are easily spread by wind and water, as well as by clothes, shoes and tools. Plant debris, soil and plants with no symptoms may also contain spores.