Overfertilization can injure or kill the roots, while underfertilization results in a lack of the minerals essential to maintain a healthy tree. Competition for water and minerals between tree roots, bushes, grass and flowers can seriously stress trees. Trees will stress if routine soil preparation for flowers damages tree roots. After a tree is established, anything that changes the soil condition or the oxygen and water supply can be extremely detrimental. The two basic types of fungi that cause root diseases are those that kill feeder roots and those that cause decay in the large, woody roots.
Many fungi occur on small feeder roots.
The more common organisms are species of Phytophthora, Pythium and Fusarium . Fungi that attack large, woody roots suppress growth, decay food-transporting cells, reduce food storage and reduce structural support for the tree. Yellow, chlorotic foliage from root disease. Typical symptoms associated with root diseases often are confused with mineral deficiencies because high numbers of dead roots reduce water and mineral uptake. Symptoms of root problems from construction damage or other detrimental activities may appear one to several years after the damage occurred.