Maintaining an Oak Tree: Avoiding Rot Maintaining an Oak Tree: Avoiding Rot

Oak tree diseases that result from rot can affect the roots and heartwood of the tree.  Care and maintenance starting from the sapling stage can help prevent some of the problems associated with rot.

Oak Wood Decay

Two fungi cause wood decay in weak or diseased trees, spreading through the bark or the roots. L. gilbertsonii, a brown rot fungus, shows up as flat orange discs on the bark. It destroys the oak cellulose, leaving the wood brittle and hollow. O. latemarginatus attacks both cellulose and lignin. Soft white fungus patches cover the tree trunk. Wood below the bark becomes mushy and white.

Inspect your oak trees and prune carefully to prevent opportunities for wood decay fungi.

Oak Root Rot

Most oak root rot is caused by waterborne algae in wet and warm conditions. Spreading through roots, the tree loses nutrition and water uptake, looking unhealthy. California live oaks grown from cuttings in tree nurseries are most often affected.  Oaks in dry cool regions do not suffer from this root rot.

Oak root fungus, on the other hand, can affect any oak weakened by over-pruning or root cuttings. The newest foliage dies off first. Look for mounds of layered fungus at the roots of the tree.


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