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Heart Rot/ Wood Rot (various fungi)
The
visible external symptom is the fruiting structures ("conks") of the fungus
projecting from the trunk [Picture ]. Eventually,
the tree declines. Species documented on citrus in Texas include Ganoderma
lucidum [Picture], which has a shiny, brown
appearance on the upper surface of the conk, and Phellinus robustus [Picture],
which appears flat on the bark surface.
These fungi, and other species, cause decay of internal wood. The fungi enter the tree through injuries to the roots or scaffold limbs or improper pruning cuts. Growth of the pathogen is favored when the tree is under environmental stress. Once infected, the tree can not be treated. Proper pruning practices, which promote rapid wound healing, will minimize the risk of infection.