Ganoderma "butt rot" of Palms
Ganoderma, caused by the fungus Ganoderma zonatum, is an infrequent but devastating palm problem. If your palm gets Ganoderma, it will die and you will not be able to safely plant another palm, of any species, in that location in your landscape. Researchers are not sure how palms become infected but it is generally agreed upon that trunk injury appears to be the primary mode of spore entry. They believe the fungus is transmitted through wounds to the roots made during transplanting, wounds to the lower trunk when pruning off boots, spike wounds made by climbing with spikes or even possibly wounds from continued weed eater damage at the base of a palm. In general, trunk injury appears to be the primary mode of spore entry.
Ganoderma zonatum is in the same family as decay fungi that cause internal decay in broadleaf trees (Ganoderma applanatum and Ganoderma lucidum) but it is not the same pathogen and will not affect broadleaf or conifer trees. The disease decays the lower 4 or 5 feet of the palm trunk. Ganoderma is soil born but not a root disease. All palms are susceptible to Ganoderma infection.
The symptoms are progressive leaf necrosis from the bottom of the crown toward the top. Finally the newest frond, the spear, dies. Often, but not always, a fruiting body (a conk) appears somewhere in the lower part of the trunk. This conk allows for easy confirmation of the disease. This fruiting body drops millions of spores that can infect other palms.
So it is a good idea to remove the conks as soon as they appear. And then remove the dead or dying tree as soon as possible. The lower part of the trunk should be placed in a landfill and not used for mulch. The upper part of the infected palm can be used for mulch.