Unfortunately, there is no known cure or treatment for a tree infected with this pathogen, which appears to be a strain of the fungus Fungus oxysporum. It is thought to spread to other palms on the wind and on pruning tools:
• Infected palms die quickly, often within a few months of the initial symptoms.
• There is no cure once a palm is infected, and no preventive fungicide treatments are
• The disease is probably spread by wind into new sites. Once established, it could also be spread by pruning tools. Pruning tools should be sterilized after each palm is trimmed.
• Palms, especially queen palms and Mexican fan palms, should not be replanted into a site where a palm with this disease was removed.
• The disease is tentatively called Fusarium decline of palms. The fungus Fusarium
oxysporum appears to be the pathogen.
Fusarium Decline of Queen Palms and Mexican Fan Palms in Florida
Prompt felling would seem to be the only way forward if you are to minimize the risk of the infection spreading to nearby trees. The above article includes detailed advice for sterilizing pruning equipment, and there is additional information about the disease here:
Palm Tree Diseases and Treatments
Fusarium Decline of Queen Palms