There's a developing story in Harris County that could affect the rest of Texas: At least one palm tree in south Harris County has been confirmed killed by Fusarium Wilt disease.
Fusarium Wilt is a deadly fungus that prevents leaves from receiving water, killing a tree from the bottom up in less than three months. Once a tree is infected, there is no cure. There is also no known prevention.
The heaviest outbreaks of Fusarium Wilt disease have been in Florida. It first appeared in the Miami area back in 2005 and spread to Orlando, Central Florida and elsewhere. Fusarium Wilt can attack both queen palm and Mexican fan palm trees.
“No other fungal disease kills the entire palm canopy so quickly,” stated Monica L. Elliott, of the Institute of Food and Agricultural Services Extension of the University of Florida, in a fact sheet about the disease.
The fungus appears to spread by airborne spores moved by wind, birds and insects, as well as via leaf-pruning equipment. It’s important nursery and landscaping personnel can identify the disease and are prudent about cleaning equipment between palms.
“The fungal pathogen is located in the vascular tissue of the leaf. Equipment used to remove leaves form an infected queen palm or Mexican fan palm (chain saw, lopper, purning shear, hand saw, etc.) will have fungus-infested leaf material (wood dust, plant sap) remaining on the blades,” Elliot stated, adding that pruning palms is a risky business and generally does not benefit the palm. Equipment should be soaked in household bleach, pine oil cleaner, rubbing alcohol or denatured ethanol solution baths for 5-10 minutes.
Palms infected but not yet showing symptoms can still spread the disease.
“If equipment is not cleaned and disinfected, the next queen palm or Mexican fan palm pruned by this equipment will be exposed to fungus-infested leaf material,” Elliott stated. “It is important to note that a palm could be infected but appear healthy (symptomless) because the disease has not developed to the point that leaf symptoms are being expressed.”
A typical case of Fusarium Wilt starts with the oldest leaves in the lower canopy of the tree. In the beginning, at least one leaf will display discolored leaflets on one side of the rachis. The whole leaf will eventually die, and the disease will progress upward, infecting younger leaves until all leaves are dead and the whole canopy is discolored and rigid. Petiole blight disease shows similar initial symptoms in Mexican fan palms, but is rarely deadly.
More information, such as how to collect samples for testing and who to send the samples to, will be coming soon. In the meantime, please contact Jim Reaves at the Texas Nursery & Landscape Association (TNLA) or Kevin Ong at the Texas Plant Disease Diagnostic Laboratory with any questions.