What is Fusarium Wilt of Queen Palm and Mexican Fan Palm? It is a lethal fungal disease, host specific to queen palm, Syagrus romazoffiana, and Mexican fan palm, Washingtonia robusta. Mule palm (a cross between S. romazoffiana and Butia capitata) and desert fan palm, W. filifera, are also known to be susceptible to the disease under experimental conditions. The pathogen, Fusarium oxysporum f. sp. palmarum, reproduces by means of short-lived spores (micro- and macro-conidia) and long-lived chlamydospores that apparently can live in the soil or in infected plant tissue for years. The fungus obstructs water conducting xylem tissue, which causes leaf wilt, leading to the decline and death of infected palms. The disease is spread by contaminated pruning tools and by air-borne spores. Laboratory diagnosis using molecular techniques is required to confirm the identity of the disease.

Occurrence of Fusarium wilt of queen palm and Mexican fan palm is most common in mature landscape palms, but it has been observed in juvenile palms in a few nurseries in Florida. Symptoms occur first in lower, mature leaves, which develop yellowing, browning and wilting of leaflets on one side of the rachis, while leaflets on other side of the leaf may initially remain green. Reddish-brown or dark-brown streaks develop on the petiole and rachis on the symptomatic side of the leaf. Eventually, the entire leaf dies, but the leaves do not droop or hang down around the trunk. As the disease develops, it progresses towards the top of the tree, wilting the younger leaves. The disease tends to progress rapidly; infected palms decline, become unmarketable and die quickly. Within 2 to 3 months after the onset of leaf symptoms, the entire canopy becomes desiccated and necrotic.

Disease Management. Disease management options are limited to limiting further spread of the disease by prompt removal and sanitary disposal of infected trees and leaves, disinfection of pruning tools and avoidance of planting host species of palms at locations where the disease has been found. Disposal of infected trees and leaves can be by incineration or by double-bagging and burial in a sanitary landfill. For further information, consult your local government or your county's office for the Texas A&M AgriLife Extension Service.

Expired Quarantine. On February 8, 2016, the Texas Department of Agriculture filed emergency quarantine regulations for Fusarium Wilt of Queen Palm and Mexican Fan Palm in the Texas Register. The emergency regulations, published in the February 19, 2016, issue of the Texas Register, became effective on filing and expired June 6, 2016.