Lethal bronzing, a disease of several types of palms, is present in Lake County. It’s a disease that gained attention over the past few years as the media covered its spread on Florida’s native sabal palm in the Hillsborough County area. Samples submitted recently from the Lake County area and sent to the UF/IFAS Ft. Lauderdale Research and Education Center tested positive for the disease. 

The disease is caused by a phytoplasma, which is a bacteria without a cell wall, and is spread by a leafhopper, Haplaxius crudus, a small insect with a hunger for palm sap.  According to Palm Beach County’s UF/IFAS Extension Agent, Bill Schall, it is believed that the insect arrived with hurricane Wilma and brought with it the disease inoculum in its mouthparts. When the insect feeds on palm leaves it delivers the phytoplasma and hence the infection to the vascular system of the palm.  

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It’s important to note that this is the same disease previously called Texas Phoenix Palm Decline (TPPD) but is now called lethal bronzing since it is found outside Texas and infects more than Phoenix palms. It is closely related to Lethal Yellowing, a disease that severely impacted coconut palms in south Florida in the 1970s. In fact, 16 palms are known hosts to the disease including the popular Canary Island date, queen, and pindo palms.

The symptoms of the disease typically appear on the fruit and flower stalks first causing fruit drop and blackened or distorted flower stalks. Lower leaves then succumb to the disease exhibiting a bronze discoloration to the leaves. Eventually the disease kills the spear leaf and the main bud and once this occurs, the palm dies. Relatively fast acting, this plant disease takes approximately four to five months from infection till death, but the time it takes to kill the palm can vary and depends on species. Oftentimes, symptoms do not occur until the palm has already been infected for a couple months. 

If lethal bronzing is suspected on one of your palms, the first step is to submit a sample to a UF/IFAS lab specializing in this disease. It’s important to follow sampling instructions carefully to prevent contamination. Special tools are needed such as a 5/16 inch six to eight-inch long drill bit, a propane torch, and more. See complete step by step instructions with a list of tools here https://edis.ifas.ufl.edu/in1197. Give your local County Extension Office a call and we can instruct you on where to send the sample.

According to UF/IFAS research-based recommendations, if the test yields a positive sample, then it is best to remove the palm as soon as possible. Asymptomatic palms in close proximity to the infected palm should also be tested. If any test positive, they too should be removed. Once a palm acquires the disease, it is fatal as there is no curative treatment. There is some hope yet for our beloved palms through the injection of an antibacterial treatment, oxytetracycline HTC. The injections must occur quarterly for the duration of the palm’s life. For more information on lethal bronzing, please visit pp16300.pdf (ufl.edu), Lethal Bronzing Disease, the source for this article.

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Brooke Moffis is the Commercial Horticulture Agent of the UF/IFAS Lake County Extension office. Email her at burnb48@ufl.edu.