Protect your palms against disease

Take a look at the photo of the Sylvester palm, submitted by a Hillsborough County resident.

This Sylvester palm tested positive for the phytoplasma that causes lethal bronzing disease. (Courtesy of Nicole Pinson, University of Florida/Institute of Food and Agricultural Sciences)

Does it look normal?

Do the leaves appear to have a nutrient or disease problem?

Many palm species are now listed as susceptible to the disease called lethal bronzing. Lethal Bronzing Disease was formerly known as Texas Phoenix Palm Decline.

When we first learned about Lethal Bronzing Disease, we knew beautiful (and often expensive) palms of the Phoenix species, such as Canary Island Date palms (Phoenix canariensis), Sylvester palms (Phoenix sylvestris) and pygmy date palms (Phoenix roebelenii), as well as our native cabbage palms (Sabal palmetto), were the top species affected by this disease.

But, recently, University of Florida/Institute of Agricultural and Sciences researchers updated the list of palms that may test positive for the disease. The expanded list includes Christmas palms (also known as Adonidia palms), Bismarck palms, coconut palms, Chinese fan palms and queen palms.

Hillsborough and Pasco counties are among several other Florida counties with confirmed cases of Lethal Bronzing Disease.

These types of palms are hosts for Lethal Bronzing Disease: Christmas, Bismarck, Pindo, Carpentaria, Coconut, Chinese Fan, Canary Island Date, Edible Date, Pygmy Date, Wild Date, Fiji Fan, Buccaneer, Mexican Palmetto, Cabbage, Queen and Chinese Windmill.

If you have one of these palms, it is important to keep an eye on it and check for disease symptoms. The disease is caused by a phytoplasma, a type of bacteria that doesn’t have a cell wall. The phytoplasma is transmitted to the sap of palms by insects, such as planthoppers, when the insects feed on the palms. The disease cannot be transmitted by pruning tools.

Symptoms of the disease include fruit drop; discoloration of the oldest (lowest) leaves; brown or dead flower clusters; the collapse of the spear leaf at the top of the palm (newest leaf); and, quick decline (usually about four months to five months).

To test for Lethal Bronzing Disease, submit a trunk sample for testing to the UF/IFAS Plant Diagnostic Center, and follow the palm trunk sampling instructions available at this link: https://plantpath.ifas.ufl.edu/misc/media/PDC/palmsampling.pdf.

The cost is $80 per sample. The lab will provide a report about whether the palm is diseased.

Queen palms have been listed recently as a host plant for lethal bronzing disease.

If you have susceptible palms without symptoms of the disease, you may inoculate them preventatively with an antibiotic called oxytetracycline. This may be done by a professional landscape company or by an arborist. Homeowners may choose to inoculate their own palms, and there are instructions available and companies online that sell the antibiotics to homeowners.

But, antibiotic injections are not a one-time cure-all. They must be injected into healthy palms every three months to four months, which may be a significant investment of time and money, over several years, for some homeowners.

If the disease is confirmed, removal is recommended. You don’t want the disease to spread to other palms in your landscape or neighborhood.

Researchers are studying this disease and considering the number of species affected in different Florida counties. Moving forward, homeowners may use this information to recognize disease symptoms, learn about preventative antibiotics, and select palms and other plants that are less susceptible to disease.

For more information on protecting your palms, consult reference materials used to provide information for this column regarding Lethal Bronzing Disease and the application of Oxytetracycline Hydrochloride (OTC-HCl) to control palm phytoplasmas.

Those materials were written by B.W. Bahder and E.E. Helmick, and were published by UF/IFAS.

For additional information, email , or call (813) 744-5519, ext. 54145.

Nicole Pinson is the Urban Horticulture Agent in Hillsborough County. Jan Ignash, UF/IFAS Extension Hillsborough County Master Gardener Volunteer, contributed to this article.

Published February 19, 2020

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