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Lethal Bronzing: A Destructive New Palm Disease

 

Lethal Bronzingpreviously called Texas Phoenix Palm Decline, is a relatively new bacterial disease (called a phytoplasma) that is causing significant palm losses in Palm Beach County.  Symptoms are similar to lethal yellowing, but affect a much smaller number of palm species.  The damaged vascular system of the palm leads to wilting, and eventually death.  University of Florida research is determining which sap feeding insect(s) may spread it.  Affected species include Sabal (Cabbage), Queen, Pygmy Date and other Phoenix species, Christmas, Bismarck, Chinese Fan and Carpentaria palms.

Symptoms

Older fronds die first and may be reddish-brown, dark-brown or grayish depending upon which species is affected, and stage of infection.  Symptoms can sometimes be confused with nutrient deficiencies like potassium, or Fusarium wilt.  Flower spikes may die prematurely, and fruit may drop off prematurely.

Lethal bronzing symptoms on sabal palm. Photo: UF/IFAS Schall

What Can You Do?

The disease is confirmed by laboratory analysis of tissue extracted from the trunk.  Remove and dispose of infected symptomatic palms.  Administer antibiotic injections to non-symptomatic susceptible species growing around removed palms.  Inject oxytetracycline at 3 grams per palm (1 gram for Christmas palm).  It is not known if the oxytetracycline will help susceptible palm species already showing symptoms.  However, once the palm spear leaf dies, the palm will die even if lower fronds are still green.

Additional information and photos can be found in the UF publication Texas Phoenix Palm Decline.

4 Comments on “Lethal Bronzing: A Destructive New Palm Disease

  1. Dear Bill, I read with interest and concern your article on TPPD, LB (phytoplasma) that is affecting so many types of palms. Up here in Northern Florida, the species you mentioned are all an important part of our cold hardy palm flora. Has it been seen in Northern Florida, and how would you prevent it from getting into a collection of palms? It seems that every day I see trucks loaded with palms heading north on I 95. Quarantine? Inspection? Also, being a veterinarian, I have access to oxytetracycline. Could you describe the device and technique for injecting a palm tree. I imagine that my 3 cc syringes with 20 gauge needles will not work, Thank you. John Rossi DVM MA

    • Dr. Rossi:

      Keeping lethal bronzing out of a palm collection would involve being diligent in looking for the problem. It may be that the disease has not been identified in your county yet. A late 2017 assessment by the Division of Plant Industry of submitted lab samples indicated the disease was from the Hillsborough to Volusia County corridor south. North of that, it has been identified in Levy, Alachua, Duval and Bay Counties in Florida. Once you have the disease on your property, immediately surrounding susceptible palm species should be treated with the oxytetracycline about every three months. Three of the commercial systems that are available are Tree Saver, Arborsystems and Mauget. All have websites where you can get a better look at the equipment. The Mauget system is self-contained, and therefore may end up being more affordable since you will not have to purchase the fairly expensive application equipment used with the other systems. Nozzel Nolen recently did a YouTube video on how they do it at: https://www.youtube.com/watch?v=tLMIyhf2Pw8 …Currently, some developers in Palm Beach County are beginning to ask for susceptible palm species to be tested prior to installation. Taking specimens does injure the trunk though. As far as I know, there is not an effort to quarantine areas that have the problem. It is known to occur all the way from the Yucatan through Texas and the Gulf Coast states and into Florida, so it is quite widespread.

  2. I have a beautiful triple Alexander Palm, but I fear it has fallen victim to the lethal bronzing. It appears two of the trunks have dead leaf spears. The third appears to still be healthy. If I cut the two dead trunks, do you think I can salvage the third and keep it healthy, or would cutting the two harm the third one? Thank you for any information or advice you can provide.

    • Alexander palms (Ptychosperma elegans) are not currently thought to be susceptible to either lethal bronzing or lethal yellowing. Die back is due to some other factor(s). Are you seeing any conks on the lower trunks. These are fan-like growth that indicate a fungal Ganoderma problem. If this is the problem, removing the dead trunks will not help. Can you email some pictures of the problem to me at bschall@pbcgov.org ? – Bill

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