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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, and throughout much of Florida.  It is believed to have originated in the Yucatan Peninsula of Mexico and may have been carried to Florida in the salivary glands of a tough insect vector by Hurricane Wilma.  The disease was first found in Florida in 2006 and initially followed the path Hurricane Wilma had taken the previous year.  Symptoms are similar to lethal yellowing, but currently are known to affect a much smaller number of palm species.  A few palm species are known to be susceptible to both diseases.

The colonized and then damaged vascular system (phloem tissue) of the palm leads to wilting, and eventually death.  University of Florida/IFAS research is determining which sap feeding insect(s) may spread it.  The one confirmed so far is Haplaxius crudus, a planthopper and palm sap feeding insect, also known as the American palm cixiid.  It spends most of its life cycle in the soil and only emerges as an adult to mate and feed on palm fronds.

Palms currently known to be affected by lethal bronzing (as of May 2019) include Christmas Palm, Bismarck Palm, Pindo Palm, Carpentaria Palm, Coconut Palm, Chinese Fan Palm, Canary Island Date Palm, Edible Date Palm, Pygmy Date Palm, Wild Date Palm, Fiji Fan Palm, Buccaneer Palm, Mexican Palmetto, Cabbage Palm, Queen Palm, and Chinese Windmill Palm.  Undoubtedly this list of susceptible palms will grow now that the disease has been detected in Miami-Dade County, where Florida’s richest diversity of palm species are found.

Symptoms

If flower spikes are on the palms, they tend to turn black and die.  If any fruit, it usually drops prematurely.  Later, symptoms begin with the older, lower fronds sometimes turning a subtle bronzish (looks more reddish-brown-grayish to some) before they turn fully grey and die.  The central spear leaf usually dies by this time.  Symptoms progress over about a 4-5 month period before the palm is completely dead.  However, single trunk palms are effectively dead once the spear leaf or leaves die, even if there are still some green lower fronds.  Symptoms are often confused with nutrient deficiencies like potassium, or Fusarium fungal wilt on susceptible palms.  Potassium deficiency can be distinguished from lethal bronzing because the potassium usually takes multiple years of deficiency between symptoms first appearing and palms dying.

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 so they cannot serve as an inoculum source for other surround susceptible palms.  Administer antibiotic injections to non-symptomatic susceptible species growing around removed palms.  Inject oxytetracycline at 3 grams per palm (1 gram for small species like Christmas or pygmy date palms). Repeat injections every three months for at least two years.  The oxytetracycline may not be adequate to save palms already showing symptoms.  This is particularly true if the spear leaf or leaves are already dead.

Additional information and photos can be found in the UF/IFAS publication Lethal Bronzing Disease.

Revised August 28, 2019

42 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

  3. The Sable and Phoenix palms are dying on massive numbers here in Palmetto fl. Seems like from northern Hillsborough to southern manatee the disease is getting outta control. And eastward through Lakeland. I drive a lots and am always saddened by the loss of the Sables. Seems like counties/ state doing nothing about it. Non of the dead dying ones are ever cut down. I see all these new developments putting in Sylvester palms they are always toast within 6 months. What a waste of money, plant something resistant please. Southern Pinellas county including st pete are getting destroyed by this disease too. I’ve seen a lot of queens palms with the disease too, although if taken care of in my experience they have more resistance then palmetto and Sylvester’s. The state planted Sylvester’s in northern manatee on I 75 Hillsborough by i4 and 275 in st pete. I’d say 90 pct of them are dead in 2 years. Why is state planting expensive susceptible palms then not removing them when dead and unsightly ? Plant royals yes the can get killed by the cold but least don’t catch and spread the disease further.

    • Hi Jeff:

      Yes, the disease was first spotted in your general area of the state in 2006. As you are indicating, thousands of palms have already been lost to lethal bronzing since then. We expect the number of affected species list will be expanded now that the disease has moved into Miami-Dade County where we find Florida’s greatest variety of palms. Below, as of July 2019, is a list of the palm species currently known to get the disease:
      Christmas Palm, Bismarck Palm, Pindo Palm, Carpentaria Palm, Coconut Palm, Chinese Fan Palm, Canary Island Date Palm, Edible Date Palm (Phoenix dactylifera), Pygmy Date Palm, Wild Date Palm (Phoenix sylvestris), Fiji Fan Palm, Buccaneer Palm, Mexican Palmetto (Sabal mexicana), Cabbage (Sabal) Palm, Queen Palm and Chinese Windmill Palm (Trachycarpus fortunei).

  4. Now in Martin County as well. I just lost my Canary Date Palm to this disease this week.

    • Hi Ms. Forster. Yes, lethal bronzing definitely affects Canary Island date palms. Loss of those vary large majestic palms is quite sad.

    • Hi Mr. Miller. No, currently Washingtonia palms are not believed to be affected by either lethal bronzing, or another similar palm disease, lethal yellowing.

  5. just let nature takes its course i have grown three coconut tress form seed they have surviveid white fly funguse etc stop messing with nature if they die it is meant to be STOP adding genictic cures which just screws up the balance of nature thats why all these infections happen man has none this to many chemicals to nature just let it go

    • Thanks Ms. Delucantonio for your comments. The problem, of course is that the disease was not here in Florida originally. It is believed to have arrived in 2006 from offshore, possibly via infected insect vectors (carriers) blown here by Hurricane Wilma in 2016. Also, remember that this disease kills our native sabal (cabbage) palms which covers all of Florida and up into the southeastern United States. If we lose many of those, it will have a huge impact on the Florida environment and the landscapes around our homes and businesses. The current treatment is not a genetically modified product, but antibiotics. Hopefully additional research will help us come up with additional, simpler ways to keep this very destructive disease from destroying sabal and about 15 other currently known palm species.

  6. Just to make sure I understand. Treat a healthy palm one time with 3 grams of oxytetracycline, or do I need some sort of maintenance program for a healthy palm?
    What about a smaller multiple or Robalini palm, same 3 grams?

    • Hi Eric:

      The 3 gram treatment needs to be repeated every 3 months. If you use the same hole, be sure to drill it a little deeper before the second 3 month treatment. For following three month treatments, drill another hole. Just how long to continue is a judgement call. Typically once you start, it needs to be continued. The 1 gram rate is for smaller palms like adonidia or Phoenix roebelenii (pygmy date palm). It makes sense to use less for the smaller palms. The rate would be per trunk. For example, if the P. roebelenii or the adonidia are triples, then each trunk would need to be treated with 1 gram of OTC for 3 grams total.

  7. We have an older (70 years) sable palm in Pinellas County(Indian Rocks Beach ) that we think may be dying due to Lethal Bronzing disease. Could you give us detailed instructions on how to get a sample. How to store the sample. A family member works at U of F, can she drop off the sample on Hull road? Thank you for any information. I am sad to see this tree that I grew up with dying.

  8. Hello, Bill. Thank you so much for your service. Above, Jeff wrote about the frequent death of Sylvester palms. I had one installed in January, and have noted the browning of fronds. I don’t know if some browning is normal or not. I have fertilized and applied Epsom salts. I would appreciate any incite.
    Mary

    • Hanks Ms Kelley:

      I received your email and photo and will take a look and respond to you directly via that email.

  9. We have experienced the Lethal Bronzing here in Columbia County. My Sego Palm just dropped dead overnight. Thanks for your article. I will be passing the word here in Lake City area.

    • Hi Liz:
      Please be aware that Sago palms are not really palms, they are cycads and are therefore not affected by either the lethal bronzing or lethal yellowing diseases.

  10. Hi Bill,

    I’m hearing about ground palm beings sold as mulch also
    soil products using palm fines as fillers. Any chance Bronzing Disease could be spread systemically by one of
    these products?

    • Hi Chris:

      Best understanding right now is that the phytoplasm needs live tissue in order to survive. Also, the insects that feed on the infected palms and then spread the disease would not be feeding on dried mulch, sawdust or other similar materials.

  11. What’s the 2019 update on this issue. I’m in Broward and need stories started to pop up yesterday evening.

    • Hi Ali:

      Best updated information source is the new University of Florida “EDIS” fact sheet located at https://edis.ifas.ufl.edu/pp163
      The only real update to the information in my original blog is that the list of known palm hosts now is up to 16 species. This list will likely grow now that the disease is in Miami-Dade County where a much larger variety of palms will potentially be exposed to the disease.

  12. I have 3 fish tail palms. 2 died in the last 6 months and the 3rd is now dying. I suspect it has lethal bronzing. Is there something I should do other than destroy it?

    • Hi Barbara:

      Fishtail palms are not yet known to be susceptable to lethal bronzing. However, they are susceptable to the very similar palm disease, lethal yellowing. We are not currently seeing any incidences of lethal yellowing in Palm Beach County, Florida, but we are seeing plenty of lethal bronzing problems. If lethal yellowing is the cause of the palm deaths, antibiotic injections may help save the one that is left, if it is not too far gone. If you email me a clear picture (wls@ufl.edu) of the remaining palm, I will see if we can make an educated guess from that. Collecting a specimen takes a little know how, and costs $75 in lab fees. So, let’s at least start with a photo or two to me. Also, as you probably know, palms can suffer from other problems that will kill them. These can include severe nutrient deficiencies, bud rots and Ganoderma.

  13. Hi, it is truly devastating to hear that Sabal palms are on the Hit list. They are a part of Florida history. My question tho, with the other palms susceptible to the disease… developers and landscaping companies continue to incorporate coconut palms, date palms, Pygmy palms etc in their building plans. Are they not aware of the lethal bronzing?!

    • Hi Mary:

      I think some are and many are not aware of the problem. We are spending a lot of time trying to educate interested residents and businesses in Palm Beach County, also you may have noticed some recent fairly heavy media coverage. Another thing to consider is that people are sometimes willing to plant certain types of plants even if there are some potential problems out there. For example, just about every know palm with a trunk is susceptable to Ganoderma, a palm trunk rotting fungi. Yet palms are still an incredibly important and frequently used component in our landscapes. Hopefully, the word does get out and people can make an informed decision on which plants to install.

  14. Hi,

    I noticed the Sabal Palms turning brown and eventually die in Western West Palm Beach along a canal
    and on the turnpike south of Southern Blvd. years ago and no one was concerned.

    I don’t know if it was something else or LBD, however, more landscapers should be aware of this disease. I live in a community where the builder planted 3 Sabal Palms in front of many homes and I hate to think they will be affected, plus the cost of replacing up to a thousand trees.

    • Hi Barbara:

      Chances are that several years ago something other than lethal bronzing killed the sabal palm on that canal bank. Most likely at that time would have been lightening, bud rot, nutrient defeciencies or Ganoderma fungal trunk rot. Other things to consider are that the sabal is the state tree of Florida and is probably the most commonly used palm tree in the state. Additionally, it naturally grows in many of the natural areas in Florida. So, all of this along with our use in the landscapes underscores how important this disease issue is.

  15. Will this antibiotic treatment help my Canary island palm? It’s almost a landmark on my street!

    • Yes, the antibotic injection can be helpful with both lethal bronzing and lethal yellowing phytoplasm diseases (the Canary Island palm can get both) if the disease is caught and treated early enough.

  16. I’m seeing conflicting reports as to whether coconut palms – Lethal YELLOWING has already killed just about all (about 5 million) of the Jamaican Tall variety in South Florida over the past 50 years – are susceptible the Lethal Bronzing. Since the “talls” are pretty much gone, I’m thinking about the remaining dwarf-to-medium height palms that have somehow escaped Yellowing.
    Thanks, Larry

    • Hi Larry:

      You are correct, according to Dr. Bahder who is conducting the UF research on lethal bronzing, coconut is now on the list of currently known to be susceptible palms. Here is the list: Christmas Palm, Bismarck Palm, Pindo Palm, Carpentaria Palm, Coconut Palm, Chinese Fan Palm,
      Canary Island Date Palm, Edible Date Palm, Pygmy Date Palm, Wild Date Palm, Fiji Fan Palm,
      Buccaneer Palm, Mexican Palmetto, Cabbage Palm, Queen Palm, and Chinese Windmill Palm.

  17. What Palms do you recommend that are resistant to lethal bronzing in the downtown St Petersburg (9b) area..

    • Hi Christina:

      Her is the list of those currently known to be susceptible to lethal bronzing:

      Christmas Palm, Bismarck Palm, Pindo Palm, Carpentaria Palm, Coconut Palm, Chinese Fan Palm,
      Canary Island Date Palm, Edible Date Palm, Pygmy Date Palm, Wild Date Palm, Fiji Fan Palm,
      Buccaneer Palm, Mexican Palmetto, Cabbage Palm, Queen Palm, and Chinese Windmill Palm.

      Your area is can get a bit colder than Palm Beach in the winter time, and as a result the list of potential non-susceptible palms you can use is smaller than further south. I suggest you contact your very excellent local UF/IFAS Pinellas County Extension office (email: gardenhelp@pinellascounty.org or telephone: 727.582.2110) for guidance on suggested palms for your area.

  18. Bill,

    First of all, thank you for putting together such a valuable article regarding this diseases affecting Palm lovers all over the US.

    Having said that, I have 2 Canary Island and 1 Phoenix Silvestri (which already died from a disease). I’m trying to save the 2 Canaries. However, I cannot identify which disease is affecting them.

    Could you be so kind to provide me your email so I can send you a picture of it?

    Thanks in advanced,

  19. Is there any indication that tetracycline treatment will help with Ganoderma in Robellini?

    • No, Ganoderma is a currently untreatable fungal problem. Current recommendation is to remover the palm(s) and replace with non-palms. Sorry

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