Lethal Bronzing: A Growing Threat to Palm Trees

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What is lethal bronzing? It is a novel phytoplasma disease that is the worst-case scenario for homeowners who have invested in palm trees costing $5,000 to $10,000 each. If you notice that your trees are turning a bronze-brown and new fronds are curling up and dying, your trees may have this terminal disease. Unfortunately, there is no cure or lethal bronzing treatment. However, there are preventative measures that can be taken to protect these palms. Our tree experts share more details below. 

In 2006, this deadly bacterial disease hit the Tampa area and quickly spread east, killing palm trees ranging from stately Canary Island date palms to the indomitable sabal palmetto palm, which is the Florida state tree. Lethal bronzing has become prevalent in Palm Beach County within the past few years. Similar to, but genetically distinct from, lethal yellowing, lethal bronzing is now common on Florida’s east coast, and it’s causing significant palm losses in Palm Beach County.1

Lethal Bronzing Prevention Tips 

Michael Zimmerman, the owner of Zimmerman Tree Service, which has offered insect and tree disease management in Palm Beach County for 39 years, says he has been doing preventive treatment for palms against lethal bronzing throughout the county, including on the barrier islands. Once infected with this disease, a tree dies. Unlike lethal yellowing, there is no treatment for lethal bronzing. However, the antibiotic oxytetracycline can be given to nearby trees for prevention against the disease, which is spread by planthopper insects.

Since its discovery in 2006, this disease has rapidly spread throughout Florida’s palms, almost tripling the initial number of infected trees. Even if there are no signs of lethal bronzing, our experts recommend preventive treatments to be safe. 

Trunk injections are a type of disease prevention that requires inserting a port in the palm trunk where the antibiotic is injected every three or four months for at least two years. Although the OTC (Oxytetracycline) injections act as a very good preventative measure, there is still a slight chance of the treated palm becoming infected with lethal bronzing. If homeowners have a big investment in one of the 16 species of trees susceptible to lethal bronzing, they’ll want to consider preventive treatment.

Symptoms of Lethal Bronzing

There are symptoms to look out for if you are concerned about your palms having lethal bronzing. Some of these symptoms include:

  • Bronze-colored dying lower fronds
  • Flower spikes that die prematurely
  • New palms that die and fold over
  • Premature fruit dropping

It is important to know that once a tree shows symptoms of lethal bronzing, it’s too late for treatment.

Proper management of lethal bronzing includes removing the infected trees and keeping other palms near it injected with antibiotics every few months as a precaution. 

Lethal Bronzing vs. Yellowing

Lethal bronzing is often misdiagnosed as lethal yellowing, which was first detected in Florida in the 1950s. Lethal yellowing, also spread by planthoppers, killed more than 30 palm tree species but was particularly devastating to tall coconut palms. Unlike trees infected by lethal bronzing, trees infected by lethal yellowing could be saved by injection of oxytetracycline every four months. Lethal yellowing is not as prevalent as it once was because of the aggressive use of oxytetracycline and the removal of diseased trees, making it rarer than it was once before.

The only way to diagnose lethal bronzing is by core sampling, which is sent for laboratory analysis because the disease is similar to other palm maladies, such as potassium deficiency. Spread only by insects, the disease cannot live outside a plant or insect, so it can’t be mechanically transmitted by pruning tools or infected roots touching new roots.

“It’s all over. We’ve seen it on the barrier islands. We’ve seen a lot of sabal palms go down, which never happened with lethal yellowing. The trees are infected by insects similar to the way mosquitoes transmit diseases” – Michael Zimmerman.

Prevention is key for saving expensive healthy palm trees that are susceptible to lethal bronzing.

Currently, some developers in Palm Beach County are beginning to ask for susceptible palm species to be tested prior to installation.1 People are putting in expensive palms, and they need to be taken care of. Preventive care for lethal bronzing is now standard health care.

Palm Trees Affected by Lethal Bronzing

There are over 50 types of palm trees, 12 of which are native to Florida and 37 that will grow well here as well. Because there is a wide variety of palms that will thrive in this environment, it is important to know which are more susceptible to lethal bronzing. These can include:

  • Christmas
  • Bismarck
  • Pindo
  • Carpentaria
  • Coconut
  • Chinese Fan
  • Date Palm – Most commonly infected species
  • Canary Island Date – Most commonly infected species
  • Edible Date
  • Pygmy Date
  • Wild date
  • Fiji Fan
  • Buccaneer
  • Mexican Palmetto
  • Sabal Palmetto
  • Sylvester Palm – Most commonly infected species
  • Queen
  • Chinese Windmill

For more information on how you can prevent lethal bronzing in your palm trees, contact Zimmerman Tree Service today. At Zimmerman Tree Service, we specialize in tree trimming in Boca Raton, Delray Beach, and the West Palm area. However, we’re also Certified Arborists in South Florida with extensive experience in insect and tree disease management. Whether you’re seeking palm tree care in Florida, tree trimming services in West Palm, or total plant health care, you can count on us.


  1. UF/IFAS – Lethal Bronzing: A Destructive New Palm Disease


When you hire Zimmerman Tree Service, you will have peace of mind knowing you are working with highly-trained and knowledgeable professionals.

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