Invasive Bacteria Threatens Florida's Palm Trees

Sep 12, 2019
Originally published on September 12, 2019 9:25 am

About one hundred yards from the University of Florida’s Institute of Food and Agricultural Sciences’ Broward Extension is a sort of palm tree graveyard.

A browned trunk of a palm stands straight. Without its canopy, the palm looks like an 18-foot pencil stuck into the ground. About five other neighboring palms have fronds that are turning various shades of brown.

The area has been ground zero for UF’s Dr. Brian Bahder.  For three years, he has been spearheading  research on the disease responsible for killing the palms, called Lethal Bronzing Disease.

The disease first popped up in Florida in Hillsborough County back in 2006 and has been spreading throughout the state ever since.

“Typically, in diseases that move really quickly and wipe out everything, they fade out very quickly,” Bahder said. “The way I see Lethal Bronzing moving, it’s somewhat slower, so it’s going to persist, I suspect, quite a bit longer, if we don’t do anything about it."

Bahder specializes in vector ecology, which in part studies how insects carry and transmit diseases.   

He has identified an insect, commonly called a treehopper, as the culprit in spreading LBD. It is typically the size of a grain of rice. 

While treehoppers are native to Florida, Bahder believes a species of the bug carrying the invasive parasitic bacteria that causes LBD was introduced to the state from elsewhere.

“Some form of natural weather pattern or natural means brought a population of this insect from somewhere else, and it came with the disease,” Bahder said.

According to Bahder, LBD kills palms from the inside. Once an infected bug transfers the parasitic bacteria into a healthy palm while feeding, it multiplies.

“Essentially its blocking up the vascular network of the palm that transports sugars and nutrients throughout the palm itself,” Bahder said. 

Once the bacteria clogs a palm’s circulatory system, it begins to die. 

Manny Nassar is an arborist with the Davey Tree Expert Company. He has been in the tree business for 30 years and said he is concerned about the spread of LBD.

“I’ve been in the industry that long and I haven't seen anything that has come on this quick and this aggressive,” Nassar said.

The palms most susceptible to LBD are Phoenix palms, which are commonly found in resorts, and Florida’s state tree, the Sabal Palm.

Nassar said that's a big problem for Florida. 

“Because that’s a commonly planted palm—along  the Turnpike, along  I-95 and along I-75,” Nassar said.  “Anytime they do any mitigation or renovation of areas around ramps or in those median areas, they usually plant the Sabal Palm.”

Once a palm is infected with LBD, it’s a goner. Infected palms need to be removed immediately to prevent further spread. 

There is a preventative antibiotic that can be injected into palms, but it costs roughly $50  per injection and lasts only  about three months. 

“It’s not cheap,” Nassar said. “So people that value their palms—if they’ve had this diagnosed in their area—will have to spend a lot of money to keep this problem hopefully away from their palms, and it’s still not a guarantee.”

LBD has been confirmed in 31 counties in Florida so far. An infected palm can go months before showing symptoms, so in many cases, people are inadvertently transporting infected palms into new areas. 

Entomologist Jefferey Eickwort is a supervisor for the Florida Forest Service

“There’s no statewide effort  to go out and try to eradicate it from the environment and frankly, I’m not even sure what such an effort would look like,” Eickwort said.

He said LBD is a difficult disease to try to wrangle, especially because the only way to confirm a case is through testing a tissue sample.  

“It’s not like it moves into a stand and then every single palm dies,” Eickwort said. “Instead it’s something that very gradually kills trees in a very scattershot way across the landscape and that makes it very difficult to come up with any effective response.” 

Palms susceptible to LBD also grow in Texas, where the disease was first found in this country, as well in Louisiana, and up to the Carolinas.  

Bahder said if the disease continues to spread, it could also devastate the landscaping and ornamental crop industries. 

“I’ve had some nursery owners tell me they’re in the millions of dollars of losses in certain plots because their plots just get completely wiped out by the disease.” Bahder said. “We haven’t done a full in-depth analysis of the impact, but it’s getting up there, quick.”

Bahder regularly hosts informational workshops on his LBD research that are open to the public. The next one is coming up Sept. 25 from 8 a.m to 5 p.m. at the IFAS Broward Extension location. 

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