UF scientists hope to stop deadly bronzing disease in Florida palm trees

It's been nearly two decades since it was discovered that the slime-colored planthopper was killing more than 20 species of palm trees in Florida by spreading a terminal bacterial infection called pyroptosis.

But a landmark study by scientists from the University of Florida has managed to decipher a warning signal — a kind of scented SOS — that diseased trees emit that triggers a protective response in nearby palms. Now they are cloning the melancholy fragrance in the laboratory in the hope that distributing it among healthy trees will prompt them to mount a defense without others having to contract the disease first.

Because once a tree is infected, there is no cure. Tricking trees into boosting their immune systems could save untold riches for farmers and landscapers who currently can only watch as their expensive palms wither and die when they become infected with disease.

“Infected palms emit an alarm, which may be in nature to warn nearby plants, and may be a last-ditch effort to save themselves, but other plants hear it and react,” said Brian Bahder, an entomologist at the University of Florida, and his team at the University of Florida. The study was conducted by the Institute of Food and Agricultural Sciences in Fort Lauderdale. “It's kind of exciting, and we want to harness it to benefit the plant.”

The deadly bronze was first identified in Central Florida in approximately 2006. It has since spread to more than half of Florida's 67 counties, according to UF. It can be particularly noticed in Palm Beach County in trees planted along the Florida Turnpike and Interstate 95 where clear signs of copper-colored branches are visible, Bahder said.

The expensive palm trees of Florida's Canary Island are a favorite target of deadly bronze

This disease, spread by the insect Haplaxius Crudus, attacks several species of palms but often favors Florida's state tree, the native cabbage palm, also known as the sabal palm. Another favorite is the Canary Island Royal Date Palm which is often used in rich landscapes as it is pruned at the top to resemble a pineapple.

What are the symptoms of fatal bronze color?

If a tree becomes infected, the bacteria break down the vascular system, eat away at the flesh under the bark and spread through the tissues that the tree uses to move water and nutrients around. The leaves turn reddish-bronze starting at the bottom and moving upward until the spear leaf or “heart” of the palm dies.

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“Not all diseases are deadly by name, and this one is deadly for good reason,” said John Roberts, a commercial horticulturist who focuses on ornamental plants at UF's IFAS in Palm Beach County. “It's definitely a landscape issue because if a palm tree dies, they have to replace it, and beautiful palm trees can be expensive.”

At Smarty Plants Nursery in Lake Worth Beach, a 10-inch Canary Island date palm in a three-gallon pot costs $25, according to its website. A 6-foot-tall palm tree in a 25-gallon pot costs $570.

Early research into the deadly bronzing disease had reached a dead end

Bahadur's research was published last year in MDPI's peer-reviewed scientific journal Plants.

He said he was initially interested in studying whether the insect that spreads the deadly bronze hue was attracted to odors, called leaf volatiles, that come from already infected palm trees so they could use those compounds as insect bait.

This turned out to be a dead end, as the insects were not attracted to the smell. Instead, what he found was that the infected palm trees were releasing a very high concentration of two different compounds, and that nearby trees were producing a defensive compound containing antimicrobial elements. Trees distant from the infected group did not produce the same defensive compound.

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The discovery represents the first documented case of volatiles being detected in palm trees infected with the bacteria that causes the deadly bronzing.

“We don't think plants are intelligent, but they communicate through these chemicals,” Roberts said. “Often they can recognize what other plants are dealing with.”

Compounds that could trigger a natural defense response are inexpensive in the laboratory, Bahadur said. The liquid can be injected into a tree, possibly treating it, placed in dispensers to evaporate, or sprayed in vulnerable areas to stimulate a defensive response.

Bahadar is looking for $500,000 to $600,000 in funding to conduct further testing.

“Early detection is important to avoid a mountain of burned palms,” Bahadur said. “If the plant becomes infected, it's a death sentence.”

Summon yours County Extension Office If you suspect your tree is infected with bruxism.

Kimberly Miller is a veteran journalist for the Palm Beach Post, part of the USA Today network in Florida. It covers real estate and how growth affects the environment of South Florida. participation in Dirt To obtain a weekly real estate report. If you have news tips, please send them to [email protected]. Help support our local journalism, subscribe today.