Florida foresters sound alarm on palm-tree killing disease

There are 25 known cases of lethal bronzing in Alachua County; just 1 in Duval

A bacterial disease called Lethal bronzing has now spread to the palm trees of Alachua County.

JACKSONVILLE, Fla. – Palm trees in line our streets and yards while adding a tropical touch to our region, but could a bacterial disease prevalent in South and Central Florida be targeting the palm trees in our back yard?

Lethal bronzing is the name of the bacterial disease that can kill large numbers of palm trees at once. First discovered in the Tampa area over a decade ago, it has now spread to Alachua County.

“The disease was originally called Texas Phoenix Palm Decline and it was named that in Texas,” said Larry Figart, an urban forestry agent with the University of Florida-Duval County Extension Service.

Figart said the disease is caused by a bacteria-like organism called phytoplasma, which can spread from tree to tree – in part thanks to some help from an insect called a planthopper.

Plant hoppers, also known as leafhoppers, are small and often on the move. “They roughly are a quarter of an inch to a half-inch long,” he said. “And what they have are piercing-sucking mouth parts.”

Using their mouths, Figart said, planthoppers attach themselves to leaves, remove the sap and move onto another tree, where the cycle repeats. So whatever the insect has is carried from tree to tree.

“The one that produces lethal bronzing is a specific leafhopper and was thought to be not very cold-tolerant,” he said. “But it has lasted through the winter as far north as Alachua County.”

So why is it traveling north? Figart said that’s the major question.

“The insects would be traveling north and it could be the transportation of infected trees,” he said.

According to the Florida Department of Agriculture, the species that causes lethal bronzing has not been identified. So far, there’s only one documented case in Jacksonville, despite 25 cases in Alachua.

Here’s what to look for: if your palm tree had fruits or dates and it had lethal bronzing, all of the fruits would drop at once. He said the spear leaf dies on infected trees and the death of the palms follow. 

Figart said these signs and symptoms are noticeable within two to three months of infection. If the disease is confirmed, he said, the tree should be cut down and its neighbors should be treated.

Not to be mistaken which potassium deficiency, which is common among palm trees, lethal bronzing requires a test to verify. Figart said UF can perform these tests, which cost up to $75. 

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