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Disease Spreads Among Sabal Palms In Hillsborough, Manatee

The Tampa Tribune
Published:   |   Updated: May 25, 2013 at 07:16 AM
TAMPA -

For the early Seminole Indians, the sabal palm was an all-in-one home improvement store-supermarket-pharmacy.

They built their houses from the logs and made rain-proof roofs from the fronds. They ate the hearts of the palms for sustenance and chewed the berries to knock out headaches.

So treasured is the sabal, also known as the cabbage palm, that it was named the state tree by the Florida Legislature in 1953. (It's also South Carolina's state tree.)

But a bacterial relative of lethal yellowing disease - spread by an unknown insect - is killing sabal palms in southern Hillsborough and northern Manatee counties, and experts fear it could wreak havoc on the sabal population in the wild.

"It's going to be severe, but I don't think it's going to be catastrophic," said Monica L. Elliott, a University of Florida professor of plant pathology and a lead investigator on the case.

It's especially worrisome because the tree is a valuable fixture in Florida ecology, said Rob Northrop, urban forester with UF's Hillsborough County Extension office. It provides a sanctuary for birds, bats, snakes and lizards.

The antibiotic oxytetracycline injected in the trunk can thwart the spread of the disease, Texas Phoenix Palm Decline, in suburbia. But injecting palms in the wild is not feasible, so pesticides may have to be used to kill the bug that carries the pathogen. First, though, scientists have to identify the bug, likely some sort of plant hopper - bugs that pierce the leaf tissue of plants with their mouth parts and feed on the sap.

Authorities would also have to make sure the pesticide doesn't damage the ecosystem that the sabal palm supports. And Elliott raises another potential problem: The insect may be a native Florida species. "So, do you wipe out the native insect to save a native tree?"

Preliminary tests show that the DNA structure of the sabal palm pathogen is similar to the bacteria that has been killing Canary Island date palms since late 2006, said Elliott, who works at a research center in Fort Lauderdale.

"We first started seeing large numbers of sabal palms with odd symptoms this past winter and spring," she said, adding that tests in May confirmed that a phytoplasma, a bacterium characterized by a lack of cell walls, was responsible. Another phytoplasma causes lethal yellowing in coconut palms.

Experts think the cabbage palm infestation is limited to Hillsborough and Manatee counties so far.

Because different diseases can cause the same symptoms, it's hard to know without testing whether Texas Phoenix Palm Decline is the problem.

The first sign of the disease may be that the tree drops its fruit prematurely. Then the oldest fronds turn brown or gray, starting at the tips. It then moves into the spear leaf.

Experts say it is difficult to eradicate the disease once the symptoms are recognizable, so they advise injecting the healthy trees near it with the antibiotic, sold under the brand name Tree Saver (go to www.palmtreesaver.com or call (561) 655-6940.

Although home gardeners can administer the injection themselves, "it isn't the easiest thing to do," Elliott said. She recommends hiring an arborist or knowledgeable landscaper to inject the tree. The shot should be given every four months for as long as the tree lives, since the medicine controls but does not eradicate the bacteria.

To treat the tree, the homeowner or arborist must drill into the trunk. That wound could be a path for other diseases, so Elliott advises against injecting healthy trees if there is no sign of infestation in the neighborhood.


Reporter Philip Morgan can be reached at (813) 259-7609 or pmorgan@tampatrib.com.

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