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Tiny insect sucking all life out of sago palms

While the bugs can be fought with insecticide, they killed 60 percent of the popular trees in southwest Florida.

© St. Petersburg Times
published November 1, 2002

TAMPA -- Yet another exotic plague is creeping across the Florida landscape.

At first glance, it seems innocuous, hardly a blip on the screen. But, for many property owners, the consequences can be ugly and costly.

The blight threatens king and queen sago palm trees, a popular staple in Florida's scenic menu.

Two of those trees are in Ada Sullivan's Forest Hills front yard.

"I didn't know what it was," said Mrs. Sullivan, who recently spotted the infestation on one of her sagos. "My lawn man seemed to know something about it, though."

The enemy is Asian cycad scale, and it's literally sucking the life out of sago palms throughout west central Florida. You'd think one good dose of insecticide du jour would do the trick, but no. A rescue takes time and elbow grease.

Asian scale is an extremely tiny white insect with an armor coating, and it multiplies fast. If your sago looks like it has a coating of fresh snow, you likely have a problem. Once the scale finds a juicy perch on a sago, it inserts its straw-like mouth and starts feeding, until the insect dies. Multiply that by, say, 3,000 insects per square inch of plant.

Experts believe scale was unknowingly introduced by a botanical expedition returning from China to the Miami area in the early 1990s. Embedded in roots, it went undetected. Before long, sago palms in Dade and Broward counties started wilting and dying in large numbers. By all accounts, the Asian scale has wiped out 60 percent of the sago palm population in southeast Florida. And now, it's in the Tampa Bay area.

How did it get here and how does it spread?

Mostly in the wind, said Hillsborough County Extension agent Dave Palmer. Scale can spread a half-mile on a windy day, he said.

"I started getting phone calls about 18 months ago," he said. "There were only a few at first. Since then, the number of calls has increased steadily."

Palmer describes the local outbreak as a "minor epidemic" that could grow into something devastating if it goes unchecked and unreported.

Tom Broome, who sells cycads in eastern Polk City, takes a dimmer view of the infestation. "It's more than a minor epidemic," he said, warning that the entire west-central Florida sago population is "at risk."

How to fight it?

Palmer suggests vigilance and special concoctions. "So far, the best home remedy is horticultural oil, such as Ortho Volck or fish oil mixed with Malathion," he said. "But you have to wet the plant thoroughly and repeat the procedure every few weeks, and stay on guard."

That's what Ada Sullivan and her lawn service are doing.

According to Palmer, pruning is helpful too, but the leaves should be incinerated or carefully double-bagged. Bury them if you can, instead of throwing them in a loose pile to be hauled away. Lawn tools should be soaked in a bleach-water mixture after pruning.

Broome takes the process a step further, to beneath the soil. "Asian scale thrives in the roots too," he said. "So drenching the top of the plant isn't enough."

His advice: Look for products containing the ingredient imidacloprid, mix according to instructions, and soak thoroughly around the base of the tree. Broome said certain grub control and advanced rose formulas contain imidacloprid. As with the leaf treatment, multiple applications will likely be necessary.

State scientists have been working on the problem in this area since spring. That's when the Florida Division of Plant Industry began releasing imported parasitic wasps in counties including Hillsborough. Palmer said the insects are a natural predator of the scale, but it will take years before they exist in sufficient numbers to be of any real help. Unlike the wasps most Floridians fear, he said, "these wasps are almost invisible to the naked eye and they won't sting anybody. You may already have some in your yard and you don't even know it."

With all the work involved in eradicating cycad scale, Broome suggests homeowners think twice before adding sago to their landscaping. He said his business has suffered very little because he deals mainly in rare cycads that are largely unaffected by the insect. Palmer reports that some landscape architects have stopped including sagos in their job proposals for the time being.

Why doesn't Asian scale affect other types of palm?

"Sagos aren't palms at all," Palmer said. "They just happen to look that way."

On the Internet

To learn more about the Asian cycad scale, try these Web sites:

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