The cycad aulacaspis scale insect is marching through Florida, and no sago is safe. Fighting them is tough work.
By TOM ZUCCO
Published December 5, 2003
The killers slipped into Miami from Thailand in 1996 and set straight to work.
Their methods are particularly gruesome; they burrow their snouts into their victims and suck out fluids until either the victims die or the killers burst, whichever comes first.
They live for only about 75 days but have armored scales for protection. And each female can lay more than 100 eggs. That, and the fact that they can travel as much as 2 miles on a windy day, explains why they've spread from South Florida to the rest of the state.
Their calling card: a white crust that looks like a fine layer of snow.
The cycad aulacaspis scale insect is upon us.
The good news is that the tiny insect's one and only target is the sago palm.
The bad news is that sagos, which are actually cycads, not palms, are one of the most popular ornamentals in Florida and a plant that traces its origin to the time of the dinosaurs. A staple of landscaping, they are found in front yards, on golf courses and around office buildings everywhere.
But an alarming number of the plants are becoming infested; an estimated 70 percent of the sagos in southeast Florida have already been wiped out.
"This sucker is really a beast," said Don Prahl, owner of Dolins Garden Center in St. Petersburg. "I've never seen anything spread like this in the 30 years I've been in business."
Prahl has seen inquiries rise from a trickle several months ago to about two dozen a week. "People call and come in with leaf samples," he said. "They want to know how to deal with the scales. How to save their plants.
"And it's weird. Some people have three sagos and only one is infected. Who knows why?"
Experts say the best treatment for the infestation, which is also called snow scale or Asian cycad scale, involves spraying with a petroleum-based horticultural oil, or a fish emulsion oil. The goal is to smother the insect.
But the plant has to be sprayed thoroughly, and the procedure must be repeated about once a week for several weeks.
Since the insects invade the roots, the soil around the plant also has to be treated.
Insecticides such as cygon and imidacloprid also have been effective, and most home centers, nurseries and lawn and garden centers carry one or several forms of treatment.
Pruning is also helpful, but the leaves should be buried, burned or carefully double-bagged. Lawn tools should be soaked in a bleach and water mixture after pruning.
"We thought we were gaining some control over it about six months ago," said Pam Brown, urban horticultural extension agent for Pinellas County. "But it's just exploded again and has nearly covered the whole state."
Brown said the dramatic spread may be related to stress on the plants caused by abundant rainfall during the summer and fall following years of drought.
There is another treatment that is almost as insidious as the insects themselves: tiny imported parasitic wasps that are not harmful to people or animals, but are deadly to Asian cycad scale. The wasps lay their eggs on the scales. When the eggs hatch, the larvae eat the insects.
Scientists from the Florida Division of Plant Industry, who have been working on the problem for nearly a year, have begun releasing the wasps in the Tampa Bay area. Although the wasps are a natural predator, it could take years before they exist in sufficient numbers to be of any real help.
"You might want to think twice about planting sagos, because to keep your plants, you have to be willing to go out and look every week," Brown said. "And if you find them, you have to spray every week.
"I have one in my yard, and I spray it every Saturday. That's a lot of work, but I love that plant."
Cycad aulacaspis scale insect
How it spreads: The cycad aulacaspis scale insect, Aulacaspis yasumatsui, was found in Miami in 1996, infesting cycads grown as ornamentals. The insect is rapidly spreading through southern Florida. In 1996, it was on sago palms in southern Miami. By 1997, it had spread to Miami Beach and cities north of Miami, including Hialeah and North Miami Beach. In 1998, it had become widespread throughout Broward County and as far north as Palm Beach County. Scale insects can be spread short distances by wind dispersal of crawlers, but the long-distance spread is by transport of infested plants.
What it looks like: Highly infested cycads are almost completely coated with a white crust that includes scales of live and dead insects. The insects are consistently more numerous on the lower than on the upper surfaces of leaflets, and in light infestations, they occupy the lower leaf surfaces exclusively. The cycad aulacaspis scale is unusual in that it also infests the roots of its host plant at depths of up to 60 centimeters. Cycads continue to appear to be highly infested after most of the insects have been killed because the scales do not readily drop off.
How to treat it: The most consistently effective treatment for controlling the insect has been spraying them with a mixture of one part fish oil to 100 parts water. Because the cycad aulacaspis scale insect infests mostly the lower surfaces of the fronds, the spray must be directed there. The fish oil treatment works to prevent insect larvae from settling on the plants. Generally, old scales become infested with fungi and fall off gradually, and at the end of several months, the plants are clean. Frequent spraying with water also helps wash off some of the dead scales.
