Bug Continues to Infect Florida Ornamentals

An insect the size of a piece of lint has been destroying a popular ornamental plant in southern Florida for more than five years, and experiments are still underway on how to keep it under control.

The Asian cycad scale insect or Aulacaspis yasumatsui has been gradually killing off King and Queen sago ornamentals, which are members of the cycad family and are seen in front of many southern Florida households. The insect was first discovered in 1996 in southern Miami, then gradually made its way north into Palm Beach, Dade and Broward counties. It's believed the scale was on plants that were shipped to the United States from Asia.

Queen sagos are round, symmetrical plants that can grow up to 15 feet high with a circumference of up to 20 feet. Queen sagos normally grow at a faster rate than King sagos, which are more compact and reach a height of only four feet. Both plants date back to prehistoric times when dinosaurs roamed the earth.

Steve Hansen, marketing director for the West Palm Beach Wholesale Growers Association, says the flat, white bug has been sucking the nutrients out of sagos, and because of this, these plants may be heading toward extinction just like the dinosaur.

"In its worst manifestation, it will cover entire leaves so they look like they were painted white," says Hansen. "When you are close to that, it's best just to discard the plant."

Hansen adds that even if the scale is killed off, it remains on the plant and often doesn't fall off. "People think they may be dead, but they provide hiding spaces for the juveniles under the dead ones," he says. "In the worst case, they are covering up the plant so much that the plant does not grow due to lack of photosynthesis."

According to Tom Broome, owner of The Cycad Jungle, a nursery in central Florida, the insect can also become airborne, making it even more difficult to eradicate.

"Even though they don't fly with wings, anytime there is a strong wind, the immature form of the insect can be carried as far as a half mile away," he says. "This means that even if you have taken care of the problem in your yard, you can get the scale again the next time there is a storm."

The female scale measures 1.2 mm to 1.6 mm long and in an eight to 12 day period, can lay up to 100 eggs. Males are even smaller, measuring about one-half millimeter.

PROFESSIONAL GROWERS SUFFER. Hansen says nursery owners throughout southern Florida who have sold the sago plants "are in despair and feeling helpless" over the destruction caused by the minute bug.

"There's a lot of switching gears; people are starting to rethink the sago market, and they are not growing it anymore," he says, adding that at his own nursery business in West Palm Beach, he has scaled back production because consumer demand has been falling.

Hansen says people who still want to buy the plants probably should not rely on the Florida market.

"You have to be very careful where you buy your starter plants so you don't get the insect to start with," he says. "The best place might be offshore or north of Florida."

However, Broome says infected plants from Miami-Dade County nurseries have been sent by chain stores to Alabama, California, Georgia, Hawaii, Louisiana, South Carolina and Texas. "From what I understand, there are parts of Hawaii that have infestations just as bad as Florida," he says.

So, what's the best way to get rid of this pesky insect?

Broome says he has been able to control the scale by using products with the active ingredient imidacloprid. "These products are applied to the soil, then the roots draw the chemicals into the plant. These chemicals work best when they concentrate in the new growth of the plant."

"I think the best combination would be to cut off all the leaves on the cycad, then spray the stem with horticultural oil to smother as many of the scales as possible," Broome adds. "By the time the new leaves are produced, the chemical will be in the system of the plant. If any new scales hatch, or if any other new scales fly onto the plant, these insects will die once they start feeding on the new leaves. I would suggest another treatment of imidacloprid approximately four months after the first application whether there are insects on the plant or not. Continued use of the product every four months should keep the plant free from subsequent infestations."

Meanwhile, Hansen says people who buy sago plants should treat them like they're going to be high maintenance items. "I like the plant myself and will continue to grow what I have," he says. "They are striking in appearance."

Broome says the scale problem is not going away anytime soon, and as long as nurseries continue to ship scale-infected plants, the scale will not only be a problem in the United States but also in warmer locations around the world. He says purchasers of King and Queen sagos should take whatever precautions are needed to control the insect.

"If people are made aware of the problem and the availability of long term remedies, I think we have a good chance of getting rid of these pests in our landscapes," he says.

This author is IPM Solutions, produced by GEMPLER'S, Inc.