There is a new insect pest invading South Florida, damaging palm trees and other ornamental vegetation and covering cars, swimming pools and lawn furniture with bug droppings and mold that grows on them.
The rugose spiraling whitefly, native to Central America, was discovered in 2009 in Miami-Dade County. Females lay eggs in a concentric spiraling or circular pattern on the bottom of leaves and cover the eggs with a white wax, according to Florida Department of Agriculture literature. Adult whiteflies are about one-tenth of an inch in size, with larval stages of the insect being smaller.
The most recent map, issued by the University of Florida in May, shows the insect in six South and Southwest Florida counties ranging from Key West to the Palm Beaches.
During the past three months, however, the bug's spread has outpaced that map. Scientists at the UF Mid-Florida Research & Education Center in Fort Pierce confirmed the whitefly has now spread to Martin, St. Lucie and Brevard counties, and a certified pest control operator said he had been treating for it in Indian River County too.
"Based on the overall health of the plant, it won't necessarily kill the plant," said Ron Lafferty of Creative Pest Management in Vero Beach, "but it could, over time. It feeds on plant juices and a black sooty mold covers the leaves and affects the plant's ability for photosynthesis."
Vivek Kumar, a postdoctoral associate at UF's Fort Pierce center, is studying the bug and natural predators that can control it in the long run. A species of beetle native to Florida shows promise.
"As the (whitefly) colony increases, it starts producing waxy material and black mold," Kumar said. "When it dries up, it starts falling off the plant. It falls on cars and pools. It's difficult to remove. You need soapy water."
Bill Snow is manager of the Hutchinson Island Beach Club Association in Jensen Beach and has been battling the whiteflies.
"My main problem here are my tall coconut palms facing the parking lot," Snow said. "I had my maintenance guys washing cars."
He didn't think the mold was damaging paint.
"It's more of an annoyance," Snow said.
The most seriously affected plants are palms — especially coconut palms — gumbo limbo, avocado and Florida black olive, according to state Department of Agriculture literature.
"Homeowners are not only plagued by the decline of health in their plants, but by the honeydew, sticky wax and bodies of dead adult whiteflies that fall onto cars, patios, patio furniture and into pools, clogging water filters," it added.
Lafferty said plant foliage can be sprayed either with commercially available products or by a professional. The most effective way to combat the pests is to have a certified pest control operator drill holes in palm trees and inject pesticide into them.
"It's something that will need to be controlled, but will probably never completely go away," he said.
What to do
Catch it early. Look for telltale spiral patterns under leaves. Spray with a horticultural oil or insecticide every seven to 10 days in the morning or evening.
• You may achieve excellent control with one of the methods listed below, but remember the white, waxy material and the sooty mold on the plant will take time to wear off unless physically washed off.
• Washing plants off with water can be an effective tool to help manage whiteflies for small infestations or small plants. But, for it to be effective, you must remove the immature stages and eggs from the leaves with the wash.
• Using a horticultural oil or insecticidal soap can also help control this pest. These types of products are strictly contact so thorough coverage of the infested leaves is required. Typically, several applications are required 7-10 days apart. Be careful about using these types of products under high temperatures because they can cause damage to plants.
• If the infestation is large, an insecticide may be needed to control the whitefly population. It is extremely important to use the appropriate insecticides, methods, and timing in order to get the best control with the least amount of detriment to the natural enemies or the environment. There are several insecticide options for both professional use (Table 1) and homeowner use (Table 2). Many of the insecticides for professional use are available in more than one formulation (i.e. wettable powder, liquid, soluble granules, granules, pellets) so you can choose the best fit for your situation.
• Contact insecticides are typically sprayed on the foliage or other infested parts of the plant or in the soil for soil-dwelling insects. Depending on the insecticide, either the insect must come into contact with the insecticide or must feed on the plant
• A systemic insecticide can be applied directly to the infested plant or to the soil. Soil applications include drenching the soil, spreading a granular formulation, or burying a pellet. Some products can also be applied as a basal trunk spray or injection into the trunk. Systemic insecticides can also be sprayed on the foliage, but often provide longer control when applied to the soil or trunk. However, it is not recommended to use the same insecticide (active ingredient) on the leaves that you use in the soil or on the trunk.
• Misuse or overuse of any insecticide can cause problems such as insecticide resistance, secondary pest problems, environmental contamination, and detrimental effects on non-target organisms. The site and method of application must be on the insecticide label. Always follow the label directions – "The label is the law". If it is necessary for you to apply several applications of insecticides, it is recommended to rotate among different chemical classes. (Information from University of Florida Extension Service).
You can also hire a certified pest control operator to apply pesticide to roots or tree trunks.
Ed Skvarch, St. Lucie County extension agent for the University of Florida's Institute for Food and Agricultural Sciences