From the University of Florida: In March, 2009, a whitefly (Aleurodicus rugioperculatus Martin: Hemiptera: Aleyrodidae), was collected in Miami-Dade County from gumbo limbo. This was the first report of this insect on the U.S. continent and it is believed to originate from Central America. Since the initial find, there have been numerous other reports, all in Miami-Dade County. It will likely spread to other southern Florida counties.
NOTE: This is not the same whitefly (ficus whitefly) that is currently causing defoliation and branch dieback of ficus in south Florida.
What are Whiteflies?
They are small, winged insects that belong to the Order Hemiptera which also includes aphids, scales, and mealybugs. These insects typically feed on the underside of leaves with their “needle-like” mouthparts. Whiteflies can seriously injure host plants by sucking nutrients from the plant causing wilting, yellowing, stunting, leaf drop, or even death. There are more than 75 different whiteflies reported in Florida.
Host Plants: This whitefly appears to have a very broad host range from palms to woody ornamentals and fruits. Thus far, it has been seen on gumbo limbo (Bursera simaruba), Calophyllum species, black olive (Bucida buceras), copperleaf (Acalypha wilkesiana), broadleaf arrowhead (Sagittaria latifolia), cocoplum (Chrysobalanus icaco), Brazilian pepper (Schinus terebinthifolius), wax myrtle (Myrica cerifera), live oak (Quercus virginiana) and mango (Mangifera indica). It has also been reported on several palms which include areca palm (Dypsis lutescens), Veitchia species, and coconut (Cocos nucifera). Additional hosts are likely to be added to the current list.
Biology: There is little information on the biology of this new whitefly, however, research is ongoing to describe the life cycle and host range. This whitefly is closely related to giant whitefly, Aleurodicus dugesii, and shares some similarities. Like giant whitefly, the adult is about 3 times larger than other whiteflies that occur in the U.S., and are more docile (slower moving) than other types of whiteflies. The adult whiteflies congregate on the undersides of the leaves to feed and reproduce. The female whitefly lays her eggs in a spiral pattern on the leaves and also deposits a white, waxy substance on the eggs. The crawler stage hatches from the eggs and crawls around before it starts to feed with its “needle-like” mouthparts. This stage is very small and difficult to see.
The crawler will molt and go through several immature stages that are oval and initially flat, then more convex. These stages do not resemble a typical insect. Some of these immature stages will secrete long white filaments of wax. It will likely survive year round in south Florida.
Plant Damage: The most noticeable symptoms of an infestation of this whitefly is the abundance of the white, waxy material covering the leaves and also excessive sooty mold. Like other similar insects, these whiteflies will produce “honeydew”, a sugary substance, which causes the growth of sooty mold. The actual effect of an infestation on the health of a plant is unknown; however, whiteflies in general can cause plant decline, defoliation and branch dieback.
Management in the Landscape: Often, when new pests arrive, they can reach very high populations and can be extremely damaging. It is not uncommon, however, that after several years, the impact is greatly reduced. Although it may be necessary to use insecticides for this pest, it is very important to understand the importance of natural enemies and the need to focus on long-term, biologically based management.
- Monitor plants for early signs of an infestation because it will be easier to manage the pest before it builds to high populations and causes major damage. If you have an infestation on a tree, be sure to search nearby trees as well because this whitefly feeds on many types of trees.
- In the landscape, one parasitoid attacking this whitefly has been identified, Aleuroctonus vittatus (Eulophidae), at very high levels. Awareness of natural enemies is very important so they are not also killed while trying to control the whitefly. Protecting natural enemies is a critical component in the long-term control of this pest. Broad spectrum or persistent insecticides often kill a high proportion of predators and parasites, particularly when applied as a foliar spray. Carbamates (i.e. carbaryl), organophosphates (i.e. malathion) and pyrethroids (i.e. bifenthrin, cyfluthrin) are especially toxic to natural enemies.
- 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 with the insecticide. Spray coverage must be thorough to get the best results, particularly in cases like this when the insect is primarily on the underside of the leaves. In general, foliar sprays are active for a few weeks and usually require more than one application. However, some of these products can be very useful for quick knockdown which can be very important with bad infestations.
- 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.
Visit here for a list of insecticides that are known to combat rugose spiraling whitefly: http://trec.ifas.ufl.edu/mannion/pdfs/Rugose%20spiraling%20whitefly.pdf.
For more information, contact your local Extension agent for additional information or http://trec.ifas.ufl.edu/mannion/
Catharine Mannion, Ph.D., Associate Professor and Extension Specialist
University of Florida, IFAS, Tropical Research and Education Center, Homestead, FL
Photo Credits: H. Glenn, UF/IFAS, Tropical Research and Education Center, Homestead, FL
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