Whiteflies have become a major issue in South Florida with at least four species of particular concern: Ficus, Rugose Spiraling, Bondar’s Nesting and Silverleaf. Residents have noticed plant leaves yellowing, dropping, covered with white waxy material called flocculent, or covered with whitefly excrement called honeydew and its accompanying sooty mold. Plants, walkways, cars, outdoor furniture and even pools may become covered with the sticky material or flocculent. Whiteflies are among the many pests that are part of living in a subtropical climate. They can be managed with proper plant cultural practices; use of other beneficial insects, mites and fungi; and judicious application of the appropriate pesticides.
This following information was developed by the Palm Beach County Whitefly Task Force, to provide accurate, unbiased and research-based information to help residents, businesses and governments find the correct answers and to sort through the misinformation that can develop around major pest issues.
You’ve probably heard about the whitefly issue in Dade, Broward and Palm Beach Counties, even if you haven’t dealt with it personally. Whiteflies can be concerning because some may significantly effect certain landscape plants. If proper management steps are taken, a healthy landscape can be maintained. There are a number of cultural, biological and pesticide strategies that can be effective to help manage whiteflies. The great thing about living in a subtropical climate is that we have an active, year-round growing season and can enjoy landscape plants that are shipped from around the world. Sometimes, however, new insects are unintentionally introduced to South Florida.
This isn’t a new phenomenon but does seem to be an ever-increasing problem. New pests have a good chance at thriving here due to our mild climate and lack of cold winters. Further, there are generally no or few natural enemies here that will feed on the new pests. Keep in mind that nature often finds a way to achieve equilibrium. An insect will have many natural enemies in its native habitat. In a new habitat, natural insect enemies may slowly emerge and control pest populations without human intervention.There are more than 75 whitefly species in Florida, and many more around the world.
Biology and Life cycle ~ The life cycle for the three whiteflies ranges from 21 to 30 days during the summer and longer during the cooler winter months. The adults usually deposit eggs on the undersides of host plant leaves. The silverleaf whitefly’s eggs are deposited in a circle, but only the rugose spiraling whitefly deposits eggs in an obvious, telltale spiral pattern. Whiteflies feed by inserting their needle-like mouthparts into the plant tissue. Both the immature and adult whiteflies will feed on the plant. Immature whiteflies do not look like the small, moth-like adult. Only adults have wings and can fly. The immature stages are not mobile, typically oval in shape and can be very flat to somewhat convex. Identification of the stages in whiteflies’ life cycles is critical to achieving good control. Both the immature and adult whiteflies can cause damage to a plant through their feeding activities. The egg stage of the life cycle is not damaging to the plant. Adult whiteflies may still deposit eggs on a plant that has been treated with insecticides. This does not mean that treatments are not working, or that damage is occurring. In the case of a systemic insecticide, whitefly populations will be controlled when the juveniles emerge and begin to feed. A secondary problem caused by whiteflies is that they produce a clear, sticky substance called honeydew. Sooty mold will grow on the honeydew and create a sticky, black mess on the plant and surrounding area. The rugose spiraling whitefly also produces huge amounts of a white, fluffy substance that is primarily made of wax. This substance also becomes sticky from the honeydew and can make the plants and surrounding areas, including pools,
Management: Although efforts to understand and control this pest are ongoing, there are several potential options for whitefly control. However, it is necessary to consider the site (landscape, hedge, large tree, container, production, etc), the size and number of trees, and the surrounding environment before taking steps to control this pest. For large trees, for example, a foliar spray may not be possible.
In the landscape, several natural enemies have been observed attacking this whitefly which can play an important role in long term control. Awareness of these natural enemies is very important so decisions for additional control measures can be made wisely so as not to also kill the natural enemies. The most commonly seen natural enemies include beetle predators, parasitoids, and lacewings.
Monitor your ficus 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. Defoliation usually occurs after the whiteflies have been there for several generations. Also, if infested trees or hedges are trimmed, either leave the clippings on the property or if removing, bag the clippings to reduce the chance of spreading the insects. If clippings are being transported in a truck, be sure to either bag them or cover these clippings with a tarp. Although the eggs and early stages of the whitefly on fallen leaves will die, the last nymphal stage of the whitefly can likely survive, emerge into an adult and attack more ficus. Insecticidal soap or oil sprays may be an effective method of control for small trees or shrubs, but, thorough coverage of the undersides of the leaves is especially important. It will also be necessary to repeat these applications every 7 to 10 days. The use of other insecticides may be necessary to control this pest. However, it is important to use products that will not be detrimental to the natural enemies. Protecting natural enemies may be a critical component in the long-term control of this pest. Insecticides with systemic properties may be very useful in whitefly control because they can be applied as a drench to the soil and provide longer lasting control.
Control in the Landscape: The current recommendation is to drench the soil around the base of the tree or hedge with a product that contains a neonicotinoid compound (see below table). If applied appropriately, these products should provide sufficient control of the whitefly for 4-8 months (or perhaps longer) depending on the size of the tree or shrub. It is advisable to monitor your plants 3 months after application for the presence of live nymphs. Foliar sprays can also be applied to treat “hot spots” or get quick knockdown in addition to the soil applications. Products that can be considered for foliar applications are listed in the next section (Control in the Nursery), but it is important to only use those products that are allowed in the landscape.
There have been reports of this whitefly killing ficus trees and hedges. There have been cases of branch dieback which sometimes can be severe and in a few cases plant death. In most cases, the trees and hedges will grow new leaves. If the tree or hedge has suffered from a massive loss of leaves, it is important not to overwater. Without leaves, the plants are less efficient at taking in the water and start to rot in the roots or lower trunk which may lead to plant death. If the twigs are still supple, the plant will produce new leaves in a few weeks. As soon as new growth is evident, a systemic insecticide applied to the soil may provide protection to the new growth.
I know this blog is very long but I hoped that it may have answered a lot of questions about the whitefly insect. If you need help regarding your landscape, we at Garden Services are fully licensed & insured to handle all of your irrigation, landscaping, lawn maintenance and tree service needs whether it’s a residential, commercial or homeowner association property If you ever have any questions, please don’t hesitate to email me and I’ll be happy to answer any questions you may have. Special thanks to UF/IFAS extension offices and the Palm Beach County Whitefly Task Force for there helpful information provided in this post.