Don’t Bet Your Hedges: IPM Guide Outlines Ficus Whitefly Management
By Muhammad Z. Ahmed, Ph.D.
Over 80 indigenous and invasive whitefly species are reported from Florida, and this number is constantly increasing. Several exotic whitefly species have invaded Florida over the last 15 years, causing substantial economic losses to Florida’s ornamental industry. The whitefly Singhiella simplex, sometimes known as the ficus whitefly, has been one of the most challenging species among them. The first report of this species in the U.S. was from Florida in 2007, and since then the trend of using Ficus hedges has been decreasing in Florida.
Worldwide, 98 whitefly species are known to feed on Ficus, with 33 were reported only from Ficus. Among them, only S. simplex has been causing damage to Ficus hedges and trees globally for the last 15 years. Though the major damage to Ficus hedges in Florida is associated with S. simplex, six more whitefly species feed on Ficus in Florida. In a new guide published this week in the open-access Journal of Integrated Pest Management (JIPM), colleagues and I at the U.S. Department of Agriculture (USDA) and University of Florida (UF) provide images of puparia and adults of those whitefly species and share a dichotomous field key for their preliminary field identification.
Ficus benjamina is one of the most preferred hosts of the ficus whitefly. Unfortunately, F. benjamina has been used extensively and homogeneously as hedges in the south Florida for many decades due to its low cost, lavish green color, prolific growth, ability to be pruned into any shape, and utility in providing a significant privacy hedge up to 15 feet high or more around houses and neighborhoods. Some F. benjamina hedges are part of the longstanding landscape in south Florida and have been there for several decades. It is vital to prevent ficus whitefly infestation or control it early to preserve the integrity of these hedges.
In addition, some cities and homeowners associations (HOAs) mandate the control of ficus whitefly on Ficus hedges in their neighborhoods. The establishment of the ficus whitefly and its damage pose a severe threat to the utility of F. benjamina hedges in south Florida. One of the most apparent symptoms of ficus whitefly infestation is defoliation, which can result from an unintended infestation of just 2–3 months (2–3 generations for the insect). In our JIPM report, we observe that, in most cases, defoliated Ficus hedges can refoliate; however, plant death can occur after several defoliation episodes.
The population of the ficus whitefly starts increasing in spring through summer and peaks again in the fall. Regular scouting is critical for ficus whitefly management to avoid economic damage.
In cases of heavy ficus whitefly infestations that result in defoliation of F. benjamina hedges, we suggest pruning out dead branches, checking the suppleness of twigs, and following our management plan. However, excessive defoliation can lead to branch dieback if the ficus whitefly is not managed. The amount of dieback is affected by the level of infestation and the health and age of the F. benjamina hedges.
Foliar and drench applications of neonicotinoids have effectively controlled the ficus whitefly. Ficus hedges do not flower, so applying neonicotinoids to Ficus hedges will likely not disturb pollinators. One of our co-authors, Catharine Mannion, Ph.D., professor emeritus at the UF Tropical Research and Education Center, recommends the appropriate use and timing of any insecticide, including neonicotinoids, to avoid future defoliation. Defoliation of community or homeowner hedges creates stress and panic, leading to inappropriate use of pesticides or pest control methods and sometimes hedge removal. This stressful situation can be avoided with early detection of the ficus whitefly, aided by our proactive management plan.
This plan also provides easy-to-follow instructions for nurseries, homeowners, and landscape companies in the form of a dichotomous key. It will help guide professionals and non-professionals during the management of the ficus whitefly to ensure correct and timely decisions.
We frequently get phone calls from clientele that the pesticide applications are not working against the ficus whitefly. We often find few to no live immature whiteflies on treated Ficus hedges when we visit such cases. We frequently find ficus whitefly exuviae with emergence holes of adult whiteflies, but these can be from past generations. Although natural factors like rain can wash whitefly exuviae off leaves, they often remain longer in the lower canopy or inside the hedges.
The clientele assume that the treated Ficus hedges are still infested, usually because of adults of the ficus whitefly that move from property to property, looking for healthier plants to feed on. Depending on when the last pesticide application was to these “healthier” plants, the immigrant or migrating adults, their eggs, and their offspring may succumb to the pesticide residues on the treated Ficus hedges. This is why co-author Lance Osborne, Ph.D., professor at the UF Mid-Florida Research & Education Center, suggests that we will have to develop coordinated area-wide management plans for this particular pest.
In some cases, we find live immature whiteflies on treated hedges that have escaped the chemical application due to several factors, including incomplete spray coverage, lack of chemical efficacy, or potential resistance. We are concerned about the potential for insecticide resistance development in the ficus whitefly due to the application of different insecticide products with the same mode of action being applied repeatedly. In south Florida, it is common for one neonicotinoid product to be applied early in the spring as a soil drench, followed by a different neonicotinoid product applied as a foliar spray. Although growers are rotating products, they are not rotating products from a different class of insecticide with a different mode of action. Co-author Cindy McKenzie, Ph.D., research entomologist at the USDA Agricultural Research Service, says that the back-to-back application of insecticides with the same mode of action eventually causes resistance to develop in whiteflies.
Several natural enemies of the ficus whitefly have been observed in the field. The parasitoid wasp Baeoentodon balios and the predatory beetle Delphastus pallidus are the most dominant among them in Florida. We are studying their potential to control the ficus whitefly. Meanwhile, conservation of natural enemies should be considered in any management plan of the ficus whitefly. Defoliation, pruning, and pesticide applications could hinder the establishment of natural enemies. We shed light on these factors in our JIPM report. My lab is working closely with McKenzie and Osborne’s labs as well as the lab of co-author Alexandra Revynthi, Ph.D., at the UF Tropical Research and Education Center to study the biological control of the ficus whitefly.
In summary, in our JIPM report we provide the current pest status of the ficus whitefly Singhiella simplex, a survey of its natural enemies, and an overview of its management plan, and we offer a few main conclusions:
- Be proactive and scout for the ficus whitefly regularly.
- Be patient and strategize the management plan. If an infestation arrives or starts building up or causing defoliation, please apply the management plan. It is important to remember that the ficus whitefly will not kill the hedge if managed on time.
- Be preventive in conserving resident natural enemies.
Journal of Integrated Pest Management
Muhammad Z. Ahmed, Ph.D., is a research entomologist in the Subtropical Insects and Horticulture Research Unit at the U.S. Department of Agriculture’s Agricultural Research Service in Fort Pierce, Florida. Email: email@example.com.