New Guide Details Management of Invasive Scale Insect in Florida
By John P. Roche, Ph.D.
The scale insect Fiorinia phantasma, sometimes known as phantasma scale, was first discovered in Florida on Canary Island date palms in 2018. This invasive insect is a pest of palm, ornamental, and fruit trees, and it has a preference for palm trees, which are a $400 million industry annually in Florida.
Fiorinia phantasma is hard to detect because it looks like other closely related species in the same genus; as a result, it might have been present in Florida before 2018 but not detected. It is now known to be present in Miami-Dade County and Palm County in Florida, and it has also been found in Hawaii since 2011. In an article published in September in the open-access Journal of Integrated Pest Management, Zee Ahmed, Ph.D., of the U.S. Department of Agriculture, Lance Osborne, Ph.D., of the University of Florida, and colleagues present a summary of the state of the threat of Fiorinia phantasma and recommendations for its control.
Scale insects are in the order Hemiptera, the “true bugs.” Female scale insects lack legs and are covered with a waxy protective scale covering—the “scale” of the insect’s name. Males have legs and look like little gnats. Scale insects feed on plant sap using a long siphon tube. There are two types of scale insects in separate families within the Hemiptera, soft scale insects and armored scale insects. Fiorinia phantasma is an armored scale insect.
Female scale insects produce first instars, called crawlers, which have legs. Crawlers can spread F. phantasma to new host plants by dispersing in the wind, riding on mammals or birds, or being carried on contaminated plant material or gardening tools. In Florida, Ahmed and colleagues say, phantasma scale has been reported in 475 sites in the past three years.
Because phantasma scale causes the loss of fronds from palm trees, which are important economically and ornamentally throughout a large portion of the U.S., developing effective control strategies is an urgent priority. Chemical control using contact insecticides is difficult with scale insects because they are protected by their scale covering. “Soil treatments of systemic insecticide also do little to control armored scale insects, “Ahmed says, “because they feed intracellularly, not extracellularly in the phloem.”
To increase efficacy of chemical control, the researchers say, managers need to choose the right insecticide, use it at the right time, and minimize the effects on natural enemies. Crawlers are the most vulnerable stage for F. phantasma because this stage is not protected by a scale, so insecticides are most effective when used against crawlers.
Biological control is viewed as promising for F. phantasma. Scale insects are susceptible to attack by a range of natural enemies. In Hawaii, phantasma scale is preyed upon by lady beetles, lacewings, and thrips. In surveys in Florida, Ahmed and colleagues have determined that several insects are attacking F. phantasma there, including predatory thrips, predatory beetles, predatory mites, lacewings, and parasitoid wasps. The researchers suggest that additional natural enemies should be sought from this species’ region of origin, which is believed to be the Philippines. In the late 1880s, Icerya purchasi, sometimes known as cottony cushion scale, was causing severe damage to citrus crops in California. In 1888, vedalia lady beetles (Rodolia cardinalis) were imported from Australia and released in California to control the scale pests. The vedalia successfully controlled I. purchasi, one of the first incidences of successful biological control of an insect pest. Managers hope to have a similar success for biological control with F. phantasma.
A key challenge in the control of phantasma scale is detecting infestations. “Fiorinia phantasma occurs in two Florida counties in the U.S.,” Ahmed says, “Miami-Dade and Palm Beach, and it is usually found on palms. Its detection is complicated by the presence of Fiorinia fioriniae, which is also commonly found on palms, and Fiorinia japonica, which infests palms and looks identical in the field to the other Fiorinia species.”
In their paper, Ahmed and colleagues address this problem of look-alike species by providing identification information to help entomologists identify F. phantasma so they can optimize its control. In addition, Ahmed says, “in an upcoming paper in Zookeys, we provide DNA barcodes and taxonomic keys to second-instar males and females of Fiorinia species in the U.S. for the first time and supply improved, previously available taxonomic keys to their crawlers and adult females.”
Another important component of control could be carefully inspecting nursery plants and horticultural tools for the presence of scale insects. Because of its relatively small range so far, with concerted control efforts and continued research, larger invasion of palms in the southern U.S. may be able to be avoided.
Journal of Integrated Pest Management
John P. Roche, Ph.D., is an author, biologist, and educator dedicated to making rigorous science clear and accessible. Director of Science View Productions and Adjunct Professor at the College of the Holy Cross, Dr. Roche has published over 200 articles and has written and taught extensively about science. For more information, visit https://authorjohnproche.com/.