The lobate lac scale, native to Sri Lanka and India (Varshney 1976), was first detected in Davie, Broward County Florida in August 1999 and then in Miami Dade during March 2000 (Hamon 2001). By the spring of 2002, the insect began to appear in alarming densities on many different host plants in Broward County. To obtain an idea of the current and potential infestation of this scale on plants in South Florida, a “snap-shot” sample was made in a single Ft. Lauderdale residential yard known to be infested with the scale during July, 2002. Although modest in terms of area examined and duration of study, this sample offers a compelling picture of the scale’s extreme polyphagy and may provide indications of relative susceptibility of different plants and plant groups.
The 1/3 acre yard examined was selected because of its diverse plantings of tropical fruit, native plants, and horticultural plants including important landscape trees and shrubs. It was also chosen because of the absence of pesticide use which might influence infestation, although county mosquito control fogging trucks operate periodically within 30 meters of the property, particularly during the summer. A total of 67 woody plant species in 30 plant families were examined for presence of the scale. A total of 83 individual plants were examined and seven species were sampled more than once. Plants sampled were at least one meter tall and present in the yard for at least one year. Each plant was scanned for about 30 seconds, except for orange and tangelo, which were examined for about five minutes because of their economic importance. If the scale was found, estimates of infestation were made by judging the number of morphologically distinct mature females in 30 cm length of branch as follows. Heavy infestations had more than 100 scales per 30 cm, moderate infestations had between 10 and 100, and light infestations had fewer than 10.
The scale was found in 37/67 (55%) of the plant species in 19/30 (63.3%) of the plant families (Table 1). Of the attacked species, 16% (6/37) had plants rated as heavily infested, 40% (15/37) had moderately infested plants, and 62% (23/37) had lightly infested plants. Of the 83 individual plants examined, 46 or 55% were infested. The most severely impacted plant was the native wax myrtle (Myrica cerifera L.); three of the five plants examined had been killed and the other two were dying. The scale completely covered branches of these plants. Other heavily infested species included native wild coffee (Psychotria nervosa Sw.), ornamental Michelia sp. and common hibiscus, and the fruit tree carambola (Averrhoa carambola L.). All of these exhibited branch dieback. Large landscape trees, such as native laurel oak and exotic black olive, bore moderate infestations. All four mango varieties (Carrie, Jakarta, Dot and Valencia Pride) were infested and three had moderate infestations. Grapefruit and kumquat had light levels of the scale, while sweet orange and tangelo were free of the insect. Emperor lychee was attacked but Brewster lychee was not. The three annonacious fruits, sugar apple, sour sop and atemoya were all attacked. One species, wild coffee, experienced the full range of infestation levels from absence to heavy. Attacked species belong to a diverse spectrum of unrelated families from the primitive Magnoliaceae and Lauraceae to the advanced Rubiaceae. Of the 17 families with more than one species in the sample, four had all species attacked, four had none attacked, and nine had both attacked and unattacked species. Seven of eight Myrtaceae and three of four Rubiaceae were infested by the scale. Three of the seven Rutaceae present were infested. Three of seven genera with multiple species had both attacked and unattacked species, while plants in the other four genera were either all attacked or unattacked.
Because it is unknown how long the scale has been at this site, infestation and level of infestation on particular plant species may reflect the state of invasion and degree of population growth. Uninfested and lightly infested plants may reflect preference of the scale for other plants, rather than absence of susceptibility. For this reason, presence of the scale in the sample is more important than its absence. What is clear is that the scale attacked the majority of species and families represented in the yard as well as the majority of individual plants examined. It also used a wide variety of plant types including native species, commercial fruit, and important landscape trees and shrubs. Paratacharina lobata lobata is becoming a serious pest, due to rapid rate of spread, wide host range, and severe impacts to plants such as branch dieback and death of some hosts.
Research is urgently needed to determine how to control the lobate lac scale and how, if possible, to limit its spread. Control research should include both chemical and biological control. Infestation of native plants indicates the scale’s ability to invade natural areas where chemical control may be difficult, cost prohibitive or inappropriate because of potential harm to non-target organisms. Indeed, preliminary examination of several preserves, such as Secret Woods Nature Center in Broward County, indicates a serious level of infestation of native species (Howard, unpublished data; Pemberton, unpublished data). During October and November 2002, the lobate lac scale was discovered in Everglades National Park, Big Cypress National Wildlife Refuge and Loxahatchee National Wildlife Refuge (Pemberton, unpublished data). For additional information on this important pest, including known host plants as of October 2002, see the recently posted Featured Creatures website (Howard et al. 2002). Biological control may offer a long term solution (Pemberton 2003).
Forest W. Howard, University of Florida, Ft. Lauderdale, and Douglas Miller, USDA-ARS Systematic Entomology Laboratory, Beltsville, MD, kindly reviewed the manuscript and contributed to its improvement.
A recent insect invader in South Florida, the lobate lac scale (Paratachardina lobata lobata) attacked 55% (37/67) of the plant species in 63% (19/30) families at a sampled site. Many important plants in southern Florida were attacked including: tropical fruits (grapefruit, mango, lychee and sugar apple), native plants (wild coffee, laurel oak and wax myrtle), and important landscape trees and shrubs (black olive, hibiscus, Surinam cherry, and gardenia). Some plants such as wax myrtle are killed by the scale. Research to develop control methods is urgently needed.