Biological control of lobate lac scale

The lobate lac scale is spreading across South Florida and damaging a variety of native and economic trees and shrubs. It congregates in large numbers and cloaks itself and its victims in black sooty mold. No larger than a pinhead, this insect is poised to create big trouble –perhaps the most significant trouble yet for gardens and natural areas in South Florida.

The lobate lac scale is a relatively new insect pest in Florida, but it already has an enormous presence. Native to India and Sri Lanka, it was first found in Broward County in 1999. By 2002, it had spread north to Lake Worth, south to Homestead, and west into the Everglades. Lobate lac scale also occurs in the Bahamas, where a recent survey found that two-thirds of plant species examined were infested.

This invasive pest has been found on over 200 species in Florida. Many important plants are highly susceptible, including rare native species, commercially important species, Everglades tree islands, and tropical hammocks. This widespread choice of hosts is what makes lobate lac scale particularly troubling. Evidence of their sap-sucking destruction includes blackened leaves and branches, branch dieback, and for susceptible species of shrubs and trees, death.

The best known member of the lac scale family (Kerriidae) is the true lac scale of Asia, and while the true lac scale has been used since ancient times to produce shellac, the lobate lac scale has no commercial value. Lobate lac scales are dark brown but often appear dull black due to a covering of sooty mold. Measuring about 1/16 inch across, the adult lobate lac scale is visible to the naked eye, and looks like a tiny, four-lobed bump of bark. These hardshelled adults are usually surrounded by dozens of other such bumps. They are found primarily on thin woody branches less than 1 inch in diameter.

The best long-term solution for controlling the lobate lac scale is using its natural enemies. For the lobate lac scale in India, some natural enemies are tiny non-stinging wasps. These wasps can be obtained from true lac scale or from the lobate lac scale in its native range. The wasps have a very narrow diet, but before these natural enemies can be used in Florida, research must confirm that they eat nothing but the lobate lac scale. Researchers with the USDA Agricultural Research Service, the University of Florida, and the Florida Department of Agriculture and Consumer Services are working with colleagues in Asia to acquire and study these natural enemies.