Genetics Underscore Mites' Promise As Climbing Fern Foe

By Marcia Wood
July 7, 2004

A tiny mite that keeps a troublesome weed, Old World climbing fern, in check in Australia might be ideal for doing that same job in Florida. The plant, known to scientists as Lygodium microphyllum, has become the state's worst invasive weed.

Agricultural Research Service entomologist John A. Goolsby at the Australian Biological Control Laboratory in Indooroopilly, near Brisbane, and colleagues there have found--for the first time--climbing fern plants in Australia that are an exact genetic match of those in Florida. From those ferns, the researchers collected the tan, eight-legged Floracarus perrepae mites.

Not all populations of F. perrepae mites will feed and reproduce on the Florida fern genotype, Goolsby's team discovered.

Now, Goolsby and ARS entomologist Robert W. Pemberton, who leads the agency's climbing fern research, are seeking federal and state permissions to release the mites in fern-infested Florida wetlands. Pemberton is based at the ARS Invasive Plant Research Laboratory in Ft. Lauderdale, Fla.

In recent years, Goolsby, Pemberton and their fellow investigators have combed the globe in search of natural enemies of the fern.

F. perrepae mites feed on and damage the edges of fern leaves, called fronds. That causes the fronds to swell and form tight curls that the mites then use for food and shelter. The damaged frond tissue eventually falls off, reducing the amount of frond surface that's available to capture the light that the fern needs for making its food.

In Florida, Old World climbing fern smothers native plants by forming dense mats along the ground, and by climbing, vine-like, up shrub stems and tree trunks, creating massive walls of flammable, dark-green vegetation.

ARS, the U.S. Department of Agriculture's chief scientific research agency, operates the Indooroopilly lab in cooperation with Australia's Commonwealth Scientific and Industrial Research Organization.

Read more about the research in the current issue of Agricultural Research magazine.