Attack of the Killer Weed

Can a hardy little moth stop the fern that wants to eat the Everglades?

Melvin, an easygoing woman with short blond hair and a deep tan, aims the boat to a nearby large tree island that became host in February to a colony of Australian moths called Austromusotima camptonozal, the first bioagent released in the battle against climbing fern. She steps off into the sawgrass ridge and follows a narrow clearing up to the tree line. "This might be an alligator trail," she warns. "Other times of the year, we could probably walk this, but they probably have a nest at the end of that trail. The females will definitely defend the nest, so I try to stay out of their way."

But the killer weed is as much a threat to that nesting alligator as to native plant life, Melvin notes.

Tree islands are as essential to Everglades fauna as a shoreline is to sandpipers and clams. Minute elevations in sea level in the Everglades -- often from small limestone plateaus -- give shrubs and trees a chance to take root where the water would otherwise be too deep. Over time, the roots and falling leaves build up and increase the elevation, so that the larger islands stay fairly dry even during the wet season. Deer, raccoons, panthers, and, of course, those nesting gators make the shady underbrush their home. Birds nest in the treetops and dine on the seeds and berries.

Ted Center and other plant researchers at the Invasive Plant Research Laboratory in Davie keep a close eye on damage done by imported herbivores, like these fern-eating larvae (following picture).
Stephen Ausmus
Ted Center and other plant researchers at the Invasive Plant Research Laboratory in Davie keep a close eye on damage done by imported herbivores, like these fern-eating larvae (following picture).
Jason D. Stanley

It's no exaggeration to say that without tree islands, the Everglades ecosystem would collapse. "Anything that needs dry ground relies on the tree islands," Melvin says standing in the blazing sun.

Old World fern wipes out tree islands.

It's hard to see it at this water level, but the tree canopy on this island, like many in the preserve, has collapsed under the immense weight of the climbing fern. "It's like this big donut, and then from there it grows out and over the trees on the outside," she says. "It becomes a huge mound of Lygodium." Indeed, aerial photos of these islands look like pro football arenas covered in green: the middle is flattened to the ground, then sweeps sharply upward at the edges.

State and federal agencies are already spending millions of dollars a year on herbicides and machete campaigns in a tough, slogging war against Old World fern. At best, the eradication campaign is slowing the weed's expansion.

But scientists are pinning their long-range hopes on the doughty little Australian moth that can't get enough of the insidious fern.

State naturalists had traveled to Japan, Southeast Asia, and Australia, finding more than 18 species of herbivores that dine on Lygodium. They spent $1 million and seven years looking for, testing, and permitting this first, single moth in order to release it in South Florida. The bright-white, wispy creature is a mere half inch wide from wingtip to wingtip and decorated with wavy brown streaks. Its adult life is short -- three to five days -- but the species' prolific females can lay 100 eggs at a time.

The moth's reign of terror against Lygodium, however, comes during its early life as a caterpillar whose hearty appetite strips the leaves into skeletons. Eating Lygodium exclusively, they can kill small plants and seriously damage the larger ones. If future testing goes well, they'll be joined by a mite, which also eats leaves and promotes plant disease, and another fern-hungry moth.


If alien plants such as Old World fern are barbarians at the gate, then the Invasive Plant Research Laboratory is among the best lines of defense in this long, weedy war. Tucked amid a plethora of college and technical school campuses to the southwest of Davie Road and I-595, the new quarantine lab is dedicated to finding the right bugs and diseases to maim and kill the worst invaders.

The man in charge is Ted Center, who wears a short, grayish, groomed beard and speaks in the slow, deliberate cadence of a man who's used to explaining the complex to the unlearned. The research leader's eyes are world-weary -- or perhaps it's just the fatigue of the ongoing move into the new digs.

"There are very few facilities of this quality in the world," he boasts of the lab, which is owned by the U.S. Department of Agriculture, his employer, but sits on University of Florida property. He should know: "I went all over the world to look at every quarantine facility to see what went right, what went wrong."

The lab isn't under full quarantine yet but should be fully operating by midsummer. It's like a set from the Andromeda Strain -- except the airtight isolation zone is for foreign bugs instead of an interstellar virus. The entrance is a series of antechambers with magnetic doors that don't allow passage until all others are sealed. Insects imported to the lab are kept in a receiving room until they've produced offspring, which are then transferred inside. The original bugs, as well as any original packaging, are then destroyed. The air in the lab is filtered heavily enough to prevent any insects or spores from escaping. All liquids drain into a heated sump that destroys anything living.

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