Project: Eradicate Old world climbing fern

By JEANNE MALMGREN

© St. Petersburg Times, published September 26, 1999

Old World climbing fern lives up to its name by smothering tall trees, such as this cypress stand. [Photo courtesy of South Florida Water Management District]

COLLIER COUNTY -- Jim Goodwin lets the swamp buggy roll to a stop on a steamy September morning and turns off the engine. He looks around at the tea-brown water beneath and the green walls rising on all sides.

"This is the mother lode," he says. Then he corrects himself: "Was the mother lode."

He squints toward the tops of tall cypress trees, where brown clumps of foliage hang like scraps of beard: Lygodium microphyllum, otherwise known as Old World climbing fern, perhaps the most alarming new pest plant threat in Florida.

Three years ago, land managers from South Florida Water Management District found the aggressive fern climbing cypress trees in this pristine wetlands adjacent to the Corkscrew Audubon Sanctuary, near Naples. Until then, isolated patches of lygodium had been found around South Florida, but the sheer size of this infestation -- 100 acres -- alarmed the managers.

Lygodium leaves are small and delicate. Their spores, seen here, can travel by wind for hundreds of miles, helping the plant spread to remote areas. [Photo courtesy of South Florida Water Management District]

Back in January a helicopter swooped low over the swamp and sprayed a potent cocktail of Rodeo, one of a handful of herbicides legal to use around water. A month later, the unwelcome fern was dead, much to scientists' delight.

"This was the first aerial spraying of lygodium, so we wanted to do it right," Goodwin says. "Everybody was a little apprehensive."

Goodwin is a land manager for South Florida Water Management District, which coordinated the spraying, along with officials from the University of Florida's Center for Invasive Plants. Goodwin revisits the site of the spraying every quarter, and so far, he has been pleased with the results. Cypress and maple trees, which were bare of leaves when the herbicide was sprayed, remain healthy. The lygodium has not resprouted.

Mission: Kill the creeps Florida is crawling with non-indigenous pest plants -- one step behind Hawaii. Most of us are blissfully unaware of the invasion, and how much it costs to combat it. Project: Biocontrol research Gary Buckingham's job is to be careful. Project: Eradicate Burma reed Burma reed is "public enemy No. 1 in Miami-Dade County," says Roger Hammer, a botanist with Natural Areas Management, a division of the county's park and recreation department. Say goodbye to these 11 plants The Florida Nurserymen and Growers Association has asked nursery owners to stop selling these plant species.

"It looks like we're not going to have to re-treat," he says.

No one is sure how or when Old World climbing fern made its way into Florida, according to Ken Langeland, an agronomist at the University of Florida and co-editor of the newly published Identification & Biology of Non-Native Plants in Florida's Natural Areas.

The plant is native to tropical Africa, India, Malaysia and Australia. Veterans of the war on pest plants are nervous about its potential, says Langeland.

"People who have been in invasive plant control for years, who have dealt with melaleuca, Australian pine, Brazilian pepper, they're looking at this baby and saying, "Man, we haven't seen nuthin' yet!' "

Twice this year, land managers from all over Florida met to discuss an emergency action plan for controlling lygodium, just as they did in the early 1990s for melaleuca. Old World climbing fern is now listed on the State Noxious Weed List, which makes it illegal to transport or plant. Scientists are petitioning the USDA to place it on the federal list.

Like all ferns, lygodium reproduces when its tiny spores are carried by wind, sometimes great distances.

"We find this thing 100 miles from nowhere," Langeland says.

Botanist Tony Pernas used to work in the Big Cypress National Preserve, where he dealt with scattered infestations of lygodium, including some on land owned by the Seminole Indians.

In late August, after starting a new job at Everglades National Park, Pernas took a helicopter ride to survey his new domain. He looked down into the vastness of the Everglades and there it was: Old World climbing fern, in a patch he estimated to be 3 to 5 acres.

"It's 17 miles from the nearest road," Pernas says, with a sigh. "It's going to be really hard to get to."

Lygodium also was found this summer at three sites in Hillsborough County, one near Riverview and the other two along the Little Manatee River.

The fern is fond of climbing trees, but also clambers along the ground, creating a thick, spongy mat called rachis that can be as deep as 4 feet, choking water movement in the soil beneath.

"It's like a trampoline," says Goodwin, the South Florida Water Management official. "You can jump up and down on it."

Lygodium carries flames high into the tops of trees that normally could survive ground fires. [Photo courtesy of South Florida Water Management District]

In cypress tree islands, lygodium acts as flame "ladders," bringing wildfire up into the tops of cypress trees that normally could withstand a ground fire. During intense fires, pieces of the fern break off and float away like kites, spreading flames further.

Mostly what lygodium does is smother whatever it climbs on, looking and acting like a tiny-leaved version of kudzu, the so-called "mile-a-minute" vine that blankets several Southeastern states.

Last year, when filmmakers needed a jungly backdrop for a Chevy Tahoe commercial, they used a site in Palm Beach County where lygodium had taken over a stand of cypress along the Loxahatchee River.

"It looked like a scene out of a science fiction movie," Goodwin says.

The site was treated with herbicide after the commercial was filmed.

In addition to chemical control, researchers are looking into biological controls for lygodium, but it may be years before they're ready to release a bug with an appetite for climbing fern.

"We're still very much in the discovery phase, trying to see what's out there," says Bob Pemberton, a USDA research entomologist at the Agricultural Research Service's Invasive Species Research Laboratory in Fort Lauderdale.

Pemberton traveled to west Africa, Hong Kong and Taiwan in search of lygodium-loving insects. The Africa trip yielded nothing, but he's hopeful about a pyralid moth found in Hong Kong that "is quite damaging to the plant."

Testing has begun with that insect at the USDA lab in Brisbane. Pemberton and his colleagues also are interested in a sawfly they found in Thailand and Vietnam. Its blue-green larva has a healthy appetite for lygodium.

Next June Pemberton will visit South America in search of insects that eat plants closely related to Old World climbing fern.

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