The newest weapons in Florida’s long and mostly losing war against exotic plants seemed in no real rush to enter the fray on Friday, clinging to their plastic containers, the hands of young students and the shirt of entomologist Ted Center.
“They’re very hardy. You can handle them,” instructed Center, pinching a bug just a little bigger than a grain of rice between his fingers and then reaching out to let it fly off into the lush forest surrounding Long Key Natural Area in Davie.
It promptly dropped straight down into the dirt.
No worries. It was just a natural defense reaction of the air potato leaf beetle, the latest pest-fighting “bio-control agent’’ unleashed by researchers from the U.S. Department of Agriculture’s Invasive Plant Research Laboratory in Fort Lauderdale. The beetle, formally known as Lilioceris cheni, soon flittered away with some 200 others in search of air potato, a vine that may sound like a diet food product but ranks among the state’s most damaging, difficult-to-control pest plants.
Judging by the results of earlier test releases across South Florida, the beetle may offer the first real hope of knocking back the notoriously resilient air potato, which can climb 60 feet and smother everything from wild coffee bushes to live oak trees in a dense, strangling cloak. The air potato, an inedible variety of yam originally from Asia, spreads by dropping gnarled potato-like growths called bulbils that can grow up to two-pound-plus, Idaho-baking size.
Though not as well-known as the melaleuca or Brazilian pepper, it’s equally problematic and found across the state and Gulf Coast. It is particularly dense in South Florida, where air potato has overtaken tropical hammocks in parks and wild areas.
In Miami-Dade County, for instance, air potato has infested just over half the 90 sites maintained by the county, said natural areas manager Joe Maguire. Fighting it is a frustrating, expensive exercise that can run more than $8,000 an acre. Periodic clean-up efforts by volunteer “spud-busters,” followed by herbicide treatments, barely hold ground. “You think you’ve done a great job and you come out the next March or April and it’s all back again,” he said.
Like many exotic pests, the air potato was brought to Florida as an ornamental plant around 1905. Its rapid growth and heart-shaped leaves made it attractive.
Pat Howell, a Broward County natural area specialist at Tree Tops Park, said homeowners didn’t initially realize how damaging they were — and some still don’t.
“They liked how they twined around mailboxes,’’ she said, but “they’ll twine your whole house if you don’t do something.’’
After more than a century, with no Florida native insects to keep it in check, the air potato has run amuck. Its vines turn brown and brittle every winter. But by spring, millions of ticking spud bombs lurking in the soil explode in a new, thicker tangle crowding out and even killing native plants. The vines, Center said, grow at an astounding rate of up to 10 inches a day.
Scientists at the USDA’s Agriculture Research Service in Fort Lauderdale went back to the air potato’s native lands in China to seek a potential “bio-control’’ — an insect that targets only a single host plant.