A swarm of tiny bugs with an enormous appetite has invaded the Louisiana marsh, and is sucking the life out of vegetation that helps keep the state’s fragile coast from further dissolving into the sea.
Scientists and agricultural experts are teaming up to stop the parasites from destroying the critical Roseau cane, but they’re beset by a major problem: They don’t fully know what the bug is, so they don’t exactly know how to attack it, and their early ideas so far — fire, insecticides and possibly the release of a microscopic wasp that preys on the bug — will likely result in nasty side effects.
Louisiana State University entomologist Rodrigo Diaz said researchers only recently discovered the foreign family of insects to which the invasive species belongs, called Aclerdidae, which is native to Japan and China. But the lab tests that identified it couldn’t reveal how it arrived — on a ship, attached to a migrating bird or even on the wind.
What’s certain is that last year a team of surveyors checking the cane, which comes in various shades of green, found stalks bent in water, brown and dead in the mouth of the Mississippi River. That’s when they began to notice significant die-offs of four varieties of cane and more open water in the hundreds of acres the cane once occupied. Two to three years before, there was a thick, unrelenting wall of marsh.
“They are feeding on it,” said J. Andrew Nyman, a professor at the School of Renewable Natural Resources at LSU. “The bugs suck the sap out. The leaves are trying to send sugar to the roots, and they suck out so much that the plant can’t function. It dies.”
Nyman said he picked up a stalk one day, and the bugs covered it. In an online seminar about the invasion, Diaz displayed a graph that said six feet of cane can have nearly 200 insects almost invisible to the naked eye, and 700 in extreme cases. He described them as translucent, extremely small but highly mobile, and moving in dense populations.
The mealy bug, as it’s also known, adds to the many invasive insects that have made their way to the United States from Asia and Europe. Animals that have ruined plants and crops, and even invaded homes, include the brown marmorated stink bug, the kudzu bug, the emerald ash borer, and aphids that are threatening Florida’s citrus industry by destroying orange groves and wreaking havoc on Christmas tree pines from West Virginia to North Carolina along the Appalachian Mountains.
The Louisiana cane is crucial to staving off land loss. It builds soil in an area that lost 250 square miles of coast to erosion and sinking land over about a half century.
Roseau cane also has a checkered history. At least one variety, the European, is itself invasive. The delta Roseau cane from North Africa and the greeny variety from Europe were introduced. Scientists aren’t sure whether a fourth variety, the Gulf Roseau cane, is invasive or introduced. But on a coast beaten down by harsh weather and erosion, even the exotic species turned out to be a godsend for stabilizing the land.
In other areas of Louisiana and other states, they are a nuisance, which is why some people, Diaz said, want to transport the parasite to those areas to destroy the cane. Bad idea, he said. Who knows where the bugs will go after the cane is gone. They could wander to native plants, even farm crops, and develop a taste for those.
But the insects don’t wait for human transport. Even now they hop aboard grackles and red-winged blackbirds that flock into the reedy cane, hoping for a ride to another healthy batch of cane to get a meal and lay eggs. They’re also known to hop into air boats piloted by fishermen. Scientists have pleaded with the owners to wash them down.
Diaz said experts are weighing options to fight the threat. An idea for a controlled burn is derived from China, where blazes are set in marshes to get rid of the swarm. But fire can spread, and the Louisiana coast has a network of oil and gas wells that could explode in flames.
Planting a plague-resistant strain of cane has come up, but no one knows whether such a thing exists. Insecticide is another consideration, but that could get expensive because of the vast area that needs spraying and would require environmental assessments. Another concern is the inadvertent contamination of speckled trout, redfish, shrimp and oysters — not to mention the birds that feed on them.
Maybe the parasite’s natural predator, a tiny wasp from Asia, can be employed. They have been considered as a solution to the stink bug problem as well, but it takes years of study before a new species can be released, for fear that the wasp might turn on native animals and start killing them, too.
Or maybe, just maybe, the insect is its own worst enemy. It might eat itself out of house and home before anything else can be done.
“What you could end up with in 10 years is the bugs will die back,” Nyman said, after killing all the cane. “They’ll become a smaller part of the landscape, both the bug and the plant.”