Tiny Asian bug destroying La. marsh cane at alarming rate
DELTA NATIONAL WILDLIFE REFUGE -- A tiny insect, barely visible to the naked eye, is killing marsh cane at an alarming rate and threatening to undo nearly a decade of coastal restoration and land-building in the delicate Mississippi River delta.
The Roseau cane mealy bug, also known as a Phragmites scale, was first discovered on some of the marsh reeds of Plaquemines Parish last summer. It was the first time the parasite native to Japan and China had ever made it into the United States.
Scientists began tracking the bug’s destructive effects in March and are shocked by how quickly it’s spreading – not only eating away at the cane reeds where it was first reported last Fall, in the iconic bird’s foot delta at the mouth of the Mississippi, but now appearing in marshes as far west as Lafourche Parish and as far north as Lafitte in Jefferson Parish.
Between March and May, the bug laid waste to 5.5 miles of Roseau cane that form the banks of South Pass. That’s led to fears that a principal navigation channel could be lost if officials can’t come up with a plan to protect the Roseau cane.
The infestation is spreading so quickly that scientists from Louisiana State University, the Louisiana Department of Wildlife and Fisheries and several federal agencies can’t get a handle on how much land has been lost or how to combat the mealy bug, but they believe 100,000 acres of marsh could be endangered by it.
Like a cancer
“It’s almost like a cancer; it keeps spreading, spreading, spreading,” said WWL-TV outdoors expert Don Dubuc. “I hope they got a sense of urgency, because by the time the two years goes by and they get a program to attack it, the patient may be dead.”
The sudden die-off is all the more shocking because it’s affecting Roseau cane, the most resilient vegetation of coastal Louisiana, biologists say. And it comes just as they were celebrating the discovery of a new Roseau cane varietal they are calling Tiger cane, named for its LSU-themed purple and gold flowers.
Acres of Tiger cane have built up in recent years along Main Pass, especially in spots where the state has dredged strategic crevasses in the river banks to funnel land-building river sediment into areas where the marsh had previously been lost.
The new marshland is considered a critical barrier against the kind of storm surge that inundated hundreds of square miles in Hurricane Katrina in 2005 and Hurricane Gustav in 2008.
And the U.S. Geological Survey is about to release its first official report on coastal erosion in Louisiana since 2011 – a report that USGS Branch Chief Tomma Barnes said will show that Louisiana’s land-loss rate has slowed significantly since 2008.
Now, Barnes said she’s concerned that the mealy bug could reverse the trend in key sections of the delta.
“This could play a major role in land-loss in coastal Louisiana,” Barnes said.
The USGS is working with state agencies to map the spread of the bug from now on, so they can come up with the best ways to contain it.
“They are going to map every two months,” she said. “I think we’re going to see some significant changes until we can get ahead of this.”
Rodrigo Diaz, an entomology professor at LSU, has been studying the biology and ecology of the bugs. His team of scientists needs more funding to create and implement a proper management plan, he said.
Earlier this month, on the last day of the State Legislature’s regular session, Rep. Chris Leopold of Plaquemines Parish took to the House floor with an infested stalk of Roseau cane, hoping his colleagues would understand the gravity of the threat.
Diaz has conferred with scientists in China who burned the infested cane they found, but that was on land, not the less flammable watery environs of Louisiana’s Roseau cane. Plus, the Chinese didn’t have to worry about blowing up any oil and gas wells like the ones that sit among much of Louisiana’s coastal marshes.
There is hope that another invasive species, a microscopic wasp, could help. It is a natural predator of the mealy bug, but it’s not been able to attack the cane-eaters quickly enough. The scientists are also considering insecticides, but haven’t determined the best way to deploy them.
It takes only one or two bugs in the young crawler stage, latching on and sucking the sap out of a 6-foot stalk of Roseau cane, to kill it. But the evidence of the invasion isn’t obvious until whole bunches of the cane turn brown and collapse. Some stalks were infected by more than 700 of the scales before they were collected for study, Diaz said.
What’s more, Diaz worries the bug could spread to area agricultural crops, such as sugar cane and sorghum. State Wildlife and Fisheries agents have already begun an educational campaign to warn hunters and fishermen to clean their boats and not carry any of the cane out of the area, where it might infect other grasses.
Roseau cane is a popular material for hunters to make duck blinds, Dubuc said.
That could explain why an invasive species that was stopped by U.S. customs officials at ports in Hawaii and California in the 1960s and never made it onto U.S. soil before, has suddenly spread so quickly across the Louisiana wetlands.
But scientists acknowledge they have no idea how it suddenly arrived in South Louisiana. Diaz said a combination of factors could have made the Roseau cane more susceptible to infestation now, including climate change, subsidence and even possible lingering impact of the BP oil spill, which lapped up on shore in the summer of 2010 at many of the same marsh areas now ravaged by the scale.
On a boat tour of infected marsh in the Delta National Wildlife Refuge last week, state Wildlife and Fisheries biologist Todd Baker showed aerial photographs from January 2015 of two circular islands lush with Roseau cane. Even though it was the middle of winter and the cane was gray, it was densely packed over the whole area of the islands.
Then he led a group on airboats to those very same islands. Now infested with the cane bugs, much of the center of those islands has been converted into open water. Dead cane stalks, blackened in their watery grave, churn to the surface as the boats pass by. Leafy elephant ear and flimsy water hyacinth have grown in the cane’s place, but those floating plants offer nothing like the sediment-stabilizing, deep root structure of Roseau cane.
“We work so hard in coastal Louisiana to preserve our wetlands,” Baker said, holding an infested stalk while standing in front of a stand of dying Roseau cane. “We have enough challenges already and to have a new invasive species come in and jeopardize that even further is just a tremendous setback. It’s a huge disappointment for us.”