Invasive Aphids are Destroying the Best Redfish Marshes on the Planet
April 17, 2017
A mysterious agricultural pest is laying waste to the coastline of Louisiana, and the potential consequences are dire. The plague has only been on the radar of researchers and environmental science experts for the last few months, and they don't even have the organism responsible fully identified at this point.
In the meantime, large sections of coastal marshland grasses that are crucial habitat for species of juvenile fish that spawn in the brackish backwaters have been decimated over the winter of 2016/17, along with the anchoring root systems of the plants that keep the Delta marshlands from washing away.
Roseau cane is an incredibly hardy coastal tall grass that has more in common with bamboo than Kentucky bluegrass. It is pervasive on the Gulf coast from Texas to Florida, and there is some debate as to whether the majority of it is an indigenous specie, or was been introduced from Europe long ago. In either case, ecologists recognize that it provides the fundamental basis for the biology of brackish water wetlands, providing soil retention during both saltwater storm tides and rain floods off the mainland, water purification through uptake via dense mats of root tubules, and shelter for the fingerlings of species such as redfish and speckled trout.
Outfitter Eric Newman (Journey South Outfitters) helped publicize the problem when he brought reporter Tristan Baurick into the marsh to see the problem firsthand.
According to NOLA.com / Times Picayune, "Roseau cane, a wetland grass considered vital to the health of Louisiana's precarious coast, is dying at an unprecedented rate in south Plaquemines Parish. Since fall, thousands of acres of cane across about 50 miles of the lower Mississippi Delta have gone from green to brown. Many areas, such as the one Newman found Friday (April 7) near Venice, are now shallow, open water."
"The likely cause: a foreign bug that's sucking the life-giving juices out of the cane. State and university scientists have been trying for weeks to identify the species, thought to be a type of scale or mealybug. As yet there is no plan to eradicate it."
Scale insects include aphids, and are a well-known agricultural problem. The insects form tough protective cases while burrowing into surfaces on host vegetation, consuming and disturbing the flow of nutrients in the plants, which invariably die. While the exact identification of the insect responsible is still in play, there is consensus that it is almost certainly an invasive species, probably brought in by boat from another continent through the port of New Orleans. Strategies for control of the pests range from burning of vegetation, application of industrial insecticides, or introduction of predatory insects such as ladybugs that eat aphids are all on the table.
NOLA.com coverage continued. "At the Pass a Loutre Wildlife Management Area on the far south end of the delta, the cane die-off is especially bad. "Of the the 110,000 acres we have there, [the insect] has affected easily 80 percent," said Vaughan McDonald, a coastal biologist with the state Department of Wildlife and Fisheries."
"State officials have kept relatively quiet about the pest invasion as they try to come up with solutions. But the damage — and the wider implications — are becoming hard to ignore. The delta has one of the world's largest stands of roseau cane. The cane is, quite literally, what holds the delta together. Its disappearance could hasten the erosion that's fast turning land into water."
"Where this is happening, in the delta of the Mississippi, is one of the largest continuous stands of [roseau cane] in the United States," said Irving Mendelssohn, professor emeritus of Louisiana State University's College of the Coast and Environment. "You'd have to go to central Europe and the Danube River to see such an extensive stand."
I spoke to veteran charter operator and fly fishing guide Eric Newman by phone. Newman was one of the first people to notice the profound changes that were happening so rapidly in Plaquemines Parish, having not only grown up in the area, but intimately working in the environment on a daily basis. "This is about more than just my job or the fishing industry. It's potentially something that is going to change the way of life here, both now and for future generations. This thing needs to be responded to at a policy level -- now."
Newman first raised the alarm early this spring with both the press and the researchers at state universities, who were at the time completely unaware of the issue, but have mounted immediate response. In the meantime, Newman has moved up the ladder to engage one of the most influential political groups in the Gulf, the Coastal Conservation Association, which has massive influence both in the Gulf and in Washington, DC.
New and unforeseen changes in the ecology and environment appear to be rapidly unfolding on the Gulf Coast that now look to require an all hands on deck response. Raising awareness among the sporting community to influence legislative response and support conservation actions is a first step in mitigating this crisis.