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A once-healthy area of Roseau cane, a cane that helps build the wetlands, has now died off in a phenomenon being seen in the Mississippi Delta. Researchers are trying to identify the causes and find a solution.

Wild-growing cane that holds together the soil of Mississippi River Delta marshlands through its dense, underground growth — stopping saltwater intrusion and keeping the river's distributary channels clear at the Gulf — is dying off at the mouth of the river.

Researchers say the plant, known as roseau cane, is being attacked on multiple fronts, from an insect infestation to other possible stressors, such as high river levels, plant diseases, toxins in the sediment and variations in soil nutrients.

Rodrigo Diaz, an entomologist with the LSU AgCenter, said the worst cases of the die-off are in Plaquemines Parish, "right at the mouth of the river, and that's where we need it the most." 

One of the factors in the cane's destruction is a species of scale insect that can be found in the thousands on infested stalks.

The insect was discovered by state Wildlife and Fisheries Department staff in late 2016 in the Pass-a-Loutre Wildlife Management Area in Plaquemines Parish, said Vaughan McDonald, a biologist with the department.

"They didn't really know what it was," McDonald said. "They had noticed a gradual die-off of cane."

The sturdy green roseau cane, a type of reed cane represented in Louisiana by four nonnative species, rises 10 feet or more from the water, but more significantly, two-thirds of the plant's mass — thick, stemlike rhizomes — lies below the waterline, unseen but vitally important.  

"It's really the glue that holds the Mississippi Delta together," McDonald said.

Last spring, the state Department of Agriculture and Forestry placed a quarantine on roseau cane in south Louisiana, and it remains in effect.

For the hunting season now underway, the department is asking hunters not to move the cane, popular for building duck blinds, more than one-quarter mile from its original location. 

"Without that roseau cane, we'll have massive coastal erosion," Agriculture Commissioner Mike Strain said. "It's absolutely critical."

Along with the LSU AgCenter, other research partners include the Coastal Protection and Restoration Authority, the U.S. Army Corps of Engineers and the U.S. Fish and Wildlife Service. 

"We're researching what the stressors are and which varieties handle stress better," Diaz said. "From there we want to develop a restoration program." 

Email Ellyn Couvillion at ecouvillion@theadvocate.com.