Roseau cane, a marsh grass that is a critical anchor in Louisiana's eroding coastal marshes and a popular camouflage for duck blinds, is dying off in the southeast corner of the state. 

State wildlife and agriculture officials suspect an invasive, fleshy white insect from Asia, dubbed Roseau cane scale, may be one of the causes and are seeking help from Louisiana outdoorsmen to keep the bug from spreading.

State wildlife officials warned waterfowl hunters and fishermen not to transport Roseau cane or tie their boats to it and to take extra precautions to clean their boats after they fish or hunt.

"These measures will limit the spread of the scale or other vectors that could be the source of the die-off of Roseau cane," state wildlife officials said in a statement last week.

The scale, formally known as Nipponaclerda biwakoensis, is believed to be able to move only short distances on its own without the assistance of people, state agriculture officials said.

Roseau cane is a tall wetland grass that is normally one of the most erosion-resistant marsh plants on Louisiana's coast. The marsh grass thrives in fresh and saline environments and holds up against tropical storms. 

The cane helps protect the Mississippi River's birdfoot delta, an important waterfowl area, and other parts of the coast. The birdfoot delta, which is the tippy-toe of Louisiana's boot and is at the river's mouth, is, in particular, suffering from Roseau cane deaths.

"We're seeing some pretty massive die-offs," said Todd Baker, biologist director with Wildlife and Fisheries.  

The scale was first discovered in Louisiana in 2016. 

LSU Agricultural Center surveys in fall 2017 found strong concentrations of Roseau cane scale in coastal parishes in southeast Louisiana and sparser numbers as far north as East Baton Rouge, Tangipahoa and St. Tammany parishes.

As the cane has died off, the marsh has converted into open water, and invasive species like water hyacinth and giant salvinia have moved in. Ian Knight, an AgCenter post-doctoral researcher who is among those doing the scale field surveys, said they are seeing the cane shift from healthy, dense walls of grass to more scattered clumps of cane that researchers can easily walk to for sampling to more open water areas.

LSU AgCenter scientists like McKnight have started experiments to see if the Roseau cane scale is, in fact, the direct cause of the die-offs, one of several causes or only correlated somehow, he said. Some of those scientists are looking at other possible factors, such as soil chemistry and plant pathogens.

But on March 26, Mike Strain, state agriculture and forestry commissioner, declared an emergency quarantine for the insect, which is also known as Phragmites scale or Roseau cane mealy bug.

The quarantine, which asserts the scale destroys the cane, means Roseau cane can't be transplanted or transported in most cases. Strain renewed the order July 23 for another 120 days while state officials follow the rule-making process for a more permanent quarantine.

The quarantine extends across 26 parishes and parts of 10 others, encompassing all areas south of La. 10, from the Mississippi-Louisiana line west until U.S. 171 in Vernon Parish. The quarantine line then moves south to U.S. 190 in DeRidder until reaching the Sabine River and Texas-Louisiana state line.

In addition to the transportation limits under quarantine, state wildlife officials said hunters and fishermen should remove all Roseau cane debris from boats before they leave the marina and wash and drain boats near the marina with soapy water.

Trey Iles, spokesman for the state Department of Wildlife and Fisheries, said many duck hunters like to use Roseau cane to camouflage their blinds. The small disguised hideouts are where hunters wait for ducks and other waterfowl to land on the water and, in the meantime, often pass the time with their friends and family.

Strain's order does have an exception for waterfowl hunters, allowing them to move Roseau cane, by boat only, no more than a quarter mile from its original location. The rule is designed to keep cane within areas that already have scale and keep potentially infested cane off the highways.   

Baker, the Wildlife and Fisheries biologist, said most hunters he has heard from say they prefer Roseau cane for their blinds but tell him the quarter-mile rule means they will have enough cane to gather for their blinds.

Hunting season for teal and a few other varieties of migratory waterfowl starts Sept. 15.

Beyond the feared impacts to the marsh, Baker said, another worry is that the scale could jump to agricultural crops, like rice and sugar cane.

In 2017, sampling showed the southwestern part of the state was free of the scale. A round of surveys this year, Knight said, found no new sites with Roseau cane scale compared with last year's survey.

At the same time, the concentrations of Roseau cane scale in the Mississippi River delta, where scale had already been found, were much higher this year than at this time last year.

"What that means for plant health, we don't know, but it's not a promising sign," Knight said. "But, again, it's hard to say. We don't know whether — are the scales doing really well because the plants are doing really poorly or are the plants doing really poorly because the scales are doing really well."

Knight said the answer is a complicated question that will take a lot of time and data to figure out.

Follow David J. Mitchell on Twitter, @NewsieDave.