WASHINGTON — The sudden and mysterious death of whole tracts of a marsh grass along the Louisiana coast have raised alarm among scientists and prompted fears of speeding erosion of the state's already shrinking coast.

Now federal scientists, armed with $500,000 in new research money set aside by Congress last week, will join state researchers in trying to understand what's decimating the Roseau cane and fight off the prime suspect, a small invasive insect known as the Phragmites scale or Roseau cane mealy bug that is believed to have arrived in Louisiana from Asia sometime in the last several years.

The federal research funding, slipped into the $1.3 trillion federal budget package by Louisiana's congressional delegation, will roughly double the amount of cash set aside to address the devastation of the Roseau cane.

The new funding for the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS) to battle back against the scale infestation comes amid growing concern about the impact the bug could have on the state's troubled coast — and whether it could spread to commercially grown grasses like sugarcane, sorghum and rice that play a major role in Louisiana's agricultural economy.

"This federal (funding) really adds some stability," said Hampton Grunewald, director of governmental affairs for the LSU AgCenter, which has led research on the Roseau cane die-off. "It allows us to really expedite the research that we’re currently doing."

It wasn't exactly clear Wednesday how APHIS plans to deploy the newly allocated funding, which Congress signed off on last Thursday. A spokesperson for the agency didn't respond to questions about its plans.

Some debate remains over whether the scale is solely — or even primarily — responsible for the rapid death of huge tracts of Roseau cane. But scientists say the scale appears to play at least a role in killing the cane.

"Everywhere there is die-off, scale has been detected, but there are areas where there is scale where the cane has not died," said Grunewald. "Is that because it’s early stage or is it not the full factor that’s causing the die-off? We don’t know, but we know the scale is having an impact."

"Certainly this scale bug is the most likely suspect," said Andy Nyman, a wetlands wildlife professor at LSU, in a phone interview Wednesday afternoon as he drove back from marshlands in Cameron Parish.

There's no evidence yet that the scale — or whatever else may be ailing the Roseau cane — has spread to other plants. But scientists and state officials are worried that the die-off might start hitting key agricultural commodities and not just Roseau cane.

Louisiana Agricultural Commissioner Mike Strain declared an emergency quarantine over much of south Louisiana on Tuesday in an attempt to control the spread of the scale.

The quarantine, which Strain said was necessary in part to prevent the scale from potentially eating away at crops, imposes strict limits on movement of marsh grasses in part or all of 36 parishes affected by the order.

The AgCenter and state agencies — including the Department of Wildlife and Fisheries and the Coastal Protection and Restoration Authority — have together put up more than $500,000 to fund further studies and responses to the Roseau cane die-off. The AgCenter is also trying to pull together another $150,000 from parish governments along the coast, Grunewald said.

Efforts to control the scale's spread have faced limitations. Burning the marshes to kill off the bugs, one way the bug is controlled in China, could cause its own problems because of the thick web of oil wells and pipelines across the coast.

Some researchers have considered introducing a specific Asian species of wasp that feeds on the scale, but bringing in another invasive species carries its own potential complications. Spraying insecticides, meanwhile, risks further damage to an already fragile ecosystem.

Nyman, the LSU professor, said it's possible that other species of marsh grass more resistant to what's killing Roseau cane could be planted along the coast to take its place.

The rapid death of Roseau cane along the coast raises a number of pressing concerns. The deep-rooted grasses, which grow in freshwater and brackish marshes, play a key roll in holding down soil and preventing or slowing erosion.

The state's coast is already shrinking and the death of Roseau cane could speed the rate at which the state's shoreline disappears into the Gulf of Mexico.

Nowhere is Roseau cane more prevalent or important to prevent erosion than along freshwater navigation channels, said Nyman. Along the Mississippi River's bird's foot delta — the slender shoot of land where the river juts out into the Gulf — Roseau cane makes up a large portion of the vegetation.

If the cane were to die off there, Nyman said, the navigation channel might silt in rapidly or erode, potentially causing massive economic damage to the shipping traffic that heads up and down the river.

"It’s not just a Louisiana issue," Grunewald said. "This could impact the entire Mississippi River watershed if (ships) can’t get out of the mouth of the river."

Follow Bryn Stole on Twitter, @BrynStole.