Coast News

Roseau Cane Mealy Bug Cuts a Destructive Path through Louisiana Marshes

A small insect, or scale, known as the Roseau Cane Mealy Bug has decimated thousands of acres of Roseau cane in southern Plaquemines Parish and continues unabated, according to biologists with the Louisiana Department of Wildlife and Fisheries and LSU AgCenter.

The scale, native from China and Japan, has been identified as Nipponaclerda biwakoensis, commonly referred to as Phragmites Scale or Roseau Cane Mealy Bug. It has had severe effects on the dominant vegetation of the Mississippi River Delta. The rate at which it seems to be expanding and the severity of its impacts is alarming.

Roseau cane is a tall wetland grass that helps protect Louisiana’s bird foot delta. The severely impacted cane appears to be brown and mostly leafless, in contrast to the 10-foot tall robust leafy green cane normally seen this time of the year.

More than 100,000 acres of Roseau cane dominated wetlands in the Mississippi River Bird Foot Delta has been affected by the scale as biologists continue to look for ways to stop its spread.

“We could be witnessing a major habitat change on the Mississippi River Delta in the next year or so because of this,’’ said LDWF Secretary Jack Montoucet. “It could be devastating. We don’t really have an answer yet or the solution. But it’s clear that everyone needs to understand this could be a catastrophic problem and we need to put this on the front burner.’’

Todd Baker, Director in LDWF’s Coastal and Nongame Resources staff, said the scale was discovered only last fall and has advanced quickly. It has been spotted in Grand Isle and in other parts of Jefferson Parish.

“Roseau cane is one of the most robust and hardiest plants that I’ve come across,’’ Baker said. “It can live in three feet of water. It can be inundated for long periods of time. It can live out of water. It can tolerate 20 parts per thousand salinity. It can tolerate fresh water. You can burn it, you can spray it and it keeps coming back. The fact that this bug can damage it to the point that it has is amazing and disturbing.’’

Unlike some marsh vegetation, Roseau cane stands up well to tropical storm events. It is one of the most erosion-resistant marsh plants on the bird foot delta. It also assists in building land by trapping sediment from the Mississippi River. The loss of it could lead to even more rapid land loss in the delta, turning what is now marsh into open water.

What also concerns biologists is that the scale could impact agriculture crops such as sugar cane and sorghum, according to Dr. Rodrigo Diaz, Assistant Professor in LSU’s Department of Entomology. He said it could have significant economic impacts to agriculture crops and native vegetation.

“Roseau cane is a grass,’’ Baker said. “What is known is that where this scale is native (Asia) it gets into other grasses and reeds. It may attack other plants in the United States. Now that it is present in Louisiana, we don’t know what it may impact. It’s a threat but we simply don’t know if it will move into other vegetative species or not.’’

The Louisiana Department of Wildlife and Fisheries is charged with managing and protecting Louisiana’s abundant natural resources. For more information, click here.

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