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Roseau cane pest continues to plague Louisiana’s coast with no signs of slowing down

June 22, 2017 12:00 AM

(Article orignally published at lacamo.org on June 21, 2017)

It’s no secret that Louisiana’s coast is facing a land loss crisis. Now, it also faces a plague.

Subsidence, sea level rise, Mississippi River levees, oil and gas canals, and saltwater intrusion are some of the factors contributing to the eroding coast. The list has recently gotten just a little longer with yet another threat: a small insect (or scale) known as the Roseau Cane Mealy Bug. This tiny bug has an insatiable appetite for an important wetland plant that helps keep our coast together.

So What’s All the Fuss About a Little Bitty Bug?

Roseau cane is a wetland grass that serves as important habitat for fish and wildlife. With 60% of the plant mass located below ground, the extensive root system of this tall grass is also critical to holding together soil, making it one of the most erosion-resistant marsh plants in the birds foot delta. The insect was discovered this past fall by fishers and charter boat captains in Plaquemines Parish after large scale die-offs were found in the marshlands.

Scientists initially did not know what this insect was but after consulting with other scientists around the world, USDA entomologist Dr. Scott Schneider identified it as Nipponaclerda biwakoenis, or more commonly known as Phragmites Scale or Roseau Cane Mealy Bug. Native to China and Japan, it’s not known exactly how the pest arrived to Louisiana’s coast.

Mealy bugs literally suck the life out of Roseau cane. They live inside of the cane, feeding on the sap and depleting the plant of nutrients. Nutrients that must travel down to the roots to store energy get intercepted by the mealy bug, resulting in the plant becoming weaker and eventually dying.

Thousands of acres of wetlands have been affected by the Roseau cane mealy bug and, sadly, there is currently no solution to stop its spread. The Louisiana Department of Wildlife and Fisheries said that about 80% (88,000 acres) of the Pass a Loutre Wildlife Management Area has been affected by the pest. While the damage to Louisiana’s coast is highest in lower Plaquemines Parish, the mealy bug has also been found as far north as the Bohemia Spillway and has also been located in Jefferson Parish at Grand Isle and Jean Lafitte and in Lafourche Parish.

Roseau cane naturally dies back in the winter, however, the plants are not growing back as full as they usually do and the regrowth is also infected. This grass also helps break storm surge and with hurricane season underway, this is cause for concern.

Pest Control: Not so easy

Controlling the spread of the pest is proving to be a difficult task. No source of funding for research has been identified. LSU entomologist Rodrigo Diaz, Ph.D. gave a presentation at the Coastal Protection and Restoration Authority’s May board meeting about the Roseau cane mealy bug and also had in hand a research proposal requesting $376,000 to fight the spread of the destructive insect. Unfortunately, no agency has stepped in to offer support, citing budget constraints.

Ideas for pest control each have their own issues. Controlled burns, a method used to kill the mealy bug in China, are dangerous because of the network of oil and gas wells and pipelines in the area that could explode. Insecticides aren’t thought to be an effective solution either due to the damage that could also be done to the beneficial bugs and the fish and shrimp in the waters below as well as the birds that feed on them. Introducing natural predators is risky because of the unknowns of what other species that predator might kill. Currently, there are three non-native wasps that have been found preying on the mealy bug in Louisiana, though it’s unknown if these wasps will be able to do enough damage to control the problem or what potential side effects could be from introducing more.

What Else Could be at Stake?

There is also concern for economically important crops such as sorghum, sugar cane and other crops with similar characteristics as Roseau cane. The fear is that if these insects over-exploit Roseau cane, they may begin to feast on these other closely related species of plants. Spartina, a wetland plant that is used in coastal restoration projects, could also be targeted.

Scientists currently have more questions than answers at the moment, which is why they are desperately seeking funding for research. In the meantime, they are doing the best with what they have to address this ongoing problem.

Boaters, Proceed with Caution

The Louisiana Department of Wildlife and Fisheries and the LSU Ag Center are urging the public not to transport or transplant Roseau cane in any other parts of the state. Boaters should avoiding coming into contact with Roseau cane and thoroughly wash their boats after each trip to avoid inadvertently transporting the pest. Both healthy cane and those showing signs of stress can carry the insect. Therefore, boaters should not assume any stands of cane that appear healthy are not infected.

LDWF Biologist Todd Baker recently took reporters out on a tour of the affected marsh. You can see that video here.

This tiny insect is causing big problems for Louisiana’s coast. As long as research funding is lacking, we’ll continue to pay the price with more damage to our wetlands.


 
 
 
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