Researchers collaborate to determine Roseau cane die-off cause

Tobie Blanchard  |  10/5/2018 6:28:45 PM

(10/05/18) BATON ROUGE, La. — LSU AgCenter researchers along with scientists from multiple agencies are collaborating to investigate the decline in health of Roseau cane or Phragmites, a vital marsh grass in the lower Mississippi River Delta.

Earlier this year, Congress directed the U.S. Department of Agriculture Animal and Plant Health Inspection Service and Agricultural Research Service to work with stakeholders to develop a pest management program for control of the Roseau cane scale infestation in the delta.

This additional funding allowed research efforts to expand into plant pathogens, soil health, and plant and insect genetics.

With support from the Louisiana Legislature, AgCenter coastal ecologist Andy Nyman will use remote sensing to measure Roseau cane health in the marsh, and Ehab Meselhe, vice president for engineering with the Water Institute of the Gulf, will model the potential impact of die-offs on navigation dredging in the lower delta.

Nyman said his goal is to determine when Roseau cane first began to die off and how much of it has died and not replaced itself.

Nyman will conduct field work in the marsh to accurately verify what is out there. He will also use satellite imagery taken over time that provides a normalized different vegetation index. This index helps the researchers determine if green vegetation is in the area and can show if die-offs happen over time.

“It is challenging because in some places other types of vegetation is growing up around the phragmites,” Nyman said.

Nyman plans to observe the cane for a year to capture the full seasonal pattern of plant health.

Also, the U.S. Army Corps of Engineers is conducting geospatial assessments of the Roseau cane die-offs in the delta to understand how the health of the marsh is changing.

“Work continues to support calls for the expansion of large-scale monitoring as well as improved species detection capabilities, especially where species differentiation can help shed light on what new species are colonizing areas of degraded Roseau cane habitat,” said Glen Suir, a research agronomist with the Corps.

AgCenter entomologist Ian Knight said different varieties of Roseau cane have varying levels of susceptibility to the scale. A delta variety and a European variety of Roseau cane are two types that grow in Louisiana marshes.

Preliminary data has shown the delta variety is more vulnerable to the scale.

“The European variety doesn’t seem to exhibit die-off symptoms as severely,” Knight said.

Knight is providing Laura Meyerson at the University of Rhode Island with cane samples so she can study the genetic characteristics of the Louisiana varieties of Roseau cane.In addition, Scott Schneider at the USDA-ARS in Beltsville, Maryland, will be studying the genetics of the Roseau cane scale.

Jim Cronin, a professor in the LSU Department of Biological Sciences, suspects multiple stressors could be affecting Roseau cane health. He is studying soil chemistry in the marsh to see if cane die-off may be caused by toxic chemicals in the soil.

“We will compare soil chemicals from where it’s died off to areas where it is healthy,” Cronin said.

With the sediments and chemicals that come down the Mississippi River and are deposited into the marshes that make up the lower river delta, phytotoxic properties could be found in the soil. Cronin plans to analyze samples from locations across coastal Louisiana to look for patterns in areas of die-off.

AgCenter plant pathologist Rodrigo Valverde also believes that more than one culprit is affecting the cane health. He is looking at the die-offs from a plant pathogen perspective.

“We are going to the affected areas, collecting samples of diseased plants and bringing them to the lab,” Valverde said.

Valverde is isolating potential pathogens from the plants he collected and is growing cultures of some of them. His plan is to inoculate healthy Roseau cane with the pathogens to see if they are causing disease or death.

The LSU AgCenter Roseau cane website, www.lsuagcenter.com/Roseaucane, offers information on die-offs, research and scale recognition. The public who come in contact with Roseau cane can assist with monitoring of the scale by filling out a distribution survey found online at http://bit.ly/2BYmDiQ.

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LSU AgCenter plant pathologist Rodrigo Valverde looks at cultures of potential pathogens he is growing in the lab from samples of diseased Roseau cane. Valverde is conducting research to see if plant pathogens are contributing to die-offs of Roseau cane, Photo by Tobie Blanchard/LSU AgCenter

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A drone image of the South West Pass of the Mississippi River Delta shows the dominance of Roseau cane in the marsh. Photo provided by Rodrigo Diaz

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A stalk of Roseau cane in the marsh at Pass a Loutre Wildlife Management Area is infested with Roseau cane scale. Photo provided by Andy Nyman.

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