While the rotary sounds of the helicopter spraying aquatic herbicides chased away ducks in a popular Louisiana hunting destination, the results of the herbicide combination field trials led by the U.S. Army Engineer Research and Development Center (ERDC) Environmental Laboratory (EL)'s Dr. Christopher Mudge are ridding 250 acres of invasive vegetation, thus improving waterfowl habitat and removing hunter access restraints.
“The results look promising,” Mudge said of the treatments he developed for the Des Ourses Swamp and surrounding land in the Sherburne Wildlife Management area and the Atchafalaya.
“As of November, the treatment controlled several of the plants and the more difficult to control plants were slowly dying with no signs of recovery,” Mudge said. The treatment site contains multiple invasive floating and emergent species, including cattail, pennywort, alligator weed, giant cutgrass, Cuban bulrush and common salvinia.
“These plants were found in a series of continuous floating mats. In order to achieve the greatest level of control, a combination of herbicides were needed since none of the registered aquatic herbicides would suffice when applied alone. I had an idea of what would work, but we wanted to make sure that when the herbicides were used in combination, they would be compatible and effective. We utilized the preliminary demonstration trial this past summer to determine which combinations and rates were the most effective,” Mudge said.
Now Happier Hunting Grounds
“Essentially the herbicide treatment now allows hunters to access the swamp and open more boat lanes, because the plants died and the floating mat fell apart,” Mudge said.
Located between Baton Rouge and Lafayette, La., portions of this popular duck hunting destination are owned by the Corps’ New Orleans District (MVN), the U.S. Fish and Wildlife Service and the Louisiana Department of Wildlife and Fisheries (LDWF), which manages the land for all agencies.
As a native of Branch, La., and invasive plant expert with a doctorate in agronomy and aquatic weed science from the University of Florida, Mudge is familiar with the Cajun term for the floating plant mat, known as a “floaton,” that can cover several hundred feet in each direction. In other states and parts of the world, these floating rafts of herbaceous plants are referred to as tussocks or floating islands.
Mudge was recently re-assigned from his six years at EL’s Environmental Processes Branch to Louisiana State University in Baton Rouge, allowing him to work more closely with LDWF and MVN, as well as other state and federal agencies.
The LDWF called on Mudge’s expertise for solutions. They used maps and surveys by boat to determine the most important areas impacted by these plants.
Factors affecting treatments
“While the entire swamp and management areas are very large, the amount of land to treat with the herbicides was based on the cost of the herbicide, cost of application, and the available budget. LDWF decided that 250 acres would be managed. The helicopter pilot has GPS and other technology to precisely place the spray mixture where it is needed.
“The Environmental Protection Agency and state-approved herbicides and rates used were based on preliminary demonstration trials conducted at a nearby field site earlier in 2013. The idea to test these specific herbicides was based on mesocosm and field research conducted over the past few years by the Chemical Control and Physiological Process Team, myself and others in the aquatic weed management field."
Mudge said an additional 450 acres of invasive aquatic plants were treated with herbicides for the LDWF in the area.
“We used different herbicides and mixtures for the two areas. The 450 acres were primarily infested with the floating weed water hyacinth, which required only one herbicide. Based on previous research and publications, water hyacinth is much easier to control, so we didn’t need to conduct any preliminary experiments to determine which herbicide to use,” Mudge said.
Mudge also said LDWF reports show the areas have improved since the treatments.
“Once the hunting season has concluded, we will conduct a follow up evaluation in February. We will also re-assess the site in the spring to determine if the plants recovered and where to conduct maintenance treatments,” said Mudge.
As a testament to Mudge’s successful herbicide experiment and follow-up treatments, this Louisiana “floaton” has met its match and is sinking fast.