A Sweet Solution to a Sticky Problem

When you’re a biologist at a site named for a legendary environmentalist, you feel a responsibility to do your job with the planet in mind.

Just ask Dr. Susan Adamowicz, Land Management Research and Demonstration Area biologist for the Northeast Region of the Fish and Wildlife Service. Stationed at Rachel Carson National Wildlife Refuge in Maine, she is tasked with finding innovative ways to manage wildlife habitat and takes inspiration from the renowned author.

In 1962’s Silent Spring, Carson, who also worked for the Service, sounded the alarm about pesticides that imperiled wildlife and people alike. She knew that many of the synthetic chemicals used to control unwanted plants and insects were dangerous to more than their targets.

For a healthy environment, Adamowicz seeks other solutions … and hopes she has found one with the help of a University of New Hampshire researcher.

A “Consummate Invasive Species”

Phragmites australis, or common reed, is an aggressive, nonnative marsh grass that pushes out native wetland plants. You’ve probably noticed its tall (up to 18 feet!), feathery, golden stalks in your neighborhood or along the freeway.

Phragmites is plentiful in the high salt marsh of the Great Marsh, the largest continuous stretch of salt marsh in New England. Three thousand acres of the 20,000-acre marsh in eastern Massachusetts lie within Parker River National Wildlife Refuge.

Phragmites changes the structure of the salt marsh, filling natural channels and tidal pools where waterbirds, fish, and invertebrates find food and safety. Many wildlife species find its dense patches impassable, and in the fall, when the stalks die back, stands of the plant turn to tinderboxes primed for wildfire, putting nearby homes and businesses at risk.

Biologists have long searched for effective ways to control Phragmites. It’s a determined adversary, however. Like those birthday candles that re-ignite, just when it seems defeated, it springs back to life.

According to Adamowicz, “Phragmites is the consummate invasive species. If you cut it or burn it, it comes back. If you can flood it for six months, that might kill it, but flooding is not always feasible.”

Phragmites grows along a marsh at Sachuest Point National Wildlife Refuge in Rhode Island. (Credit: Tom Sturm, USFWS)

While restoring natural tidal flow to coastal marshes is the preferred way to fight Phragmites,  replacing culverts, filling ditches, and improving drainage can take a long time. Treating it directly is necessary to keep it in check in the meantime.

Sadly, there’s been no good way to do that. Herbicides work in certain locations but pose a risk to native vegetation and groundwater — certainly not a solution Rachel Carson would embrace.

So Adamowicz teamed up with Dr. David Burdick, research associate professor and interim director of the Jackson Estuarine Laboratory at the University of New Hampshire, to explore innovative ways to control Phragmites. One of the methods they tested was sweet and simple.

Turning the Tables

Burdick had a hunch that sugar, the same kind you put in your coffee, might be Phragmites’ Kryptonite.

Dr. David Burdick takes notes at Parker River National Wildlife Refuge. (Credit: Gregg Moore, UNH)

Each summer, rising air temperatures and increased plant growth stimulate bacteria in salt marsh soils to convert organic matter and oxygen into carbon dioxide, water, and energy — a process called aerobic (“with air”) respiration. The activity quickly uses up soil oxygen, forcing other groups of bacteria to make energy using anaerobic (“without air”) respiration.

One by-product of anaerobic respiration is hydrogen sulfide gas, a potent toxin for plants as well as people. At typical levels, the gas is not deadly to most native plants, but it can be toxic to Phragmites.

Burdick thought increasing bacterial respiration, and therefore hydrogen sulfide levels, could kill the invasive.

“Because Phragmites is a master at getting oxygen to its roots for its own respiration, we could use this strength to kill it,” he mused. “By elevating soil hydrogen sulfide levels, we might stimulate the plant to oxidize the gas into a strong acid that it may not be able to tolerate.”

While he couldn’t control air temperatures, he could increase fuel for the bacteria — using glucose in the form of table sugar.

Pour Some Sugar on It

Burdick and his team first tested their idea in the greenhouse. They soaked Phragmites plants with bay water for three hours every two weeks to mimic the flooding that high-marsh plants get during the extra-high “spring” tides that come with the full and new moons each month.

Some plants (the control) received only the bay water; others got water with table sugar; still others water with extra salt; and the remaining, water with sugar and salt.

In the greenhouse study, plants receiving sugar or sugar-plus-salt (right, top and bottom) showed clear signs of distress within weeks of treatment. (Credit: Gregg Moore, UNH)

Both the sugar and sugar-and-salt treatments showed signs of stress within weeks and eventually died. Only the plants that received plain bay water or bay water with added salt lived.

The sugar-treated plants had very high soil acidity, possibly caused by sulfuric acid, the product of hydrogen sulfide oxidation. This supported Burdick’s theory.

Next, Burdick and Adamowicz headed to Parker River Refuge to set up a field study in the northern part of the Great Marsh. The research was supported by federal funds for Hurricane Sandy recovery and resilience projects.

Following the greenhouse trial, Burdick and his team tested the treatments in the Great Marsh at Parker River National Wildlife Refuge. (Credit: Gregg Moore, UNH)

They isolated individual Phragmites plants and applied the same treatments as in the greenhouse. Sugar and salt were put on the plants every two weeks, after the spring tides flooded the marsh.

The plants that got sugar had far greater mortality than the other treatments, even with uncontrollable environmental factors, such as rain — a clear sign that sugar is not sweet to Phragmites.

Refining the Technique

Adamowicz is pleased with the study results so far and eager to set up more field trials. She’s exploring ways to treat Phragmites with sugar and salt more efficiently and broadly, perhaps using a backpack sprayer to apply corn syrup at more-frequent intervals than every two weeks.

“This is another tool in our toolbox, and it’s nontoxic to wildlife, which is very desirable,” she said. “The more complicated response to Phragmites is ecosystem restoration, but in the meantime, we need a fast-acting tool to help native plants come back and buy time.”

If Rachel Carson were alive today, she would certainly approve of this environmentally sound method — and just might be thinking, “Sweet!”

18 Comments on “A Sweet Solution to a Sticky Problem

  1. This is unrealistic and not helpful to those of us who are actually tasked with controlling phragmites. It is hardly “another tool in the toolbox” at this point and misleads people into thinking this is a ready to use magic bullet “non toxic”solution to phrag control.

    • It seems that spraying sugar water is just as possible as herbicide spraying…no? At the least, this is a very promising treatment…and Non-Toxic!

    • We apologize if you feel misled, Ned. Our intent was to convey enthusiasm about an innovative, and possibly promising, approach. Further testing is necessary before this technique is adopted as a management tool, but the potential of a treatment that controls Phragmites and doesn’t harm other plants or wildlife was too exciting not to share. We’ll let you know when it’s ready for widespread use! Thanks for following the blog.

      • I think this would be a wonderful possibility for home owners especially. No nasty chemicals to deal with. For example, on my road, there are starter populations of Phrag. It would be very easy to spray a sugar solution once a week or so on the 1 sq ft populations scattered along the road.

  2. Might commercial drones built out to carry tanks of sugar water be able to fly low over patches of Phagmites and dose them? Or carry a spray hose out to the patch and empty a sugar water mix onto the patch? They seem to be able to remember where they were before and so repeated trips to cover the marsh efficiently should be possible. Just thinking aloud.

  3. Has this research been published? If so, where can I find it. I do invasive species management (focusing on invasive Phragmites) in the Saginaw Bay Watershed in Michigan, and we have landowners who are interested in replicating this study.

  4. I wonder if beet sugar would work. They spray some concoction of the beet sugar on our roads here in some areas for ice control. Wouldn’t it be interesting to find out if it ends up the phrag filled ditches and has some effect.

  5. This is exciting to learn. Way to go Susan! Thanks for sharing. Jen

  6. But hopefully the corn syrup won’t be glyphosphate rich GMO corn syrup. We are already losing biodiversity to pollution caused by corn-centric society.

  7. We at the Friends of Exton Park, Exton, Chester County, PA have a phragmites problem as well. Please let us know if there will be any further testing or if we could be a part of some testing. None of our efforts have produced results in eliminating or even reducing the infestation.

  8. There is a type of phragmite that is taking over ditches and wetlands in southern Ontario. My favourite elderberry patch is gone. I am going to create some sugarblocks that rainfall will dissolve and see if it controls a patch on my farm.

  9. We love the enthusiasm in these comments! Unfortunately, this treatment is applicable only to saltwater systems. The process depends upon high concentrations of sulfate, which is in seawater, but not freshwater. Sulfate is the second most common salt in saltwater (after NaCl).

  10. Will this work on cat and nine tails that are taking over my fire pond?

    • Probably not, Sharon, since it’s specific to seawater.

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