Herbicide key to success in eradicating phragmites
The phragmites invasion in southern Ontario threatens 23 endangered species of plants and animals in the Long Point area. Among them is the Blanding’s turtle, which frequently expires after getting lost and trapped in the dense growth. CONTRIBUTED PHOTO
Progress is being reported in the campaign to roll back the phragmites invasion that is threatening the Long Point ecosystem.
Several years of aerial spraying with the herbicide glyphosate followed by controlled burning has reclaimed large areas of the Long Point biosphere for native plants and animals.
“They are winning the battle in Long Point,” reports Dr. Janice Gilbert, a wildlife biologist who sounded the alarm on phragmites several years ago.
“It gives me great pleasure to see the ecosystem recover once we apply the right tools.”
Key to the success in Long Point is glyphosate – the active ingredient in the broad-spectrum herbicide RoundUp.
Glyphosate is in general use in the United States for phragmites control. However, the Pest Management Regulatory Agency (PMRA) in Ottawa restricts the use of glyphosate in aquatic areas. It is being used in Long Point under a special permit.
Elsewhere in the Great Lakes, phragmites eradication relies on other methods. Gilbert has been involved with phragmites control along the Lake Huron shoreline for the past several years.
That campaign involves chopping the hearty reed beneath the water line and hoping it drowns. Gilbert said it is hard, painstaking work, adding it is difficult to make a dent in the problem with this method.
Phragmites reed is a devilish plant. Agriculture and Agrifood Canada describes it as the worst invasive plant in the country.
Phragmites is a problem because it replaces native plants with a dense, nearly impenetrable monoculture. The reed grows 15 feet tall. Each seed head produces 2,000 seeds. These can travel more than 10 kilometres on the wind.
Phragmites roots grow to a depth of eight feet. The roots produce a toxin that kills surrounding plants. There are concerns it is expanding its range into Ontario woodlots.
Roots grow out from the plant to a great distance. Each root is crowded with rhizomes, each one capable of putting up a new shoot.
Efforts to eradicate phragmites often help spread it. Root pieces stick to machinery that is then transported to new locations. Each fragment represents a potential new stand of phragmites.
The eradication campaign in Long Point was the subject of a recent Master’s thesis at the University of Toronto.
In her report, Anamika Ray, a member of the Faculty of Forestry, says research indicates that glyphosate spraying over aquatic areas is safe.
She cites The Journal of Toxicology and Environmental Health, which said that “Glyphosate is of small acute toxicity to aquatic inveterbrates, fish and wildlife, and that the risk to aquatic organisms is negligible at suggested application rates.”
Ray also cites an as-yet unpublished study that says glyphosate shows up in only trace amounts in aquatic areas one hour after it is applied. The amounts detected, Ray reports, are below limits prescribed by Health Canada.
In her report, Ray says phragmites eradicators in Canada should have the same weapons at their disposal as the team in Long Point and in the United States.
“The inability to conduct chemical control in aquatic areas is crippling efforts to control phragmites and is critically endangering unique wetland biospheres,” Ray writes.
“Since 80 per cent of the phragmites biomass is underground, rhizomes can persist through most disturbances. Herbicide is the only known method to effectively kill phragmites roots and rhizomes and leave the area in a condition which can support other plants.”