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Herbicides:
Questions & Answers
How will the herbicides be applied? The herbicides will be sprayed onto the phragmites by a contractor crew who will use a Marsh Master, an amphibious vehicle equipped with pontoons and treads.
How do the herbicideswork?
The herbicides (Accord and Habitat) are applied directly to the foliage of the
targeted aquatic plant (in our case, Phragmites). To work, the herbicides must come into direct
contact with the exposed leaves. The best time to apply the herbicides is from the end of the growing season to the first killing frost, because as the plants pull sugars and starches into their root systems in preparation for the winter, they draw the herbicides in with them. The ingredients
rapidly move through the plant tissues and into the roots,
and effectively stop the plant from growing, causing treated plants
to yellow, turn brown, and eventually die.
When the herbicides are broadcast onto the targeted plant, the droplets land on the
surface of the leaf. Within a few hours, they are
absorbed through the cuticle of the leaf into the plant.
Because their active ingredient (glyphosate and salt of imazapar) have a structure similar
to the naturally occurring plant amino acid glycine, target
plants have trouble telling glyphosate and glycine
apart. As a result, glyphosate travels with glycine as it
moves through the plant vascular system toward the
actively growing roots and shoots, effectively inhibiting the production of
EPSP synthase, an enzyme vital to the production
of three aromatic amino acids essential for protein synthesis.
This metabolic pathway is found only in plants.
As protein production stops, the plant begins to die.
The herbicides also
inhibit chlorophyll synthesis which causes the leaves to
lose color. Actual absorption time may depend on the
weather, but on average, one to three hours are required. Then it takes one to two weeks for the plants
to show symptoms of exposure (yellowing of leaves, followed by
wilting, and finally death).
What will the Phragmites look like after the application?
Visible effects include gradual wilting or yellowing, followed
by complete browning, deterioration of plant tissue
and ultimate decomposition of the underground
roots and rhizomes. Late summer application results
are often not apparent until the following spring.
These include failure to break bud and small, deformed
leaves. In addition, the upper portion of the stem or
leaders may be pale in color, dry, and brittle.
Will the herbicides harm people, pets, or wildlife in the
treated area?
Used in the prescribed manner, the herbicides (sold under the brand names Accord and Habitat) are nontoxic to humans,
pets, and wildlife. There are no restrictions on the use of
water in areas that have been treated with the herbicides.
Do the herbicides harm plants not directly sprayed?
The herbicides must come into direct contact with the exposed leaves
and will affect only the aquatic plants that have been directly
sprayed. The active ingredients are non-volatile, meaning they do not produce
vapors that could move into the air and cause unreasonable adverse effects to non-target vegetation or odors to
disturb the public.
Do the herbicides affect soil or water quality?
Because they are"foliar active" - they only affect plants
- so it has no activity in the surrounding soil or water.
It is also biodegradable. The ingredients will be absorbed onto soil
particles in water or sediment in the area. Microorganisms
in both the water and sediment rapidly break the chemicals into naturally occurring compounds, including carbon dioxide.
Who has cleared the herbicides for use on aquatic
sites?
The Environmental Protection Agency (EPA) has given its approval
for the use of these herbicide on all types of aquatic sites,
including estuaries. They must be applied by a licensed professional.
The Maine Dept. of Inland Fisheries and Wildlife, US Fish
& Wildlife Service, Friends of Scarborough Marsh, and our restoration partners have recommended its
use for the control of Phragmites on selected sites within
the Scarborough Marsh watershed over the next few years. >>MORE
What's the next step and how often will the herbicides be used?
In the winter, the crew will return with a mowing attachment on the vehicle to remove dead Phragmites and make way for native species that have been crowded out by the prolific intruder. The process will be repeated as needed over the next two years, at which point the amount of invasive Phragmites could be reduced by as much as 95 percent.
Where can I find out more?
For more information about the use of the herbicides on the Phragmites found in
that area, contact Scott Lindsay, Regional Wildlife Manager,
Maine Dept. of Inland Fisheries & Wildlife (207) 657-2345.
