South Dakota Department of Game, Fish and Parks
Aquatic Nuisance Control Applications/Permits
Information Sheet
When aquatic weeds fill in ponds and lakes, residents typically resort to aquatic plant management
techniques. Within South Dakota, most of these techniques involve herbicide application to state waters.
This activity involves an application to SD Game, Fish and Parks, as well as approval from the
Commission.
Plants are natural and important components of the aquatic environment. Microscopic plants (algae) form
the base of the aquatic food chain, while larger plants provide food and habitat for fish and other
organisms. All plants produce oxygen as they photosynthesize during the daylight hours. However,
excessive growth of aquatic plants can be problematic.
Some of the problems caused by aquatic plants:
*interfere with or prohibit recreational activities such as swimming, fishing and boating.
*detract from the aesthetic appeal of a body of water.
*fish kills (caused by die-offs of algal blooms)
*algae can give water bad tastes and odors
Identification is the first step in managing aquatic weeds. Most herbicide control methods are aimed at a
specific weed or groups of weeds with similar growth habits. Aquatic weeds can be divided into two
groups, algae and flowering plants.
Algae: Microscopic algae form scums and/or color the water green or yellow-green. Algae
blooms can occur where abundant nutrients are reaching the water. Filamentous algae
(moss) form floating, mat-like growths which begin around the edges and bottom of
ponds in early spring.
Flowering Plants: These can be grouped into broad categories according to where they are found
in a body of water.
Submersed plants are rooted in the bottom sediments and grow up through the water.
Flowers or flowering spikes can emerge through the water’s surface. The main criteria
for identification are leaf arrangement and leaf shape. Common submersed plants
include curly leaf pondweed, leafy pondweed, coontail, milfoil.
Floating Plants: Seed-bearing plants that float free on the water’s surface. They never become
rooted in the soil and can completely cover the surface of a pond. The most common
example is duckweed, which is generally found in nutrient rich waters. The easiest
treatment for this type of weed is to eliminate input of wastewater from sources such as
livestock feedlots and septic tanks from entering the lake.
Rooted Floating Plants: Water lily, spatterdock. Plants are rooted; leaves come above the
water’s surface, usually flowering.
Emergent (shore or marginal) Plants: Cattails, bulrushes, spike rushes, reed canary grass, and
other grass-like perennial plants.
Permission to control aquatic weeds by means of herbicide is the most common requested method of
control in South Dakota. For most aquatic weed problems, properly used herbicides control vegetation
without harming fish. Aquatic herbicides are available in sprayable or granular forms. The sprayable
forms must generally be mixed with water and applied over the surface area to be treated. Granular
formations are in pellet form and are distributed by spreader and will sink to the bottom of the water body.
Slow release granules are available and will release the active ingredient over an extended period of time.
Floating and immersed weeds can be killed with direct sprays on the foliage. Sprays are applied
as surface water treatments, particularly in shallow water. The herbicide is then dispersed mainly
by wave action.
Submersed weeds and algae can be treated using sprays or granular formations. Advantages to
granular formations include:
*treatment is confined to the bottom area where submersed weeds are found.
*slow-release formulas can provide extended control
*low concentrations can be used
*toxicity to fish may be reduced
The most important considerations for an applicant to consider before he buys and applies a herbicide for
aquatic weed control are:
1.
2.
3.
4.
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6.
Identify the Problem Weed
Restrictions on Water Treated with Herbicide- Although most aquatic herbicides break
down readily and rapidly in water and pose no threat to human or animal health, there are
waiting periods on the use of water treated with most herbicides. These restrictions- usually
on fishing, swimming, domestic use, livestock watering or irrigation- dictate which herbicides
will be appropriate for the pond or lake. Always check label restrictions.
Dosage- Calculate carefully and don’t overdo it.
Timing- Late spring is usually the best time to apply aquatic herbicides. The plants are
young, actively growing, and susceptible to herbicides. If an applicant waits until late
summer to treat, vegetation is extensive and thick and the water is warm and still.
Temperature- Aquatic weeds are not affected by herbicides when the water is too cold. The
water temperature should be in the 60-70 degree range. As soon as the plants are up and
actively growing, and the water temperature is right, the herbicide should be applied.
Retreatment- More than one treatment may be required for adequate control. Plants
regenerate each spring from seeds, spores and underground rhizomes, as these are generally
not affected by herbicides.
The most common types of aquatic herbicides are:
Copper Sulfate- Primarily used to control algae. Copper can interfere will gill functions, and if
improperly used, can be toxic to fish.
Chelated Copper- (Cutrine®, Komeen®, K-Tea®). Copper held in an organic complex. Used to control
planktonic and filamentous algae. Sometimes mixed with diquat to control certain species of
submerged plants as well. Slightly less toxic to fish than copper sulfate.
Diquat- (Reward®, Weedtrine-D®). Contact herbicide that can be sprayed on or injected into water to
control submerged weeds and filamentous algae. Can also be sprayed on duckweed or emergent
vegetation. Not effective in muddy water or mud-coated weeds.
Endothall- (Aquathol®, Hydrothol®). Available in liquid or granular. Hydrothol is more toxic to fish and
aquatic invertebrates and controls algae and many submerged weeds. Aquathol is generally used in
commercial ponds and controls submerged weeds but is not effective against algae. Both are
contact herbicides and can be used for spot control or partial pond treatments.
Glyphosate- (Rodeo®). Foliar applied herbicide used to control most shoreline vegetation and emergent
weeds such as spatterdock. Most effective when applied during the flowering stage.
2,4-D- Available in liquid or granules. Granular form is used to control submerged weeds and emergent
weeds. Liquid formations are used to control floating weeds and emergent weeds.
Persons wishing to treat public waters with herbicide must fill out the “Application for Permit for Control
of Aquatic Nuisances”. The application will then be presented to the South Dakota Game, Fish and Parks
Commission for their review and approval/denial.
The South Dakota Department of Environment and Natural Resources should also be notified of proposed
action, as they have a 10-day public notice and comment period.