Duckweed Control

Duckweed Control
Duckweed is an agressive pond weed that covers a pond quickly with a green scum.
Duckweed (Lemnaoideae) is something I am actually very fond of...of course when a large pond is infested with this plant it is no fun but in smaller water gardens and backyard ponds duckweed can actually be a helpfull addition to the ecosystem!

Myself, I've actually gone to the garden store and bought a container full of duckweed to add to my backyard cost me $5 and my wife asked me if I was losing my marbles because duckweed can be found in almost any farm dugout or stagnant swamp in the area!

I am asked at least twice a week about methods for controlling duckweed and other aquatic plants and algae of course.

In a large pond duckweed can be an invasive plant that can cover the surface quickly and it often is a real nuisance for the pond owner who suddenly can't see anything in the pond!

Before we kill the duckweed with an aquatic herbacide, yes there are some good algaecides that can eliminate duckweed from a pond, lets make sure we actually do want to do it because this floating plant is actually a real wonder of the pond!

Duckweed can absorb a whole bunch of nutrients from the water and will provide a great umbrella of shade for it will keep waters cooler and also suck out phosphates from the pond. These phosphates and other nutrients are the junk in the pond that cause the big blooms of floating green algae and algae that grows on the bottom of the pond.

Why You May Love Duckweed:
Duckweed is a small delicate plant that drifts on the pond surface, filling in spaces between the lily pads, creating a lovely green blanket across the pond. This provides a lush habitat for frogs and fish and insects of the pond.

The layer of floating aquatic plants provides shade to the pond keeping it cooler during stifling hot days of overhead sun. Waterfowl will feed voraciously on the duckweed thus nest nearby and live in the pond.

Duckweed grows rapidly and absorbs mineral elements like nitrogen and phosphates from the water column so it can be an important part in the aquatic rehabilitation of any pond or lake as these nutrients can cause problems like algae and cyanobacteria. It is especially good at removing ammonia from ponds.

Beyond providing shade for fry bluegill and a place to live for bullfrogs the duckweed helps reduce evaporation which can be a problem in a clear pond without any cover to slow the rate of pond evaporation. Sometimes just the rich green color of the plant alone is enough to make us feel like our pond is a healthy and natural aquatic system!

A bit like a stained glass window on the pond, duckweed is a wonderful and beautiful plant, that with a bit of understanding and acceptance is actually a very beautiful thing!

Why You May Hate Duckweed:
Duckweed is an invasive and agressive aquatic weed that can rapidly multiply and if conditions are right will completely cover a pond with a thick green cover of tiny green plants that are only a few milimeters in size.

The thick matting of pond weed can literally choke out a pond and if conditions, temperatures and nutrient levels are right can completely hide the water and create a cover that hides the pond and makes it almost unpleasant. Frogs and ducks and turtles will live in what looks like a swamp! Maybe it provides food for swans and geese and a mallard duck or two but it can choke out oxygen levels.

Two Ways of Getting Rid of Duckweed
Well, actually you could just ignore the duckweed and live with the problem! So that means there are three options for this aquatic plant. Adding natural bacteria to control muck and nutrients will assist in slowly reducing the amount of food available for this aquatic floating bugger. The beneficial bacteria, over time, will have an impact on the amount of duckweed in your pond...but it can be a long process and manual removal will greatly help this process. So basicially, beyond ignoring it you have two ways to deal with duckweed:

1 - The Chemical Way
Fluridone is the most effective and cost-efficient treatment you can buy for the selective, long-term control of undesirable weeds.

Fluridone is available in formats of 4 ounces up to 1 gallon

Weeds Controlled Duckweed, Salvinia, Watermeal, American PondWeed, Bladderwort, Clasping-leaf Pondweed, Coontail, Curly-Leaf Pondwed, Elodea, Eurasian Watermilfoil, Fanwort, Flat-Stemmed Pondweed, Floating-Leaf PondWeed, Horned Pondweed, Hydrilla, Large-Leaf Pondweed, Naiads, Sago Pondweed, Small Pondweed, Variable-Leaf Watermilfoil.

How to Apply Fluridone
Fluridone manages undesirable aquatic vegetation and is recommended for use in water bodies with soft or muck bottoms. Fluridone is easy to apply and just one application will provide season-long enjoyment of your pond.

Fluridone can be applied in early spring, at the first sign of weed growth, through midsummer. Pond Level Best control is obtained when discharge can be stopped for thirty days or longer.

Pond levels should be at or near normal when water level when treated. Excessive outflow dilutes Fluridone and reduces the chance of control. Dose The typical dose of Fluridone is one (1) quart per surface acre with an average of depth of 4-6 feet. Use 1.5 quarts per surface-acre for watermeal.

Control Time
Plants should start turning white as control begins in 15 to 30 days. It may take 30 to 90 days for final results.

This slow rate of control is beneficial as it greatly decreases the chance for a severe change in oxygen levels which can harm fish. Active Ingredient 41.7% Fluridone (Substitute for Sonar® AS).

Cannot be shipped to: AK, CA, CT, DC, HI, ME, NJ, NY, PR, RI, VT, WA or Canada

Easy Application: simply mix in a bucket of pond water and pour in directly from shore. Allow 30 - 45 days for best results Great for entire bodies of water but not meant for treating a portion of a pond or lake Stays suspended in the water for longer control

Sonar® Aquatic Herbicide

Sonar ready-to-use RTU represents an exciting new era in pond weed management for the do-it-yourselfer the innovative new RTU formulation allows anyone to make water usable for recreation, bring fish populations back into balance and restore property values.

We're so sure that applications of sonar RTU conducted according to directions will control target aquatic vegetation listed on the label that we'll work with you until you see the results you expect.

There's never been a better time to trust your lake or pond to sonar.

Sonar RTU and duckweed many pond owners consider duckweed to be their toughest aquatic weed problem. Duckweed is a very comma on nuisance aquatic weed that is spread from pond to pond via waterfowl or other wildlife.

While it is comma only mistaken for algae, duckweed is actually a tiny plant with an explosive reproductive capacity that can completely cover a pond in just a few weeks to the point that the infested waterbody resembles a golf-course green.

Fortunately, no other aquatic herbicide is more effective on duckweed. Sonar provides complete, long-lasting control of duckweed and other stubborn unwanted aquatic vegetation.

Aquatic herbicides and pond weed killers

Aquatic algaecides and herbicides are very effective at controlling duckwweds and other unwanted invasive pond species. You should understand that such algae problems,'s not reaslly an algae but an aquatic weed plant, if they are treated with herbiceds can lead to a dependance or resistance and scientists generally agree that chemical selection pressure that is applied applied to aquatic weed populations for a long enough period of time eventually leads to resistance. This means that while the chemical pond weed killer may work quickly and effectively for the first few years, unless you are adding a positive treatment with aeration and natural beneficial bacteria you will just be "chasing the dragon" so to speak!

2 - The Natural Way

Natural bacteria for ponds
If the pond is small enough just the best way to remove the small little flowering plant known as duckweed is to use a fine meshed net and just manually remove it day by day, hour after hour, until there is none left. Of course it is really tough to completey eradicate the problem but you can keep it under control just like keeping the dandelions out of the vegetable garden!

You need a net with a long handle or a good quality aquatic rake to harvest this pond weed if you want to deal with this problem naturally or of course you can invite a family of ducks or geese or swans into your pond and they will love the free food supply offered by these floating flowering plants but you will still need the manual removal...if you don't want to accept the duckweed or don't want to perform the manual work or invite the Duckworth family into the pond then you need to go to the next option..

WhiteCap® selective herbicide
White Cap Selective Herbicide Control aquatic weeds and grasses in fresh water ponds, lakes, and drainage/irrigation canals with WhiteCap™ SC selective herbicide, a proven reformulation of the popular active ingredient fluridone. WhiteCap effectively controls a wide range of floating, submersed and emersed aquatic vegetation, including Duckweed, Hydrilla, Bladderwort, Watermilfoil, Naiad, Elodea, Water-lily, Pondweed, and Coontail See The List of Aquatic Weeds that White Cap SC will control before you buy. Email us if you're not sure.

Susceptible aquatic weeds absorb WhiteCap SC through the shoots and roots. For effective control, contact of WhiteCap with the target plant must be maintained for at least 45 days. Effective control is reduced if conditions exist that dilute the concentration of WhiteCap in the water to below labeled rates.

Apply WhiteCap as a surface spray or subsurface injection at rates between 10 and 90 ppb for single applications, or if multiple applications are made, do not exceed 150 ppb per growing season.

Water treated with WhiteCap SC at rates greater than 5 ppb must not be used for irrigation of certain crops and newly seeded turf. If the concentration of WhiteCap is less than 10 ppb, established tree crops, established row crops or turf can be irrigated with WhiteCap treated water.

Do not apply WhiteCap at rates greater than 20 ppb within ¼ mile of any functioning potable water intake.

WhiteCap effectively controls a wide range of floating, submersed and emersed aquatic vegetation, including Hydrilla, Bladderwort, Watermilfoil, Naiad, Elodea, Water-lily, Pondweed, Coontail and Duckweed. Selective control.

At low use rates, it is safe for most native beneficial aquatic plants; WhiteCap SC selectively removes the nuisance plants, while having little impact to desirable species. Low use rates provide for cost-effective aquatic plant control.

Complete control.
Readily moves and disperses throughout the water column, providing complete and thorough control of target nuisance aquatic weeds Slow control. Works slowly to remove excessive aquatic weeds with minimal impact to aquatic ecosystems No human or livestock use restrictions. Water treated is potable water safe and may be used immediately for human recreation and for watering livestock.

Average Water Depth of Treatment in Feet
Fluid ounces per acre
to achieve desired herbicide concentration
Application Directions
45 ppb
90 ppb
3.8 oz.
7.7 oz.
ApplyWhiteCap to the entire surface area of the pond.
Single Applications: Use the amount of WhiteCap listed to give 45 to 90 ppb .fluridone in treated water. Higher rates should be used for dense weed infestations, for dif.cult-to-control species, and for smaller ponds (less than 5 acres in size and average water depths of less than 4 feet). Split or Multiple applications: Use when dilution of the treated water is likely to occur. Do not exceed 90 ppb per annual growth cycle.
7.7 oz.
15.7 oz
11.8 oz.
23.4 oz.
15.7 oz.
31.4 oz.
19.5 oz.
35.0 oz.
23.4 oz
46.7 oz.
27.2 oz.
54.4 oz.
31.4 oz.
62.4 oz.
35.2 oz.
70.1 oz.
39.0 oz.
78.1 oz.
Vascular Aquatic Plants Controlled by WhiteCap
Floating Plants
Emersed Plants
Submersed Plants
Shoreline Grasses
common duckweed
(Lemna minor)
(Nuphar luteum)
(Utricularia spp.)
(Urochloa mutica)
(Nymphaea spp)
common coontail
(Ceratophyllum demersum)
common elodea
(Elodea canadensis)
egeria, Brazilian elodea
(Egeria densa)
fanwort, cabomba
(Cabomba caroliniana)
(Hydrilla verticillata)
(Najas spp.)
(Potamogeton spp., except Illinois pondweed)
(Myriophyllum spp., except variable-leaf milfoil)

Suggested bApplication Rates For Duckweed
75' x 75' Pond (.13) Acre 4 ft avg depth. - Amount required: 2 - 4 ounces
105' x 105' Pond (.25) Acre 4 ft avg depth. - Amount required: 4 - 8 ounces
148' x 148' Pond (.50) Acre 4 ft avg depth. - Amount required: 8 - 16 ounces
208' x 208' Pond (1.0) Acre 4 ft avg depth - Amount required: 16 - 32 ounces

Duckweed Information Websites
Here are some websites we recommend if you are looking for more information.

Washington State Department of Ecology ntid2/descriptions/lemmin.html
Lemna minor (lesser duckweed) and Lemna trisulca (star duckweed) Duckweeds are among the world's smallest flowering plants. Individual lesser duckweed plants are tiny, round, bright green disks, each with a single root.
PLANTS Profile for Lemna valdiviana (valdivia duckweed) | USDA PLANTSA PLANTS profile of Lemna valdiviana (valdivia duckweed) from the USDA PLANTS database.: Kingdom Plantae – Plants Subkingdom Tracheobionta – Vascular plants Superdivision Spermatophyta – Seed plants Division Magnoliophyta – Flowering plants Class Liliopsida – Monocotyledons Subclass Arecidae Order Arales Family Lemnaceae – Duckweed family Genus Lemna L. – duckweed Species Lemna valdiviana Phil. – valdivia duckweed

Lemnaoideae - Wikipedia, the free encyclopedia 24 May 2009 ... Duckweed is an important food source for waterfowl and are eaten by humans in ... Classification of the duckweeds in the family Lemnaceae is ... - Cached - Similar - Lemna - Wikipedia, the free encyclopediaLemna is a genus of free-floating aquatic plants from the duckweed family. .... Lemna Ecotox testing Duckweed growth inhibition tests and standardisation ...
Duckweed and waterquality... a blessing in disguise. In fact, duckweed does much more than suck up every particle of Nitrate in your tank. In depth study will reveal that duckweed attacks ammonia vigorously, as well as Nitrates, Nitrites and just about any other molecule with the nitrogen atom in it, lol. In addition to that, duckweed sucks up phosphorus like a thin milkshake, actually removes suspended solids, and organic material and even other toxins!. As if that weren't impressive enough, it produces oxygen like nobodies business!

Homemade Duckweed Skimmer
If you are looking for a homemade duckweed skimmer then we saw on the PondBoss Forums of a fellow who used a "prickly rope" that he rigged up using a simple nylon rope and zip-ties to create an ingenious pond skimmer system that basically corrals the duckweed and traps it in the circle of the "prickly rope" where it can be easily removed. You have to see it to believe it and I bet it works too!
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Sonar® Aquatic Herbicide
This 41.7% Fluridone product is excellent for whole pond and lake treatments. A selective systemic aquatic herbicide for management of aquatic vegetation in fresh water ponds, lakes, reservoirs, drainage and irrigation canals. It is important to maintain the recommended concentration in contact w..
Starting at: $395.00

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