College ofAgricultural Sciences

Aquatic PlantControl

&PondManagement

3 Pond Management

3 Pond Construction

4 Pond Maintenance

4 Nutrient Management

5 Types of Aquatic Plants

5 Algae

5 Submerged Aquatic Vegetation

6 Emergent Plants

6 Floaters

7 Aquatic Plant Control—Management

Contents

Alternatives

7 Physical and Mechanical Control

8 Biological Control

9 Chemical Control

12 Commonly Controlled Aquatic Plants of PA

13 Algae

15 Submerged Aquatic Vegetation

18 Emergent Plants

20 Floaters

Pond Construction

Creating a pond that is an asset to apiece of property involves addressingmany variables before and during itsconstruction. The pond’s intendedpurpose—including recreation,irrigation, livestock watering, aesthetics,and fish production—usually dictatesits setting. As a result, expectations fora pond should be well defined andreasonable. Pond features are designedand constructed according to recom-mended standards. These standards,published by the U.S. NaturalResource Conservation Service, addresssafety, best construction practices, andease of maintenance. Expert advice andinformation can be indispensablebefore and during pond construction.

Groundwater sources are the bestcontributors of water to a successfulpond. If groundwater is not available,surface runoff or a small stream can bethe primary source of water. Ponds fedby surface runoff can have too littlewater in the summer months and toomuch after storm events. The drainagearea should be large enough to ensurethat combined surface runoff andseepage through the soil will maintainwater in the pond even during thedriest years. The best water sourcesexclude obvious nutrient input sourcessuch as agricultural runoff and sewage.

Other important pond features includesoil composition, water depth, andwater removal features such as aspillway, an overflow pipe, or adrainpipe. Soil composition is a criticalelement in pond construction. Soilmust contain enough clay to preventleakage. To characterize a pond site’ssoil and geological conditions, have aprofessional consultant undertake a siteinvestigation. The local U.S. NaturalResource Conservation Service orCounty Conservation District may beable to offer a partial listing ofexperienced pond contractors andconsultants in your county.

A good pond construction referencepoint is a water depth of at least 3 feetat a point 9 feet from the shoreline (a1:3 bank slope). This discourages algaeand aquatic plant growth. It is best toslope the banks at this angle at thetime of construction.

Pond Management

Pond construction.

3

A drainpipe is helpful to manipulatethe water level for fish managementpractices, pond repairs, or emergencysituations. Cutoff or anti-seep collarsplaced around the drainpipe duringconstruction prevent water fromseeping along the outside of the pipeand cutting a channel through thedam. A combination overflow pipe anddrainpipe is highly desirable for waterlevel management. The overflow pipeis always open to maintain a normalpool level, and the drainpipe is openonly at the discretion of the pondowner. These pipe sizes are determinedby the pond’s drainage area and storagecharacteristics.

Finally, an emergency spillway allowssafe overflow of storm water from a 50-to 100-year rainfall event. The spillwayusually is flat-bottomed and con-structed in an undisturbed bank at oneend of the dam. To prevent scouring,establish a good sod mixture. Toprovide an outlet for the normal flowof water, install the overflow pipe orL-shaped trickle tube through the damapproximately 12 inches below theemergency spillway. The tube shouldbe large enough to drain the full ponddown to normal water level within 24hours after the flow through theemergency spillway ends.

Pond Maintenance

A pond must be maintained ad-equately if its intended purposes are tobe realized throughout its expectedlife. Routine inspections and propercare of problems as they occur willsave time and frustration later. In somelocalities, burrowing animals such asgroundhogs and muskrats cause severedamage to dams or spillways. Preven-tion of burrowing pests can be builtinto the pond during the constructionby anchoring chicken wire over thearea to be protected. Installing riprapat least three feet below the watersurface also discourages burrowingrodents.

Nutrient Management

Runoff from barnyards, cropland,feedlots, sewage systems, and inten-sively managed turf areas such as golfcourses can introduce large quantitiesof nutrients to a pond. The nutrientswill contribute to increased aquaticplant growth.

The best way to control excessive algaeis to limit nutrient entry into the waterbody. The pond owner therefore musttreat the source of the problem ratherthan the symptoms. Nutrient reduc-tion efforts will not immediatelydecrease established rooted plants, butmay lead to long-term growth reduc-tion. Agricultural best managementpractices, reduction of lawn fertilizers,tall grass buffer strips, forestedcorridors, and on-lot septic systemmaintenance are a few ways to addressnutrient management.

If sediment enriches and fills a pond,dredging can be a remedy, albeit anexpensive one. The first steps in anydredging project should be to locatewhere the sediment originates, andthen to determine how the sedimentrelease may be controlled. Restorationof a pond to its original configurationusually provides significant benefits,but they can be short-lived. Dredgingis a regulated activity, and pond ownersshould consult the Department ofEnvironmental Protection beforebeginning any project.

Final stages of pond construction with emergency spillway.

Nutrient addition (cows and runoff).

4

Most water bodies support some type of plant life, depending on the environment inwhich they are located. Aquatic plants can be separated into four categories—algae,submerged aquatic vegetation, emergent plants, and floaters. These categories aredescribed in greater detail in the Commonly Controlled Aquatic Plants of PA sectionof this guide.

Types of Aquatic Plants

Algae, the most well-known andwidely distributed of all aquatic plants,occur in three different types—plankton, filamentous, and an attachedbranched form. Plankton algae(phytoplankton) are the minute,single-celled suspended types thatusually make the water pea-soup green,reddish, or brown. Filamentous algae,erroneously described as moss or slime,are filaments that can form dense matson rocks and other objects underwater.Attached branched algae, known asChara and Nitella, resemble someflowering plants but have no rootsystem. They often are gritty to thetouch and have a skunk-like odorwhen crushed.

Algae (see pg 13)

Submerged aquatic vegetation growsin deeper water and usually is rootedin the bottom of the pond. Mostleaves remain underwater until flowersand seeds form out of the water.Examples of submergents includecoontail, pondweeds, and commonelodea.

Submerged Aquatic Vegetation (see pg 15)

5

Most floaters are rooted plants thathave much of their plant structure,especially their leaves, floating on thewater surface. Examples of floatersinclude water lilies and spatterdock.They also can be unattached likeduckweed, which obtains its nutrientsthrough small rootlets dangling in thewater.

Floaters (see pg 20)

Emergents, such as cattails and rushes,grow along edges of the water body,with only short portions of their stemsand roots submerged. Sometimescalled marsh plants, they tend to causefewer problems for water users thanother plants do.

Emergent Plants (see pg 18)

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Aquatic plants become weeds whenthey impair the use of the impound-ment. An integrated pest management(IPM) approach to weed control canprevent aquatic vegetation fromreaching nuisance levels. Reducingsubmerged and floating aquatic plantsleads to increased algae growth byreleasing nutrients formerly bound upin living plant material. The IPMapproach combines water quality andpond construction features withphysical, mechanical, biological, andchemical controls to create a balancedmanagement plan. A cause-and-effectrationale must form the basis forcreating a customized plan for yourpond.

Physical and MechanicalControl

Several aquatic plant control alterna-tives exist. Physical removal is mosteffective for small quantities of plantsnear the shorelines. This techniqueconsists of cutting, mowing, raking,digging, or pulling. Pulling or cuttingmust be repeated several times toeliminate new growth as it appears.Most submerged aquatic vegetationcan reproduce through fragmentation.Harvesting cut plants reduces the rateof regrowth and the amount ofavailable nutrients.

Aquatic Plant Control—ManagementAlternatives

Physical removal of filamentous algae.

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oxygenate the water to some degree,push the oxygen-poor water to thesurface where it is reaerated through anexchange with atmospheric oxygen.Surface aeration (fountains) mayprovide limited plant control benefits.Aerating pond waters can activate anumber of complex processes that canhelp control blue-green algae. Pleasenote that aeration alone is not aneffective method of controlling aquaticweed and algae growth.

Biological Control

Biological plant control may beachieved by introducing a vegetation-eating fish. The triploid grass carp canbe very effective at controllingsubmerged aquatic vegetation, itspreferred food. Partial control offilamentous algae may occur as well.The triploid grass carp is a sterile, non-reproducing fish. This geneticallyaltered carp was created by exposingthe fertilized eggs to heat shock,causing both sexes of the fish to havethree sets of chromosomes (triploid)rather than the normal two (diploid).A negative characteristic of the triploidgrass carp is its defecation of consumedplant material, which causes recyclingof nutrients back into the water. Pondowners must obtain permits from thePennsylvania Fish and Boat Commis-sion before stocking triploid grass carp.

The use of mechanized weed controlequipment can be expensive because ofhigh maintenance costs. The mostwidely used type of mechanizedequipment is called a plant harvester(weed cutter). Plant harvesters cut offthe underwater rooted vegetation 4 to5 feet below the water surface, and areused mainly on large lakes. One of theadvantages of cutting includes theability to collect all aquatic vegetation,including filamentous algae andvascular plants. Weed cutters that donot harvest or collect the weeds fortransport to shore are not recom-mended because plant fragments canlive for long periods of time, developroot systems, and grow in areas thatpreviously were unaffected with a weedproblem. No additional equipment orprotective clothing is needed, andlimited operating experience or permitsare required.

Altering the pond environment tocontrol plants also is a viable option.Seasonal drawdowns can be helpful forsome lakes and ponds. A drawdowninvolves lowering the water in a pond,lake, or reservoir to expose sedimentsin the nearshore area. The degree ofplant control from a drawdown isdependent on plant species andtemperature. A drawdown accompa-nied by freezing temperatures providesthe greatest aquatic plant control. Apermit for drawing down an impound-

ment is required for ponds larger thanone acre or for any pond drawn downto conduct an activity that requiresanother state permit, such as aPennsylvania Department of Environ-mental Protection Waterways Obstruc-tion and Encroachment Permit.Additional information is availablethrough the Pennsylvania Fish andBoat Commission and the Pennsylva-nia Department of EnvironmentalProtection.

Aeration can provide limited aquaticplant control. The most efficient typeof aeration involves introducing airbubbles at the bottom of the lake orpond. The rising air bubbles, which

Mechanical harvester.

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Drawdown.

Koi, common carp, and Israeli carp arenot exclusive plant eaters and are notrecommended by the Fish and BoatCommission for plant control.

Chemical Control

Herbicides offer a widely used solutionto nuisance vegetation control, butshould be handled carefully. Select thecorrect chemical for the identifiedproblem plant, and make precise watervolume and chemical measurements.Read and follow the product labelcarefully. Using the wrong herbicidewill result in failure to control thetarget plant. Excessive application ratesalso can cause damage to nontargetplants and animals. Chemical controlalso indirectly may cause a fish kill,because oxygen is consumed by therapid decay of dead plants. To reducethis danger, treat only one-third toone-half of the pond at a time whencontrolling widespread growth. Whenapplying herbicides along shorelines orspot-treating weed beds, start applica-tions along the shoreline or in theshallowest area and apply out to thedeeper water. This will enable fish tomove into deeper water to escape thechemical.

Chemical control of algae can be aperplexing task. Chemicals of choicefall into two major categories, dyes andcopper compounds. Algicidal dyesblock sunlight penetration and inhibit

photosynthesis. They are chemicallybenign, but unsuitable in cases wherethe pond overflows, or where algaemats already have formed at the pond’ssurface. Copper compounds areeffective algicides, but may kill trout,channel catfish, triploid grass carp, andother sensitive fish at commonly useddoses (0.25 to 0.50 parts per million).When ponds overflow, downstreamaquatic life may be at risk from copper

treatments. Some resistant forms ofalgae require species-specific identifica-tion and specialized treatment bestprovided by a professional aquaticpesticide applicator. Effective algaecontrol usually integrates nutrientmanagement into the control plan.

Piscicides such as rotenone andantimycin have become important incontrolling excess fish populations. Usethese chemicals when stunting occursfrom overpopulation of certain fishspecies, or when manipulation of thefish community is desirable.

Permit Requirement

Use of an aquatic pesticide is aregulated activity, even if the chemicalis to be used in a private pond. A jointPennsylvania Fish and Boat Commis-sion/Pennsylvania Department ofEnvironmental Protection “Applicationand Permit for Use of an Algicide,Herbicide, or Fish Control Chemicalin Waters of the Commonwealth” must

Triploid grass carp.

Granular application of herbicide.

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be submitted and approved by bothagencies before the pesticide is used.Aquatic pesticides must be registeredwith the U.S. E.P.A., listed with thePennsylvania Department of Agricul-ture, and labeled specifically foraquatic use. The permit applicationrequires the following information:

● name and location of the waterbody

● specific uses of the water body● presence of warmwater or coldwater

fish● total area of the water body and the

treatment area● average depth of the water body● name of plant or fish to be

controlled● commercial and manufacturer’s

name of the chemical to be applied● dosage of each chemical to be

applied● number of treatments to be made

throughout the year

Effects of the chemical in and down-stream from the impoundment areconsidered in the approval process. Ifthe water body overflows, downstreamaquatic life may be affected. In animpoundment with a wet weatherdischarge, avoid problems by treatingwhen little or no overflow is occurring.Treatment is more likely to be effectiveif the chemical stays in the water body.

Determining Chemical Dose

The most important differencebetween treating aquatic and terrestrialsettings is that some treatments arecalculated three-dimensionally (i.e., byvolume rather than by area). Anaccurate calculation of the amount ofchemical to be used must begin withaccurate determinations of pond areaand volume. Determine area geometri-cally or with a map and planimeter.Determine volume by accuratelycalculating average depth and multiply-ing by impoundment area. Thestandard unit of volume is an acre-foot,

Cutrine application.

10

equivalent to one acre of water with adepth of one foot or 325,804 gallons.Volume changes markedly with waterlevel variations. Accumulated sedimentor organic material diminishesimpoundment area and volume overtime. Accommodate these changeswhen calculating the amount ofchemical to use. An example follows.

Given:

1 acre = 43,560 square feet

Area of a rectangle in acres =

length in feet x width in feet

43,560 feet2

Area of a triangle in acres =

1/2 length of base in feet x height in feet

43,560 feet2

Area of a circle in acres =

3.14 x (radius in feet)2

43,560 feet2

Volume in acre-feet =

area in acres x average depth in feet

Area and Volume CalculationsUsing the pond-specific and generalinformation provided above, make thefollowing calculations:

Area of nearly rectangular sample pond =

335 feet x 130 feet

43,560 feet2

0.99977 acre =

1.0 acre

Average depth =

8 + 6 + 3 + 7 + 4 + 2 feet

6

30 feet

6

5 feet

Volume of example pond =

1.0 acre x 5 feet average depth =

5 acre-feet

Determining Amount of ChemicalSelect the chemical dose using theproduct label and the plant to becontrolled.

Chemical #1 example:The pond above has a heavy algaegrowth. Treat only half of the pondarea at a time to prevent oxygendepletion. To determine the amount ofalgicide needed, use the followingcalculations when treating with adosage of 0.7 gallon/acre-foot.

Treatment volume =

5 feet deep x 0.5 acre =

2.5 acre-feet

2.5 acre-feet x 0.7 gallon/acre-foot =

1.75 gallons of algicide

Chemical #2 example:For control of pondweed (Potamogeton)in one-third of the example pond, usea chemical dose of 1.5 gallons/acre.

Pond area =

1 acre x 1/3 pond =

0.33 acre:

0.33 acre x 1.5 gallons/acre =

0.5 gallon of aquatic herbicide

For typical application rates ofcommonly used aquatic herbicides, seethe table on page 22.

Chemical Mode of Action

The following information explains themodes of action for some pesticidescommonly used in Pennsylvania.

Aquatic DyesAquatic dyes are a blend of blue andyellow dyes specifically designed toshade portions of the light spectrumrequired by underwater aquatic plantand algae growth. These dyes normallyare used to control planktonic algae,but also can inhibit photosynthesis infilamentous algae and submergedaquatic vegetation if applied earlyduring the growing season.

Copper Sulfate and Chelated CopperProductsCopper sulfate controls many speciesof algae in lakes, ponds, and reservoirs.Copper works well because it disruptsthe cell membrane, which inhibits thecell growth. Trout and other sensitivespecies of fish may be killed atapplication rates necessary to controlalgae. Chelated copper products orcopper complexes kill algae using thesame mode of action as copper sulfatebut do not precipitate out of solutionin hard water as easily as coppersulfate. Copper products can be usedin combination with other productsfor specialized treatment of submergedaquatic vegetation. Copper is moretoxic when water is soft (< 50 ppmCaCO3 hardness) and acidic (pH < 7.0).

Diquat DibromideDiquat is a chemical that is quicklyabsorbed by plant tissues and interfereswith photosynthesis. If it does notcontact plant tissue, it binds rapidlyand firmly to soil particles, sediments,and bottom mud. Diquat decomposesin aquatic environments throughmicrobial degradation and exposure tolight.

FluridonePlant shoots absorb the active ingredi-ent fluridone from water, and aquaticplant roots absorb it from hydrosoil.Absorbed fluridone inhibits caroteneformation. The absence of carotenepigment causes unprotected chloro-phyll to photodegrade.

GlyphosateGlyphosate moves through the plantfrom the point of foliage contact toand into the root system. This resultsin a cessation of growth, cellulardisruption, and eventually plant death.

EndothallAquatic herbicides containingendothall as the active ingredientfunction as contact-type, membrane-active herbicides that inhibit photosyn-thesis. No endothall or toxic metabo-lite is accumulated in water orhydrosoils; however, fish consumptionis prohibited for 3 days followingendothall application.

2,4–DThe application of 2,4–D causes theplant cells to divide rapidly andrespiration to increase while photosyn-thesis decreases. The food supply oftreated plants is nearly exhausted attheir death. The roots of the treatedplants lose their ability to take up soilnutrients, and stem tissues fail to movefood effectively through the plant. Thekilling action is not caused by anysingle factor, but results from theeffects of several disturbances in thetreated plant.

Depth soundings

Example:

335 feet (pond length)

13

0 fe

et(p

ond

wid

th)

6’ 3’8’

7’ 4’ 2’

=

=

=

11

V V V

Commonly Controlled Aquatic Plants of PA

12

Algae

Algae are simple plants without true roots, leaves, or flowers. They reproduce by cell division, by plant fragmentation, or by spores.They are found either free-floating in the water or attached to other plants, bottom sediments, rocks, or other solid substrates.Three types of algae (see chart below) include microscopic algae, mat-forming filamentous algae, and attached branched algae, alsoknown as Chara and Nitella.

Nitella

13

Algae

Chara

Commonly used herbicides for algae control.

Aquatic herbicide Active ingredient Planktonic algae Filamentous algae Chara and Nitella

Aquashade/Aquashadow/ Acid blue 9 dye 23.6% xLesco Hydroblock Acid yellow 23 dye 2.4%

Copper Sulfate CuSO4 99% x x

Cutrine-Plus Copper, elemental 9% x x x(triethanolamine complex)

Cutrine-Plus (granular) Copper, elemental 3.7% x x x(ethanolamine complex)

Earthtec Copper, elemental 5% x x x

Hydrothol 191 Monopotassium salt of x x xendothall 53%

K-Tea Copper, elemental 8% x x x(triethanolamine complex)

Lescocide-Plus Copper, elemental 9% x x x(ethanolamine complex)

Lescocide-Plus (granular) Copper, elemental 3.7% x x x(ethanolamine complex)

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Submerged Aquatic Vegetation

Submerged plants grow in deeper water and usually are attached to the bottom of the pond. They remain underwater until flowersand seeds form out of the water. Examples include pondweed, milfoil, and coontail. Additional plants are included in the chart onpage 17.

Curlyleaf pondweed

Eurasian watermilfoil

15

Largeleaf pondweed

Coontail

Elodea

16

Naiad

Bladderwort

Commonly used herbicides for submerged aquatic vegetation control.

Aquatic Pondweed Bladder-herbicide Active ingredient (Potamogeton) Milfoil Coontail Naiad Elodea wort

Aquathol-K Dipotassium salt of x x x xendothall 40.3%

Reward or Diquat Diquat dibromide 35.3% x x x x x

Weedtrine-D Diquat dibromide 8.53% x x x x x x

Hydrothol 191 Monopotassium salt of x x x x xendothall 53%

Sonar SRP Fluridone 5% x x x x x x

Komeen Copper, elemental 8% x x x x(ethylenediamine complex)

17

Emergent Plants

Emergents grow along the water body edges, with only short portions of their stems and roots submerged. Sometimes called marshplants, they tend to cause fewer problems for water users than the other plants. Examples include cattail, water lily, rushes, andarrowhead. Additional plants are included in the chart on page 19.

Cattail

18

Common reed (Phragmites)

Bulrush

Commonly used herbicides for emergent plant control.

CommonAquatic Active reed Purpleherbicide ingredient Cattail (Phragmites) Bulrush Arrowhead Pickerelweed loosestrife

Rodeo Glyphosate 53.8% x x x x

Weedtrine II 2,4–D (28.9%) x x x

19

Purple loosestrife

Floaters

Floaters are rooted plants that have much of their plant structure, especially leaves, floating on the water surface. They also can beunattached like duckweed, which obtains its nutrients through small rootlets dangling in the water. Examples include watermealand spatterdock. Additional plants are included in the chart on page 21.

Water lily with extracted root system

Duckweed

20

Watermeal (on index finger, compare to larger duckweed)

Commonly used herbicides for floating plant control.

Aquatic herbicide Active ingredient Watermeal Water lily Duckweed Spatterdock Watershield

Rodeo Glyphosate 53.8% x x x

Sonar A.S. Fluridone 41.7% x x x x

Aqua-Kleen/Aquacide/ 2,4–D (20–27.6%) x x xNavigate

21

Spatterdock

Watershield

Dosages and summary of commonly used herbicides for aquatic plant control.

Aquatic herbicide Active ingredient Controls Dosage

Algae

Aquashade/Aquashadow/ Acid blue 9 dye 23.6% Filamentous algae, early sup- 1 qt/acre-ftLesco Hydroblock Acid yellow 23 dye 2.4% pression of some submerged plants.

Copper Sulfate CuSO4 99% Flagellated algae .68–1.36 lb/acre-ft

Cutrine-Plus Copper, elemental 9% Planktonic/filamentous algae, 0.6 gal/acre-ft(triethanolamine complex) Chara and Nitella 1.2 gal/acre-ft

Cutrine-Plus (granular) Copper, elemental 3.7% Planktonic/filamentous algae, 60 lb/acre(ethanolamine complex) Chara and Nitella

Earthtec Copper, elemental 5% Planktonic/filamentous algae, 0.22 gal/acre-ftChara and Nitella

Hydrothol 191 Monopotassium salt of Planktonic/filamentous algae, 0.6–2.2 pt/acre-ftendothall 53% Chara and Nitella

K-Tea Copper, elemental 8% Planktonic/filamentous algae, 0.7–1.7 gal/acre-ft(triethanolamine complex) Chara and Nitella 1.7–3.4 gal/acre-ft

Lescocide-Plus Copper, elemental 9% Planktonic/filamentous algae, 0.6 gal/acre-ft(ethanolamine complex) Chara and Nitella 1.2 gal/acre-ft

Lescocide-Plus (granular) Copper, elemental 3.7% Planktonic/filamentous algae, 60 lb/acre(ethanolamine complex) Chara and Nitella

Submerged aquatic vegetation

Aquathol-K Dipotassium salt of Pondweed (Potamogeton), milfoil, 0.6–1.9 gal/acre-ftendothall 40.3% coontail, naiad

Reward or Diquat Diquat dibromide 35.3% Coontail, elodea, naiad, pondweed, 1–2 gal/acremilfoil

Weedtrine-D Diquat dibromide 8.53% Bladderwort, coontail, elodea, naiad, 5–10 gal/acrepondweed, milfoil

Hydrothol 191 Monopotassium salt of Naiad, elodea, coontail, pondweed, 0.7–3.4 gal/acre-ftendothall 53% milfoil

Sonar SRP Fluridone 5% Bladderwort, coontail, elodea, naiad, 3.2–5 lb/acre-ftpondweed, milfoil

Komeen Copper, elemental 8% Milfoil, elodea, pondweed, 1.7–3.3 gal/acre-ft(ethylenediamine complex) coontail (not an algicide)

Emergent plants/floaters

Rodeo Glyphosate 53.8% Cattail, water lily, arrowhead, spatter- 0.75 gal/acredock, watershield, purple loosestrife,common reed

Sonar A.S. Fluridone 41.7% Duckweed, watermeal, spatterdock, < 5’ deep .16–1.25 qt/afwater lily. Also coontail, elodea, > 5’ deep 1–1.5 qt/afpondweed, milfoil

Weedtrine II 2,4–D 28.9% Arrowhead, bulrush, creeping water 200 lb/acreprimrose, pickerelweed

AquaKleen/Aquacide/ 2,4–D 20–27.6% Water lily, spatterdock, watershield. 150–200 lb/acreNavigate Also milfoil, bladderwort 100–150 lb/acre

Note: See product label for use and dose details.

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IllustrationsRae Chambers

Photo creditsDaniel J. AngeloMark HartleHoward NuernbergerAnn F. Rhoads, Morris Arboretum,University of PennsylvaniaStroud Water Research CenterArchives

Prepared by Daniel J. Angelo, PennState University Pesticide EducationProgram, Mark Hartle, PennsylvaniaFish and Boat Commission, Divisionof Environmental Services, andWinand K. Hock, professor of plantpathology and director of the PesticideEducation Program.

Penn State College of Agricultural Sciencesresearch, extension, and resident educationprograms are funded in part by Pennsylvaniacounties, the Commonwealth of Pennsylvania,and the U. S. Department of Agriculture.

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Where trade names appear, no discrimination isintended, and no endorsement by the Penn StateCollege of Agricultural Sciences is implied.

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© The Pennsylvania State University 1998

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