Aquatic Plant Management (2003)

8/11/2019 Aquatic Plant Management (2003)

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quatic Plant Aquatic PlantMan agement Man age ment quatic PlantAquatic PlantMan agement Man age ment

Carole A LembiCarole A. Lembi

Professor of BotanyProfessor of BotanyPurdue UniversityPurdue University

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Table of Contents

The Bene ts of Aquatic Vegetation . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Problems Caused by Excessive Aquatic Vegetation . . . . . . . . . . . . . . . .1Aquatic Plant Identi cation Guide Algae . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3 Flowering Plants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Aquatic Plant Management Methods Preventive Control Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Mechanical Control Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8 Biological Control Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9 Habitat Alteration Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 Chemical Control Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10 What You Need to Know Before Using a Chemical . . . . . . . . . . . . . .11 Algicides and Aquatic Herbicides . . . . . . . . . . . . . . . . . . . . . . . . . . . .12 Algicide and Aquatic Herbicide Guidelines and . . . . . . . . . . . . . . . . .14 Water Use RestrictionsSpeci c Algae and Aquatic Plant Problems . . . . . . . . . . . . . . . . . . . . .15Comments on the Use of Barley for Algae Control . . . . . . . . . . . . . . .16


3/211Aquatic Plant Management

6. A diversity of aquatic plant life, both around andin the water, can add visual interest and beauty toa water body. One of the largest growing sectorsof the home nursery industry is water gardening.Many people now recognize and appreciate theaesthetic and natural qualities of aquatic veg etation,whether in a backyard set ting, around a retentionpond in an urban area, or along the shoreline of alarge lake.

Because of these many bene ts, some aquaticplant growth is always desirable. The goal ofman age ment should never be to totally eliminateaquatic veg eta tion from a site.

Problems Caused by ExcessiveAquatic Veg e ta tionUnfortunately, plant growth can get out of hand.Excessive plant growth is usually due to the factthat many of our bodies of water are shallow, which

allows sunlight to penetrate to the bottom andsupport photosynthesis. Also, our bodies of watertend to be rich in nutrients such as nitrogen andphosphorus (substances that are needed by plants forgrowth). In some cases, exotic species of plants thatare extremely aggressive have been introduced andhave taken over large areas of aquatic habitat. Someof the problems caused by excessive aquatic plantgrowth are as follows:

The Benets of AquaticVegetationAlthough this guide is primarily devoted to man agingor reducing the amount of aquatic veg etation presentin a body of water, the reader should be aware thataquatic plants have many important functions inaquatic systems. Just as on land, plants in water arenatural and essential components of the environment,and without them, life as we know it could not exist.All plants, whether on land or in the water, utilize

sunlight, carbon dioxide, and water to photosynthesize.The process of pho tosyn thesis results in the productionof new plant tissue (biomass) and oxygen. In water,new plant biomass takes the form of either microscopicplants or larger plants called macrophytes. Why arethese plants so im por tant to the aquatic environment?

1. Microscopic plants (algae) form the base of theaquatic food chain. Another term for these plantsis phytoplankton or plant plankton. They,in turn, are fed upon by zooplankton, or themicro scop ic animal plankton. Zooplankton arefed upon by small sh, small sh by larger sh,and so on up the food chain to humans and othertop predators.

2. The macrophytes (larger algae and oweringplants) provide habitat and shelter for sh, shfood organisms, wa ter fowl, and other wildlife.

3. Macrophytes provide food for insects, wa ter fowl,and mammals such as muskrats and beaver.However, bass, bluegill, and cat sh do not, asa rule, eat macrophytic vegetation.

4. All plants produce oxygen as they pho tosyn thesizeduring the daylight hours. Photosynthesis is themajor source of oxygen for aquatic animal life.

5. Rooted plants stabilize shorelines and bot tomsediments; uprooting these plants can lead toshoreline erosion and increased turbidity in abody of water.

AQUATIC PLANT MANAGEMENTCarole A. Lembi, Pro fessor of Botany

Department of Botany and Plant Pa thol ogy, Purdue UniversityE-mail: [email protected]

Purdue Extension ! Knowledge to Go


4/212 Botany and Plant Pathology

1. Recreational activities such as swimming, shing, and boating can be impaired and evenpre vent ed.

2. Excessive growths can lead to sh stunt ing andoverpopulation. This occurs because the pro duc tionof too much habitat prevents effective pre dationof small sh by larger sh.

3. Aquatic plant and algae growths can play a rolein causing sh kills. This usually occurs be causeoxygen is taken out of the water. During the day,plants produce oxygen through pho tosyn the sis;at night (as well as day), they con sume oxygenthrough respiration. If plant growth is excessive,plants at night can use up most of the oxygenin the water. In fact, sh that are stressed foroxygen often die just before dawn when theoxygen content is lowest. Sometimes they canbe ob served coming to the surface and gaspingfor air during the early morning hours. This isa sure sign that the sh are oxygen stressed andmay die.

Oxygen depletion also occurs when algae and plantsdie and decompose. When plants die, pho tosyn thet icproduction of oxygen ceases, and the bacteriaand fungi, which break down (decompose) thedecaying plant material, use up the oxygen in theirown respiration. Unfortunately, it is dif cult topredict when a plant die-off will occur under natural

conditions. Changes in water temperature, pro longedperiods of cloud cover, shifts in wind pat terns, anddepletion of nutrients are just some of the factorsthat may trigger a plant or algae die-off. Anothercause of plant death and oxygen depletion is thetreatment of too much vegetation with a herbicide(see page 11 f or more information).

Similarly, it is almost impossible to predict whenor if sh are going to die because of veg etation-related oxygen depletion. Fish kills typically occur

in the summer or in the winter. Summer

sh killscan be caused, as already described, by die-offs anddecom position of algae and plant growth. Anothercause can be due to a dense cover of algae or free- oating plants such as duckweed or watermealon the sur face of a body of water. These surfacegrowths reduce light penetration to the deeperwaters which in turn inhibits photosynthesis andoxygen pro duc tion. Anything that stirs or brings

these deox ygen ated waters to the surface (such asa brisk wind) can result in lowered oxygen levelsthroughout the water column and cause a sh kill.Even if sh are not immediately killed, pro longedexposure to low oxygen concentrations can lead togreater sh susceptibility to diseases and toxicants.

Fish kills in winter occur when snow ac cumulateson ice cover. Light is blocked, thus pre vent ingphotosynthesis and oxygen production by any livingplants or algae. Decomposition of plants that diedin the fall causes further oxygen depletion. Thefact that a site has undergone a winter sh kill maynot even be recognized because the dead sh candecom pose and disappear under the ice or as the icebreaks. It may not be until spring or early summerthat people notice that shing is not what it used tobe. Other causes of sh kills include natural stress eson sh as they come out of the winter and into

the spawning season, insecticide runoff, am monialeakage from storage tanks, and diseases.

4. Aquatic weed growth provides quiet water areasideal for mosquito breeding.

5. Certain algae can impart foul tastes and odorsto the water.

6. Weeds impede water ow in drainage ditches,irrigation canals, and culverts and cause waterto back up.

7. Deposition of weeds, as well as sediment anddebris, can cause the gradual lling in of bodiesof water.

8. Excessive weed growth can lower propertyvalues and decrease aesthetic appeal of a bodyof water.

9. Exotic aquatic plant species (e.g., Eur asianwatermilfoil, purple loosestrife) can invade andcompletely take over stands of native veg etation.This process upsets the natural balance in anaquatic system and can have adverse effects onthe animals that depend on the native vegetationfor habitat and food.

What are the aquatic plants that most fre quent lycause these problems? The following guide isintended to help you identify these plants.



Aquatic Plant Identication GuideMost aquatic plants can be divided into two bo tan ical groups: algae and owering plants. Algae are usuallyvery simple in structure, but some (for example, Chara) can resemble owering plants. For effectivemanagement, it is essential that you dis tinguish between algae and owering plants.

AlgaeThere are three general types of algae: microscopic algae, lamentous mat-forming algae, and Chara.

A bloom of microscopic algae causing a surface scum.

Mat-forming algae.

Chara, an alga.

Chara or stonewort usually grows in very hardwater and often is calci ed and brittle. The plantis rooted, and leaves are arranged along the stem inwhorls. Because of this overall structure, it is oftenconfused with owering plants, but it is an alga andshould be managed as such. The plant is completelyunderwater and has a very distinctive musky smell.In bodies of water where it is low-growing, itpro vides valuable habitat for sh and sedimentstabilization. Under these conditions it should notbe disturbed. In shallow water it can, however, growup to the surface and be troublesome.

Filamentous, or mat-forming algae (often in cor rect ly called moss) form oating, mat-like growths that usuallybegin around the edges and bottoms of bodies of water in the spring. This type of growth is probably the mostcommon in ponds in the Midwest.

Microscopic algae form scums and/or color thewater green or yellow-green. Sometimes they cancause red, black, or oily streaks in the water. Whenin suf cient numbers to color the water they arecalled blooms. Die-off of these algae can cause sh kills. Blooms usually occur where abun dantnutrients (e.g., nitrogen and phosphorus fer tilizers)are reaching the water. The best solution formicroscopic algal blooms is to prevent the inputof nutrient-laden water.

Mat-forming algae.



Flowering PlantsFlowering plants are more complex in their structure than algae. In addition to producing owers, they havean internal conducting system which algae lack. Flowering plants can be grouped into broad categoriesaccording to where they are found in a body of water.

Submersed PlantsSubmersed plants are rooted in the bottom sediments and grow up through the water. Flowers or oweringspikes sometimes emerge above the water surface. Some of the pondweeds, such as American pondweed,have both underwater leaves and leaves that oat on the water surface. The main criteria for identi cationare leaf arrangement and leaf shape. The plants shown here are some of the most common underwaterplants with weedy char acter istics. However, within almost every group there are species that have value for sh and/or wildfowl habitat. For example, curly-leaf pondweed is an invasive weed, but beds of large-leafpondweed provide good shelter for game sh. Eurasian watermilfoil also is a very aggressive, introducedweed, but other milfoil species are native and have less potential as weeds. Information beyond what thisbulletin can provide is necessary for complete aquatic plant identi cation.

Curly-leaf pondweed

Alternate leaf arrangement(one leaf per node). Growsbest in the spring and tends todie out in the summer. Foundin both lakes and ponds.

Leafy pondweed

Very narrow leaves alternate leaf arrangement.Extremely common in farmponds in the summer.

EmergentPlants

Rooted-FloatingPlants

Free-FloatingPlants

SubmersedPlants

American elodea

Three leaves at a node. Verycommon in lakes and ponds.



Sago pondweed

Leaves are almost thread-like. Individual leavestend to be slightly curved. Although a weed in somesituations, the seeds and underground tubers arevaluable as food for waterfowl.

American pondweed

Leaves that oat on top of the water surface areabout 1 to 4 inches long. Usually restricted toshallow water.

Brittle naiad

Opposite (two leaves per node) leaf arrangement;sometimes three leaves appear at a node. Leavesslightly spined. More common in southern portionsof the north central region.

Southern naiad

Opposite leaf arrangement, sometimes appearingas three leaves at a node. Very common in lakesand ponds.

Coontail

Whorled leaf arrangement (more than two leavesat a node); leaves branched and spined. Verylightly rooted or oating in the water column.Very common in shallow, marsh-like areas.Diagram: an individual leaf.

Eurasian watermilfoil

Four leaves at a node. Each leaf is feather-like. Aserious and rapidly spreading invader. Eurasianwatermilfoil typically has more than 10 lea et pairsper leaf whereas native milfoils have fewer than 10.Diagram: an individual leaf.



Free-oating PlantsFree- oating plants such as duckweed and watermeal can completely cover the surface of a pond.Complete surface coverage by these plants shades out underwater plants, thus causing oxygen depletion inthe deeper water. These plants are extremely small. Duckweed is no more than 1/4 to 1/2 inch in diameter;each plant has a small root that hangs into the water. Watermeal plants have no roots and look like tiny greenseeds or green corn meal. Both plants are found in nutrient-rich waters; therefore, restricting nutrient inputscan be helpful in management.

DuckweedNote the roots hanging from the plants.

Watermeal

Most of these very tiny plants are watermeal. There

are also some duckweed plants and an air bubble.

A pond totally covered with watermeal.Watermeal plants look like tiny green seeds.

Rooted-oating PlantsRooted- oating plants include waterlily, spat terdock, and watershield. These plants are generally found inshallow water less than 4 to 5 feet deep. Spatterdock has a massive underground rhizome from which newplants can sprout. It differs from waterlily in having a heart-shaped rather than round leaf, and the leavescome above the surface of the water rather than oat. Spat terdock has yellow owers and is sometimescalled yellow cow lily. This group of plants provides valuable wildlife habitat and should be protected innatural lake and wetland areas.

Spatterdock Waterlily



Emergent PlantsEmergent (shoreline or marginal) plants include grass-like and broadleaved plants. Grass-like plantscommonly include cattails, bulrushes, spikerushes, and reed canarygrass. Broadleaves include willowtrees, creeping water primrose, and purple loosestrife. Purple loosestrife is an invader of wetland areas, hasno wildlife value, and is con sid ered a serious weed. Many of these plants spread rapidly by undergroundsystems as well as by seed.

WatershieldThe leaves are only 2 to 5inches in length. The petiolesand undersides of the leavestend to be slimy. Note howthe petiole joins the leaf atthe middle of the leaf.

CattailPlants 5 - 7 ft. tall.

SpikerushPlants usually no more than 1 ft. tall.

BulrushPlants 3 - 7 ft. tall.

Creeping water primrosePlants low growing in shallow water.

Purple loosestrife

A serious wetland invader.Flowers are purple.

Watershield leaves oating on thewater surface.

Phragmites

Also called common reed.An aggressive grass; plantstypically 10 to 12 ft. tall.Rapidly spreading alongroadsides, ditches, and intowetlands.



2. Maintain a good sod and grass cover around thebody of water or areas that drain into the water.The planting of native perennial species such assweet ag, water iris, and certain types of sedgesis also effective in absorbing nutrients that might ow into a body of water and in reducing soilerosion. These plants can give a body of watera more natural look, and it is thought that tallervegetation reduces the chances of Canada geesecolonizing a water site. Consult with the plantsupplier to make sure the species you choose arenot overly invasive. For example, some supplierssell Phragmites and com mon cattail. Theseplants can be dif cult to keep from spreading.However, dwarf species of each are available andshould be less aggressive.

3. Do not apply lawn fertilizers any closer than10-20 feet from the shoreline.

4. Do not allow livestock access to a pond exceptunder conditions of extreme heat stress. If thewater is used for livestock, fence the pond. Waterthe animals from a stock tank below and outsidethe fence. Animals in the water will increaseturbidity and fertility and tear down the banks.

5. Check septic tanks for possible leakage or seepageinto the water. New septic drainage elds shouldbe directed away from the body of water.

6. Do not permit runoff from chicken coops,feedlots, etc. to enter the body of water. If thiskind of runoff is occurring upstream from yourwater site, you should check with your countyboard of health to see if anything can be doneabout it.

7. Establish a settling or retention pond or wetlandarea to receive and settle out nutrients before the ow reaches the main body of water.

All of these measures will help prevent weedgrowth, particularly in a newly constructed bodyof water. In older bodies, these measures will aidin gradually reducing infestations of free- oatingplants such as microscopic algae and duckweed.

Mechanical Control MethodsEven with preventive measures, many bodies ofwater still have severe plant infestations. Hand-pulling or raking plants is a possible method ofcontrol. Since most aquatic plants are perennial,

Aquatic Plant ManagementMethodsThe goal for a person managing a body of wateris to achieve a balance. As discussed earlier, somevegetation, particularly native species, is highlydesirable and adds interest and appeal. A sterile,swimming pool effect for a natural body of

water should be avoided. How do we achievethis balance between too much vegetation and toolittle? We attempt to do it by careful use of one orseveral management methods. These are preventive,mechan ical, biological, habitat alteration, andchemical methods.

Preventive Control MethodsMany aquatic plants or their seeds are carried into abody of water by wind, birds, sh introduction, boattrailers, shermen, etc. Plant fragments, even less

than an inch long, that do not completely dry outduring transfer can survive and produce new plants.It is quite possible that the recent proliferation ofCanada geese has resulted in the increased spreadof algae and certain aquatic plants. Prevention startswith eliminating or re duc ing these causes of spread;e.g., discourage geese from visiting your water body,wash plant fragments off of boat trailers and boatsbefore moving to a new site, and remove plantfragments from live wells and when moving shor sh bait from one site to another.

Newly introduced plants become infestationsonly if the water conditions are just right. Goodgrowing conditions usually mean that the body ofwater is shallow or has shallow areas with goodlight pen etra tion, and has an available source ofnutrients (nitrogen and phosphorus), either in thewater or stored in the sediment. Often nutrientsenter a body of water from runoff or stream ow.Nutrient inputs can be reduced by initiating agood man age ment plan for the watershed (the area

that drains into the body of water). In addition tosurveying the watershed and reducing or eliminatingobvious nutrient or sediment sources, you can do thefol low ing things:

1. Do not fertilize your pond or lake. MostMidwestern waters are suf ciently rich inplankton and other food organisms to supportlarge sh without being fertilized.



with underground portions that can resprout newshoots, it is essential that below-ground growth also beharvested. In the case of larger plants such as cattails,this is dif cult to do. Hand-held devices for cuttingor pulling plants in small areas are available fromdealers that specialize in aquatic/ sheries supplies.

For larger bodies of water, motor-driven un der waterweed harvesters are available. This equipmentusually is a major investment and may have tobe operated several times during the season toeffec tive ly keep the vegetation cut back. Thepremise is the same as mowing a lawn. The plantswill not be eliminated, but they can be preventedfrom growing to the surface and becoming anuisance. Mechanical harvesters have been usedsuccessfully to cut chan nels through vegetation,which allows boat traf c to move out to open water.The cut vegetation should be harvested and dumped

where it cannot reenter the water. Plant fragmentsleft to oat in the water can produce a new plant.The harvested material can be satisfactorily used asa fertilizer or mulch in gardens or as land ll.

Some states require permits for harvesting on nat urallakes; check with your state regulatory agenciesto determine if such permits are required. Indianaresidents: A permit from the Indiana Departmentof Natural Resources is required for the mechanicalharvesting of vegetation in public waters that are

more than 25 feet along the shoreline, greater thana water depth of 6 feet, and greater in area than 625square feet. A permit is not required for privatelyowned lakes, ponds, or drainage ditches.

More information on mechanical harvesters canbe obtained at the fol lowing Web sites: UnitedMarine International , Aquarius Systems , and Aqua marine Aquatic Plant Harvesters. These are only three ofseveral companies; their listing does not implyan endorsement of their products.

Biological Control MethodsBiological controls (organisms that control pestorganisms) have received considerable publicity.Bacteria, fungi, and insects currently are beingtested for their ability to reduce aquatic plantinfes tations. Certain insects appear to have potentialfor the control of Eurasian watermilfoil and purple

loosestrife. Insects have been released at selectedsites in the Midwest for the control of both plants,but it is too early to know whether they will beeffective on a widespread scale. Waterfowl suchas swans can keep small ponds weed-free, but theyrequire husbandry and protection from predators.They also are extremely aggressive during andfollowing the breeding season.

Check with the appropriate state regulatory agencyor sh and game agency to determine if a biologicalcontrol agent is legal in your state and for permittinginformation and restrictions if it is. Indianares idents: A permit from the Indiana Departmentof Natural Resources is required for the introductionof a biological control agent in all public waters.A permit is not re quired for privately owned lakes,ponds, or drainage ditches (however, note restrictionsbelow on use of grass carp in private waters).

The most widely used bi olog ical control agent todate is a herbivorous sh, the grass carp (also knownas the white amur).

The grass carp is native to China and Russia. Itcan live 15-20 years. This sh consumes some lamen tous algae and most submersed plants. Sinceit has the potential to denude a body of water of itsunder water veg etation, it must not be released innat ural lakes and wetland areas where vegetationis critical to sh and wildlife. In Indiana the land

surrounding the pond or lake must be totally inprivate ownership and all precautions must be takento prevent escape of the sh from the stocked area.Barriers should be erected at the spillway or out ows.

The type of grass carp that is most commonlylegal is the triploid grass carp, a form that will notrepro duce itself. In Indiana, sh must be purchasedfrom a holder of an Aquaculture Permit. The permitholder must deliver and stock the sh and presentthe purchaser with a bill of sale and copy of triploid

cer ti

cation. It is the responsibility of the purchaserto retain these documents for at least two years.

In Indiana, stocking rates are 15 or 30 sh pervegetated acre. Fish should be 8-12 inches long.Vegetation can be thinned with as few as ve shper vegetated acre. Smaller sh will be rapidlyremoved by predators such as bass. The lowerstocking rate is recommended for most ponds so thatsome vegetation remains. Where total vegetation
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control is desired (e.g., in ponds on golf courses),the higher stocking rate can be used. Vegetationcontrol may not be observed for a yearor more; after about ve years, the grass carp slowsits feeding rate, so that more sh may be needed tomaintain adequate vegetation control.

Although the grass carp has provided good controlof aquatic vegetation in some situations, it is not thesolution for all ponds. Since its effects on veg etationmay not be noticed for a year or more, it may bedif cult to determine if enough sh are still presentin the pond to be effective. In addition, the grasscarp prefers certain plant species over others. Forexample, it will consume native species such aspondweeds before it will feed on truly troublesomeweeds such as Eurasian watermilfoil or mat-form ingalgae. It is not effective on duckweed or watermeal.

Triploid grass carp are legal for use in Indiana,Illinois, and Ohio. They have not been approvedfor use in Michigan, Minnesota, and Wisconsin.

Habitat Alteration MethodsCertain methods of manipulating or altering theaquatic environment can be effective in aquatic plantmanagement. One of the more successful methodsis the drawdown technique in which water levels arelowered over the winter. Exposure of the sedimentsin the shallow areas of a lake or pond to alternatefreezing and thawing action will kill the un der groundstructures of many aquatic plants. This methodhas been successful for the control of Eur asianwatermilfoil and waterlilies, although the degreeof control depends on the severity of the winter.

Other types of habitat manipulation includeriprap ping shorelines or anchoring black plasticsheeting on the bottom sediments to prevent rootedplant growth. Dyes such as Aquashade are used toinhibit light penetration throughout the water. Thisblue dye can be applied right out of the bottle along

the shoreline. It mixes throughout the body of waterwithin 24 hours. The dye intercepts light normallyused for photosynthesis by underwater plants.The dye can only be effective if its concentrationis maintained. Some general rules for usingAquashade or other dye products are as follows:

1. Do not apply where water out ow will reducethe dye concentration.

2. Apply in March or April before plants reach

the water surface. Midsummer reapplication isusually necessary.

3. Dyes are effective only on rooted underwaterplants growing at depths greater than 2 to 3 feet.Supplemental treatments of copper sulfate areoften needed for algae control.

4. Do not use in muddy water.

Aeration has been publicized as another meth odof weed control. Although aeration is de nitelyben e cial for sh life and can help pre vent shkills, there is no evidence that aeration inhibits weedgrowth. If you do install an aerator to provide oxygenfor sh, make sure that you pur chase a unit thatintroduces air to the bottom of the pond, not just afountain that sprays surface water. Indiana residents :A permit from the Indiana Department of NaturalResources is required for habitat alteration methodssuch as bottom barriers and dyes in public waters thatare more than 25 feet along a shoreline, greater thana water depth of 6 feet, and greater in area than 625square feet. A permit is not required for privatelyowned lakes, ponds, and drainage ditches.

Chemical Control MethodsWhen properly applied, certain herbicides cancontrol aquatic vegetation without harming the shand other wildlife. In some instances, herbicides canbe used selectively, that is, to control certain plantspecies without killing others. Aquatic her bicidesalso can t into an aquatic plant management planwhen it is desirable to treat some vegetated areasand leave others untreated. They can be par ticular lyeffective for controlling certain aggressive weedspecies such as Eurasian watermilfoil.

However, it should be noted that, in most cases,aquatic herbicides offer only temporary solutions.The target species usually will reappear, andretreatment or application of another control methodusually will be necessary.

All of the herbicides discussed in this pub licationare registered with the federal EnvironmentalPro tec tion Agency (EPA) and, when used in wateras directed, pose no signi cant threat to theenviron ment or to public health. Most herbicides,however, ARE TOXIC IF TAKEN INTERNALLY,and direct contact with the chemical should beavoided. Pro tec tive clothing, gloves, and a facemask or res pirator should be worn during mixing



and application. If a herbicide comes in contact withthe skin, it should be washed off immediately withwater. If a herbicide is accidentally swallowed, goto a phy sician immediately and consult the containerlabel for rst aid information.

Because these chemicals are toxins and requirespecial precautions, the remainder of this bulletinis devoted to the proper use of aquatic herbicides.

Check with the appropriate state regulatory agencyfor a list of the herbicides approved for use inyour state, and for other restrictions and importantinfor mation. Indiana residents: A permit from theIndiana Department of Natural Resources is re quiredfor the chemical treatment of vegetation in publicwaters that are more than 25 feet along the shoreline,greater than a water depth of 6 feet, and greater inarea than 625 square feet. A permit is not required for privately owned lakes, ponds, or drainage ditches.

What You Need to Know Before Usinga ChemicalBefore buying and applying a herbicide it isessen tial that you READ THE LABEL to determinewhether the product will meet your needs. Im por tantconsiderations in choosing a herbicide include:

1. Identity of the plant . This can save you a lot ofmoney because certain chemicals will work onlyon some plants and not on others. Iden ti cation

help can be obtained from your county oruniversity Cooperative Extension Service, pestdiagnostic services, sheries biologists, or dealersof aquatic herbicides. Always transport or mailthe plant in a plastic bag without extra water.

2. Restrictions on use of water treated withherbicides . Although most aquatic herbicidesbreak down readily and rapidly in water andpose no threat to human or animal health, thereare waiting periods on the use of water treatedwith most her bicides. These restrictionsmostlyon shing, do mes tic use, livestock watering,or irrigationdictate which herbicides will beappropriate for your lake or pond. At the currenttime there are no swimming re stric tions on theherbicides listed in this publication. However,it is always wise to encourage at least a 24 hourperiod before swimmers are allowed back intotreated water. Always check the herbicide labelfor possible restrictions.

If you are interested in learning more aboutthe environmental and human health impactsof aquatic herbicides, you can go to a Web siteentitled Why Aquatic Herbicides Affect AquaticPlants and Not You! at . The three major factors that protectus from harmful effects are that currently EPA-registered algicides and aquatic herbicides 1)are used at extremely low doses in water, 2) donot persist very long in water (usually only afew days), and 3) do not bioaccumulate in fattytissues of humans or animals. Chemicals thatare not EPA-registered for aquat ic use maynot have these characteristics and thereforeshould never be used in or around water.Read the herbicide label. If it does not provideinformation for aquatic use, its ap pli ca tion towater is illegal and can cause en viron men tal

or human health problems. An example of aherbicide that is not cleared for aquatic useis Karmex.

3. Dosage . Calculate the dosage carefully and donot apply more chemical than is needed. Someaquatic herbicide labels give dosages on the basisof acre-feet (a volume measurement). Acre-feetare calculated by multiplying the surface area bythe average depth. For example, a pond with asurface area of 1/2 acre and an average depth of4 feet contains (1/2 acre X 4 ft) 2 acre-feet. Theherbicide label can then be consulted for theamount of chemical to apply per acre-foot.

4. Timing . Late spring is usually the best time toapply aquatic herbicides (exceptions are notedunder the individual chemicals). The plants areyoung and actively growing and most susceptibleto herbicides. Do not wait until July or August!If you wait until late summer to treat, you arerunning a serious risk of killing sh. By thattime, the vegetation is usu ally extensive and

thick. Also the water is warm and still. Killing allvegetation at once under these conditions couldseriously deplete the water of its oxygen andcause a sh kill. If you must treat this late inthe summer, treat only a portion of the weedgrowth at a time.

5. Temperature . Aquatic plants are not affected byherbicides when the water is too cold. The watertemperature should be in the 60 ! s, pref erably
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the upper 60s (in the area to be treated). Thesetemperatures usually occur from late April toearly June in Indiana. This means that as soon asthe plants are up and actively growing, and if thewater temperature is right, the herbicide shouldbe applied.

6. Contact versus translocated herbicides . Some herbicides (contacts) work very quicklyby killing the plant tissue that they come intocontact with. These herbicides can be used forspot treatments; that is, treatments of selectedpatches of vegetation. These chemicals includethe copper algicides, endothall, and diquat.Other herbicides (trans locat ed) move into theplant and work on other parts of the plant (e.g.,underground rhizomes or tubers) rather than justthe leaf tissue. They tend to work more slowlythan contact herbicides. One of these, uridone,

cannot be used as a spot treatment be cause it maymove away from the treated area before it canhave an effect. The other trans locat ed herbicides(2,4-D, triclopyr, and glyphosate) can be used asspot treatments, but again, they work slowly.

7. Retreatment . More than one treatment aseason (e.g., copper sulfate on algae) may berequired for adequate control. Retreatment isusually required in succeeding years. Plants canregenerate each spring from seeds, spores, and

underground structures. Seeds and undergroundstructures that lie dormant over the winter arenot affected by most aquatic herbicides.

Algicides and Aquatic Herbicides1. Copper sulfate . Trade names are various. Available

as granular crystals, diamond form, and powder.

Copper sulfate is used only for algae control; itis not effective on other types of weeds. Whenpurchased as copper sulfate pentahydrate (25%metallic copper), the recommended dosage is

2.7 pounds per acre-foot of water. Concentratethe treatment in the area of growth.

The granular form is best applied by putting itin a burlap sack and towing it by boat around thepond until it is dissolved. Tossing the granulesinto the water is not very effective because thosethat land on the sediment may be rapidly adsorbedby soil par ticles and will not be available foruptake into the algae.

The powder form is best used by dissolving it inwater and spraying directly onto the algae matsand into the water around the mats.

Copper sulfate is highly corrosive to metals soplastic, enameled, or copper-lined containers and ttings are needed for mixing and applying thealgicide. Sprayers should be thoroughly cleanedand rinsed out after every operation to preventcorrosion damage.

2. Copper chelates . Trade names include CutrinePlus, Algae Pro, Captain, K-Tea, and others.Available as liquids; Cutrine Plus is alsoavailable as a granule.

The copper chelates are used primarily for algaecontrol, particularly at sites where hard watermay cause copper sulfate to precipitate out ofthe water and reduce its effectiveness. Theseproducts tend to be less corrosive to metals thancopper sulfate. Mix the liquid formulations withwater in a container and spray or inject intothe infested area. Granular formulations can bebroadcast into the water using a seeder. Bothliquid and granular formulations can be usedas spot treatments.

3. Endothall . Trade names include Aquathol andHydrothol. Both are available as liquids andgran ules.

Aquathol is used for submersed plant controland, along with diquat, is a standard treatmentfor these plants. Mix the liquid formulationswith water in a container and spray or inject intothe infested area. Granular formulations can bebroadcast into the water using a seeder. Bothliquid and granular formulations can be usedas spot treatments.

Hydrothol liquid can control both algae andsub mersed plants, but it is recommended foruse only by certi ed applicators who have hadspecial train ing in handling aquatic pesticides.It can cause sh kills and severe skin burns tothe applicator.

4. Diquat . Trade name is Reward. It is availableonly as a liquid.

Diquat is used for submersed plant control and,along with Aquathol, is a standard treatment forthese plants. It can also be used for burndown



treatments of duckweed and watermeal, althoughthese plants will usually recover. Mix the Rewardwith water in a container and spray or inject intothe infested area. The herbicide can be used as aspot treatment. Do not use when water is muddybecause the soil particles will remove the diquatfrom the water.

5. Fluridone . Trade names are Sonar and Avast!Sonar is available as A.S. (aqueous solution),SRP (slow release pellet), PR (pre cision re lease),and Q (quick release).

Fluridone is used primarily for the control ofsub mersed plants and duckweed. Mix Sonar A.S.and Avast! with water in a container and spray orinject into the infested area. The pelleted formscan be dispersed with a seeder. Fluridone is noteffec tive as a spot treatment, therefore, it mustbe applied to the entire surface area of ponds. Inlakes and reservoirs it should be applied to areasgreater than 5 acres to prevent dilution. Sincethe chemical must stay in contact with targetplants for several weeks, it is not recommendedfor sites where there is a lot of water exchange. Thechemical is slow acting, and it may take 30-90days to see results. However, under optimalconditions, target plants may be controlled for upto 2 or more years. This chemical is par ticular lyeffective at removing the invasive species Eurasian

watermilfoil without affecting native species.6. 2,4-D . Trade names are Navigate and Aquakleen.

Both are granular formulations.

2,4-D granules are used for speci c plant speciessuch as Eurasian watermilfoil, coontail, andwaterlilies. Since 2,4-D is a broadleaved weedkiller, it can be used selectively to remove thesetarget species and retain grasses and grass-likespecies (many of which are native species). Thegranules should be distributed evenly over the

infested area. 2,4-D liquid for mulations are notcurrently registered for in-water use. Only amineformulations of 2,4-D liquid should be used forvegetation control around water (for ex ample,vegetation along drainage ditchbanks) but checkthe label to make sure the product is reg isteredfor that use; liquid ester formulations are highlytoxic to sh and should not be used around water.

7. Triclopyr . Trade name is Renovate 3. It isavailable only as a liquid.

Triclopyr is used to control many of thesame plant species as 2,4-D and has thesame selectivity; in other words, it controlsbroadleaved plants but does not affect grassesor grass-like plants such as cattails. One ofits advantages is that it is a liquid formulationwhereas 2,4-D is approved for in-water use onlyas a granule formulation. Therefore, triclopyroffers additional exibility for the control ofEurasian watermilfoil. Its other major use isfor the control of broadleaved emergent plantssuch as purple loosestrife and creeping waterprimrose. Use of a non-ionic surfactant in thespray mixture is recommended for emergentplant control.

8. Glyphosate . Trade names are Rodeo, Aqua Neat,and Eagre. These products are avail able only asliquids.

Glyphosate is used for the control of emergentvegetation such as cattails. It is not selective;therefore, it can kill any emergent plant that itcomes into contact with. It does not work onplants that are under the water surface . Allof the current formulations require the additionof a non ion ic surfactant (wetting agent) to theglyphosate-water mix. The solution is sprayed

directly on the foliage. The best time for treatmentis late summer or early fall, before the rsthard freeze. The so lution can be used as a spottreatment or as a wipe-on application (wearprotective gloves to apply the chemical witha sponge directly on the foliage of the targetspecies) to kill only speci c plants.



Algicide and Aquatic Herbicide Guidelines and Water Use RestrictionsAquatic weed Herbicide Typical product dose 1 Restrictions 2

Algae (microscopic, Copper sulfate 2.7 lb/A-ft. Do not use in lamentous, Chara) (25% Cu) trout-bearing

waters

Copper chelates Rate varies with Do not use in formulation trout-bearing waters

Endothall F= 3 days; (Hydrothal 191) I, L, D = 7-25 days Liquid 0.6 to 8.8 pt/A-ft. Recommended for Granular 2.2 to 13.2 lbs/A-ft. use by certi ed

applicators only.

Submersed plants Endothall F= 3 days;(pondweeds, naiads, (Aquathol K liquid) 0.6 to 1.3 gal/A-ft. I 3, L, D =elodea) (Aquathol Super K 27 to 54 lbs/A-ft. 7-25 days

granular)

Diquat (Reward) 1 to 2 gal/SA I = 1-5 days; D= 1-3 days; L = 1 day

Fluridone (Sonar, Dose varies with I = 7-30 days: Avast!) formulation do not apply within 1/4 mile of potable water intakes

Submersed plants 2,4-D (Nav igate) 100 to 200 lbs/SA Do not apply(Eurasian watermilfoil, to waters forcoontail) I, D

Fluridone (Sonar, As above As above Avast!)

Submersed plants Triclopyr 0.7 to 2.3 gal/A for each See label for(Eurasian watermilfoil) (Renovate 3) ft. of depth (see label) required setback distances from potable water intakes

Free- oating plants Diquat (Re ward) 1 gal/SA; add surfactant As above(duckweed, watermeal)

Fluridone (Sonar AS, 1 to 1.5 qt/SA As above Avast!)

Rooted- oating plants Glyphosate (Rodeo, Consult label. Do not apply(waterlilies, spatterdock) Aqua Neat, Eagre) within 1/2 mile plus surfactant upstream of potable water intake



Triclopyr (Renovate 3) 2 to 8 qt/SA As above plus surfactant

Emergent plants Glyphosate (Rodeo, Consult label. As above(Most plants including Aqua Neat, Eagre)cattails, grasses, purple plus surfactantloosestrife, willows)

Emergent plants Triclopyr (Renovate 3) 6 to 8 qt/SA Minimize overspray(Purple loosestrife, creeping plus surfactant to open waterwater primrose)

Specic Algae and AquaticPlant ProblemsAlgae ControlThe rst step in algae control is to reduce the runoffof nutrients (nitrogen and phosphorus) into a bodyof water. This is particularly true for the man age mentof green water blooms caused by microscopic algae.If chemical treatment is needed, the algae shouldbe treated with chemicals before they cause anoticeable color in order to prevent a sh kill.

Microscopic algae are not consumed by grass carp.Mat-forming algae may be eaten when grass carpare young, but generally the sh will eat sub mersed owering plants in preference to algae. The bluedye products are not particularly effective on algae,particularly in shallow water. However, it may beuseful to add dye after a copper treatment to preventnew growth from rising to the surface.

Control of mat-forming algae and Chara is mostlyaccomplished with a copper-based product. Thestandard product is copper sulfate. Sometimescopper sulfate is not very effective. Copper sulfatetends to be inactivated in very hard (alkaline)waters. Also, some types of algae are not very wellcontrolled with copper sulfate. If copper sulfateis ineffective, it may well be worthwhile to try achelated copper product. Both copper sulfate and

copper chelates are best applied by mixing in waterand spraying directly on and around the algaemats. Good coverage of the mats is critical to goodcon trol. For some extremely copper-tolerant algae,repeated copper treatments over the summer seasonmay be necessary to keep the mats to a minimum.

Chara can be dif cult to control once it has becomeestablished and has a heavy coating of calciumcarbonate (limestone) around its body. Coppercompounds should be used when the plants are stillyoung and not heavily calci ed. The gran ular formof Cutrine, which is dropped into the vegetation, canbe an effective control.

There are no water use restrictions after the use ofthe copper products (although they should never beused in trout-bearing waters). Even so, it is wiseto restrict swimming, shing, using the water forirrigation or drinking, and other activities for 24hours after application

Although Hydrothol is labeled for algae con trol,it must be used with caution, and preferably bycerti ed aquatic applicators, to avoid killing sh.Hydrothol should only be used as a spot treatmentso that ample untreated, fresh water is available for sh to move into. Sometimes small sh will notmove away from the treated area quick ly enoughand can be killed.

Footnotes1SA= surface acre; A-ft = acre-feet. These dosages are given only as an indication of amount to use and will varyaccording to target species, state re stric tions, etc. Please read the label to de ter mine actual dosage for thetarget plant.2F = shing; I = irrigation; L = drinking water for livestock; D = drinking water for humans. Where range of days isgiven (e.g., 7-25 days), the waiting time depends on dose used. These re stric tions apply to Indiana. If you wish to usethese chemicals outside of Indiana, be aware that ad dition al re stric tions can be imposed by other states. Check withlocal and state regulatory agencies.3

Liquid formulation only: treated water can be used for sprinkling bent grass immediately.



Submersed Plant ControlSubmersed plants can be controlled with a varietyof methods, including the grass carp, me chan icalharvesting, and dyes. However, the grass carp is notvery effective in controlling Eurasian watermilfoil.

Aquathol and Reward are the most commonly usedchemicals for submersed plant control. They can

be tank mixed with copper products to control bothalgae and submersed plants. They are effectiveas spot treatments; therefore, they can be used tocontrol vegetation in one area while leaving otherareas untreated. They act quickly, and burn-downshould be visible within a week of treatment.They are extremely short-lived in water; therefore,waiting periods to use the water for various purposesare short (see table).

Although burn-down of Eurasian watermilfoilcan be achieved with Aquathol and Reward, thisinvasive species is more effectively controlled with2,4-D (Navigate or Aquakleen), triclopyr (Renovate 3)or uridone (Sonar or Avast!). Although the uridoneproducts are quite expensive, they can be used atextremely low dosages (parts per billion) to removeEurasian watermilfoil from native plant stands.

Free-oating Plant ControlDuckweed and watermeal are dif cult to control.They are not consumed by grass carp, and mechanicalremoval is very dif cult. Surface applications ofReward primarily burn the plants, but they tendto come back within a week or two. Therefore,continual treatments with Reward are requiredthroughout the season, starting as soon as the plantsappear on the water surface. Furidone (Sonar orAvast!) can be more effective on duck weed thanReward and if used correctly can some times providemore than one year of control. Pond out ow mustbe blocked for at least 30 days or longer becausethe plant has to be exposed to the chemical for at

least this long in order to be ef fec tive ly controlled.The dose for duckweed (1 quart per acre) should besplit and applied in two applications about 10-14days apart. SePRO, the company that sells Sonar,guarantees the results on duckweed if its publishedprocedures are followed. For a copy of thosepro cedures, call 1-800-419-7779.

Watermeal is typically harder to control thanduckweed. A higher dose of uridone (1.5 quarts

per acre) in a split application is suggested.Although uridone usually provides successfulcon trol, there can also be failures. A Web site onwatermeal and duckweed control is available at.

Rooted-oating and Emergent PlantControlCutting or digging these plants can be ex treme lylaborious because the underground rhi zomes mustalso be removed for effective control. Grass carp donot feed on these plants.

The glyphosate products (Rodeo, Aqua Neat, Eagre)plus a nonionic surfactant are effective as foliarspray or wipe-on treatments on almost all vegetationthat stands above the water surface. Surfactants(wetting agents) can usually be pur chased at thesame place as the glyphosate. Al though Reward also

is labelled for emergent plant control, it primarilyburns the foliage and does not move into theunderground parts of the plant. Glyphosate, on theother hand, does move down ward and effectivelykills underground structures. This movementis essential for long-term control of the plant.Glyphosate acts slowly; therefore, effects on thevegetation may not be seen for several weeks aftertreatment.

Although glyphosate applications can be made assoon as vegetation appears in the spring, it is mosteffectively applied in the late summer or early fallbefore the rst hard freeze. If the undergroundstructures are successfully killed, the vegetationshould not reappear in the spring.

Triclopyr (Renovate 3) and some 2,4-D products canbe used selectively to remove purple loosestrife andother broadleaved weeds from grasses or grass-likeplants such as cattails and bulrushes.

Comments on the Use of Barleyfor Algae ControlBarley straw has been promoted as a meansof controlling algae. Although widely used inEngland and other countries, research results inthe United States have been inconsistent. Forinfor mation on barley for algae control, go to.
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Notes


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About the Author

Carole A Lembi, Professor

Department: Botany and Plant Pathology

Area of Expertise: Aquatic Biology - aquatic weed science and phycology with emphasis

on ecology, physiology, and management of nuisance algae.

Carole Lembis laboratory has studied a number of issues integral to aquatic plant

management, particularly those that deal with finding 1) more ecologically-friendly

alternatives to herbicides/algicides and 2) solutions for difficult-to-control algal species.

Alternatives studied included plant growth regulators, barley straw, a bacterial biocontrol

agent, and the herbivorous fish, the grass carp. Their studies on Pithophora (an

algicide-tolerant alga that infests waters throughout the U.S.) and Nostoc (a

cyanobacterium that infests California rice fields) form the basis for understanding the

ecology of difficult-to-control mat-forming species and the potential for inserting control

mechanisms into appropriate stages of the life cycle.


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It is the policy of the Purdue University Cooperative Extension Service, David C. Petritz, Director, that allpersons shall have equal opportunity and access to the programs and facilities without regard to race,color, sex, religion, national origin, age, marital status, parental status, sexual orientation, or disability.

Purdue University is an Afrmative Action institution.This material may be available in alternative formats.

REVISED 5/03

Documents

Aquatic Plant Management (2003)