AQUATICS
Bob Parker
Revised October 31, 2008

In many ways, aquatic weeds are similar to terrestrial or land weeds. There are annuals and perennials. Many flower and produce seed, whereas others propagate only asexually. Some produce tubers or winter buds, some are more shade tolerant than others, and nearly all respond to fertilization. Therefore, the management and control of these pests is similar in many respects to that of land weeds.
Usually, aquatic weeds are separated into four broad categories: emersed, submersed, floating, and algae. Emersed plants are those rooted or anchored in the substratum with most of the leafstem tissue above the water surface and not lowering or rising with the water level. Examples are cattail, tules, and yellow waterlily. Submersed plants are adapted to grow with all or most of their vegetative tissue below the water surface. Examples of submersed plants are pondweeds, coontail, and elodea. Floating plants are those that are either free-floating or anchored to the substratum and produce most of their leafstem tissue or thalli at or above the water surface. Leaves or thalli of floating plants rise or lower with the water level. Examples of floating plants are the duckweeds, azolla, and white waterlily. Most algae are also submersed and free-floating. However, some may be anchored by holdfasts to the substratum, rocks, old stumps, and other things. Algae do not have true roots, stems, or leaves and are frequently called “pond scums” or slime.
Wise water management is necessary if aquatic vegetation control is to be more than temporary. Management must begin by evaluating all uses of a given body of water. Chemical, biological, and physical factors should be manipulated as much as possible to get the maximum use of the water for the benefit of the greatest number of people.
Our expanding population and water use increase the need to prudently manage our limited water supply. Increased fertilization, for example, stimulates aquatic plant growth and accelerates aging in a body of water. Prime sources of fertilization are (1) discharging untreated or septic-tank-treated wastes from shoreline homes, (2) storm sewer drainage from fertilized lawns and gardens, (3) uncontrolled drainage from heavily fertilized farmland and livestock feeding lots, (4) discharging effluents from municipal sewage treatment plants, (5) drainage from garbage dumps near watercourses, and (6) discharging treated or untreated wastes from industrial plants. Eliminating faulty practices together with good land and water management are essential in controlling unwanted aquatic vegetation.
Control of Bank and Aquatic Weeds
Management: Constructing ponds, reservoirs, ditches, and other impoundments
Steep banks with a 1 to 1.5 slope that extends at least 3 ft below the designed water level will help prevent many emergent and bank weeds from establishing. Remove fertile topsoil from the pond or reservoir basin. If a beach area for swimming and other recreational purposes is desired, remove the fertile topsoil and replace it with sand. If possible, prevent water heavily laden with silt and nutrients from entering an impoundment. For ditchbanks, plant grasses and use a 2,4-D program to keep out most undesirable broadleaf plants. East of the Cascades, seed redtop or creeping red fescue at the waterline and crested wheatgrass on the shoulders and top of the ditchbank. Provide roadways on both ditchbanks for weed control and other operations. Provide means to control water levels and water flow.
Mechanical Control
1.	Cut the submersed and emersed weeds with an underwater mower, a mechanical weed harvester, or a chain, and remove severed vegetation from the water.
2.	Cut the ditchbank weeds with a mower or scythe.
3.	Burn ditchbank weeds. Sear the first time and burn thoroughly 7 to 10 days later.
Chemical Control
1.  Analyze the problem.
a.  Biological aspects:
	•  Identify the problem species
•  Identify other species present
•  Determine density, stand, or scope of problem and stage of weed growth
•  Determine fish species present
b. Water-use aspects:
	•  Irrigation, potable, recreational, fish production, livestock, and wildlife
•  Length of time water can be quarantined from each use
•  Amount of and destination of outflow. Can outflow be regulated? If so, for how long?
c.  Physical aspects:
	•  Size of channel or pond to be treated
•  Water depth and movement or velocity
•  Water turbidity
•  Water temperature
•  Water quality
2.	Select the herbicide. Consider safety, effectiveness and selectivity, residues, and cost.
3.	Determine whether the chemicals are registered for use in aquatic sites.
After analyzing the problem, select the best control method. Check with local state game department or other regulatory personnel before applying herbicides to lakes, ponds, and other impoundments. In Washington, the Washington Department of Ecology has to issue permits before any herbicides are used in aquatic sites. The purchase and application of herbicides used in aquatic systems must be made by properly licensed applicators.
Calculations for Treating Canals
(definitions: ppm  =  parts per million; cfs  =  flow in cubic feet per second)
ppm  =  (Number of gallons of solvent  x  1,000,000) ÷  (Number of cfs  x  450  x  time in minutes)
Gallons of solvent per cfs =  (450  x  time in minutes  x  ppm)  ÷ 1,000,000
Total gallons of solvent  =  450  x  time in minutes  x  ppm  x  cfs  ÷  1,000,000
Calculations for Treating Ponds and Lakes
1.	Concentration based on parts per million by volume (ppmv)
Q = A  x  D  x  C  x  0.33
Q = Number of gallons of herbicide required
A = Area of water surface in acres
D = Average depth of the pond or lake in feet
C = Desired final concentration of herbicide in ppmv
2.	Concentration based on parts per million by weight (ppmw) 
P = A  x  D  x  C  x  2.72
P = Number of pounds (active ingredient) of herbicide required 
A = Area of water surface in acres
D = Average depth of the pond or lake in feet
C = Desired final concentration of herbicide in ppmw
3.	Concentration based on parts per billion by weight (ppbw) 
P = A x D x C x 0.0027
P = Number of pounds (active ingredient) of herbicide required 
A = Area of water surface in acres
D = Average depth of the pond or lake in feet
C = Desired final concentration of herbicide in ppbw
Caution!
The information provided in this handbook is not intended to be a complete guide to herbicide use. Before using any chemical, read the recommendations on the label. Before a chemical can be recommended for a specific use, it must be thoroughly tested. Recommendations on the manufacturer’s label, when followed, can prevent many problems arising from the wrong use of a chemical. 
AQUATICS—Algae in Lakes, Ponds,  Reservoirs, and Irrigation Channels
•  copper sulfate pentahydrate  
Rate  0.5 to 2 ppmw (concentration) suspended in burlap bags, poured directly into water of irrigation channels or applied over water surface of impoundments
Time  Apply early in spring and at 2- to 3-wk intervals thereafter.
Remarks  Safe in potable and irrigation water. Do not wait until a severe algae problem develops before applying.
Caution  May be toxic to fish, especially trout.
Site of action  Plant cells
Chemical family  Inorganic
•  dimethylamine salts of endothall  (Hydrothol 191)
Rate  0.05 to 0.2 ppmw (concentration) sprayed on the water or injected below surface
Time  Apply when algal growth appears.
Remarks  Apply if algae in the irrigation channel must be removed to allow water delivery. However, water-use restrictions apply. See Caution below.
Caution  A restricted-use herbicide. May be toxic to fish in dosages above 0.3 ppm. Do not use treated water for irrigation or agricultural sprays on food crops, watering livestock, or domestic purposes within 7 days after application.
Site of action  Not well understood
Chemical family  None generally recognized
AQUATICS—Submersed Weeds in Flowing Canals and Ditches
•  acrolein (Magnacide H)
Rate  0.1 ppmw (concentration) for 48 hours in canal flows of more than 300 cfs, or 0.6 ppmw for 8 hours in canal flows of less than 300 cfs
Time  Apply when weed growth is no more than 4 to 6 inches tall.
Remarks  Repeat treatments every 3 to 4 wk during the remainder of the season.
Caution  Do not let humans or animals drink treated water. Toxic to fish and many other aquatic organisms. Special application equipment required. Use only oxygen-free nitrogen for a pressurizing agent. Do not release treated water after application into any fish-bearing water or area that might drain into fish-bearing water until the minimum waiting period defined on the appropriate label.
Site of action  General cell toxicant
Chemical family  None generally recognized
•  petroleum distillate (xylene)  (Aquatic Weed Killer)
Rate  8 to 10 gal per cfs of water flow
Time  Apply over a 30- to 60-minute period any time after weed growth is well established but before it is matted at the surface or channels the water.
Remarks  Mix with emulsifier and inject under pressure, preferably in turbulent flow. Use 1.5 gal of emulsifier per 100 gal of xylene.
Caution  Toxic to fish and many other aquatic organisms. Do not flood-irrigate seedling crop plants with treated water.
Site of action  General cell toxicant
Chemical family  None generally recognized
•  dimethylamine salts of endothall (Hydrothol 191)
Rate  0.2 ppmw in flowing water for up to 120 hours
Time  Apply if submersed weeds in irrigation channel must be removed to allow water delivery. 
Remarks  Apply where water is slightly turbulent to facilitate mixing. Treated water may be used for irrigation, swimming, fishing, watering livestock, or preparing agricultural sprays immediately after treatment.
Caution  User agrees to take every precaution to ensure the security of the herbicide where it enters the application site.
Site of action  Not well understood
Chemical family  None generally recognized
AQUATICS—Submersed Weeds in Nonflowing Canals and Ditches
•  diquat (Diquat Herbicide or Reward)
Rate  2 to 4 lb ai/A
Time  Apply before weed growth reaches the water surface.
Remarks  Pour directly from container into water or inject below the water surface. Safe for fish at the rates given. This treatment is not effective on the attached algae or chara. There are no swimming or fishing restrictions in treated water.
Caution  A moderately toxic herbicide that requires protective gear for handling and application. Do not use treated water for domestic purposes, animal consumption, spraying, or irrigating food crops for 1 to 5 days depending on water use and rate applied. Do not let spray contact skin, eyes, or clothing. Do not breathe spray mist. Do not use in turbid water.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  fluridone (Sonar or Avast!)
Rate  15 to 40 ppb. Sum of all applications must not exceed 80 ppb/yr.
Time  For best results, apply just before or when weeds begin active growth.
Remarks  Treat when water movement will be minimal. Results are best when fluridone contacts target plants for at least 45 days. Conduct an Enzyme-Linked Immunoassay Test (ELISA) to determine the concentration of active ingredient in the water. Use an application pattern that gives uniform distribution; avoid concentrating the herbicide. Do not apply within 0.25 mi of any potable water intake.
Caution  Irrigation with treated water may injure irrigated crops. See label for irrigation times after application. Do not irrigate established tree crops for at least 7 days after application. Depending on formulation and application site, do not irrigate other crops for 7 to 30 days after application. May injure vegetation growing along shoreline. Do not apply at rates greater than 20 ppb within 0.25 mi of any potable water intake.
Site of action  Group 12: bleaching; inhibits carotenoid biosynthesis
Chemical family  None generally recognized
•  carfentrazone (Stingray)
Rate  200 ppbw (concentration by weight)
Time  Apply in spring or early summer to actively growing weeds.
Remarks  Inject into water with a boat-mounted injection system. Material may be applied as a surface spray only in combination with a suitable polymer or similar adjuvant that will ensure rapid sinking and mixing of the spray mix. Apply only to water with little or no outflow.
Caution  Do not exceed 200 ppb in treated water. Note label restrictions on setback distances for application to potable water intakes. Do not treat more than half the body of water at one time. Consult label for water use restrictions.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  Triazinone
• imazamox (Clearcast)
Rate  50 to 100 ppb surface applied or injected
Time  Apply early in the growing season
Remarks  Surface apply or inject into water column. Injection more effective on some species. Consult label. Apply to water with little or no flow. Repeat applications may be made. There are no restrictions on livestock watering, swimming, fishing, or domestic use as long as the setback restriction is observed, or for agricultural sprays.
Caution  Do not use treated water to irrigate greenhouses, nurseries, or hydroponics. Do not use treated water for other irrigation purposes less than 24 hours after application is completed and only as long as concentrations in water are equal to or less than 50 ppb. Note label restrictions on setback distances on applications to potable water intakes. 
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone

AQUATICS—Submersed Weeds in Lakes and Ponds
•  diquat (Diquat Herbicide or Reward)
Rate  2 to 4 lb ai/A
Time  Apply before weeds reach the water surface.
Remarks  Pour directly from container into water or inject below water surface. Safe for fish at rates given. Not effective on attached algae or chara. No swimming or fishing restrictions after using.
Caution  A moderately toxic herbicide that requires protective gear for handling and application. Apply only to ponds and lakes with little or no outflow. Depending on application rate, do not use treated water for domestic purposes for 1 to 3 days, or for animal consumption within 1 day. Do not use treated water for spraying or irrigating food crops for 5 days after treatment. Do not let spray contact skin, eyes, or clothing. Do not breathe spray mist. If weeds are abundant, treat a third of the pond or lake at a time to avoid fish kill (due to low oxygen level from decomposing weeds). Do not use in turbid water.
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  dipotassium salt of endothall (Aquathol K)
Rate  0.5 to 4 ppmw (concentration) spread or sprayed on the water or injected below the water surface
Time  Apply after growth develops in late spring or early summer and water is at least 65°F.
Caution  A restricted-use herbicide. Depending on formulation and rate, do not use treated water for irrigation, watering livestock, or other domestic use within 7 to 25 days of treatment. This formulation, at given concentrations, is not effective on elodea or chara. In abundant weeds, treat a third of the pond or lake at a time to avoid fish kill (due to low oxygen level from decomposing weeds).
Site of action  Not well understood
Chemical family  None generally recognized
•  dimethylamine salts of endothall  (Hydrothol 191)
Rate  0.5 to 2.5 ppmw (concentration) sprayed on the water or injected below the surface
Time  Apply after growth has developed in late spring or early summer.
Caution  A restricted-use herbicide. Toxic to fish. Do not use treated water for any purpose within 7 to 25 days after treatment, depending on concentration applied. Marginal or sectional treatments rather than an overall treatment is recommended.
Site of action  Not well understood
Chemical family  None generally recognized
•  2,4-D granules (AquaKleen 20G)
Rate  19 to 38 lb ae/A
Time  Apply in spring or early summer before plants reach the water surface.
Remarks  This material is for coontail and milfoil control only. Apply granules uniformly over water surface either by hand or with a rotary spreader.
Caution  Do not use treated water for watering animals, agricultural sprays, domestic use, or irrigation. If weeds are abundant, treat a third of the pond or lake at a time to avoid fish kill (due to low oxygen from decomposing weeds). Safe for fish at rate given.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  carfentrazone (Stingray)
Rate  200 ppbw (concentration by weight)
Time  Apply in spring or early summer to actively growing weeds.
Remarks  Inject into water with a boat-mounted injection system. Material may be applied as a surface spray only in combination with a suitable polymer or similar adjuvant that will ensure rapid sinking and mixing of the spray mix. Apply only to water with little or no outflow.
Caution  Do not exceed 200 ppb in treated water. Note label restrictions on setback distances for application to potable water intakes. Do not treat more than half the body of water at one time. Consult label for water use restrictions.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  Triazinone
•  2,4-D dimethylamine salt (DMA 4IVM)
Rate  10.8 lb ae/acre ft
Time  Apply in spring or early summer when aquatic weeds appear.
Remarks  Apply to obtain a concentration of 2 to 4 ppm. A second application may be needed when weeds show signs of recovery.
Caution  Do not treat areas free of weeds. Do not exceed 10.8 lb ae/acre ft (2.84 gal). Do not apply within 1500 ft of an active potable or irrigation water intake. Treat no more than half a lake or pond at one time. Do not use water for irrigation if approved assay indicates 2,4-D concentration is above 0.1 ppm (100 ppb). Do not use treated water for drinking if approved assay indicates 2,4-D concentration is above 0.07 ppm (70 ppb).
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  triclopyr (Renovate 3 or Renovate OTF)
Rate  0.75 to 2.5 ppm ae concentration in water
Time  Apply in spring or early summer to actively growing, susceptible weeds.
Remarks  Treat one-third to half of the water body at a time and wait 10 to 14 days between applications to prevent possible fish kills due to oxygen depletion. Rates higher in the range are recommended in areas of greater water exchange. Apply as a surface or subsurface application in water that has little or no continuous outflow. When using liquid triclopyr to treat plants 6 ft below the water surface, use trailing hoses along with an approved aquatic sinking agent. There are no restrictions on recreation, including swimming and fishing, in the treated area or on livestock consumption of water.
Caution  Do not apply when conditions favor drift to sensitive areas. Observe minimum setback distances from functional potable water intakes for human consumption. Do not exceed 2.5 ppm per season.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  fluridone (Sonar or Avast!)
Rate  Ponds 45 to 90 ppb; whole lakes 10 to 90 ppb
Time  For best results, apply just before or just as weeds begin active growth.
Remarks  For fluridone, a pond is defined as body of water 10 acres or less. A lake or reservoir is defined as having a surface area greater than 10 acres. Treat when water movement will be minimal. Rate is determined by area and depth of water treated and density of target vegetation. May be applied to a pond’s entire surface area. In lakes and reservoirs, apply to areas greater than 5 acres. Results are best when fluridone is in contact with target plants for at least 45 days. Make an Enzyme-Linked Immunoassay Test (ELISA) to determine the active ingredient’s concentration in the water. See label for rates for split or multiple applications to whole lakes and reservoirs and for partial lake treatment rates.
Caution  Irrigating with treated water may injure crops. See label for irrigation times after applying. Do not irrigate established tree crops for at least 7 days after application. Depending on formulation and application site, do not irrigate other crops for 7 to 30 days after application. May injure vegetation along shoreline. Do not apply within 0.25 mi of any active potable water intake at rates greater than 20 ppb.
Site of action  Group 12: bleaching; inhibits carotenoid biosynthesis
Chemical family  None generally recognized
•  imazamox (Clearcast)
Rate  50 to 100 ppb surface applied or injected
Time  Apply early in the growing season
Remarks  Surface apply or inject into water column. Injection more effective on some species. Consult label. Apply to water with little or no flow. Repeat applications may be made. There are no restrictions on livestock watering, swimming, fishing, or domestic use as long as the setback restriction is observed, or for agricultural sprays.
Caution  Do not use treated water to irrigate greenhouses, nurseries, or hydroponics. Do not use treated water for other irrigation purposes less than 24 hours after application is completed and only as long as concentrations in water are equal to or less than 50 ppb. Note label restrictions on setback restrictions to potable water intakes.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
AQUATICS—Emersed, Marginal, and Bank Weeds in Marshes
•  glyphosate (Rodeo, Eagre, AquaNeat, AquaPro, AquaMaster, Cinco, or Accord Concentrate)
Rate  0.75 to 3.75 lb ae/A applied as a broadcast spray or 0.75 to 1.5% solution in water applied through hand-held or high-volume equipment
Time  Apply when weeds or brush are actively growing.
Remarks  See product label for application rate and growth stage of weed and brush species. If water is in the area to be sprayed, add a surfactant labeled for use in water at 2 quarts or more per 100 gal spray solution. If water is not present, add 2 or more quarts of any nonionic surfactant per 100 gal spray solution. Surfactant must be at least 50% ai.
Caution  Rain within 6 hr after application may reduce effectiveness. Do not apply within 0.5 mi upstream of potable water intakes. Apply to moving bodies of water only while traveling upstream. Do not exceed 3.75 lb ae/A in any single application.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  triclopyr (Renovate 3)
Rate  1.5 to 6 lb ae/A
Time  Apply to actively growing broadleaf weeds and woody plants.
Remarks  Use a labeled nonionic surfactant. Use the higher rates if hard-to-control species are prevalent or applications are in late summer or weeds are mature. There are no restrictions on recreation, including swimming and fishing, in treatment area or on livestock consumption of water.
Caution Do not apply when conditions favor drift to sensitive areas. Observe minimum setback distances from functional potable water intakes for human consumption. Do not exceed 6 lb ae/A per annual growing season.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  imazapyr (Habitat)
Rate  0.25 to 1.5 lb ae/A
Time  Apply to vigorously growing emersed and floating vegetation.
Remarks  Controls several annual, biennial, and perennial grass and broadleaf species. Rate depends on weed species and growth stage at time of application. Postemergence applications require adding a spray adjuvant approved for use in aquatic sites. Controls emerged and floating vegetation that has most of its foliage above the water surface. Unless imazapyr residues in the water are below 1 ppb, as determined by laboratory analysis, wait at least 120 days after application before using water for irrigation. No restrictions on recreational or livestock use of treated water.
Caution  Do not apply more than 1.5 lb ae/A (6 pints/A product) per year. Do not apply within 0.5 mi of a potable water intake in a standing body of water unless the intake can be turned off for at least 48 hr after treatment. Do not apply to irrigation water.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  imazamox (Clearcast)
Rate  0.125 to 0.5 lb ai/A (32 to 64 oz product\A)
Time  Apply as a foliage spray to actively growing emersed and floating plants. 
Remarks  Rate depends on species to be controlled. Postemergence applications require adding a spray adjuvant approved for use in aquatic sites. There are no restrictions on livestock watering, swimming, fishing, or domestic use as long as the setback restriction is observed, or for agricultural sprays.
Caution  Do not use treated water to irrigate greenhouses, nurseries, or hydroponics. Do not use treated water for other irrigation purposes unless concentrations in water are equal to or less than 50 ppb. Note label restrictions on setback restrictions to potable water intakes.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
AQUATICS—Emersed, Marginal, and Bank Weeds along Drainage Ditches
•  2,4-D
Rate  2 to 3 lb ae/A
Time  Apply as foliage spray in the spring or early summer.
Remarks  For broadleaf control, apply in 20 to 100 gal/A of water carrier for ground application and at least 2 gal/A for aerial application. Regrowth of perennials such as Canada thistle may require retreatment in the fall.
Caution  Do not contaminate domestic water sources or fishing waters. 2,4-D formulations may be toxic to fish. Do not apply to water that will be used to sprinkler-irrigate susceptible crops, especially grapes and tomatoes.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  glyphosate (Rodeo, Eagre, AquaNeat, AquaPro, AquaMaster, Cinco, or Accord Concentrate)
Rate  0.75 to 3.75 lb ae/A
Time  Apply when weeds and brush are actively growing.
Remarks  See label for application rate and growth stage of weed and brush species. Apply as a 25% solution through wiper-type applicators. May be applied to and along ditches and canals containing water. Add a nonionic surfactant to spray solution to enhance spray effectiveness. If water is present, add a surfactant labeled for use in water at 2 quarts or more per 100 gal spray solution. Surfactant must contain at least 50% ai. May be applied through hand-held or high-volume equipment as a 0.75 to 1.5% solution.
Caution  Rain within 6 hours after application may reduce effectiveness. Do not apply within 0.5 mi upstream of potable water intakes. Apply to moving bodies of water only while traveling upstream. Do not overlap bankside applications more than 1 ft into open water. Do not exceed 3.75 lb ae/A in a single application. Do not spray across open, moving bodies of water.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  imazamox (Clearcast)
Rate  0.125 to 0.5 lb ai/A (16 to 64 oz product/A)
Time  Apply as a foliage spray to actively growing emersed and floating plants. 
Remarks  Rate depends on species to be controlled. Postemergence applications require adding a spray adjuvant approved for use in aquatic sites. There are no restrictions on livestock watering, swimming, fishing, or domestic use as long as the setback restriction is observed, or for agricultural sprays.
Caution  Do not use treated water to irrigate greenhouses, nurseries, or hydroponics. Do not use treated water for other irrigation purposes unless concentrations in water are equal to or less than 50 ppb. Note label restrictions on setback restrictions to potable water intakes.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
AQUATICS—Emersed, Marginal, and Bank Weeds along Irrigation Ditches
•  glyphosate (Rodeo, Eagre, AquaNeat, AquaPro, AquaMaster, or Accord Concentrate)
Rate  0.75 to 3.75 lb ae/A
Time  Apply when weeds and brush are actively growing.
Remarks  Refer to label for application rate and growth stage of weed and brush species. Apply as a 25% solution through wiper-type applicators. May apply to and along ditches and canals containing water. Add a nonionic surfactant to the spray solution to enhance spray effectiveness. If water is present, add a surfactant labeled for use in water at 2 quarts or more per 100 gal spray solution. Surfactant must contain 50% ai or more. May apply through hand-held or high-volume equipment as a 0.75 to 1.5% solution.
Caution  Rain within 6 hours after application may reduce effectiveness. Do not apply within 0.5 mi upstream of potable water intakes. Apply to moving bodies of water only while traveling upstream. Do not overlap bankside applications more than 1 ft into open water. Do not exceed 3.75 lb ae/A in a single application. Do not spray across open, moving bodies of water.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  2,4-D (Weedar 64, 2,4-D Amine 4, or DMA 4 IVM)
Rate  0.95 to 1.95 lb ae/A
Time  Apply as foliage spray in the spring or early summer.
Remarks  For broadleaf control, apply in 20 to 100 gal/A of water carrier. For harder-to-control weeds, a repeat application may be needed. Regrowth of perennials such as Canada thistle may require retreatment in the fall. Travel upstream when applying. Any overspray into water should average less than 1 ft.
Caution  Do not contaminate domestic water sources or fishing waters. 2,4-D formulations may be toxic to fish. Do not apply to water that will be used to sprinkler-irrigate susceptible crops, especially grapes and tomatoes.
Site of action  Group 4: synthetic auxin.
Chemical family  Phenoxy acetic acid
AQUATICS—Broadleaf, Floating, Emersed, Marginal, and Bank Weeds of Ponds and Lakes
•  2,4-D dimethylamine salt (Weed-Rhap A-4D or DMA 4 IVM)
Rate  2 to 3 lb ae/A
Time  Apply as foliage spray in the spring or early summer.
Remarks  Use at least 100 gal/A of water carrier for ground application and at least 7.6 gal/A for aerial application. Regrowth of perennials such as Canada thistle may require retreatment in fall.
Caution  Do not contaminate water used for domestic purposes. 2,4-D formulations may be toxic to fish. Do not contaminate fishing waters.
Site of action  Group 4: synthetic auxin
Chemical family  Phenoxy acetic acid
•  glyphosate (Rodeo, Eagre, AquaNeat, AquaPro, AquaMaster, or Accord Concentrate)
Rate  0.75 to 3.75 lb ae/A applied as a broadcast spray or 0.75 to 1.5% solution in water applied through hand-held or high-volume equipment
Time  Apply when weeds and brush are actively growing.
Remarks  Refer to label for application rate and growth stage of weed and brush species. Add labeled surfactant at 2 quarts or more per 100 gal of spray solution. Floating mats of vegetation may require retreatment. If emerged infestations require treating the total surface of impounded water, treating the area in strips may avoid oxygen depletion, due to decaying vegetation, and prevent subsequent fish kill.
Caution  Avoid washing off sprayed foliage by spray boat, recreational boat backwash, or rain within 6 hours of application. Do not apply within 0.5 mi upstream of potable water intake. When applying bankside, do not overlap more than 1 ft into open water. Do not exceed 3.75 lb ae/A in any single application.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
•  triclopyr (Renovate 3)
Rate  1.5 to 6 lb ae/A
Time  Apply to actively growing broadleaf weeds and woody plants.
Remarks  Use a labeled nonionic surfactant. Use the higher rate when plants are mature or weed mass is dense or for difficult-to-control weeds. Repeat as necessary to control regrowth and plants missed in the previous application. There are no restrictions on recreation, including swimming and fishing, in the treated area or on livestock consumption of water.
Caution  Do not apply when conditions favor drift to susceptible vegetation. Do not exceed 6 lb ae/A triclopyr (8 quarts/A of Renovate) per annual growing season. Consult label for setback distances from potable water intakes when applying to control floating and emerged weeds in lakes, reservoirs, or ponds.
Site of action  Group 4: synthetic auxin
Chemical family  Pyridine
•  imazapyr (Habitat)
Rate  0.25 to 1.5 lb ae/A
Time  Apply to vigorously growing emersed and floating vegetation.
Remarks  Controls several annual, biennial, and perennial grass and broadleaf species. Rate depends on weed species and growth stage at time of application. Postemergence applications require adding a spray adjuvant approved for use in aquatic sites. Controls emerged and floating vegetation that has most of its foliage above the water surface. Begin treatment along the shore and proceed outward in bands to allow aquatic organisms to move into nontreated areas. Unless imazapyr residues in the water are below 1 ppb, as determined by laboratory analysis, wait at least 120 days after application before using water for irrigation. No restrictions on recreational or livestock use of treated water. May be applied as a drawdown treatment after water has been drained; allow 14 days before reintroducing water.
Caution  Do not apply more than 1.5 lb ae/A (6 pints/A product) per year. Do not apply within 0.5 mi of a potable water intake in a standing body of water unless the intake can be turned off for at least 48 hours after treatment. Do not apply to irrigation water. Do not treat more than half the surface area of water in a single application, and wait 10 to 14 days between treatments.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  imazamox (Clearcast)
Rate  0.125 to 0.5 lb ai/A (16 to 64 oz product\A)
Time  Apply as a foliage spray to actively growing emersed and floating plants. 
Remarks  Rate depends on species to be controlled. Postemergence applications require adding a spray adjuvant approved for use in aquatic sites. There are no restrictions on livestock watering, swimming, fishing,or  domestic use as long as the setback restriction is observed, or for agricultural sprays.
Caution  Do not use treated water to irrigate greenhouses, nurseries, or hydroponics. Do not use treated water for other irrigation purposes unless concentrations in water are equal to or less than 50 ppb. Note label restrictions on setback restrictions to potable water intakes.
Site of action  Group 2: acetolactate synthase (ALS) inhibitor
Chemical family  Imidazolinone
•  carfentrazone (Stingray)
Rate  0.05 to 0.2 lb ai/A (3.4 to 13.5 fl oz/A product)
Time  Apply to foliage of actively growing broadleaf weeds.
Remarks  Use higher rate range when plants are mature, when the weed mass is dense, or for difficult- to-control species. Add an aquatic labeled nonionic surfactant or methylated seed oil at manufacturer’s recommended rate. Thorough wetting of foliage is essential for maximum effectiveness. 
Caution  Do not treat more than half the body of water at one time and wait at least 14 days before re-treating or treating the remaining half. Do not exceed 0.2 lb ai/A (13.5 fl oz/A product) in any single application. Note label restrictions on setback distances for application to potable water intakes. Consult label for water use restrictions after application.
Site of action  Group 14: protoporphyrinogen oxidase inhibitor
Chemical family  Triazinone
AQUATICS—Floating Weeds in Lakes, Ponds, Irrigation Canals, and Drainage Ditches
•  diquat (Diquat Herbicide or Reward)
Rate  1 to 2 lb ai/A
Time  Apply whenever weeds become a problem.
Remarks  Add Ortho X-77 surfactant (nonionic) at 8 fl oz/100 gal of spray mix. Apply in at least 150 gal/A water carrier for ground application and at least 7.5 gal/A for aerial application. Use diquat in waters that are totally under your control. In public waters, only federal or state public agencies or contractors under their direct control may use this product. There are no fishing or swimming restrictions following a diquat application.
Caution  A moderately toxic herbicide that requires protective gear for handling and application. Do not allow spray to drift or come in contact with adjacent crops. Do not use treated water for domestic purposes, animal consumption, spraying, or irrigation for 1 to 5 days depending on water use and rate applied. Safe for fish at rates given. Do not let spray come in contact with skin, eyes, or clothing. Do not breathe spray mist
Site of action  Group 22: photosystem I electron diversion
Chemical family  Bipyridilium
•  glyphosate (Rodeo, Eagre, AquaNeat, AquaPro, AquaMaster, Cinco, or Accord Concentrate)
Rate  0.75 to 3.75 lb ae/A applied as a broadcast spray or 0.75 to 1.5% solution in water applied through hand-held or high-volume equipment
Time  Apply when weeds are actively growing and most foliage is above the water surface.
Remarks  Refer to label for application rate and growth stage of weed and brush species. Add labeled surfactant at 2 quarts or more per 100 gal spray solution. When emerged infestations require treating the total surface of impounded water, treating the area in strips may avoid oxygen depletion, due to decaying vegetation, and prevent subsequent fish kill. Floating mats of vegetation may require retreatment.
Caution  Avoid washing off sprayed foliage by spray boat, recreational boat backwash, or by rain within 6 hours of application. Do not apply within 0.5 mi upstream of potable water intakes. Applications to moving bodies of water must be made while traveling upstream. Do not exceed 3.75 lb ae/A (7.5 pints/A) in any single application.
Site of action  Group 9: inhibits EPSP synthase
Chemical family  None generally accepted
AQUATICS—Other Registered Herbicides
•  dicamba + 2,4-D (Brush Buster)
Weed and brush control on drainage ditch banks only.
•  diuron (Karmex DF)
Used for long-term, residual plant control in irrigation and drainage ditches. Not often used due to erosion of ditches. Apply only in fall.
•  fosamine (Krenite S)
Woody plant control on drainage ditch banks and noncropland, including land adjacent to and surrounding domestic water.
•  bromacil + diuron (Krovar DF)
Used for long-term, residual weed control on outside bank of drainage ditches only. Do not let material drift or move into irrigation water.