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Aquatic Herbicides
An overview of the herbicides permittedfor use in Region 8 aquatic applications
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Aquatic VegetationEmergents -rooted in soil
leavesextend into air
Floaters - eitherlacking roots or
roots not growingin soil
Submergents -rooted in soil - leaves
do not extend out of water
Immersed
Plants completely submerged- not rooted
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Acre FootA measure of
WATER1 surface acre in area
X 1 foot deep =
43,560 square feet X 1 foot =
43,560 cubic feet
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Chelation
From Chela a lobsterlike claw
When an ion is held to two other
non-metal ions in a ringcompound by coordinate bonds
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Chelation
More simplythough less accurately
An ion held to - but not partof - another chemical
compound
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Copper Compounds
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Copper compound
formulations
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Copper compounds summaryCOMMON NAMECopper compounds (all below are chelated compounds)
BRAND NAMESCutrine-Plus (0.909 lbs elemental copper/gal)labeled
for use in AQUATIC SITES to control algae
Cutrine-Plus Granular (0.0366 lb elemental copper per lb.formulated weight) - labeled for use in AQUATIC SITES to
control algae
K-Tea (0.8 lb metallic copper/gal) - labeled for use in
AQUATIC SITES to control algae
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Copper compounds summary
MODE OF ACTION
Copper ion released after application is toxic to vegetation
Unfortunately, the copper ion concentration needed to killalgae is only slightly lower than that which kills fish
Relatively slow release of the copper ion from theseformulations makes them slightly less risky than copper
sulfate that was used in the past
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Copper compounds summary
SELECTIVITY
Selective; kills algae but not other aquaticvegetation
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Copper compounds summary
SOIL ACTIVITY AND MOBILITY
Not soil active
Copper is strongly adsorbed to clay and organicmatter
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Copper compounds summary
PERSISTENCE AND BREAKDOWN
Remains in soil indefinitely; however, atapplication rates used it is essentiallychemically inactive a short time after
application
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Copper compounds summaryTOXICITY TO HUMANS AND WILDLIFE
Generally low in toxicity; rat oral LD50is listed as 1,312mg/kg for K=Tea and 1,930 mg/kg for Cutrine Plus
Due to the relatively slow release of copper ions bythese products, fish toxicity is fairly low; LC50for bluegill
is 1.2 ppm for Cutrine PlusIrritating to eyes and skin; Cutrine-Plus carries thesignal word DANGER due to the potential for it to
cause irreversible eye and skin damage
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Copper compounds summary
APPLICATION TIMING
During the active growing season for algae coppercompounds should be applied early in the day on sunnydays when the water is relatively warm (at least 60oF)
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Copper compounds summaryWEAKNESSES OR LIMITATIONS
Wear goggles or a face shield and rubbergloves when handling Cutrine-Plus
Hard water interferes with the action of thereleased copper ions and makes dose
calculation difficult
Copper triethanolamine complex (K-Tea) shouldnot be used where water pH is below 6
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Copper compounds summaryWEAKNESSES OR LIMITATIONS
Some states require permits for application ofcopper herbicide to water
Despite the eye and skin damage potential ofthe concentrated formulations, there is nowaiting period after application for use as
drinking water or for swimming; both activitiesmay begin immediately after application
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2,4-D
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2,4-D formulations
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2,4-D summary
COMMON NAMES
2,4-D
BRAND NAMES
Aqua-Kleen (0.19 lb a.i./lb)labeled forAQUATIC use
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2,4-D summary
NOTE
Many other 2,4-D products are available, with or withoutother a.i.s in the formulation
Terrestrial application of 2,4-D may be made only withprior approval of the Regional Forester, and often
products in this compendium are equally or more effectivewithout the toxicological concern raised by 2,4-D
Labels for products to be applied to terrestrial sites arenot included in this discussion
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2,4-D summaryMODE OF ACTION
Growth regulator; causes plant tissues tooutgrow their ability to feed themselves
Absorbed by both leaves and roots, andtranslocated to actively growing areas
Aqua-Kleen is a granular formulation whichsinks to the bottom of treated water areas
It is absorbed primarily through the roots
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2,4-D summary
SELECTIVITY
Selective; see label for susceptible aquaticplants
In terrestrial applications, grasses are tolerantwhile trees and broadleaf weeds tend to be
susceptible
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2,4-D summary
SOIL ACTIVITY AND MOBILITY
Soil active
Amine formulations are readily mobile in soil ifpercolating water is present
Ester formulations are less mobile
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2,4-D summary
PERSISTENCE AND BREAKDOWN
Short half-life, generally 1-4 weeks; breakdownis by microbial action
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2,4-D summaryTOXICITY TO HUMANS AND WILDLIFE
Moderately toxic; rat oral LD50is 639 mg/kg;formulated Aqua-Kleens oral LD504,050
mg/kg for male rats
Ester formulations can be highly toxic to fishAnimal studies have indicated possible
carcinogenicity
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2,4-D summaryPRIMARY FORESTRY USES
Aquatic use is primarily to control water milfoil or
water stargrass in ponds
Little current use in Region 8; past use has beenprimarily in combination with other herbicides
May be useful for broadleaf weed control in wildlifeopenings or rangelands
Any terrestrial use of 2,4-D requires Regional Foresterapproval
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2,4-D summary
APPLICATION TIMING
Should be applied during periods of active growth
Do not treat an entire pond or lake at one time;treat strips or quadrats and wait at least two
weeks before follow-up treatments are made soas to avoid oxygen depletion resulting fromdecomposition of dead plant material and
subsequent fish kill
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Diquat
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Diquat formulations
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Diquat summaryMODE OF ACTION
Contact herbicide; rapidly absorbed by vegetation, butnot readily translocated
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Diquat summary
SELECTIVITY
Nonselective
Effective in controlling most submergedaquatic plants
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Diquat summarySOIL ACTIVITY AND MOBILITY
Not soil active
Strongly adsorbed to clay particles
Rapidly deactivated by muddy water
Also, degraded by water with low pH
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Diquat summaryPERSISTENCE AND BREAKDOWN
Breakdown is primarily by photolysis, although
persistence is generally limited by adsorption ratherthan chemical breakdown
When bound to soil diquat is very persistentbut is
biologically unavailable
Microbial degrade is limited and almost completelystops once diquat adsorbs to vegetation
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Diquat summary
TOXICITY TO HUMANS AND WILDLIFE
Moderately toxic; rat oral LD50is 230 mg/kg;for Reward it is 810 mg/kg
Relatively low toxicity to fish
However, dermal toxicity to mammals is generallyhigher than oral toxicity, and care must be taken to
avoid dermal exposure
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Diquat summary
APPLICATION TIMING
Should be applied when target plants areactively growing
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Diquat summaryWEAKNESSES OR LIMITATIONS
Due to risk associated with dermal toxicity, this product is apoor choice if lower-risk products are effective on the targetspecies
Rapid plant kill can result in oxygen depletion in ponds,
which can cause fish killDiquat is rapidly inactivated when applied in muddy water
Do not allow swimming in treated areas for 24 hoursfollowing treatment
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Endothall
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Endothall formulations
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Endothall summaryCOMMON NAME
Endothall
BRAND NAMES
Aquathol (0.101 lb a.i./lb of formulation product)labeled for aquaticweed control in LAKES and PONDS
Aquathol K (3.0 lbs a.e./gal) - labeled for aquatic weed control inLAKES, PONDS, and DRAINAGE DITCHES
Hydrothol 191 (2 lbs a.i./gal) - labeled for algae and aquatic weedcontrol in LAKES, PONDS, and DRAINAGE DITCHES
Hydrothol 191 (granular) (0.112 lb a.i./lb of formulation weight) -labeled for algae and aquatic weed control in LAKES, PONDS, and
DRAINAGE DITCHES
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Endothall summary
MODE OF ACTION
Interferes with RNA synthesis
Acts as a contact herbicide, with littletranslocation
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Endothall summary
SELECTIVITY
Nonselective
Generally used against submerged aquatic plants
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Endothall summary
SOIL ACTIVITY AND MOBILITY
Some soil activity, although absorption isprimarily through leaf surfaces in aquatic
applications
Mobile in water
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Endothall summary
PERSISTENCE AND BREAKDOWN
Broken down in both soil and water bymicrobial action at rates which are dependent
on temperature and nutrient availability
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Endothall summaryTOXICITY TO HUMANS AND WILDLIFE
Highly to moderately toxic, depending on formulationRat oral LD50for technical endothall acid is 38 mg/kg; for
sodium salt, 182 mg/kg; for amine salt, 206 mg/kg
Formulated products have lower toxicities: rat oral LD50
for Hydrothal 191 granular is 1,540 mg/kg and for the
liquid it is 233 mg/kg
Dermal toxicity is higher than oral toxicity, so precautionsmust be taken to avoid dermal exposure
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Endothall summary
TOXICITY TO HUMANS AND WILDLIFE
Endothall is also an eye irritant, and inhalation ofvapors or dusts can cause irritation and injury
Generally nontoxic to fish at concentrations of
500 ppm or lessHydrothol formulations are more toxic to fish
than Aquathol formulations
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Endothall summary
APPLICATION TIMING
Apply when water temperature is 65degrees or above, and plants are actively growing
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Endothall summaryWEAKNESSES OR LIMITATIONS
Due to its toxicity, endothall should not be usedif other products are available which will
effectively control the target species
Granular formulations are preferred to liquidsdue to reduced risk of dermal absorption
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Fluridone
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Fluridone summaryCOMMON NAME
Fluridone
BRAND NAMES
Sonar A.S. (4 lbs a.i./gal)labeled for aquatic vegetationcontrol in FRESH WATER LAKES, PONDS, RESERVOIRS,
and DRAINAGE DITCHESSonar SRP (0.05 lb a.i./lb of formulation weight)labeledfor aquatic vegetation control in FRESH WATER LAKES,
PONDS, RESERVOIRS, and DRAINAGE DITCHES
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Fluridone summarySELECTIVITY
Selective; generally used against submergedaquatic plants
Most aquatic plant species are susceptible, buta few (algae, many floaters, reeds, cattails, and
others) are not
Identification of target species is critical whenusing this product
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Fluridone summaryACTIVITY AND MOBILITY
Strongly adsorbed to organic matter in soil andin water; extremely limited soil-activity or soil-
mobility (leaches slowly in soil)
Mobile in moving water
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Fluridone summaryPERSISTENCE AND BREAKDOWN
Broken down in water primarily by light, howeversome breakdown by microorganisms and aquatic
plants
In soil primarily broken down by microbial activityPersistence ranges from 21 days in water to 90
days in hydro-soils, depending upon light,
temperature and microbial populations
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Fluridone summaryTOXICITY TO HUMANS AND WILDLIFE
Generally low order of toxicity; technicalfluridone has a rat oral LD50>10,000 mg/kg
Slightly to moderately toxic to aquatic organisms
and fish; 96 hour LC50values are 11.7 mg/L forrainbow trout, 14.3 mg/L for bluegill, and 10 mg/Lfor channel catfish
There are no restrictions on use of treated water
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Fluridone summaryAPPLICATION TIMING
May be applied before or during activegrowth period for target vegetation as long asthe weeds are visible and water movement is
minimal
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Fluridone summaryWEAKNESSES OR LIMITATIONS
Does not control algae, rushes and severalother plant species as listed on the label
It also has little effect on most floaters and oncattails
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Fluridone summaryWEAKNESSES OR LIMITATIONS
Very expensive product, with cost of approximately $1,000/gal
Label rates require from 1 pint to 1 gallon of Sonar A.S. persurface acre (depending on depth), to produce a concentrationof approximately 200 ppb; costs from $125 to $1,000 per acre
foot
While this concentration is necessary with moving water,concentrations as low as 10-12 ppb have been proven effectivewhere treated water will stay in place for at least 60 days; this
reduces costs to the range of $7 to $50 per acre foot
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Glyphosate
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Glyphosate formulation
Details
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Rotenone (a piscicide)
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Rotenone summaryCOMMON NAME
Rotenone (piscicide)
BRAND NAMES
Noxfish (0.15 lb a.i. + associated resins/lb formulated weight)RESTRICTED USE PESTICIDE labeled for the eradication of fish from
LAKES, PONDS, RESERVOIRS, and STREAMS
Nusyn-Noxfish ([0.05 lb a.i. + associated resins + 0.025 lb piperonylbutoxide[/lb of formulated weight) - RESTRICTED USE PESTICIDE
labeled for the eradication of fish from LAKES, PONDS,RESERVOIRS, and STREAMS
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Rotenone summaryBRAND NAMES
Chem-Sect Brand Chem Fish Regular (0.10 lb a.i. + associated
resins/lb formulated weight)RESTRICTED USE PESTICIDE labeledfor use to SURVEY FISH POPULATIONS IN FRESH OR SALTWATER PROVIDED THERE IS NO INTENT TO CONTROL SUCH
POPULATIONS
Chem-Sect Brand Cube Powder Fish Toxicant (0.185 lb a.i. +
associated resins/lb formulated weight)RESTRICTED USEPESTICIDE labeled for the eradication of fish from LAKES, PONDS,
RESERVOIRS, and STREAMS (IMMEDIATELY ABOVE LAKES,PONDS OR RESERVOIRS).
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Rotenone summaryMODE OF ACTION
Interferes with oxygen uptake by gills andsuffocates fish
It is also a potent insecticide (not usable as such
under the labeling of these products)
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Rotenone summary
SELECTIVITY
Non-selective; kills all types of fish plus insectsand many other aquatic organisms
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Rotenone summary
SOIL ACTIVITY AND MOBILITY
Not soil active or mobile in soil
Highly mobile in moving water
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Rotenone summaryPERSISTENCE AND BREAKDOWN
Moderately persistent
After use in lakes or ponds, a waiting periodof several weeks must be observed before
restocking is attempted, unless the rotenoneis neutralized
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Rotenone summaryTOXICITY TO HUMANS AND WILDLIFE
May be highly toxic; dependant on speciesRat oral LD50 is 561 mg/kg for Nusyn Noxfish and 178 mg/kgfor Noxfish; but it has relatively high dermal toxicity, and a 4-
hour inhalation LC50of 0.049 mg/l
It is highly toxic to fish
Labeling carries the DANGER / POISON signal words
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Rotenone summary
APPLICATION TIMING
Timing is not critical; applications aregenerally made during warm weather, mostly for
applicator comfort
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Rotenone summaryWEAKNESSES OR LIMITATIONS
Some formulations are flammableUse of a respirator is required for applicators
Avoid skin contact or exposure to mists or vapor
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