Aquatic Herbicides

8/12/2019 Aquatic Herbicides

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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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SELECTIVITY

Selective; kills algae but not other aquaticvegetation


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SOIL ACTIVITY AND MOBILITY

Not soil active

Copper is strongly adsorbed to clay and organicmatter


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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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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 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


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


Some soil activity, although absorption isprimarily through leaf surfaces in aquatic

applications

Mobile in water


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Endothall summary


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


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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Aquatic Herbicides

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