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Aquatic Herbicides. An overview of the herbicides permitted for use in Region 8 aquatic applications. Aquatic Vegetation . Emergents - rooted in soil – leaves extend into air. Floaters - either lacking roots or roots not growing in soil. Immersed Plants completely submerged

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aquatic herbicides
Aquatic Herbicides
  • An overview of the herbicides permitted for use in Region 8 aquatic applications
slide2

Aquatic Vegetation

Emergents -

rooted in soil –

leaves

extend into air

Floaters - either lacking roots or roots not growing in soil

Immersed

Plants completely submerged

- not rooted

Submergents -

rooted in soil - leaves

do not extend out of water

acre foot
Acre Foot

A measure of

WATER

1 surface acre in area

X 1 foot deep =

43,560 square feet X 1 foot =

43,560 cubic feet

chelation
Chelation

From “Chela” – a lobsterlike claw

When an ion is held to two other non-metal ions in a ring compound by coordinate bonds

chelation1
Chelation

More simply – though less accurately

An ion held to - but not part of - another chemical compound

copper compounds
Copper Compounds

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copper compounds summary
Copper compounds summary

COMMON NAME

Copper compounds (all below are chelated compounds)

BRAND NAMES

Cutrine-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

copper compounds summary1
Copper compounds summary

MODE OF ACTION

Copper ion released after application is toxic to vegetation

Unfortunately, the copper ion concentration needed to kill algae is only slightly lower than that which kills fish

Relatively slow release of the copper ion from these formulations makes them slightly less risky than copper sulfate that was used in the past

copper compounds summary2
Copper compounds summary

SELECTIVITY

Selective; kills algae but not other aquatic vegetation

copper compounds summary3
Copper compounds summary

SOIL ACTIVITY AND MOBILITY

Not soil active

Copper is strongly adsorbed to clay and organic matter

copper compounds summary4
Copper compounds summary

PERSISTENCE AND BREAKDOWN

Remains in soil indefinitely; however, at application rates used it is essentially chemically inactive a short time after application

copper compounds summary5
Copper compounds summary

TOXICITY TO HUMANS AND WILDLIFE

Generally low in toxicity; rat oral LD50 is listed as 1,312 mg/kg for K=Tea and 1,930 mg/kg for Cutrine Plus

Due to the relatively slow release of copper ions by these products, fish toxicity is fairly low; LC50 for bluegill is 1.2 ppm for Cutrine Plus

Irritating to eyes and skin; Cutrine-Plus carries the signal word DANGER due to the potential for it to cause irreversible eye and skin damage

copper compounds summary6
Copper compounds summary

APPLICATION TIMING

During the active growing season for algae copper compounds should be applied early in the day on sunny days when the water is relatively warm (at least 60o F)

copper compounds summary7
Copper compounds summary

WEAKNESSES OR LIMITATIONS

Wear goggles or a face shield and rubber gloves when handling Cutrine-Plus

Hard water interferes with the action of the released copper ions and makes dose calculation difficult

Copper triethanolamine complex (K-Tea) should not be used where water pH is below 6

copper compounds summary8
Copper compounds summary

WEAKNESSES OR LIMITATIONS

Some states require permits for application of copper herbicide to water

Despite the eye and skin damage potential of the concentrated formulations, there is no waiting period after application for use as drinking water or for swimming; both activities may begin immediately after application

2 4 d
2,4-D

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2 4 d summary
2,4-D summary

COMMON NAMES

2,4-D

BRAND NAMES

Aqua-Kleen (0.19 lb a.i./lb) – labeled for AQUATIC use

2 4 d summary1
2,4-D summary

NOTE

Many other 2,4-D products are available, with or without other a.i.s in the formulation

Terrestrial application of 2,4-D may be made only with prior approval of the Regional Forester, and often products in this compendium are equally or more effective without the toxicological concern raised by 2,4-D

Labels for products to be applied to terrestrial sites are not included in this discussion

2 4 d summary2
2,4-D summary

MODE OF ACTION

Growth regulator; causes plant tissues to outgrow their ability to feed themselves

Absorbed by both leaves and roots, and translocated to actively growing areas

Aqua-Kleen is a granular formulation which sinks to the bottom of treated water areas

It is absorbed primarily through the roots

2 4 d summary3
2,4-D summary

SELECTIVITY

Selective; see label for susceptible aquatic plants

In terrestrial applications, grasses are tolerant while trees and broadleaf weeds tend to be susceptible

2 4 d summary4
2,4-D summary

SOIL ACTIVITY AND MOBILITY

Soil active

Amine formulations are readily mobile in soil if percolating water is present

Ester formulations are less mobile

2 4 d summary5
2,4-D summary

PERSISTENCE AND BREAKDOWN

Short half-life, generally 1-4 weeks; breakdown is by microbial action

2 4 d summary6
2,4-D summary

TOXICITY TO HUMANS AND WILDLIFE

Moderately toxic; rat oral LD50 is 639 mg/kg; formulated Aqua-Kleen’s oral LD50 4,050 mg/kg for male rats

Ester formulations can be highly toxic to fish

Animal studies have indicated possible carcinogenicity

2 4 d summary7
2,4-D summary

PRIMARY FORESTRY USES

Aquatic use is primarily to control water milfoil or water stargrass in ponds

Little current use in Region 8; past use has been primarily in combination with other herbicides

May be useful for broadleaf weed control in wildlife openings or rangelands

Any terrestrial use of 2,4-D requires Regional Forester approval

2 4 d summary8
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 so as to avoid oxygen depletion resulting from decomposition of dead plant material and subsequent fish kill

2 4 d summary9
2,4-D summary

WEAKNESSES OR LIMITATIONS

In general, other products are available which pose less risk and are more effective

Fish kill can result from treating too large an area of aquatic vegetation at one time

Some states have additional restrictions on the use of 2,4-D

Terrestrial application may be made only with Regional Forester approval

diquat
Diquat

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diquat summary
Diquat summary

COMMON NAME

Diquat

BRAND NAMES

Reward (2 lbs a.i./gal) – labeled for AQUATIC use

diquat summary1
Diquat summary

MODE OF ACTION

Contact herbicide; rapidly absorbed by vegetation, but not readily translocated

diquat summary2
Diquat summary

SELECTIVITY

Nonselective

Effective in controlling most submerged aquatic plants

diquat summary3
Diquat summary

SOIL ACTIVITY AND MOBILITY

Not soil active

Strongly adsorbed to clay particles

Rapidly deactivated by muddy water

Also, degraded by water with low pH

diquat summary4
Diquat summary

PERSISTENCE AND BREAKDOWN

Breakdown is primarily by photolysis, although persistence is generally limited by adsorption rather than chemical breakdown

When bound to soil diquat is very persistent – but is biologically unavailable

Microbial degrade is limited and almost completely stops once diquat adsorbs to vegetation

diquat summary5
Diquat summary

TOXICITY TO HUMANS AND WILDLIFE

Moderately toxic; rat oral LD50 is 230 mg/kg; for Reward it is 810 mg/kg

Relatively low toxicity to fish

However, dermal toxicity to mammals is generally higher than oral toxicity, and care must be taken to avoid dermal exposure

diquat summary6
Diquat summary

APPLICATION TIMING

Should be applied when target plants are actively growing

diquat summary7
Diquat summary

WEAKNESSES OR LIMITATIONS

Due to risk associated with dermal toxicity, this product is a poor choice if lower-risk products are effective on the target species

Rapid plant kill can result in oxygen depletion in ponds, which can cause fish kill

Diquat is rapidly inactivated when applied in muddy water

Do not allow swimming in treated areas for 24 hours following treatment

endothall
Endothall

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endothall summary
Endothall summary

COMMON NAME

Endothall

BRAND NAMES

Aquathol (0.101 lb a.i./lb of formulation product) – labeled for aquatic weed control in LAKES and PONDS

Aquathol K (3.0 lbs a.e./gal) - labeled for aquatic weed control in LAKES, PONDS, and DRAINAGE DITCHES

Hydrothol 191 (2 lbs a.i./gal) - labeled for algae and aquatic weed control 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

endothall summary1
Endothall summary

MODE OF ACTION

Interferes with RNA synthesis

Acts as a contact herbicide, with little translocation

endothall summary2
Endothall summary

SELECTIVITY

Nonselective

Generally used against submerged aquatic plants

endothall summary3
Endothall summary

SOIL ACTIVITY AND MOBILITY

Some soil activity, although absorption is primarily through leaf surfaces in aquatic applications

Mobile in water

endothall summary4
Endothall summary

PERSISTENCE AND BREAKDOWN

Broken down in both soil and water by microbial action at rates which are dependent on temperature and nutrient availability

endothall summary5
Endothall summary

TOXICITY TO HUMANS AND WILDLIFE

Highly to moderately toxic, depending on formulation

Rat oral LD50 for 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 precautions must be taken to avoid dermal exposure

endothall summary6
Endothall summary

TOXICITY TO HUMANS AND WILDLIFE

Endothall is also an eye irritant, and inhalation of vapors or dusts can cause irritation and injury

Generally nontoxic to fish at concentrations of 500 ppm or less

Hydrothol formulations are more toxic to fish than Aquathol formulations

endothall summary7
Endothall summary

APPLICATION TIMING

Apply when water temperature is 65 degrees or above, and plants are actively growing

endothall summary8
Endothall summary

WEAKNESSES OR LIMITATIONS

Due to its toxicity, endothall should not be used if other products are available which will effectively control the target species

Granular formulations are preferred to liquids due to reduced risk of dermal absorption

fluridone
Fluridone

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fluridone summary
Fluridone summary

COMMON NAME

Fluridone

BRAND NAMES

Sonar A.S. (4 lbs a.i./gal) – labeled for aquatic vegetation control in FRESH WATER LAKES, PONDS, RESERVOIRS, and DRAINAGE DITCHES

Sonar SRP (0.05 lb a.i./lb of formulation weight) – labeled for aquatic vegetation control in FRESH WATER LAKES, PONDS, RESERVOIRS, and DRAINAGE DITCHES

fluridone summary1
Fluridone summary

MODE OF ACTION

Inhibits formation of carotenoid pigments in leaves, allowing chlorophyll to be bleached by sunlight and preventing plants from synthesizing food

fluridone summary2
Fluridone summary

SELECTIVITY

Selective; generally used against submerged aquatic plants

Most aquatic plant species are susceptible, but a few (algae, many floaters, reeds, cattails, and others) are not

Identification of target species is critical when using this product

fluridone summary3
Fluridone summary

ACTIVITY AND MOBILITY

Strongly adsorbed to organic matter in soil and in water; extremely limited soil-activity or soil-mobility (leaches slowly in soil)

Mobile in moving water

fluridone summary4
Fluridone summary

PERSISTENCE AND BREAKDOWN

Broken down in water primarily by light, however some breakdown by microorganisms and aquatic plants

In soil primarily broken down by microbial activity

Persistence ranges from 21 days in water to 90 days in hydro-soils, depending upon light, temperature and microbial populations

fluridone summary5
Fluridone summary

TOXICITY TO HUMANS AND WILDLIFE

Generally low order of toxicity; technical fluridone has a rat oral LD50 >10,000 mg/kg

Slightly to moderately toxic to aquatic organisms and fish; 96 hour LC50 values are 11.7 mg/L for rainbow trout, 14.3 mg/L for bluegill, and 10 mg/L for channel catfish

There are no restrictions on use of treated water

fluridone summary6
Fluridone summary

APPLICATION TIMING

May be applied before or during active growth period for target vegetation as long as the weeds are visible and water movement is minimal

fluridone summary7
Fluridone summary

WEAKNESSES OR LIMITATIONS

·Does not control algae, rushes and several other plant species as listed on the label

It also has little effect on most floaters and on cattails

fluridone summary8
Fluridone summary

WEAKNESSES 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. per surface acre (depending on depth), to produce a concentration of 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 effective where treated water will stay in place for at least 60 days; this reduces costs to the range of $7 to $50 per acre foot

rotenone summary
Rotenone summary

COMMON 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 piperonyl butoxide[/lb of formulated weight) - RESTRICTED USE PESTICIDE labeled for the eradication of fish from LAKES, PONDS, RESERVOIRS, and STREAMS

rotenone summary1
Rotenone summary

BRAND NAMES

Chem-Sect Brand Chem Fish Regular (0.10 lb a.i. + associated resins/lb formulated weight) – RESTRICTED USE PESTICIDE labeled for use to SURVEY FISH POPULATIONS IN FRESH OR SALT WATER 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 USE PESTICIDE labeled for the eradication of fish from LAKES, PONDS, RESERVOIRS, and STREAMS (IMMEDIATELY ABOVE LAKES, PONDS OR RESERVOIRS).

rotenone summary2
Rotenone summary

MODE OF ACTION

Interferes with oxygen uptake by gills and suffocates fish

It is also a potent insecticide (not usable as such under the labeling of these products)

rotenone summary3
Rotenone summary

SELECTIVITY

Non-selective; kills all types of fish plus insects and many other aquatic organisms

rotenone summary4
Rotenone summary

SOIL ACTIVITY AND MOBILITY

Not soil active or mobile in soil

Highly mobile in moving water

rotenone summary5
Rotenone summary

PERSISTENCE AND BREAKDOWN

Moderately persistent

After use in lakes or ponds, a waiting period of several weeks must be observed before restocking is attempted, unless the rotenone is neutralized

rotenone summary6
Rotenone summary

TOXICITY TO HUMANS AND WILDLIFE

May be highly toxic; dependant on species

Rat oral LD50 is 561 mg/kg for Nusyn Noxfish and 178 mg/kg for Noxfish; but it has relatively high dermal toxicity, and a 4-hour inhalation LC50 of 0.049 mg/l

It is highly toxic to fish

Labeling carries the “DANGER / POISON” signal words

rotenone summary7
Rotenone summary

APPLICATION TIMING

Timing is not critical; applications are generally made during warm weather, mostly for applicator comfort

rotenone summary8
Rotenone summary

WEAKNESSES OR LIMITATIONS

Water temperature, alkalinity, and turbidity may affect the activity of the product

In flowing streams rotenone MUST be neutralized with potassium permanganate as it passes out of the treatment zone

Failure to properly neutralize rotenone in flowing water will result in fish kills downstream

rotenone summary9
Rotenone summary

WEAKNESSES OR LIMITATIONS

Some formulations are flammable

Use of a respirator is required for applicators

Avoid skin contact or exposure to mists or vapor