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 Submergents - rooted in soil - leaves do not extend out of water Immersed Plants completely submerged - not rooted

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 From “Chela” – a lobsterlike claw When an ion is held to two other non-metal ions in a ring compound by coordinate bonds

Chelation More simply – though less accurately An ion held to - but not part of - another chemical compound

Copper Compounds Skip details

Copper compound formulations

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 ( 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 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 summary SELECTIVITY Selective; kills algae but not other aquatic vegetation

Copper compounds summary SOIL ACTIVITY AND MOBILITY Not soil active Copper is strongly adsorbed to clay and organic matter

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 summary TOXICITY TO HUMANS AND WILDLIFE Generally low in toxicity; rat oral LD 50 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; LC 50 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 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 60 o F)

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 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 Skip details

2,4-D formulations

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 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 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 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 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 summary PERSISTENCE AND BREAKDOWN Short half-life, generally 1-4 weeks; breakdown is by microbial action

2,4-D summary TOXICITY TO HUMANS AND WILDLIFE Moderately toxic; rat oral LD 50 is 639 mg/kg; formulated Aqua-Kleen’s oral LD 50 4,050 mg/kg for male rats Ester formulations can be highly toxic to fish Animal studies have indicated possible carcinogenicity

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 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 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 Skip details

Diquat formulations

Diquat summary COMMON NAME Diquat BRAND NAMES Reward (2 lbs a.i./gal) – labeled for AQUATIC use

Diquat summary MODE OF ACTION Contact herbicide; rapidly absorbed by vegetation, but not readily translocated

Diquat summary SELECTIVITY Nonselective Effective in controlling most submerged aquatic plants

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 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 summary TOXICITY TO HUMANS AND WILDLIFE Moderately toxic; rat oral LD 50 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 summary APPLICATION TIMING Should be applied when target plants are actively growing

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 Skip details

Endothall formulations

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 summary MODE OF ACTION Interferes with RNA synthesis Acts as a contact herbicide, with little translocation

Endothall summary SELECTIVITY Nonselective Generally used against submerged aquatic plants

Endothall summary SOIL ACTIVITY AND MOBILITY Some soil activity, although absorption is primarily through leaf surfaces in aquatic applications Mobile in water

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 summary TOXICITY TO HUMANS AND WILDLIFE Highly to moderately toxic, depending on formulation Rat oral LD 50 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 LD 50 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 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 summary APPLICATION TIMING Apply when water temperature is 65 degrees or above, and plants are actively growing

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 Skip details

Fluridone formulations

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 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 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 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 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 summary TOXICITY TO HUMANS AND WILDLIFE Generally low order of toxicity; technical fluridone has a rat oral LD 50 >10,000 mg/kg Slightly to moderately toxic to aquatic organisms and fish; 96 hour LC 50 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 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 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 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 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

Glyphosate

Glyphosate formulation Details

Rotenone (a piscicide) Skip details

Rotenone formulations

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

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

Rotenone summary SOIL ACTIVITY AND MOBILITY Not soil active or mobile in soil Highly mobile in moving water

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 summary TOXICITY TO HUMANS AND WILDLIFE May be highly toxic; dependant on species Rat oral LD 50 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 LC 50 of mg/l It is highly toxic to fish Labeling carries the “DANGER / POISON” signal words

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

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 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