Aquatic Herbicides

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Aquatic Herbicides

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

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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
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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

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Chelation

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

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Chelation

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

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Copper Compounds
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Copper compound formulations
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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
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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 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
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Copper compounds summary
SELECTIVITY Selective kills algae but not other
aquatic vegetation
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Copper compounds summary
SOIL ACTIVITY AND MOBILITY Not soil active Copper
is strongly adsorbed to clay and organic matter
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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
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Copper compounds summary
TOXICITY TO HUMANS AND WILDLIFE Generally low in
toxicity rat oral LD50 is listed as 1,312 mg/kg
for KTea 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
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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)
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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
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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
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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 for AQUATIC use
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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
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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
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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
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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
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2,4-D summary
PERSISTENCE AND BREAKDOWN Short half-life,
generally 1-4 weeks breakdown is by microbial
action
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2,4-D summary
TOXICITY TO HUMANS AND WILDLIFE Moderately
toxic rat oral LD50 is 639 mg/kg formulated
Aqua-Kleens oral LD50 4,050 mg/kg for male
rats Ester formulations can be highly toxic to
fish Animal studies have indicated possible
carcinogenicity
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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
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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 so as to avoid
oxygen depletion resulting from decomposition of
dead plant material and subsequent fish kill
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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
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Diquat
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Diquat formulations
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Diquat summary
COMMON NAME Diquat BRAND NAMES Reward (2 lbs
a.i./gal) labeled for AQUATIC use
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Diquat summary
MODE OF ACTION Contact herbicide rapidly
absorbed by vegetation, but not readily
translocated
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Diquat summary
SELECTIVITY Nonselective Effective in
controlling most submerged aquatic plants
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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
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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
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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
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Diquat summary
APPLICATION TIMING Should be applied when target
plants are actively growing
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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
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Endothall
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Endothall formulations
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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
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Endothall summary
MODE OF ACTION Interferes with RNA synthesis Acts
as a contact herbicide, with little translocation
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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 is primarily 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 by microbial action at rates which
are dependent on temperature and nutrient
availability
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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
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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
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Endothall summary
APPLICATION TIMING Apply when water temperature
is 65 degrees or above, and plants are actively
growing
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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
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Fluridone
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Fluridone formulations
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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
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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
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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
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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
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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
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Fluridone summary
TOXICITY TO HUMANS AND WILDLIFE Generally low
order of toxicity technical fluridone has a rat
oral LD50 gt10,000 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
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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
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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
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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
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Glyphosate
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Glyphosate formulation
Details
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Rotenone (a piscicide)
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Rotenone formulations
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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
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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).
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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)
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Rotenone summary
SELECTIVITY Non-selective kills all types of
fish plus insects and 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 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
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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
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Rotenone summary
APPLICATION TIMING Timing is not critical
applications are generally made during warm
weather, mostly for applicator comfort
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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
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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
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