aquatic herbicide / algaecide toxicity john h. rodgers, jr. 2012 mn ais symposium march 7-8, 2012...
TRANSCRIPT
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Aquatic Herbicide / Algaecide Toxicity
John H. Rodgers, Jr.
2012 MN AIS Symposium March 7-8, 2012
St. Paul, MN
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Adaptive Water Resource Management
1. Risk assessment – problem or not?
2. Consider all available options
3. No decision / action vs. decision / action
4. Implement viable option(s)
5. Monitor results modify approach if indicated
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Why use herbicides or algaecides?
• Invasive and exotic species move at unprecedented rates.
• We have changed the landscape – e.g. canals, reservoirs, stormwater detention basins, etc.
• Human population increase – plant / people interface.
• Changing climate – globally• Pressure on water resources.
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Myriophyllum spicatum
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Didymosphenia geminata
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Cylindrospermopsis raciborskii
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Prymnesium parvum
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Effects of a P. parvum “Bloom”
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Problems Caused by Vascular and Nonvascular (Algae) Plants
• Aesthetics• Devalue property• Disrupt transportation• Taste and odor problems/ Toxin production• Impact fisheries and endangered species• Impede irrigation• Human health• Interfere with water resource uses!
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Prymnesium parvum
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30-mile fish kill in Dunkard Creek
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Problem?► Response
• Response “Triggers”
• No Action – Action
Consider all the “competing” water resource uses!
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Factors influencing herbicide selection
• Target plant species (strain)
• Water resource usages
• Water body and water characteristics
• Efficacy
• Costs
• Margin of safety for non-target species
• Social acceptance (Regulatory approval)
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Chemical Control Options for Aquatic Vascular Plants and Algae
• Carfentrazone ethyl• Copper formulations• Diquat• 2,4-D formulations• Dyes• Endothall formulations• Fluridone
• Glyphosate• Imazamox• Imazapyr• Penoxsulam• Peroxide formulations• Triclopyr formulations
Conditional registration:FlumioxazinBispyribac Sodium
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Herbicides / Algaecides can take advantage of unique physiology
• Plants ≠ Fish, invertebrates, etc.
• Plants have “systems” that animals do not have.
• Unique physiology!
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Auxin Mimics
• 2,4-D formulations – auxin-type herbicide (plant hormone)
• Triclopyr – auxin-type herbicide
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ALS Inhibitors
• Imazapyr – inhibits ALS
• Penoxsulam – inhibits ALS
• Bispyribac Sodium – inhibits ALS
• Imazamox – inhibits the enzyme acetohydroxyacid synthase (AHAS) in plant species, which is involved in the synthesis of three branched-chain aliphatic amino acids: isoleucine, leucine and valine
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Enzyme or Biochemical Inhibitors
• Carfentrazone ethyl - protoporhyrinogen oxidase inhibitor or 'protox' inhibitor
• Fluridone – inhibits phytoene dismutase, blocks carotenoid biosynthesis
• Glyphosate – inhibits ESPS synthesis• Endothall – inhibits lipid and protein synthesis• Flumioxazin - inhibition of protoporphyrinogen
oxidase, an enzyme important in the synthesis of chlorophyll.
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Redox Reactions
• Diquat –redox reactions
• Peroxide – oxidation reactions
• Copper formulations - redox reactions, membrane transport
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Light Attenuation
• Dyes – light absorption
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Toxicity – Non-target species
• Peroxide – Sodium carbonate peroxyhydrate
• Copper formulation
• Triclopyr (TEA salt)
• Imazapyr
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Animal Testing Species for Margins of Safety for Nontarget Species
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Sodium Carbonate Peroxyhydrate
Sodium percarbonateIUPAC name : sodium carbonate—hydrogen peroxide (2/3)
other names : PCS, solid hydrogen peroxide, sodium carbonate hydrogen peroxide, sodium carbonate peroxyhydrate
CAS number : 15630-89-4 Properties Molecular formula : Na2CO3·1.5H2O2 Molar mass : 157.01 g/mol Appearance : white solid (granular) Solubility in water : 150 g/L
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What is SCP?
• Sodium carbonate peroxyhydrate
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SCP Algaecide
• Made by combining 2 molecules of sodium carbonate with 3 molecules of hydrogen peroxide.
• Free-flowing granular.
• Stable source of alkaline hydrogen peroxide.
• In water, produces hydrogen peroxide and sodium carbonate.
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SCP Algae Treatments
• 0.3 mg/L – 10.2 mg/L H2O2
• 3.0 – 100 pounds / acre-foot
• 48 hours between applications
• Large lake or heavy infestation (bloom) – treat 1/3 – 1/2 of the area and wait 2-3 days before treating the remaining water.
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SCP Algaecide
• Algaecide – SCP concentration = 85%
• = 27.6 % hydrogen peroxide
• Registered by US EPA as algaecide for use in ponds, lakes, reservoirs and drinking water.
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SCP Toxicity
• Pimephales promelas 96-h LC50 = 70.7 mg/L
• Pimephales promelas 96-h NOEC = 1 mg/L
• Daphnia pulex 48-h EC50 = 4.9 mg/L
• Daphnia pulex 48-h NOEC = 1 mg/L
• No bioconcentration, bioaccumulation
• Abiotic degradation
• Low toxicity of ultimate degradation products (H2O, O2)
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Scientific name Algaecide
96 hLOECa
Pimephales promelas
(mg Cu / L)
EC100 b
Prymnesium parvum
(mg Cu / L)
MOS c=
LOEC of Pimephales promelas / [Cu]
required to control Prymnesium parvum
(mg Cu / L)
Pimephales promelas
Cutrine®- Plus
0.750 0.2 3.75
Margin of Safety (MOS)
a Lowest Observed Effect Concentration (Murray-Gulde et. al, 2002)
b [Cu] used to control Prymnesium parvum (EC100) c Margin of Safety (MOS)
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Triclopyr Toxicity
• The TEA salt is "slightly toxic" to fish with 96h LC50 values of 552 and 891 ppm for rainbow trout and bluegill sunfish respectively.
• The corresponding values for the unformulated triclopyr are 117 ppm for rainbow trout and 148 for bluegill sunfish.
• Both species were less sensitive to the TEA salt than to the active ingredient.
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Imazapyr Toxicity
• The 48- and 96-h LC50s for rainbow trout, bluegill sunfish, channel catfish, and the water flea (Daphnia magna) are all >100 mg/L (WSSA 1994).
• Concentrations up to 1,600 mg/L did not affect the osmoregulatory capacity of Chinook salmon smolts (Patten 2003).
• The 96-h LC50 for rainbow trout fry is 77,716 mg/L (ppm) ( ~22,305 ppm of the active ingredient).
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Acute, Chronic Studies
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Herbicides / Algaecides can take advantage of differences in responses to exposures
• Fish may detect and avoid herbicide or algaecide.
• Pattern and timing of application.• Pulse or episodic exposure vs. continuous
exposure.• Formulation (e.g. granular vs. liquid)
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Herbicide / Algaecide Fateand Persistence
• Well Studied
• Laboratory Studies
• Semi-field Studies
• Field Studies
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Conclusions – Aquatic Herbicides and Algaecides
• Effective for target algal species.
• MOS (margin-of-safety) for non-target species varies.
• Research ongoing to improve and expand data, uses and effectiveness.
• Development of new chemistries and formulations underway.
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Thank you!