Aquatic Herbicide Algaecide Toxicity John H Rodgers Jr

Aquatic Herbicide / Algaecide Toxicity John H. Rodgers, Jr. 2012 MN AIS Symposium March 7 -8, 2012 St. Paul, MN

Adaptive Water Resource Management 1. 2. 3. 4. 5. Risk assessment – problem or not? Consider all available options No decision / action vs. decision / action Implement viable option(s) Monitor results modify approach if indicated

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.

Myriophyllum spicatum

Didymosphenia geminata

Cylindrospermopsis raciborskii

Prymnesium parvum

Effects of a P. parvum “Bloom”

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!

Prymnesium parvum

30 -mile fish kill in Dunkard Creek

Problem? ► Response • Response “Triggers” • No Action – Action Consider all the “competing” water resource uses!

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)

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: Flumioxazin Bispyribac Sodium

Herbicides / Algaecides can take advantage of unique physiology • Plants ≠ Fish, invertebrates, etc. • Plants have “systems” that animals do not have. • Unique physiology!

Auxin Mimics • 2, 4 -D formulations – auxin-type herbicide (plant hormone) • Triclopyr – auxin-type herbicide

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

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.

Redox Reactions • Diquat –redox reactions • Peroxide – oxidation reactions • Copper formulations - redox reactions, membrane transport

Light Attenuation • Dyes – light absorption

Toxicity – Non-target species • Peroxide – Sodium carbonate peroxyhydrate • Copper formulation • Triclopyr (TEA salt) • Imazapyr

Animal Testing Species for Margins of Safety for Nontarget Species

Sodium Carbonate Peroxyhydrate Sodium percarbonate IUPAC name : sodium carbonate—hydrogen peroxide (2/3) other names : PCS, solid hydrogen peroxide, sodium carbonate peroxyhydrate CAS number : 15630 -89 -4 Properties Molecular formula : Na 2 CO 3· 1. 5 H 2 O 2 Molar mass : 157. 01 g/mol Appearance : white solid (granular) Solubility in water : 150 g/L

What is SCP? • Sodium carbonate peroxyhydrate

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.

SCP Algae Treatments • • 0. 3 mg/L – 10. 2 mg/L H 2 O 2 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.

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.

SCP Toxicity • Pimephales promelas 96 -h LC 50 = 70. 7 mg/L • Pimephales promelas 96 -h NOEC = 1 mg/L • Daphnia pulex 48 -h EC 50 = 4. 9 mg/L • Daphnia pulex 48 -h NOEC = 1 mg/L • No bioconcentration, bioaccumulation • Abiotic degradation • Low toxicity of ultimate degradation products (H 2 O, O 2)

Margin of Safety (MOS) Scientific name 96 h LOECa Algaecide EC 100 b Pimephales Prymnesium parvum promelas (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 a Lowest Observed Effect Concentration (Murray-Gulde et. al, 2002) b [Cu] used to control Prymnesium parvum (EC 100) c Margin of Safety (MOS) 3. 75

Triclopyr Toxicity • The TEA salt is "slightly toxic" to fish with 96 h LC 50 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.

Imazapyr Toxicity • The 48 - and 96 -h LC 50 s 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 LC 50 for rainbow trout fry is 77, 716 mg/L (ppm) ( ~22, 305 ppm of the active ingredient).

Acute, Chronic Studies

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)

Herbicide / Algaecide Fate and Persistence • • Well Studied Laboratory Studies Semi-field Studies Field Studies

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.

Thank you!