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

Adaptive Water Resource Management 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 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

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 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.

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 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)

Margin of Safety (MOS) Scientific name Algaecide 96 h LOECa Pimephales promelas (mg Cu / L) EC100 b Prymnesium parvum MOS c= LOEC of Pimephales promelas / [Cu] required to control Prymnesium parvum   Cutrine®- Plus 0.750 0.2 3.75 Algae in a two site waters were evaluated. The pH ranged from 7.8 to 8.3. The hardness ranged from 312 to 427 mg/L as calcium carbonate. Alkalinity ranged from 130 to 335mg/L and conductivity ranged from 1604 to 2700. The fathead minnow is about the size of a 12 point font comma (,). a Lowest Observed Effect Concentration (Murray-Gulde et. al, 2002) b [Cu] used to control Prymnesium parvum (EC100) c Margin of Safety (MOS) Table 1. Water Characteristics of Lake Whitney, Clemson University Culture, Unnamed Area (MI), and Sandy Hills Nursery Table 1. Water Characteristics of Lake Whitney, Clemson University Culture, Unnamed Area (MI), and Sandy Hills Nursery

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.

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).

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!