Aquatic Herbicide / Algaecide Toxicity

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

2. 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

3. 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.

4. Myriophyllum spicatum

5. Didymosphenia geminata

6. Cylindrospermopsis raciborskii

7. Prymnesium parvum

8. Effects of a P. parvum “Bloom”

9. 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!

10. Prymnesium parvum

11. 30-mile fish kill in Dunkard Creek

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

15. 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)

16. Carfentrazone ethyl Copper formulations Diquat 2,4-D formulations Dyes Endothall formulations Fluridone Glyphosate Imazamox Imazapyr Penoxsulam Peroxide formulations Triclopyr formulations Chemical Control Options for Aquatic Vascular Plants and Algae Conditional registration: Flumioxazin Bispyribac Sodium

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

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

19. 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

20. 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.

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

22. Light Attenuation • Dyes – light absorption

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

24. Animal Testing Species for Margins of Safety for Nontarget Species

25. 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 : 15630-89-4Properties Molecular formula : Na2CO3·1.5H2O2 Molar mass : 157.01 g/mol Appearance : white solid (granular) Solubility in water :150 g/L

26. What is SCP? • Sodium carbonate peroxyhydrate

27. 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.

28. 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.

29. 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.

30. 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)

31. 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) 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

32. 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.

33. 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).

34. Acute, Chronic Studies

35. 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)

36. Herbicide / Algaecide Fateand Persistence • Well Studied • Laboratory Studies • Semi-field Studies • Field Studies

38. 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.

39. Thank you!