Presentation on theme: "Aquatic Herbicide / Algaecide Toxicity John H. Rodgers, Jr. 2012 MN AIS Symposium March 7-8, 2012 St. Paul, MN."— Presentation transcript:
Aquatic Herbicide / Algaecide Toxicity John H. Rodgers, Jr MN AIS Symposium March 7-8, 2012 St. Paul, MN
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
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.
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!
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!
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.
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 : Properties Molecular formula : Na2CO3·1.5H2O2 Molar mass : 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 – 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.
Table 1. Water Characteristics of Lake Whitney, Clemson University Culture, Unnamed Area (MI), and Sandy Hills Nursery Scientific nameAlgaecide 96 h LOEC a Pimephales promelas (mg Cu / L) EC 100 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 Margin of Safety (MOS) a Lowest Observed Effect Concentration (Murray-Gulde et. al, 2002) b [Cu] used to control Prymnesium parvum (EC 100 ) c Margin of Safety (MOS)
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.