Presentation on theme: "Aquatic Herbicide / Algaecide Toxicity"— Presentation transcript:
1 Aquatic Herbicide / Algaecide Toxicity John H. Rodgers, Jr MN AIS Symposium March 7-8, 2012 St. Paul, MN
2 Adaptive Water Resource Management Risk assessment – problem or not?Consider all available optionsNo decision / action vs. decision / actionImplement 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 – globallyPressure on water resources.
9 Problems Caused by Vascular and Nonvascular (Algae) Plants AestheticsDevalue propertyDisrupt transportationTaste and odor problems/ Toxin productionImpact fisheries and endangered speciesImpede irrigationHuman healthInterfere with water resource uses!
15 Factors influencing herbicide selection Target plant species (strain)Water resource usagesWater body and water characteristicsEfficacyCostsMargin of safety for non-target speciesSocial acceptance (Regulatory approval)
16 Chemical Control Options for Aquatic Vascular Plants and Algae Carfentrazone ethylCopper formulationsDiquat2,4-D formulationsDyesEndothall formulationsFluridoneGlyphosateImazamoxImazapyrPenoxsulamPeroxide formulationsTriclopyr formulationsConditional registration:FlumioxazinBispyribac Sodium
17 Herbicides / Algaecides can take advantage of unique physiology Plants ≠ Fish, invertebrates, etc.Plants have “systems” that animals do not have.Unique physiology!
19 ALS Inhibitors Imazapyr – inhibits ALS Penoxsulam – inhibits ALS Bispyribac Sodium – inhibits ALSImazamox – 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' inhibitorFluridone – inhibits phytoene dismutase, blocks carotenoid biosynthesisGlyphosate – inhibits ESPS synthesisEndothall – inhibits lipid and protein synthesisFlumioxazin - inhibition of protoporphyrinogen oxidase, an enzyme important in the synthesis of chlorophyll.
27 SCP AlgaecideMade 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-foot48 hours between applicationsLarge 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 peroxideRegistered by US EPA as algaecide for use in ponds, lakes, reservoirs and drinking water.
31 Margin of Safety (MOS)ScientificnameAlgaecide96 hLOECaPimephales promelas(mg Cu / L)EC100 bPrymnesium parvumMOS c=LOEC of Pimephales promelas / [Cu] required to control Prymnesium parvumCutrine®- Plus0.7500.23.75Algae in a two site waters were evaluated. The pH ranged from 7.8 to 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 NurseryTable 1. Water Characteristics of Lake Whitney, Clemson University Culture, Unnamed Area (MI), and Sandy Hills Nursery
32 Triclopyr ToxicityThe 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 ToxicityThe 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).
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 Fate and Persistence Well StudiedLaboratory StudiesSemi-field StudiesField 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.