Mike Meyer – Wildlife Toxicologist Rhinelander, Wisconsin Evaluating the Toxicity Risk of Aquatic Herbicide Use in the Ceded Territories Mike Meyer – Wildlife Toxicologist WDNR Science Services 107 Sutliff Avenue Rhinelander, Wisconsin

Herbicides are Increasingly Used to Manage Aquatic Plants in Wisconsin Lakes Large-scale aquatic herbicide treatments are conducted in Ceded Territory lakes to combat Eurasian water milfoil and curly leaf pondweed, with documented short-term success The benefits of reducing aquatic invasive species with herbicides must be balanced against the risk of creating other problems – including toxicity for humans and non-target species (plants, invertebrates, amphibians, and fish)

Herbicides Commonly Used to Manage Aquatic Plants in the Ceded Territories 2,4-D – Eurasian water milfoil Triclopyr – Eurasian water milfoil Endothall – Curly-leaf pondweed Fluridone – Eurasian water milfoil Diquat – limited use for spot treatment of EWM and curly-leaf pondweed

How do they kill aquatic plants? 2,4-D – absorbed by plant tissue; inhibits plant growth and cell division Triclopyr – absorbed by plant tissue; inhibits plant growth and cell division Endothall – contact herbicide, blocks production of essential plant proteins required for plant respiration, disrupts cell membranes Fluridone – blocks production of compound (carotene) which protects chlorophyll from UV (sun) damage Diquat – fast acting, disrupts cell membranes

Will they kill non-target native aquatic plants/manoomin? 2,4-D – Yes/Yes, early stage sensitive to 1mg ae/L Triclopyr – Yes/Yes, early stage less sensitive, no effect when <0.75 mg ae/L Endothall – Yes/Yes, early stage Fluridone – Yes/Yes, early stage Diquat – Yes/Yes, early stages Mature wild rice less vulnerable to herbicides

Are herbicides “safe” for human health and the environment? Registration by the EPA does not mean that the use of the herbicide poses no risk to humans or the environment, only that the benefits have been determined to outweigh the risks . Because product use is not without risk, the EPA does not define any pesticide as “safe”. It is prudent to minimize herbicide exposure whenever possible.  

USE OF HERBICIDES IN WISCONSIN LAKES Directions of Use are found on the product Master Label “It is a violation of federal law to use this product in a manner inconsistent with its labeling” including maximum amount of herbicide that can be applied, conditions and methods of application, disposal, and human/environmental hazards. Herbicide applicator must be licensed WDNR permit review required to evaluate specific aquatic invasive species treatment plans

Chemical Name: 2,4-D 2,4-dichloro-phenoxyacetic acid Product Names: Navigate, SculpinG (granular), DMA 4, Aqua-Kleen (liquid) Treatment Concentration Range: 0.2-4.0 ppm Persistence: half-life=12-40 days (aerobic); >300 days anaerobic; microbial degradation and adsorption Human Health Hazards: Applicators: Corrosive, irreversible eye damage; harmful if swallowed, inhaled, or absorbed by skin Drinking water: setback >600’, 21 days or lake water <0.07 ppm Fishing/Swimming: Navigate - 24 hours swimming, others none Environmental Hazards: Irrigation and Domestic Animals: 21 days or lake water <0.1 ppm Aquatic life: avoid O2 depletion; Navigate formulation (ester) toxic to fish and aquatic inverts at application rates, but breaks down quickly to amine; amine much less toxic, but endocrine disruptor?

Chemical Name:Triclopyr Triethylamine salt (3,5,6-trichloro-2-pyridinyloxyacetic acid) Product Names: Navitrol, Rennovate 3 (liquid) Treatment Concentration Range: 0.75 – 2 ppm Persistence: half-life 0.5-7.5 days, photo and microbial degradation Human Health Hazards: Applicators: corrosive, irreversible eye damage, harmful if swallowed or absorbed. Drinking water: intake setback up to 2600’ (depends on rate), lake water <0.4 ppm Fishing/Swimming: no restrictions, does not accumulate in fish Environmental Hazards: Irrigation and Domestic Animals: crops - 120 day wait or <1ppb, grasses/livestock-none Aquatic life: avoid O2 depletion, TEA practically non-toxic to fish, Triclopyr BEE highly toxic to fish, not used in aquatic systems

Chemical Name: Endothall Dicarboxylic acid class of chemicals and is applied as either a dipotassium salt or an N, N-dimethylalkylamine salt. Product Names: Aquathol K (liquid, dipotassium salt) Treatment Concentration Range: 0.5 - 5 ppm Persistence: half life = 5-10 days; degradation=60 days Human Health Hazards: Applicators: Corrosive, severe eye and skin irritant Drinking water: apply >600’ from intake; lake water <0.1 ppm Fishing/Swimming: none Environmental Hazards: Irrigation and Domestic Animals: treatment 0.5 ppm =no use for 7 days; treatment 5 ppm= no use for 25 days Aquatic life: avoid use of Endothall amine salt, highly toxic to fish and aquatic inverts; dipotassium salt practically non-toxic to slightly toxic.

Chemical Name: Fluridone Product Names: Avast! SC, Sonar AS (both liquids) Treatment Concentration Range: slow acting, requires long-term contact (45-90 days at 0.01 – 0.15 ppm max) Persistence: whole lake treatment, half-life 4-97 days Human Health Hazards: Applicators: Harmful if swallowed, absorbed, or inhaled. Drinking water: none Fishing/Swimming: none, will be found in fish tissue when continuous exposure occurs – tolerance <0.5 ppm Environmental Hazards: Irrigation and Domestic Animals: Irrigation may be restricted up to 14 days, no restriction for domestic animals Aquatic life: low toxicity to fish, mortality of aquatic invertebrates at label application rates

Chemical Name: Diquat Diaquat dibromide Product Names: Reward, Littora (liquid) Treatment Concentration Range: 100 ppb max, fast-acting Persistence: persistent, binds irreversibly to soil Human Health Hazards: Applicators: Potentially fatal if absorbed, harmful if swallowed or inhaled, temporary eye irritant Drinking water: 3 days Fishing/Swimming: none Environmental Hazards: Irrigation and Domestic Animals: irrigation 3-5 days, livestock 1 day Aquatic life: decomp depletes O2, toxic to fish and aquatic invertebrates, walleye sensitive at label concentrations but risk likely minimized by affinity to sediment

WDNR and partners are conducting monitoring and research to further evaluate 2,4-D toxicity risk to non-target plants, aquatic organisms, and human health Monitoring persistence and concentration of herbicides in lake water and sediment following application (ongoing - WDNR, partners) Conducting research to evaluate long-term exposure risk to Wisconsin fish (fathead minnow) and native plants (ongoing - WDNR/UW, partners)

Aquatic Herbicide Treatment Strategies WEED CONTROL 2.5-4.0 ppm Concentration 0.25-0.5 ppm 0.5-2 days Exposure Time 14-21 days Treatment Type High Dose ► Short Exposure Time Spot Low Dose ► Long Exposure Time Whole-lake Onterra, LLC Lake Management Planning

High Dose/Short Duration Monitoring Study Evaluate the human health and ecological toxicity risk of using the herbicide Navigate (2,4-D) to treat Eurasian Water Milfoil in the Eagle River Chain of Lakes 2008.

Application of Navigate to the Eagle River Chain May 28 – June 2, 2008 The treatment plots received 100 lbs/acre or 150 lbs/acre of Navigate® 2,4-D Contractor applied 24,725 pounds (lbs) of Navigate® to chemically treat 188 acres of Eurasian watermilfoil

Intensive Sampling Site Midpoint

Water samples collected pre- and post-application of herbicide On May 21 and 22, 2008 the “pre-treatment” water samples for the chain of lakes were collected.

2,4-D Toxicity Thresholds EPA Safe Drinking Water < 70 μg/L EPA Safe Irrigation Water <100 μg/L EPA Safe Child Swimming <900 ug/L Walleye fry 96hr LC50 = 660 μg/L Amphipod 48hr LC50 = 600 μg/L 2,4-D BEE Chronic Toxicity NOEC = 55 μg/L

Intensive Monitoring Centerpoint Pre-application No 2,4-D detected at all sites

Intensive Monitoring Centerpoint Day 1 Cranberry

Intensive Monitoring Centerpoint Day 4 Yellow Birch

Intensive Monitoring Centerpoint Day 7 NM

Intensive Monitoring Centerpoint Day 14

Intensive Monitoring Centerpoint Day 21

Intensive Monitoring Centerpoint Day 28

Conclusions – Human Health Human drinking water and irrigation thresholds exceeded at intensive sites on Cranberry, and Scattering Rice day 1 post-application. Yellow Birch exceed these standards day 1 & 4. No monitoring sites exceeded 70 ug/L day 14 or beyond. Child swimming standards (900 ug/L) not exceeded at any sites any day Human health concerns are adequately addressed by posting treatment areas for 14 days.

Conclusions – Ecological Risk Impacts to fish and aquatic invertebrates likely low at all sites except Cranberry and Scattering Rice during week 1 where 2,4-D concentrations ranged 260 – 450 ug/L. Risk depends on whether it was in ester or acid form which is unknown. Current aquatic organism toxicity studies not sufficient to predict with certainty 2,4-D concentrations associated with fish reproduction.

Low Dose/Long Duration Research Project

Zachary A. DeQuattro dequattro@wisc.edu Effects of 2, 4-Dichlorophenoxyacetic acid aquatic herbicides on the reproduction and development of fathead minnows: a preliminary report Zachary A. DeQuattro dequattro@wisc.edu

Objective Investigate the effects of commercial 2,4-D formulations on fathead minnow reproduction at ecologically relevant concentrations using the Fish short term reproduction assay Fathead Minnow (male)

Research Questions Do commercial 2,4-D formulations disrupt the reproductive capacity of fish at permitted application concentrations (i.e. the fathead minnow)? Do commercial formulations affect early embryonic development (i.e. fertilization and hatchability)?

Amine Salt Formulation Tested Commercial aquatic herbicide formulation 46.8% Dimethyl amine Salt and 53.20% Other?

The Fathead Minnow native Sexually dimorphic under hormonal control Sexual characteristics are quantifiable or at minimum observable Fractional spawners which is under a dynamic hormone control Spawn to a substrate (i.e. eggs adhere to a substrate)

Methods Fish Short-Term Reproduction Assay Pre-exposure period: Flow-through system Pre-exposure period: 14 days establish baseline fecundity 2 reproductively mature females and one male/replicate Exposure period: Treatments: 0.00, 0.05, 0.50, 2.00 ppm (2,4-D) (< LDL, 0.044 ± .000538, .477 ± .009005, 2.20 ± .035277; n=3) 28 day exposure 12 replicates/treatment

Exposure system

Cumulative Egg Production

Jonkherre-Terpstra Test Fecundity Z=-1.5547, p = 0.0577, n=48 Jonkherre-Terpstra Test

Tubercle Score Decreased in Males * * * F3,44 = 4.202, p = 0.011; SEM * p < 0.05 by Dunnett’s

Next Steps Assess whether reduced fecundity is due to endocrine disruption Test additional 2,4-D herbicide DMA 4IVM (ongoing)

Questions?