1. 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

2. 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)

3. 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

4. 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

5. 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

6. 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.  

7. 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

12. Chemical Name: 2,4-D 2,4-dichloro-phenoxyacetic acid
Product Names: Navigate, SculpinG (granular), DMA 4, Aqua-Kleen (liquid)
Treatment Concentration Range: 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?

13. 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 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 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

14. 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: 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.

15. 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

16. 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

17. 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)

18. Aquatic Herbicide Treatment Strategies
WEED CONTROL
ppm
Concentration
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

19. 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.

21. 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

22. Intensive Sampling Site
Midpoint

23. 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.

24. 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

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

26. Intensive Monitoring Centerpoint Day 1
Cranberry

27. Intensive Monitoring Centerpoint Day 4
Yellow Birch

28. Intensive Monitoring Centerpoint Day 7NM

29. Intensive Monitoring Centerpoint Day 14

30. Intensive Monitoring Centerpoint Day 21

31. Intensive Monitoring Centerpoint Day 28

32. 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.

33. 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.

34. Low Dose/Long Duration Research Project

35. 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

36. 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)

37. 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)?

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

39. 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)

40. 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, ± , .477 ± , 2.20 ± ; n=3)
28 day exposure
12 replicates/treatment

41. Exposure system

42. Cumulative Egg Production

43. Jonkherre-Terpstra Test
Fecundity
Z= , p = , n=48
Jonkherre-Terpstra Test

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

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

46. Questions?