Effects of Whole Lake Early Season 2,4-D on Eurasian Watermilfoil

(Myriophyllum spicatum)

Wisconsin Department of Natural Resources

John SkogerboeUS Army Corps of Engineers

Michelle Nault, Jennifer Hauxwell, Alison Mikulyuk, Scott van Egeren

Baseline sampling of aquatic plants Goals and Applications

1) In-lake ecology and management-Snapshot of one lake today…

and over time

2) Regional and state-wide ecology and 2) Regional and state-wide ecology and management

-Comparisons among many lakes today… and over time

-Provides CONTEXT

In-lake examples:

Enterprise Lake, Langlade Co.

http://www.uwsp.edu/cnr/uwexlakes/ecology/APM/PI-Protocol-2010.pdf

Species Frequency of occurrence (%)

Species Frequency of occurrence (%)

E. canadensis 45.0 B. schreberi 2.3

Nitella spp. 26.4 M. tenellum 1.9

V. americana 14.3 Chara spp. 1.9

P. pusillus 11.2 Isoetes spp. 1.9

N. flexilis 11.2 P. amplifolius 1.6

N. gracillima 8.1 M. beckii 1.6

In-lake examples:

Summary statistics

Enterprise Lake, Langlade Co.

N. gracillima 8.1 M. beckii 1.6

C. demersum 7.8 N. odorata 1.2

P. richardsonii 4.7 P. strictifolius 1.2

S. fluctuans 4.7 E. palustris 0.8

C. demersum 4.7 M. heterophyllum 0.4

E. acicularis 4.3 N. variegata 0.4

P. robbinsii 3.9 P. crispus 0.4

U. purpurea 3.9

P. spirillus 3.1

M. spicatum 2.7

Utricularia purpurea

In-lake examples:

Maps of species distributions

Myriophyllum spicatum

Sites with plants

purpurea

N

Enterprise Lake, Langlade

Regional/statewide examples:Lakes Surveyed By DNR Research Crews

Questions about EWM

1) Ecology-What are the possible outcomes when EWM establishes in a lake?-What factors contribute to different outcomes?-Interannual variation?-Interannual variation?

2) Management-Past management (non strategic) = short term nuisance relief?

-Future management (strategic) = restoration?

Littoral Frequency of Occurrence of EWM Statewide

Littoral Frequency of Occurrence =

# of sites with EWM .

# sites shallower than the maximum depth of plant colonization

X100

n = 146

Past management – What would we like to see?

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Heavy ManagementLight ManagementNo Management

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0 10 20 30Years since initial detection

EW

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100T

od

ay's

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%)

Heavy Management

Light Management

No Management

100 Lake EWM Study

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Years Since Initial Detection

To

day

's E

WM

Lit

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Current Research

Long term EWM study of “strategic management”

- 24 lake long-term management study

- Sandbar/Tomahawk, Bayfield Co.- Sandbar/Tomahawk, Bayfield Co.

- Kathan Lake, Oneida Co.

-How does strategic management affect long-term EWM population levels?Annual aquatic plant survey and biomass collection on 24 lakes over time3 ecoregions, established and new populations, managed and unmanaged

24 Lake Long-term EWM Management Study

Northern Lakes & ForestsUnmanaged

Managed

Sandbar

Kathan

Bear Paw

Connors

Silver

7 IslandArrowhead

Tomahawk

Hancock

Little Bearskin

Manson

30

40

50

EW

M L

itto

ral %

FO

C

North Central Hardwood ForestsUnmanaged

Managed

MontanaLoon

0

10

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30

2004.5 2005 2005.5 2006 2006.5 2007 2007.5 2008 2008.5 2009 2009.5 2010 2010.5

Year

EW

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ral %

FO

C

Crystal

LuluCrooked

Round

BerryUnderwood

Gibbs

Ivanhoe

L. Green

Unmanaged

Managed

Southeastern Till Plains

Kettle Moraine

Turtle

Wingra

L. Green

1) What are the effects of early season 2,4-D on Eurasian watermilfoil?

2) What about native plants?

Sandbar/TomahawkWDNR, Army Corps of Engineers, Town of Barnes,

Bayfield County

2) What about native plants?

Approach: Monitor annual changesin plant communities in experimental lakes (herbicide or reference)

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Application Timing/PhenologyEarly Spring Herbicide Applications

•Exotic species are small and most vulnerable

•Native species are •Native species are dormant

•Minimal microbial degradation

Blackhawk Lake, Eagan, MN

J. Skogerboe, US Army Corps of Engineers

Concentration/Exposure Time Relationship 2,4-D

J. Aquatic Plant Management 28:27-32

Study design

• Low dose liquid 2,4-D (0.5 mg/L ae) treatment to whole lake (May 20, 2008)

• Aquatic plant surveys conducted 2006-2010

• Biomass collected during

• Reference lake – no treatment

• Aquatic plant surveys conducted 2007-2010

• Biomass collected during

Tomahawk Sandbar

• Biomass collected during 2007-2010 surveys

• Biomass collected during 2007-2010 surveys

Tomahawk vs. Sandbar, Bayfield Co.July 2007 Summary Stats

Lake and plant community variables Tomahawk Sandbar

Lake size (ha) 53.1 51.3

Maximum depth (m) 12.8 14.9

Maximum depth of plant colonization 6.8 7.0

Percentage of littoral zone vegetated 86.4 86.8 Percentage of littoral zone vegetated 86.4 86.8

Number of species 20 17

Mean number of species per site (littoral) 2.6 2.8

Simpson’s Diversity Index 0.90 0.89

Eurasian watermilfoil frequency of

occurrence within littoral zone (%)

39.9 25.8

2006 2007

# points sampled 315 313

# of sites with vegetation 256 260

littoral FOC 85.1 86.4

simpsons diversity 0.89 0.90

Pre-treatment

Tomahawk Lake, Bayfield Co.2006 - 2010 Summary Stats

2008 2009 2010

299

141

54.2

0.81

Post Treatment

316

161

54.0

0.83

328

173

58.8

0.84simpsons diversity 0.89 0.90

avg. # species per site (littoral) 2.4 2.6

avg. # species per site (vegetated sites) 2.8 3.0

avg. # natives per site (littoral) 2.1 2.2

avg. # natives per site (vegetated sites) 2.5 2.7

species richness 20 22 (2 unverified)

species richness (+ visuals) 25 25

max depth of plant growth (ft) 20.5 25.5

0.81

0.9

1.6

0.9

1.6

11

13

17.0

0.83

0.6

1.4

0.6

1.4

13

16

26.0

0.84

1.0

1.6

1.0

1.6

12

16

27.0

Tomahawk Lake, Bayfield Co.Species % Frequency of Occurrences

20

30

40

% F

req

uen

cy o

f O

ccu

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ces

(Lit

tora

l)

20062007200820092010

**

**

*** ***

****** ***

***

***

*** * ***

*

0

10

Robbin

s' po

ndwee

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Elodea

EWM

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spp.

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Filamen

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Species

% F

req

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(Lit

tora

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* = p ≤ 0.05** = p ≤ 0.01

*** = p ≤ 0.001

*** ****

** *

***

** ***

Sandbar Lake, Bayfield Co.2007 - 2010 Summary Stats

2007 2008 2009 2010

# points sampled 190 125 221 182

# of sites with vegetation 131 107 126 119

littoral frequency of occurrence 86.75 88.43 83.44 82.07

simpsons diversity 0.89 0.88 0.89 0.90

avg. # species per site (littoral) 2.8 2.54 2.02 2.43

avg. # species per site (vegetated sites) 3.23 2.87 2.95 2.97

avg. # natives per site (littoral) 2.54 2.22 1.75 2.02

avg. # natives per site (vegetated sites) 2.95 2.61 2.66 2.69

species richness 17 14 15 19

species richness (+ visuals) 19 14 16 20

max depth of plant growth (ft) 23 21 26 23.5

Sandbar Lake, Bayfield Co.Species % Frequency of Occurrences

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70

% F

req

uen

cy o

f Occ

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ence

s (L

itto

ral)

2007200820092010

0

10

20

Variable/Ill

inois

pondweed

Chara spp.

ElodeaEW

M

Water celery

Needle spike

rush

Small pond

weed

Najas spp.

Dwarf wate

rmilfo

il

Large-leaf

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Robbins' pondw

eed

Brown fruite

d rush

Species

% F

req

uen

cy o

f Occ

urr

ence

s (L

itto

ral)

* = p ≤ 0.05** = p ≤ 0.01

*** = p ≤ 0.001

*

2,4-D Treatment No Treatment

Tomahawk Sandbar

Residual Sample Locations

Pre, 1, 2, 3, 5, 7, 14, 21, 28, 35, and 42 days after treatment

Tomahawk & Sandbar

J. Skogerboe, US Army Corps of Engineers

Sandbar

Tomahawk 2,4-D Residuals

500

600

700

800

900

10002,

4-D

res

idu

es, u

g/L

T1T2T3T4T5

Application Rate = 500µg/L

0

100

200

300

400

0 20 40 60 80 100 120 140 160 180

Days after treatment

2,4-

D r

esid

ues

, ug

/L

J. Skogerboe, US Army Corps of Engineers

Short-term Results for EWM

Short-term Results for Natives

Long-term Results for EWM?

Long-term for Natives?

Short- and Long-term Economic Costs?

1) What are the effects of early season 2,4-D on Eurasian watermilfoil?

2) What about native plants?

Kathan Lake, Oneida Co.WDNR, Army Corps of Engineers, Kathan Lake

Association, Onterra LLC

2) What about native plants?

Approach: Monitor annual changesin plant communities pre- and post- treatment

Kathan��������������

Study design

• Low dose liquid 2,4-D (early May 2010)

• Applied at 0.5 ppm to 115 acres of mapped EWM to achieve a lake-wide concentration of 0.25 ppm

• Aquatic plant surveys conducted 2007-2010

• Biomass collected during 2007-2010 surveys

Kathan Lake

Map courtesy of Onterra, LLC

Kathan Lake, Oneida Co.2007-2010

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% F

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Lit

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2007200820092010

***

****** *

0

10

20

Elodea

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dens

isEW

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Najas f

lexilis

Cerato

phyll

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Nitella

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Brase

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Utricula

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term

edia

% F

req

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f O

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Lit

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2010

* = p ≤ 0.05** = p ≤ 0.01

*** = p ≤ 0.001

****** ***

*

Kathan Lake, Oneida Co.Average Total Biomass Per Site

15

20

25

Dry

wei

gh

t (g

ram

s)

Natives

0

5

10

15

2007 2008 2009 2010

Year

Dry

wei

gh

t (g

ram

s)

Natives

EWM

Future Research

DISCUSSIONQuestions?

Comments?

michelle.nault@wisconsin.gov