eurasian watermilfoil management program and water quality

Ramsey County Beach, White Bear Lake, June 4, 2018

Eurasian Watermilfoil Management Program andWater Quality Summary for White Bear Lake,

Washington County, Minnesota, 2018

EWM Delineation Conducted on June 4, 20182018 EWM Treatment: June 20, 2018, 69.9 acres

EWM Assessment Conducted on August 23, 2018

Prepared for:White Bear Lake Conservation District

Prepared by:Steve McComas

Blue Water ScienceSt. Paul, MN 55116

November 2018

Eurasian Watermilfoil Management Program andWater Quality Summary for White Bear Lake,


Summary

White Bear Lake (MnDNR ID: 82-0167) is a 2,428 acre lake located in Washington County,Minnesota. An Eurasian watermilfoil delineation was conducted by Blue Water Science onJune 4, 2018 (Figure 1). Milfoil was widely distributed in June, ranging from light to moderategrowth. Moderate growth had the potential to produce heavy growth and areas with thepotential to produce heavy growth were delineated for treatment. An herbicide applicationtreated a total of 69.9 acres. A follow-up Eurasian watermilfoil assessment was conducted onAugust 23, 2018 to evaluate the status of Eurasian watermilfoil in the treated areas as well asother areas around the lake. The herbicide treatment was generally successful from theperspective that only a few acres of Eurasian watermilfoil had moderate growth based on theassessment survey. No heavy growth or surface matted conditions were observed.

Figure 1. [left] EWM delineation map with treatment polygons for June 4, 2018.[right] The August 23, 2018 EWM assessment found mostly light to moderate EWM growth(shown with green dots = light growth, yellow dots = moderate growth, red dots = heavy growth,and black dots = no EWM growth) in the 69.9 acres treated in 2018.

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EWM Assessment on August 23, 2018

A total of 69.9 acres were treated and 64 acres were evaluated as having fair, good, orexcellent control. However, 5.8 acres (Treatment Areas 3 and 4) were considered to exhibitlimited control although matted EWM was not observed. Native plant distribution did not appearto be hindered (Table 2).

Table 1. Summary of herbicide treatment results for 11 areas totaling 69.9 acres for White Bear Lake in 2018. Density ratings are on a scale from 1 to 3 with 3 the heaviest.

Herbicide TreatmentAreas

Acres Delineation (6.4.18) Assessment (8.23.18) EWMControlResults

% EWM(occurrence within

treatment area)

AverageEWM

Density

% EWM(occurrence within

treatment area)

AverageEWM

Density

Liquid Triclopyr - 1.5 ppm 1 2.57 58% 7/12 1.0 20% 2/10 1.0 Fair

Liquid Triclopyr - 1.5 ppm 2 5.17 80% 8/10 1.4 38% 3/8 1.0 Fair

Liquid Triclopyr - 1.5 ppm 3 3.56 89% 8/9 1.0 60% 6/10 1.0 Limited

Liquid Triclopyr - 1.5 ppm 4 2.3 86% 6/7 1.3 50% 7/14 1.1 Limited

Liquid Triclopyr - 1.5 ppm 5 15.07 52% 13/25 1.2 8% 1/13 1.0 Good

Liquid Triclopyr - 1.5 ppm 6 19.69 80% 12/15 1.1 17% 2/12 1.0 Good

Liquid Triclopyr - 1.5 ppm 7 11.14 67% 6/9 1.3 0% 0/8 0 Excellent

Depth Charge* 8 3 100% 4/4 1.3 0% 0/7 0 Excellent


2,4-D, 4 ppm 10 3.07 75% 3/4 1.0 0% 0/5 0 Excellent


TOTAL 69.9*Depth Charge: 2,4-D and flumioxazin at 2.0 ppm

Table 2. Native plant occurrence and densities within treatment area. Density ratings are on a scale from 1to 3 with 3 the heaviest.

TreatmentAreas

Native Plants Native Plants

%(occurrenc

e withintreatment

area)

NativePlant

AverageDensity

%(occurrenc

e withintreatment

area)

NativePlant

AverageDensity

1 100%12/12 1.1 70% 7/10 1.7

2 50% 5/10 1.0 88% 7/8 1.0

3 78% 7/9 1.4 100% 10/10 1.1

4 86% 6/7 1.0 100% 14/14 1.0

5 72% 18/25 1.4 100% 13/13 1.1

6 80% 12/15 1.2 100% 12/12 1.3

7 56% 5/9 1.4 88% 7/8 1.3

8 100% 4/4 1.3 86% 6/7 1.3

9 75% 3/4 1.3 100% 5/5 1.6

10 100% 4/4 1.5 100% 5/5 1.0

11 100% 4/4 1.3 100% 5/5 1.0

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Figure 2. Historical herbicide use in White Bear Lakefrom 1988 to 2018.

Eurasian Watermilfoil Treatments from 1988 - 2018

Eurasian watermilfoil was first observed with a single plant collected near a public dock on thewest side of the lake in 1988. A history of Eurasian watermilfoil control measures is shown inTable 3. From 1991 through 1995, an aggressive EWM treatment program was implementedto try to stop the spread of EWM within White Bear Lake. The aggressive treatmentapproaches were discontinued after 1995. EWM had basically spread around White Bear Lakeat mostly light to moderate growth with some patches of heavier growth. After 1995, there wasa period of 13 years (1996-2008) where Eurasian watermilfoil treatments were less than 20acres (which includes shoreline treatments) per year. Since 2009, Eurasian watermilfoil hasbeen more abundant and is reflected in an increase in treatment acreages. A graph oftreatment areas from 1988 through 2018 is shown in Figure 2.

Table 3. Eurasian watermilfoil treatment history in White Bear Lake.

Year Herbicide(permitted

acres)

Mechanical(acres)

Hand-pulling(acres)

1988 2

1989 8.8

1990 4

1991 19.2 12

1992 95.9 3

1993 60.6 3

1994 20.5

1995 46.0

1996 11.5

1997 minimal

1998 5

1999 11.0

2000 13.0

2001 16.2

2002 17.2

2003 16.5

2004 12.9

2005 14.7

2006 15.1

2007 19.8

2008 17.8

2009 12.3 35

2010 174

2011 41.6

2012 126

2013 100

2014 32.8

2015 85

2016 60.4

2017 65.1

2018 69.9

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Overlay of Treatment Areas Showing Persistent EWMGrowth from 2010 to 2018

Figure 3. Overlay of treatment maps from 2012-2018.

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White Bear Lake Proposed 2019 EWM TreatmentBased on Treatments from Previous Years

For EWM control in 2019 it is proposed to treat the persistent heavy growth areas early andthen delineate the lake again in June to determine if additional areas of EWM treatment areneeded.

Areas of persistent growth and potential treatment are shown in Figure 5 and total about 62acres. These areas have been treated at least 4 out of the last 7 years. A MnDNR permitapplication for these areas would be submitted in winter. Then EWM would be checked in lateMay or early June to verify its presence. If it is present in the polygon then that area would betreated.

There would be a EWM assessment in August or September to assess EWM control.

Figure 4. Proposed2019 EWM treatment.

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Figure 5. Secchi disc summer averages (from May-September, unless data are lacking) for White

Bear Lake. (2005-2017 data are from Ramsey County).

Figure 6. Lake levels for White Bear Lake.

Secchi Disc(meters)

Ordinary high waterlevel (924.89 feet)

White Bear Lake Water Quality Summary

White Bear Lake Water Clarity and Lake Levels Through 2017: Secchidisc readings for 1969 through 2017 are shown in Figure 5. From 2007 through 2016, waterclarity was not as good compared to the period of 2000 through 2006. Lake water levels havefluctuated over the years (Figure 6).

White Bear Lake levels from 1924 - 2018

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Additional Information on the Eurasian WatermilfoilManagement Program for White Bear Lake,


White Bear Lake, Washington County (ID: 82-0167)Lake Area: 2,428 acres (MnDNR)Littoral Area: 1,314 acres (MnDNR)Maximum depth: 83 ft (MnDNR)

Project Setting

White Bear Lake has a variety of native and non-native aquatic plants. The objectives of the2018 aquatic plant delineation and assessment were to delineate treatment areas of Eurasianwatermilfoil and then assess treatment effectiveness in the 69.9 acres that were treated withherbicides.

Figure 7. USGS map of White Bear Lake, Washington County, Minnesota.

White Bear Lake Eurasian Watermilfoil Management Program, 2018 1

Methods

Eurasian Watermilfoil Delineation and Assessment: Eurasian watermilfoil delineations wereconducted by Blue Water Science with the assistance of Mike Parenteau on June 4, 2018. Thedelineations involved cruising around the entire lake and observing milfoil growth and samplingaquatic plants with rakes. A total of 273 sample sites were checked. Areas to be treated wereselected based on the growth status of milfoil in late June, the known previous occurrence ofmilfoil and the importance for navigation and/or recreation in the area.

An herbicide application was conducted by Lake Management Inc and a total of 69.9 acres weretreated.

A follow-up Eurasian watermilfoil assessment was conducted by Steve McComas, Blue WaterScience, on August 23, 2018 to evaluate the effectiveness of the herbicide treatment for Eurasianwatermilfoil control. A total of 97 sites were checked on the August 23, 2018 assessment. EWM density ratings used in the June delineation and August assessment are shown in the chartbelow.

Chart of EWM Density Ratings for EWM

Figure 8. Eurasian watermilfoil rake density ratings from 1 to 3. Native plants used the same rake fullnessrating as well.


Results - June 4, 2018 EWM Delineation

Figure 9. June 4, 2018 delineation map. Eleven areas were delineated for treatment in 2018.


EWM and Native Plant Results for Individual Sample Sites

Table 4. EWM delineation on June 4, 2018.

Treat-mentArea

Site Depth(ft)

EWM CLP Cab-bage

Chara Coon-tail

Clasp-ingleaf

Elodea Fern Native Noplants

1 9 1

1 2 9 1 1 1 1

3 10 1 1 1

1 4 10 1 1

1 5 10 1 2

6 11 2

7 11 2

8 12 1

9 16 1 1

10 16 1 1 1

11 13 1

12 13 1 1

13 10 2 1 2

14 10 1

15 9 1 1

16 7 1 1

17 10 1

18 7 1 1

19 7 1 1

20 12 1 1

21 9 1

22 9 2

23 12 1

24 12 1 1 1

25 13 1

26 14 1

3 27 13 1

3 28 10 1 1

3 29 10 1 2

3 30 10 2

3 31 11 1 2

3 32 10 1 1

3 33 12 1 1

3 34 12 1

3 35 12 1 1

36 12 1 2

2 37 9 1 1

2 38 9 1 1

2 39 9 2

2 40 9 2

2 41 10 1 1

2 42 1 1 1

2 43 8 2

2 44 10 1

2 45 9 1

2 46 10 1

47 10 1

48 12 1

49 12 1 1

50 12 1 1

51 14 1

52 13 1 1

53 11 2

54 10 1

55 13 1

56 16 1

57 13 1

58 13 1 1

59 10 1

60 11 1

61 12 1

62 12 1

63 9 1

64 13 1 1

65 14 1 1

66 12 1

67 11 1

68 11 2

69 11 1

Treat-mentArea

Site Depth(ft)

EWM CLP Cab-bage

Chara Coon-tail

Clasp-ingleaf


70 10 2

71 11 2

72 11 1

73 11 1

74 8 1

75 13 1

76 12 1

77 13 1

78 14 1

79 11 1

4 80 12 1 1

4 81 11 1

4 82 11 1 1

4 83 10 1

4 84 11 2 1

4 85 10 2 1

4 86 11 1 1

87 12 1

88 13 1

89 13 1

90 13 1

91 11 2

92 10 2

93 12 1

94 13 2

95 13 1

96 10 1

97 11 1

98 11 2

99 11 1

100 11 1 1

101 11 1

102 10 1

103 10 1

104 13 1

105 10 2

106 12 2

107 17 1

108 12 1

109 12 2

110 11 1

111 11 2

112 12 1

113 11 1

114 10 1

115 10 1

116 10 1

117 10 1

118 10 1

119 11 1

120 10 1

121 14 1

122 18 1

123 10 1

124 14 1

125 16 1

126 11 1

127 9 1

128 10 1 1

129 10 1 2

130 10 2

131 9 1

132 9 1

133 14 1 1 1

134 16 1

135 16 1

136 10 1

137 10 2

138 9 1


Treat-mentArea

Site Depth(ft)

EWM CLP Cab-bage

Chara Coon-tail

Clasp-ingleaf


139 14 1

140 11 1

141 9 1

5 142 11 2 1

5 143 12 2 1

144 17 1

5 145 16 1

5 146 12 2

5 147 11 1 2

5 148 14 1 1 1

5 149 12 1 1

5 150 11 1 2

5 151 16 1

5 152 11 2

5 153 12 1

5 154 12 1

5 155 11 1 2

5 156 12 1

5 157 14 1

158 9 1

159 10 1

5 160 12 1

5 161 13 2

5 162 11 2 2

5 163 12 1 1

5 164 14 1

5 165 17 1

5 166 12 1 2

167 9 1

5 168 12 2 1

5 169 16 1

5 170 14 1 1

171 11 1

172 22 1

11 173 12 1 2

11 174 11 1 1

11 175 12 1 1

11 176 12 1 1

177 12 2

178 12 1

179 11 2

180 12 1

181 13 1

182 12 1 2

183 12 2

10 184 5 1 1

10 185 5 1 1

10 186 6 2

10 187 6 1 2

188 4 1

189 5 2

190 7 1

191 7 1

192 7 1

6 193 12 1 1

6 194 11 1

6 195 11 2 1

6 196 11 1

6 197 10 1 2

6 198 10 1 1

6 199 10 2

6 200 9 1

6 201 10 1

6 202 10 1 1

6 203 10 1 1

6 204 8 1 1

6 205 8 1 1

6 206 8 1 1

6 207 9 1 1

208 11 1

209 15 1

210 8 1 2

8 211 8 1 2

8 212 7 2 1

8 213 7 1 1

Treat-mentArea

Site Depth(ft)

EWM CLP Cab-bage

Chara Coon-tail

Clasp-ingleaf


8 214 7 1 1

215 7 2

216 10 2

217 12 1 1

9 218 12 1 1

9 219 10 1 1

9 220 12 2 1

9 221 10 2

222 15 1

223 18 1

224 11 1

225 10 2

226 14 1

7 227 12 1

7 228 14 1

7 229 13 1 1

7 230 13 1 2

7 231 11 2

7 232 11 2

7 233 11 1

7 234 12 1

7 235 11 1 2

236 11 2

237 17 1

238 10 1

239 10 1 1

240 12 1 1

241 12 1

242 11 1

243 8 1

244 12 1

245 11 1

246 11 1

247 10 1

248 12 2

249 12 2

250 12 1 1

251 14 1

252 12 1

253 10 2

254 12 2

255 11 1 2

256 10 2

257 9 1

258 10 1

259 14 1

260 17 1

261 7 1 1

262 6 1

1 263 9 1 1

1 264 9 1

1 265 10 1 1

1 266 9 1

1 267 10 1

268 10 1

269 11 1

1 270 9 1

1 271 9 1 1

1 272 9 1 1

1 273 7 1

Average 1.1 1.1 1.0 1.5 1.1 1.0 1.0 1.0 1.3

Occurrence (273) 108 14 1 2 21 1 3 1 179 42


White Bear Lake Eurasian Watermilfoil Assessment, August 23, 2018

Figure 10. Location of the 16 treatment sites around White Bear Lake on August 23, 2018.


Table 5. EWM assessment on August 23, 2018.

Treat-mentArea

Way-Points

Depth(ft)

EWM EWMfrom

surface

Natives No plants

1 1 12

1 2 10

1 3 10

1 4 9 1 7 2

1 5 9 1 8 2

1 6 9 2

1 7 9 2

1 8 9 1

1 9 10 2

1 10 10 1

3 11 10 1 1

3 12 10 2

3 13 10 1

3 14 10 1

3 15 10 1 8 1

3 16 13 1

3 17 12 1 6 1

3 18 12 1 7 1

3 19 10 1 7 1

3 20 11 1 8 1

2 21 14 1

2 22 11 1

2 23 10 1 6 1

2 24 10 1

2 25 10 1

2 26 10 1 7 1

2 27 12 1 8 1

2 28 13 1

4 29 14 1

4 30 13 1

4 31 10 1 5 1

4 32 11 1

4 33 10 1 7 1

4 34 1

4 35 1 1

4 36 1 1

4 37 10 1

4 38 11 2 5 1

4 39 10 1 7 1

4 40 11 1 9 1

4 41 8 1

4 42 12 1

5 43 12 1

5 44 13 1

5 45 12 1

5 46 13 1 11 1

5 47 13 1

5 48 12 1

5 49 11 1

5 50 13 1

5 51 12 1

5 52 13 1

5 53 11 1

5 54 11 2

5 55 13 1

11 56 13 1

11 57 11 1

11 58 11 1

11 59 11 1

11 60 12 1

6 61 13 1

6 62 10 1

6 63 11 1

6 64 10 1 8 1

6 65 10 1

Treat-mentArea

Way-Points

Depth(ft)

EWM EWMfrom

surface

Natives No plants

6 66 10 1

6 67 10 1

6 68 9 1

6 69 9 2

6 70 10 1 8 2

6 71 9 2

6 72 9 2

7 73 9 1

7 74 12 1

7 75 11 1

7 76 13 2

7 77 10 1

7 78 10 1

7 79 11 1

7 80 12 2

8 81 8 2

8 82 8 2

8 83 8 1

8 84 7 1

8 85 8 1

8 86 8 1

8 87 8 1

9 88 10 2

9 89 10 2

9 90 10 2

9 91 10 1

9 92 10 1

10 93 5 1

10 94 5 1

10 95 6 1

10 96 6 1

10 97 6 1

Average 1.0 1.2

Occurrence (97) 21 91 3


Eurasian Watermilfoil Treatment Maps for 2010 - 2018

2010 (174 ac) 2011 (41.6 ac) 2012 (144 ac)

2013 (100 ac) 2014 (32.8 ac) 2015 (85 ac)

2016 (60.4 ac) 2017 (65.1 ac) 2018 (69.9 ac)

Figure 11. Acres of treated EWM for 2010-2018.


Potential Future Growth of Eurasian Watermilfoil in WhiteBear Lake Based on Lake Sediment Characteristics

Eurasian Watermilfoil Growth Potential in White Bear Lake: Eurasian watermilfoil hasbeen in White Bear Lake since 1988. Lake sediment sampling results from 1998, 2009, and 2010have been used to predict lake bottom areas that have the potential to support light, moderate, orheavy Eurasian watermilfoil growth in the future. Based on the key sediment parameters of NH4

and organic matter (McComas, unpublished), a table and map were prepared that predict whattype of milfoil growth could be expected (Table 6 and Figure 12).

The sediment nitrogen conditions in White Bear Lake range from low to moderate concentrationswith high nitrogen levels found at 3 sites. Sediments over 10 ppm of nitrogen are candidates forheavy milfoil growth. It has also been found that Eurasian watermilfoil does not grow well insediments with over 20% organic matter. Site 6, sampled in 2009, and Sites 13 and 14, sampledin 2010 have high organic matter and are not predicted to support heavy milfoil growth eventhough nitrogen is high. Eurasian watermilfoil may grow widely through the littoral area inWhite Bear Lake but it is predicted that it will not sustain extensive perennial nuisance mattingconditions (which are defined as heavy growth conditions) on a long-term basis.

Table 6. White Bear Lake sediment data and ratings for potential heavy EWM growth.

NH4 Conc(ppm)

OrganicMatter (%)

Potential for HeavyEWM Growth

Site Depth<10 <0.6 or >20

Light (green) to Moderate (yellow)

1998 2009/2010

>10 >0.6 or <20 Heavy (red)

1998 Data

1 4 0 0.8 0.6 Light

2 5 1 0.9 0.7 Moderate

3 6 2 0.7 0.4 Light

4 6 2 0.6 0.5 Low

5 5 1 0.9 0.6 Light

6 5 1 0.6 0.7 Moderate

7 7 3 0.6 0.8 Moderate

8 7 3 0.9 0.8 Moderate

9 7 3 0.8 0.5 Low

10 7 3 0.5 0.5 Low

11 7 3 0.6 0.5 Low

12 6 2 4.2 2.7 Moderate

13 6 2 1.2 0.6 Light

14 4 0 1.1 1.5 Moderate

15 2 0 0.8 0.6 Light

16 4 0 1.3 0.7 Light

17 4 0 1.2 1.3 Moderate

18 5 1 4.4 11.6 Moderate

19 5 1 0.7 1.9 Moderate

20 5 1 5.2 10.8 Moderate

21 6 2 0.2 0.5 Low

22 6 2 48.1 8.7 Heavy

23 5 1 2.7 2.1 Moderate

24 7 3 2.3 2.7 Moderate

25 4 0 1.0 0.6 Light

NH4 Conc(ppm)

OrganicMatter (%)

Potential for HeavyEWM Growth

Site Depth<10 <0.6 or >20

Light (green) to Moderate (yellow)

1998 2009/2010

>10 >0.6 or <20 Heavy (red)

2009 Data

1 14 10 3.6 0.8 Moderate

2 14 10 3.2 0.9 Moderate

3 14 10 3.1 1.5 Moderate

4 14 10 2.8 1.9 Moderate

5 14 10 5.7 0.7 Moderate

6 13 9 10.1 30.5 Moderate

7 14 10 3.0 0.9 Moderate

2010 Data

8 14 8.5 3.1 0.9 Moderate

9 14 9.5 3.5 2.0 Moderate

10 14 10 4.3 0.7 Moderate

11 14 11 5.4 0.8 Moderate

12 14 11 8.5 7.1 Moderate

13 13 12 7.2 24.6 Light

14 14 12 10.0 31.9 Light


White Bear Lake Eurasian Watermilfoil Growth PotentialBased on Lake Sediments

Figure 12. Sediment sample locations are shown with squares (1998 data) and circles (2009 and 2010 data). The color indicates the potential for heavy Eurasian watermilfoil to occur at that site. Key: green = low;yellow = medium; red = high potential.


White Bear Lake Water Quality from 2005 - 2016: A summary of seasonal waterquality averages from 4 sample sites from 2005 - 2016 is shown in Table 7. The location of thesample sites is shown in Figure 13. Transparency has ranged from 3 to 4 meters at most of thesites from 2005 - 2016. Chlorophyll has ranged from 3 to 7 ug/l over the same period. Totalphosphorus appears to have increased stating in 2010 but it has not significantly influencedchanges in water clarity or in chlorophyll.

Table 7. Water quality data for 4 sites around White Bear Lake from 2005 through 2016 (June -September averages). (Source: Ramsey County).

Secchi disc (m) Total phosphorus (ug/l) Chlorophyll a (ug/l)

229 230 231 234 AVE 229 230 231 234 AVE 229 230 231 234 AVE

2005 4.78 4.34 4.66 5.14 4.7 11 10 9 14 11 3.7 2.4 2.7 3.6 3.1

2006 4 4.1 3.8 3.9 4 17 12 12 19 15 7.2 5.1 5.9 6.5 6.2

2007 3.34 3.04 2.97 3.71 3.3 14 11 12 14 13 6.4 5.5 6.5 7 6.4

2008 3.67 3.49 3.67 3.84 3.7 13 13 15 18 15 5.3 3.2 4.9 5.8 4.8

2009 3.95 3.03 3.63 4.2 3.7 14 12 13 17 14 3.5 2.5 3.7 3.3 3.3

2010 3.94 2.8 3.55 4.15 3.6 21 22 21 22 22 5 3.3 4.8 4.6 4.4

2011 3.05 2.91 3 3.41 3.1 21 22 18 22 21 6 4.3 5.5 5.6 5.4

2012 3.39 2.84 2.53 3.01 2.9 22 21 23 21 22 5.7 3.7 6.5 5.9 5.5

2013 3.89 3.28 3.66 3.93 3.7 15 19 17 19 18 4.8 3.5 6.4 5.1 5

2014 3.18 3.03 3.3 3.34 3.2 21 19 16 21 19 4.6 3.6 4 4.8 4.3

2015 3.4 2.5 3.1 3.0 3.0 19 19 18 17 18 5.7 4.3 5.1 6.2 5.3

2016 3.93 3.69 3.85 3.91 3.8 13 12 13 15 13 3.3 2.3 3.3 3.4 3.1

Figure 13. Water quality sampling sites.


eurasian watermilfoil management program and water quality

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