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Bone Lake, Washington County, Minnesota, May 20, 2014

Curlyleaf Pondweed and Eurasian WatermilfoilDelineation, Treatment, and Assessment for

Bone Lake, Washington County, Minnesota in 2015

Delineation Treatment Assessment

CLP April 18May 5 (1.65 ac, 5 gallons)

May 28 (0.8 ac, 1.9 gallons)June 4 and 9

EWM June 4 and June 29 July 17 (3.44 ac, 44 gallons) October 7

Prepared for:Comfort Lake/Forest LakeWatershed DistrictForest Lake, Minnesota

Prepared by:Steve McComas

Jo StuckertBlue Water Science

March 4, 2016

Curlyleaf Pondweed and Eurasian WatermilfoilDelineation, Treatment, and Assessment for


Summary

Curlyleaf Pondweed Delineation, Treatment, and Assessment: Bone Lake (MnDNR ID#82-0054) is a 221 acre lake located in Washington County, Minnesota. An initial curlyleafpondweed delineation was conducted on April 18, 2015 by Blue Water Science to characterizeareas that could be treated. Results of the curlyleaf delineation on April 18, 2015 foundcurlyleaf pondweed present at six sample sites and a 1.65 acre delineated site was treated onMay 5, 2015. Two additional areas totaling 0.8 acres were delineated by Lake Managementand were treated on May 28, 2015.

A curlyleaf assessment conducted on June 4, 2015, found curlyleaf pondweed at 32 sites atlight to heavy densities (Figure S1). A second curlyleaf assessment conducted on June 29,2015 found curlyleaf at 33 sites with several areas of heavy growth (Figure S1). It appearscurlyleaf had sprouted and grew in a number of areas throughout June. This type of growth forcurlyleaf pondweed in June is fairly uncommon.

Figure S1. [left] Curlyleaf pondweed was found at 32 sample sites in Bone Lake on June 4, 2015.[right] Curlyleaf pondweed was found at 33 sample sites on June 29, 2015.Key: green = light growth, yellow = moderate growth, and red = heavy growth.

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Eurasian watermilfoil Delineation, Treatment, and Assessment: Eurasian watermilfoil(EWM) was verified in Bone Lake in 2006. An EWM delineation on June 4, 2015, found EWMat 31 sites, mostly on the north and south ends of the lake with light to moderate growth out to 4feet of water depth (Figure S2). There was very little heavy growth of EWM and no areas weredelineated. However, on a second EWM delineation on June 29, 2015, EWM was found at 35sites and moderate to heavy growth was observed in 9 areas totaling 3.44 acres. On July 17,2015, a total of 3.44 acres of EWM was treated. A follow-up assessment was conducted onOctober 7, 2015 and no heavy EWM growth was observed, although the peak biomass wouldlikely have declined by this date.

Figure S2. [left] EWM coverage for Bone Lake on June 4, 2015.[right] EWM coverage for Bone Lake on June 29, 2015. Key: green = light growth, yellow = moderate growth, and red = heavy growth.

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Curlyleaf Pondweed and Eurasian Watermilfoil Delineation, Treatment, and Assessment for


Bone Lake, Washington County (ID: 82-0054)Size: 221 acres (MnDNR)Littoral area: 124 acres (MnDNR)Maximum depth: 30 ft (MnDNR)

Introduction

Curlyleaf pondweed (CLP) and Eurasian watermilfoil (EWM) are non-native species and bothare present in Bone Lake. CLP and EWM delineations were conducted on 221 acre Bone Lake,Washington County in 2015. After herbicide treatments, curlyleaf pondweed and Eurasianwatermilfoil assessments were conducted to check the distribution and abundance of curlyleafpondweed and Eurasian watermilfoil.

Methods

The aquatic plant delineations and assessments of Bone Lake were conducted by Blue WaterScience on April 18, June 4, June 29, and October 7, 2015. For the delineation on April 18,2015, 66 sites were sampled around Bone Lake and for the assessment on June 4, 58 sites weresampled. The June 29 survey had 52 sample sites and the October 7 assessment was qualitative. Sample sites were randomly selected in the littoral zone around Bone Lake. At each samplepoint, a sampling rake was lowered into the water and a plant sample was taken. The plantspecies were recorded and the density of each species was assigned. Densities were based on thecoverage on the teeth of the rake. Density ratings were from 1 to 5 with 1 being sparse and 5being a nuisance. Based on these sample sites, plant distribution maps were constructed.

Figure 1. Water lilies were found in BoneLake in 2015. Here white water lilies andcurlyleaf pondweed are found together onJune 2, 2015.

Bone Lake Aquatic Plant Survey, 2015 1

Results of the Curlyleaf Pondweed Delineation on April 18, 2015

Results of the delineation conducted on April 18, 2015 found curlyleaf pondweed present at sixsample sites and Eurasian watermilfoil was present at eight sites (Table 1 and Figure 2). A totalof 66 sites were sampled. An area of 1.65 acres was delineated for curlyleaf pondweed treatment (Figure 2).

Table 1. Occurrence of plants by depth in Bone Lake out to a depth of 9 feet on April 18, 2015.

Depth(feet)

Number of Sites Sampled

Curlyleafpondweed

Eurasianwatermilfoil

1

2 1

3 5 1

4 6 1 1

5 8 3

6 14 1 2

7 11 1 1

8 7 2

9 10 1

10-12 4

Sites Sampled to 9 feet

66 6 8

Figure 2. Curlyleaf pondweedcoverage for Bone Lake on April18, 2015. Key: green dots = light growth,red dots = heavy growth, andblack dots = no growth.


Treatment of the Curlyleaf Pondweed on May 5 and 28, 2015

Two curlyleaf pondweed treatments occurred in 2015. On May 5, 2015 a 1.65 acre area wastreated and on May 28, based on a delineation from Lake Management, Inc, 0.8 acres weretreated (Figure 3). An endothall herbicide was used in both treatments.

Figure 3. Curlyleaf pondweed treatment areas for Bone Lake on May 5, 2015 (1.65 acres) and on May 28,2015 (0.8 acres).


Results of the Curlyleaf Pondweed 1st Assessment on June 4, 2015

After the May 5 curlyleaf treatment of 1.65 acres, curlyleaf conditions were assessed. Results ofthe assessment conducted on June 4, 2015 found that curlyleaf had sprouted at a number of newareas and was present at 32 sample sites. Curlyleaf in the original 1.65 acre site treated on May5, either resprouted or was not controlled by the treatment (Figure 2).

New areas that were delineated by Lake Management, were treated on May 28 were not impactedat the time of the June 4 assessment.

Table 2. Bone Lake occurrence of plants by depth in Bone Lake out to a depth of 7 feet on June 4,2015. A total of 58 sites were sampled.

Depth(feet)


White lilies Curlyleafpondweed


1

2 1 1

3 3 1 3

4 47 3 29 28

5 4 1

6 2

7 1


58 3 32 31

Figure 4. Curlyleaf pondweed wasfound at six sample sites in Bone Lake onJune 4, 2015.Key: green = light growth, yellow = moderate growth, red = heavy growth, and black = no curlyleaf growth.


Results of the Curlyleaf Pondweed 2nd Assessment, June 29, 2015

A curlyleaf pondweed assessment conducted on June 29, 2015 after herbicide treatments on May5 and May 28. Curlyleaf was present at 33 sample sites and several sites had heavy growth(Figure 5 and Table 3). It appears that 2015 was somewhat of an unusual year. Curlyleafpondweed seemed to sprout in June and was still alive on June 29, 2015. The north side andsoutheast side of the lake supported moderate to heavy patches of curlyleaf pondweed.

Table 7. Occurrence of plants by depth in Bone Lake out to a depth of 8 feet on June 29, 2015.

Depth(feet)


White lilies Curlyleafpondweed


Stringypondweed

1

2 1 1 1

3 12 1 10 9

4 23 1 16 15 2

5 13 2 6 10

6 2

7

8 1


52 4 33 35 2

Figure 5. Curlyleaf pondweedcoverage for Bone Lake on June 29,2015. Key: green = light growth, yellow = moderate growth, red = heavy growth, and black = no curlyleaf growth.


Results of the Eurasian Watermilfoil Delineation on April 18, June 4, and June 29, 2015

Eurasian watermilfoil (EWM) was delineated at the same time that curlyleaf pondweed wasdelineated. On April 18, EWM was found at 8 sites (Figure 6) and was not ready for treatment. The next EWM delineation occurred on June 4 and EWM was found at 31 sites (Table 2) at lightto moderate densities (Figure 6). No treatment areas were delineated. However, on June 29,2015, a second EWM delineation occurred and EWM was found at 35 sites. A total of 9 areaswith a combined area of 3.44 acres was treated on July 17, 2015 (Figure 6). EWM was assessedon October 7, 2015, but the peak biomass had died back naturally. No heavy growth of EWMwas observed.

Figure 6. [top-left] Eurasian watermilfoil coverage on April18, 2015.[top-right] Eurasian watermilfoil coverage on June 4, 2015.[bottom-left] Eurasian watermilfoil coverage on June 29, 2015Key: green = light growth, yellow = moderate growth, red = heavy growth, and black = no EWM growth.


6 acres treated

Curlyleaf Pondweed and Eurasian Watermilfoil in 2014 and 2015

Both curlyleaf pondweed and Eurasian watermilfoil growth was heavier in 2015 compared to2014 (Figure 7). Natural variation in distribution and abundance is common with aquatic plantsincluding curlyleaf and EWM.

Figure 7. Curlyleaf pondweed and Eurasian watermilfoil maps for 2014 and 2015.


APPENDIX - Individual Site Data for Plant Surveys

Individual Sample Point Plant DataLow plant diversity was found in Bone Lake with curlyleaf pondweed and EWM the only aquaticplant species observed on the April 18, 2015 delineation.

Aquatic plant occurrence and density for individual sample points in Bone Lake, April 18, 2015.

Site Depth(ft)

Curlyleafpondweed


1 4

2 5

3 6

4 7

5 6

6 3

7 5

8 4

9 5

10 8

11 7

12 2

13 5

14 8 1

15 4 1

16 8

17 10

18 9 1

19 7

20 7

21 9

22 11

23 7 1

24 6 1

25 6 1

26 8 1

27 3

28 5

29 5 5

30 5 4

31 6

32 6

33 7

34 6

35 6

Site Depth(ft)

Curlyleafpondweed


36 5 5

37 7 5

38 6 5

39 6

40 8

41 9

42 9

43 7

44 10

45 6

46 12

47 9

48 9

49 9

50 9

51 9

52 8

53 3

54 6

55 8

56 7

57 7

58 9

59 7

60 6

61 6

62 3

63 4 1

64 3

65 4

66 4

Average 4.2

occurrence (66 sites) 6 8

% occurrence 9 12


Individual Sample Point Plant DataCurlyleaf pondweed and Eurasian watermilfoil were common on the June 4, 2015 survey.

Aquatic plant occurrence and density for individual sample points for June 4, 2015.

Site Depth (ft) CLP EWM White lilies No plants

60 3 161 4 2 262 6 163 5 164 4 165 5 166 4 2 167 4 168 4 2 169 3 270 3 1 271 2 172 4 1 373 4 3 374 4 475 4 176 4 4 477 4 478 4 479 4 3 280 4 281 4 182 4 383 4 3 384 4 3 385 4 486 4 1 287 6 188 4 489 4 3 290 4 1 391 4 1 192 4 1 193 4 3 294 4 5 395 4 5 396 4 5 297 5 598 4 599 4 5100 4 5 1101 7 1102 5 1103 4 2104 4 1 1105 4 1106 4 1107 4 1108 4 1109 4 1110 4 2111 4 1 2112 4 2 3113 4 1114 4 1115 4 2116 4 1117 4 3

Average 2.9 2.0 3.0

occurrence (58 sites) 32 31 3 15

% occurrence 0.55 0.53 0.05


Individual Sample Point Plant DataCurlyleaf pondweed and Eurasian watermilfoil were common plants observed on the June 29,2015 survey.

Aquatic plant occurrence and density for individual sample points for June 29, 2015.

Site Depth(ft)

CLP Bed - Patch

EWM Bed - Patch

Treat or Not

White lilies

Stringy No plants

47 2 3 4 B N48 4 N49 4 3 3 ?50 4 3 3 ?51 3 4 3 N52 4 4 3 N53 5 4 254 4 3 355 5 156 3 4 3 T57 4 4 P ?58 4 4 T59 660 4 4 3 T61 6 162 5 163 3 4 364 5 4 P N65 5 4 P66 5 3 P N67 5 3 P N68 3 3 N69 3 4 P70 4 171 3 3 3 N72 3 4 4 T73 4 3 T74 4 3 3 N75 4 4 2 N 476 3 4 3 N 477 4 4 2 ?78 4 3 2 N79 5 3 2 N80 5 1 3 N81 5 1 3 T 482 5 3 3 T 483 4 3 N 584 4 2 N 485 5 3 3 N86 8 N 187 3 3 P N88 4 189 3 3 N90 3 291 3 3 192 593 4 294 4 295 4 2 B96 4 2 B97 4 3 3 N98 4 3 B 1

Average 3.0 2.9 4.0 4.5

occurrence (20 sites) 33 35 4 2 6

% occurrence 1.65 1.75 0.20 0.10


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