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Poskin Lake Aquatic Plant Management Plan

Poskin Lake Three-Phase Aquatic Plant and

Lake Management Study

Barron County, Wisconsin

DNR Project No. LPL-___-__ SEH No. POSKI 106161

November 2010

November 19, 2010 RE: Poskin Lake Three-Phase Aquatic Plant and Lake Management Study Poskin Lake Aquatic Plant Management Plan Barron County, Wisconsin DNR Project No. LPL-___-__ SEH No. POSKI 106161

Mr. Larry Kahl Poskin Lake Association 856 15th Avenue Almena, WI 54805 Dear Larry: Sincerely, Dave Blumer Lake Scientist DLB/ls p:\pt\p\poski\106161\reports&specs\rep\apm plan.docx


Poskin Lake Three-Phase Aquatic Plant and Lake Management Study Barron County, Wisconsin

Prepared for: Poskin Lake Association

Poskin, Wisconsin

Prepared by: Short Elliott Hendrickson Inc.

1701 West Knapp Street, Suite B Rice Lake, WI 54868-1350

715.236.4000

Jake Macholl Lake Scientist

Date

Dave Blumer Lake Scientist

Date

Distribution List

No. of Copies Sent to

2 Larry Kahl Poskin Lake Association 856 15th Avenue Almena, WI 54805 2 Pamela Toshner Wisconsin Department of Natural Resources 810 W. Maple Street Spooner, WI 54801

Poskin Lake Aquatic Plant Management Plan POSKI 106161 Poskin Lake Association

Executive Summary

Poskin Lake (WBIC 2098000) is a 150-acre stratified, drainage lake located in west-central Barron County. It is eutrophic in nature with summer Secchi readings averaging 3.3ft and a littoral zone that extends to 10.5ft. The Poskin Lake Association (PLA) is concerned about poor water quality in the lake and wondered what impact aquatic plant growth might be having on it. Curly-leaf pondweed (Potamogeton crispus) (CLP), a non-native aquatic invasive species, is known to be in Poskin Lake. The PLA wanted to know the extent of the population and decide what, if any, management would be appropriate to control CLP. They also wanted to know if Eurasian water milfoil (EWM) was present in the lake as it is in other nearby Barron County lakes including Echo, Horseshoe, Shallow, Beaver Dam, Duck, and Lower Vermillion. Lower Vermillion Lake is upstream of Poskin Lake on the Vermillion River providing a source for natural introduction in addition to the possibility of human introduction via the two boat launching facilities on the lake. If it is not in the lake, the PLA wants to know what to do to prevent it from getting there.

Before any aquatic plant management can be done, the Wisconsin Department of Natural Resources (WDNR) requires an assessment of the lake’s aquatic plant community, water quality and clarity, physical characteristics (including the overall watershed), and all possible management alternatives that may be used in Poskin Lake. The WDNR also requires that public input be sought in determining the best management recommendations for the lake. The PLA applied for and was awarded a three-phase lake management planning grant to fund the necessary pieces of an aquatic plant and general lake management plan. Endangered Resource Services, LLC (ERS) completed the aquatic plant survey work and wrote the initial survey reports. SEH developed a Lake Property Owners Survey and the PLA distributed this to all property owners on the lake. Using results from the aquatic plant survey, property owners survey, and WDNR aquatic plant management strategies, the following Aquatic Plant Management (APM) Plan was developed.

There are seven broad goals followed by the specific objectives and actions necessary to meet those goals over the course of the next five years. This five-year document is intended to be a fluent document able to be revised based on the results attained each year. Minor changes and adaptations are expected and will be made annually, but any major change in activities or management philosophy will be presented to the PLA membership and the WDNR for approval. The six goals for this project are as follows:

AIS education and prevention planning AIS control and management Water quality monitoring Promotion of shoreland best management practices Native species preservation, enhancement, and protection Project assessment and evaluation

The goals and the objectives associated with them in this APM Plan will be completed by the PLA, their consultants, and through partnerships formed with the WDNR, Barron County Soil and Water Conservation Department, local Township authorities, and local clubs and organizations.

Funding for the activities in this APM Plan will be generated through PLA finances, contributions from partners, and through volunteer and donated services.

SEH is a registered trademark of Short Elliott Hendrickson Inc. Poskin Lake Aquatic Plant Management Plan POSKI 106161 Poskin Lake Association Page i

Table of Contents

Letter of Transmittal Certification Page Distribution List Executive Summary Table of Contents

Page

1.0 Introduction ............................................................................................................. 1

2.0 Aquatic Plant Survey .............................................................................................. 2

3.0 Wild Rice .................................................................................................................. 7

4.0 Non-native Aquatic Invasive Species .................................................................... 9

4.1 Curly-leaf Pondweed ...................................................................................... 10

4.2 Purple Loosestrife and Eurasian Watermilfoil ................................................. 13

5.0 Public Participation ............................................................................................... 13

6.0 Past Management Activities ................................................................................. 13

7.0 Aquatic Plant Management Discussion ............................................................... 13

7.1 Agricultural Runoff .......................................................................................... 14

7.2 Curly-leaf Pondweed ...................................................................................... 14

7.3 Re-establishing Native Plant Communities by Planting and Restoration ......... 14

8.0 Management Alternatives ..................................................................................... 15

8.1 WDNR Northern Region Aquatic Plant Management Strategy ........................ 17

8.2 Hand Pulling/Manual Control .......................................................................... 17

8.3 Chemical Control and Management................................................................ 17

8.3.1 Large-scale Herbicide Application ....................................................... 19

8.3.2 Small-scale Herbicide Application ....................................................... 20

8.3.2.1 USEPA Approved Aquatic Herbicides in Wisconsin ............ 20

8.3.2.1.1. Endothall............................................................ 20

8.3.2.1.2. Glyphosate ........................................................ 20

8.3.2.1.3. 2,4-D .................................................................. 20

8.3.2.1.4. Triclopyr ............................................................. 21

8.3.2.1.5. Diquat ................................................................ 21

8.3.2.1.6. Fluridone............................................................ 21

8.4 Mechanical Control and Management ............................................................ 21

8.4.1 Large-scale Mechanical Harvesting .................................................... 21

8.4.2 Alternative Mechanical Management .................................................. 22

8.4.3 Suction Harvesting and Suction Dredging ........................................... 23

8.5 Aquatic Plant Habitat Disruption ..................................................................... 23

8.5.1 Dredging ............................................................................................. 24

8.5.2 Water-level Manipulation ..................................................................... 24

8.5.3 Benthic Barriers and Light Reduction .................................................. 24

8.6 Biological Control and Management ............................................................... 25

Table of Contents (Continued)

POSKI 106161 Poskin Lake Aquatic Plant Management Plan Page ii Poskin Lake Association

8.6.1 Native Plant Restoration and/or Enhancement .................................... 25

8.6.2 Insects, Animals, or Pathogens ........................................................... 25

8.6.2.1 Biological Controls Approved for Use in Wisconsin ............. 25

8.6.3 Barley Straw ....................................................................................... 26

8.6.4 Other Algicides.................................................................................... 27

9.0 Documentation of Plant Problems/Need for Management ................................. 27

10.0 Aquatic Plant Management Goals, Objectives, and Actions .............................. 28

11.0 Five-year Time Line of Activities .......................................................................... 28

12.0 References............................................................................................................. 29

List of Tables

Table 1 Aquatic Macrophyte P/I Survey Summary Statistics Poskin Lake . Error! Bookmark not defined.

Table 2 Floristic Quality Index of Aquatic Macrophytes Poskin Lake ... Error! Bookmark not defined.

List of Figures

Figure 1 – Point-intercept survey points for Poskin Lake (WDNR) ....................................... 2

Figure 2 – Littoral or plant growing zone on Poskin Lake (Berg 2009) ................................. 3

Figure 3 – Native Species Richness and Total Rake Fullness Rating .................................. 5

Figure 4 – Suggested sensitive areas for aquatic plant growth ............................................ 7

Figure 5 – Wild Rice locations during the 2009 warm water point-intercept survey .............. 8

Figure 6 – 2010 Wild Rice Beds on Little Poskin ................................................................. 9

Figure 7 – CLP in May and July 2009 (ERS) ..................................................................... 10

Figure 8 – 2009 CLP Locations (Beaver Creek Reserve) .................................................. 11

Figure 9 – May 2009 CLP Bed Map (ERS) ........................................................................ 12

Figure 10 – 2010 Additional CLP Bed (SEH) ..................................................................... 12

List of Appendices

Appendix A Title

Appendix B Photographs

Appendix C Title

November 2010

POSKI 106161 Page 1


Poskin Lake Three-Phase Aquatic Plant and Lake Management Study

Prepared for Poskin Lake Association

1.0 Introduction

Poskin Lake (WBIC 2098000) is a 150-acre stratified, drainage lake located in west-central Barron County. It is eutrophic in nature with summer Secchi readings averaging 3.3ft and a littoral zone that extends to 10.5ft. The Poskin Lake Association (PLA) is concerned about poor water quality in the lake and wonder what impact water quality is having on aquatic plant growth. Curly-leaf pondweed (Potamogeton crispus) (CLP), a non-native aquatic invasive species, is known to be in Poskin Lake. The PLA wanted to know the extent of the population and decide what, if any, management would be appropriate to control CLP. They also wanted to know if Eurasian water milfoil (EWM) was present in the lake as it is in other nearby Barron County lakes including Echo, Horseshoe, Shallow, Beaver Dam, Duck, and Lower Vermillion. Lower Vermillion Lake is upstream of Poskin Lake on the Vermillion River providing a source for natural introduction in addition to the possibility of human introduction via the two boat launching facilities on the lake. If it is not in the lake, the PLA wants to know what to do to prevent it from getting there.

Before any aquatic plant management can be done, the Wisconsin Department of Natural Resources (WDNR) requires an assessment of the lake’s aquatic plant community, water quality and clarity, physical characteristics (including the overall watershed), and all possible management alternatives that may be used in Poskin Lake. The WDNR also requires that public input be sought in determining the best management recommendations for the lake. The PLA applied for and was awarded a three-phase lake management planning grant to fund the necessary pieces of an aquatic plant and general lake management plan. Endangered Resource Services, LLC (ERS) completed the aquatic plant survey work and wrote the initial survey reports. SEH developed a Lake Property Owners Survey and the PLA distributed this to all property owners on the lake. Using results from the aquatic plant survey, property owners survey, and WDNR aquatic plant management strategies, SEH developed the plant management recommendations in this Aquatic Plant Management (APM) Plan.

It is the intention of the PLA to begin implementation of the recommendations in this APM Plan beginning with the 2011 open water season.

The APM Plan for Poskin Lake is intended to be a companion document to the more comprehensive Whole-lake Management Plan, also completed by SEH.

POSKI 106161 Poskin Lake Aquatic Plant Management Plan Page 2 Poskin Lake Association

2.0 Aquatic Plant Survey

The PLA, SEH, and the WDNR authorized a series of full lake plant surveys as part of developing an APM Plan. On May 27, 2009 ERS completed a full lake CLP density and bed mapping survey, and on July 13, ERS conducted a warm water point/intercept survey of all aquatic macrophytes. The surveys used the WDNR’s statewide guidelines for conducting systematic point intercept macrophyte sampling. These guidelines ensure that all sampling in the state will be conducted in the same manner, thus allowing data to be compared across time and space. The immediate goals of the plant surveys were to quantify the level of a known CLP infestation, determine if Eurasian water milfoil (Myriophyllum spicatum) had invaded the lake, and to establish baseline data on the diversity, abundance and distribution of other native aquatic plant populations in the lake. These data provide a baseline for long-term monitoring of the lake’s macrophyte community. A full report of the 2009 aquatic plant survey results (Berg, 2009) can be found on the accompanying CD

Using a standard formula that takes into account the shoreline shape and distance, water clarity, depth and total lake acreage a 403 point sampling grid was generated by the WDNR for Poskin Lake (Figure 1).

Figure 1 – Point-Intercept Survey Points for Poskin Lake (WDNR)

Poskin Lake Aquatic Plant Management Plan POSKI 106161 Poskin Lake Association Page 3

An on-lake assessment prior to the actual point-survey work determined the maximum depth of aquatic plant growth to be 10.5-ft. In the early-season cool water CLP survey and bed mapping 112 of the 403 points were considered to be in the littoral (plant growing) zone of the lake (Figure 2).

Figure 2 – Littoral or Plant Growing Zone on Poskin Lake (Berg 2009)

During the warm water mid-season full point-intercept survey, only 92 of these points had vegetation. During the mid-season survey, approximately 23% of the entire lake bottom (82% of the littoral zone) had growing plants. The average depth for aquatic plant growth was only 3-4 ft. Substrate in the littoral zone was mostly much with some sand and rock. Summary statistics based on the 2009 mid-season point-intercept survey are included in Table 1.


Table 1 Aquatic Macrophyte P/I Survey Summary Statistics Poskin Lake, Barron County

July 13, 2009

Total number of points sampled 403 Total number of sites with vegetation 92 Total number of sites shallower than the maximum depth of plants 112 Frequency of occurrence at sites shallower than maximum depth of plants 82.14 Simpson Diversity Index 0.89 Maximum depth of plants (ft) 10.50 Number of sites sampled using rope rake (R) 2 Number of sites sampled using pole rake (P) 160 Average number of all species per site (shallower than max depth) 3.20 Average number of all species per site (veg. sites only) 3.89 Average number of native species per site (shallower than max depth) 3.11 Average number of native species per site (veg. sites only) 3.78 Species Richness 27 Species Richness (including visuals) 33 Species Richness (including visuals and boat survey) 36 Mean depth of plants (ft) 4.06 Median depth of plants (ft) 3.00

Overall diversity was relatively high with a Simpson Diversity Index value of 0.89. Species richness was also relatively high for such a small lake with 36 total species found growing in and immediately adjacent to the water. Although the littoral zone went to 10.5ft., coontail (Ceratophyllum demersum), was the only species that regularly occurred in water deeper than 5ft. In general, species richness, diversity and total rake biomass declined rapidly with increasing depth (Figure 3).


Figure 3 – Native Species Richness and Total Rake Fullness Rating

The most abundant aquatic plant species in the lake in July was coontail with a frequency of occurrence in all sites with vegetation of nearly 83%. The frequency of occurrence drops off substantially after that with white water lily and flat-stem pondweed found in 24 and 22% of all sites with vegetation; common waterweed, spatterdock, and CLP each found in about 16% of all sites with vegetation, and wild celery and northern water milfoil found in just shy of 10% of all sites with vegetation. Several free floating plant species, common watermeal, small duckweed, and large duckweed each occurred in approximately 43% of all sites with vegetation. All other species identified in the lake occurred in less than 4% of all sites with vegetation sampled (Berg 2009).

A total of 25 native plants were identified to species during the point intercept survey. They produced a mean Coefficient of Conservatism of 5.7 and a Floristic Quality Index (FQI) of 28.4 (Table 2). Nichols (1999) reported an Average mean C for the Northern Central Hardwood Forests Region of 5.6 putting Poskin Lake almost exactly average for this part of the state. The FQI of 28.4 was slightly above the mean FQI of 20.9 for the Northern Central Hardwood Forests Region (Nichols 1999). To be included in the calculation of the FQI, a plant species had to have been included in at least one of the rake samples. Plants identified during the visual or boat survey, were not included. If these plants were added, the FQI would increase.


Table 2 Floristic Quality Index of Aquatic Macrophytes Poskin Lake, Barron County July 13, 2009

Species Common Name C Calla palustris Wild arum 9 Callitriche palustris Common water starwort 8 Carex comosa Bottle brush sedge 5 Ceratophyllum demersum Coontail 3 Elodea canadensis Common waterweed 3 Heteranthera dubia Water star-grass 6 Isoetes echinospora Spiny-spored quillwort 8 Lemna minor Small duckweed 5 Myriophyllum sibiricum Northern water milfoil 7 Najas flexilis Bushy pondweed 6 Nuphar variegata Spatterdock 6 Nymphaea odorata White water lily 6 Potamogeton nodosus Long-leaf pondweed 7 Potamogeton pusillus Small pondweed 7 Potamogeton strictifolius Stiff pondweed 8 Potamogeton zosteriformis Flat-stem pondweed 6 Ranunculus aquatilis Stiff water crowfoot 7 Schoenoplectus tabernaemontani Softstem bulrush 4 Sparganium eurycarpum Common bur-reed 5 Spirodela polyrhiza Large duckweed 5 Typha angustifolia Narrow-leaved cattail 1 Typha latifolia Broad-leaved cattail 1 Vallisneria americana Wild celery 6 Wolffia columbiana Common watermeal 5 Zizania palustris Northern wild rice 8 N 25 mean C 5.7 FQI 28.4

It does not appear that a Sensitive Areas or Critical Habitat designation has ever been completed on Poskin Lake. Poskin Lake has a limited plant community that appears to be affected by both water clarity and quality so protecting this plant community is essential. Most sensitive species in Poskin Lake are rare and local which makes them vulnerable to lake wide extinction. With that in mind, there are a couple of areas that stand out in terms of the diversity of aquatic plants found in them. Little Poskin Lake, also known as the north basin, more than any other place on the lake, provides suitable habitat for many of these rare species including wild rice, sessile-fruited arrowhead, white-stem pondweed, spiny quillwort, common water starwort, and large-leaf pondweed. This entire basin should be considered sensitive area for aquatic plants. A second sensitive area should be established along the southwest shoreline of the main lake from the last developed western lot along the south shore to the inlet of the western-most intermittent stream (Figure 4). Both of these areas contain as many as seven or more different species per rake sample.


Figure 4 – Suggested Sensitive Areas for Aquatic Plant Growth

3.0 Wild Rice

Wild rice was identified in the north basin of Poskin Lake, also known as Little Poskin Lake in the 2009 point-intercept survey (Figure 5). In 2009, the wild rice that was present was mostly clipped by geese and not expected to produce much seed (Berg 2009). An impromptu survey of the north basin (Little Poskin Lake) was completed in the late summer of 2010 by SEH to again look for wild rice. In 2010, wild rice had expanded to nearly 4.5 acres, ringing the entire basin with several meters of plant material, and had established several areas that could be classified as dense growth (Figure 6). This definite expansion of wild rice in Little

The Red Ovals indicate areas

of Poskin Lake that should be

considered sensitive areas for

aquatic plant growth.


Poskin was surprising since wild rice in northern Wisconsin generally had a bad year in 2010. Wild rice is a highly protected emergent plant species in WI because of it cultural significance to Native Americans, and because it is a tremendous natural resource providing food and habitat for many wildlife species common to WI.

Figure 5 – Wild Rice Locations During the 2009 Warm Water Point-Intercept Survey


Figure 6 – 2010 Wild Rice Beds on Little Poskin

Wild rice is a highly nutritional food source but only gets that way because of the tremendous amount of nutrients it pulls from the sediment in a single year. Wild rice is an annual grass species, which means it grows from seed to seed bearing mature plant in a single season. In addition to pulling a lot of available nutrients from the sediment, the wild rice stalks provide a place for filamentous algae and other small macrophytes to attach and grow. These small macrophytes pull phosphorous in its dissolved state directly from the water and can help to improve water quality conditions.

One of the recommendations for improving water quality in Poskin Lake included in the Comprehensive Lake Management Plan, an accompanying document, is to remove barriers that restrict flow built onto the existing Poskin Lake dam at the outlet of the Vermillion River. Once these barriers are removed, it is very possible that large water level fluctuations in the lake will be minimized. If this occurs, it may actually promote more wild rice growth in the lake. According to a Natural Resource Conservation Service conservation sheet about wild rice (Wild Rice Establishment 644b, April 2001), fluctuations of water level less than six inches throughout the growing season when wild rice is in the floating-leaf stage, are needed for successful growth.

4.0 Non-native Aquatic Invasive Species

At the time of the July 2009 survey, no evidence of EWM was found in Poskin Lake despite its presence in other lakes further upstream in the Vermillion River Watershed. Reed canary grass is widely distributed in undeveloped shoreline areas of the lake, but this ubiquitous plant does provide some habitat for wildlife and there is no easy or cheap way to eliminate it. Curly-leaf pondweed was widespread but not abundant in May and had largely senesced by


the time of the July survey. Although no purple loosestrife (Lythrum salicaria) was found, it is common in the area and should be monitored for. Undeveloped, muck bottom areas like along the southwest bay and east of the channel would provide especially suitable habitat for this invasive wetland plant

4.1 Curly-leaf Pondweed

In 2009, CLP was widespread in Poskin Lake, but not abundant (Figure 7). It was the opinion of ERS that CLP has overtaken all suitable habitat in the lake but does not appear to play a big part in the lake’s overall plant community. Another aquatic plant survey was completed in 2009 by the Beaver Creek Reserve (Appendix A) as a part of a four county, multiple-year project to identify aquatic invasive species in area lakes. This survey was completed using transects placed at 1,500 ft intervals around the perimeter of the lake, instead of point-intercept points, but also shows that CLP is widespread in the lake. CLP was found in 7 of 15 transects used for sampling aquatic plants (Figure 8).

Figure 7 – CLP in May and July 2009 (ERS)


Figure 8 – 2009 CLP Locations (Beaver Creek Reserve)

In the 2009 CLP bed mapping work completed by ERS, only one area of CLP was considered dense enough to be considered a bed (Figure 9). Determining a bed is based on two criteria: CLP plants must make up greater than 50% of all aquatic plants in the bed, and the CLP has to be canopied at the surface or be close enough to the surface to interfere with normal boat traffic (Berg 2009). This canopied bed of CLP and coontail was 0.71 acres in size and had a perimeter of 372m. Impromptu CLP survey work completed in 2010 by SEH identified another bed of CLP in a shallow area off the southeast corner of the lake (Figure 10). This area does fit the definition of a bed and covers approximately 1-1/3 acres.


Figure 9 – May 2009 CLP Bed Map (ERS)

Figure 10 – 2010 Additional CLP Bed (SEH)


CLP may not be causing any significant problems in Poskin Lake. Because the lake lacks abundant plant growth to begin with, it is likely that CLP provides important early season cover for both baitfish and gamefish. Although widely distributed throughout the lake in 1-2m of water over muck and sandy/muck substrate, it was still fairly uncommon during the 2009 ERS survey. CLP was only identified in 11 rake samples with an additional two points having visual CLP (Figure 7). Only nine points had a rake fullness rating of a two or a three equating to just over 2% of the lake having a sizable population.

4.2 Purple Loosestrife and Eurasian Watermilfoil

Neither of these aquatic invasive species was identified in Poskin Lake, however there is ample habitat that could support both. Active monitoring including watercraft inspection and in-lake monitoring by lake residents needs to be a part of the APM Plan.

5.0 Public Participation

The Poskin Lake Association understands that keeping the lake residents informed and involved in the process whereby plant and lake management recommendations are made is important. To that end, a twelve page Lake Property Owners Survey was developed and distributed by hand to more than 60 land owners on and around Poskin Lake. The survey was made available at the Clinton Town Hall in Poskin, at the Poskin Lake Resort, and on a public website www.sehinc.com/online/poskin. Public notification of the survey was given in the local paper and at the Poskin Lake Association Annual Picnic in early August 2009. The survey was distributed in August and September with an original return date of the end of September, extended to the end of October 2009. Thirty-one completed surveys were returned to Poskin Lake Association board members or this consultant. The final survey distributed to lake residents is included in Appendix B; and a complete Survey Response Summary Report is included in Appendix C.

6.0 Past Management Activities

There has been no aquatic plant management work done in Poskin Lake except for the occasional physical plant removal completed by property owners. The PLA does participate in watercraft inspection, in-lake monitoring, and in water quality monitoring through the Citizen Lake Monitoring Network.

7.0 Aquatic Plant Management Discussion

Aquatic plant species diversity is pretty good in Poskin Lake, except that only a few areas provide most of the diversity due to limited light penetration caused by algae dominated water. In the majority of the littoral zone, coontail is the most abundant and often only plant of any significance in a given area. Coontail is not a rooted aquatic plant and does not need light penetration to the bottom of the lake to grow, so it does well in degraded water quality conditions. Promoting the expansion of more desirable native plant growth is an important management goal, and is tied to increasing water quality and clarity by reducing phosphorous and chlorophyll (a measure of the amount of algae) concentrations in the lake. There are several significant non-point sources of nutrients to the system including agricultural runoff from the watershed, nearshore runoff (including on-site wastewater treatment facilities) from riparian properties, and internal recycling of nutrients already present in the system. CLP is also a source of phosphorous, as is wind and rain, and groundwater.

http://www.sehinc.com/online/poskin


7.1 Agricultural Runoff

The agriculturally based watershed of Poskin Lake is a major source of nutrients to the system. Making changes in agricultural activities in the watershed and striving to make changes along the shoreline of the lake should benefit the promotion of greater, more desirable, native aquatic plant growth. Total contributions from the watershed and best management practices to improve the situation are addressed in the accompanying Comprehensive Lake Management Plan.

7.2 Curly-leaf Pondweed

Curly-leaf pondweed is present in the lake, but it the present time does not appear to be causing significant problems in the lake. Decaying CLP and other vegetation releases phosphorous into the lake water. The reported phosphorous content of CLP varies widely and is likely dependent on a variety of existing conditions in any given lake. The phosphorous content of the CLP from Big Chetac Lake in 2007 was measured at 0.26% by the WDNR (Roesler, 2008) based on plant samples from 10 different sites. The median CLP biomass was calculated to be 245 g/m2. If it is assumed that the biomass of CLP in Poskin Lake is similar to Big Chetac Lake, then, based on an area of CLP covering two acres the total phosphorous mass potentially released from CLP in Poskin Lake is estimated at 11.4 lbs. This assumes that 100% of the phosphorous contained in the CLP will go directly into the water column. This is probably not the case. Naturally senescing CLP generally settles to the lake bottom where a substantial portion of the decomposition occurs. This would likely result in some of the phosphorous released by CLP being immediately captured in the sediment. Filamentous algae present in the area where CLP is decaying and periphyton on the remaining plant community would likely use up some of the phosphorous released from the CLP as well (Roesler, 2008). With that in mind, a better value to consider for Poskin Lake might be 50% of the potential phosphorous released from the CLP making it to the water column. If this is the case, then CLP contributed around six lbs of phosphorous, and is a very limited source.

There is some concern over the impacts decaying CLP has on dissolved oxygen levels in a lake. While decaying CLP may slightly reduce dissolved oxygen levels near the deep water edges of the littoral zone, in general, decay occurs in that area of the littoral zone that receives oxygen recharge. A more likely impact of curly-leaf pondweed, other than the phosphorous released from the plant itself, is an increase in pH that usually accompanies extensive plant and algal growth which removes carbon dioxide changing the overall alkalinity of the lake water. Additional phosphorous release can occur from sediments in contact with high pH waters even though dissolved oxygen levels are stable.

CLP distribution and density in Poskin Lake should be monitored every year to determine if it is invading greater areas of the littoral zone, but removal through the use of herbicides or larger-scale mechanical methods is not suggested at this time. If levels increase then it is likely that management will be undertaken.

7.3 Re-establishing Native Plant Communities by Planting and Restoration

Another way to keep AIS like CLP in check is to use native plants to out-compete non-native plants, either by encouraging their growth if they already exist or by introducing or re-introducing them into a system. This can also increase the distribution of and density of plants in a lake, and is a desirable management technique. Re-establishment of native plants may happen naturally if seeds and other propagules are still present. Making the decision to re-introduce aquatic vegetation is not an easy one, because once it is decided that desired pants have disappeared completely and have to be artificially introduced, the costs are high.


A source for fairly large quantities of new plants will be needed, physical protection from fish and birds will likely be needed, stabilization and protection of sediment in the planting area from wind and waves will likely be needed, and substantial labor needs for collection of stock, planting and maintenance will be required.

There are essentially three types of aquatic plants: emergent, floating leaf, and submergent. Emergent plants include reed, bulrush, cattail, grasses (like wild rice), sedges, and tall herbs. Floating leaf plants include water lilies, floating leaf pondweeds, and common waterweed. These plants generally grow in shallow water down to 2 or 3 meters. Submerged plants are usually rooted to the bottom of a lake (but not always) and completely under water except for certain parts like flowers, at certain times during the year.

By inventorying existing plants in a body of water, even just remnant populations, a list of species to re-introduce can be established. If no plants exist, then vegetation in surrounding lakes could provide a place to start, and general lake structure can help further define the species to reintroduce. Once decided, plants may be able to be collected from other areas of the same lake, collected from other lakes, or purchased from commercial vendors. Collecting plants from the same or other water bodies may require a permit. If commercial plants are purchased care should be taken to not introduce unwanted vegetation at the same time.

A good rule of thumb is to plant as many submerged or floating leaf plants as possible given resource constraints, as these plants are likely the most susceptible to failure. It may not be as important to do this for emergent plant species (Moss et al., 1996). There are many sources for more information. Smart et al., 1998 discuss many techniques for establishing native aquatic plants in reservoirs with an absence of vegetation or low species diversity. The Langlade County, Wisconsin Land Records and Regulations Department has a Shoreland Restoration Web Site which provides a great deal of information for re-establishing native plants (Langlade County Land Records and Regulations Department, 2007). A complete review of these techniques and others would be necessary before undertaking a planting project.

Re-establishing or introducing desirable native plants species is a management technique that could be used to protect and enhance existing plant communities in Poskin Lake. At this time though, it is not recommended except on a very small scale. Improving water clarity may be enough to enhance more desirable aquatic plant growth.

8.0 Management Alternatives

Although no substantial aquatic plant management is to be recommended for Poskin Lake, it is good to know what management alternatives are available. Problematic aquatic plants in a lake can be dealt with in many different ways. When addressing non-native invasive plants like CLP and EWM eradication is generally not a feasible goal, but preventing them from

Langlade County, Wisconsin "Buffer Blocker" System


becoming a more significant problem is. Targeted early season and mid-season treatment or removal of non-native plants can minimize negative impacts to a lake. However, just because an invasive species is present, does not necessarily mean it should be treated. Sometimes no management is the best alternative.

Protecting native plants should be a primary focus of plant management in any lake. Managing to maintain or improve water quality will help to increase aquatic plant diversity and quality and will help to prevent certain native plants that can cause lake use and navigation issues of their own from becoming a problem. Certain native aquatic plants like coontail, northern watermilfoil, and common waterweed may be considered beneficial native plants, but can become an issue when degrading water quality makes them the predominant species in the lake. These plants do well in the presence of man-made disturbances, often increasing when other plants more sensitive to human disturbances are disappearing. Emergent plants like pickerel weed, arrowhead, various bulrushes, and wild rice may be considered a nuisance by some riparian owners, but in general are extremely beneficial to a lake and removal should be minimized. In the case of wild rice, it is a highly protected emergent aquatic plant species and basically untouchable.

Regardless of the target plant species, native or non-native, areas considered critical habitat for fish and wildlife may best be left alone. In these areas plant management except to control problematic invasive species should be minimal. Only if management of non-native plant species in critical habitat areas is expected to benefit that area, should it be considered.

Control methods for nuisance aquatic plants can be grouped into four broad categories: mechanical/ physical control; chemical control; biological control; and aquatic plant habitat manipulation. Examples of plant habitat manipulation include dredging, flooding and drawdown. Biological control methods include organisms that use the plants for a food source or parasitic organisms that use the plants as hosts. Biological control may also include the use of species that compete successfully with the nuisance species for resources. Chemical control is typified by the use of herbicides. Mechanical and physical control methods include pulling, cutting, raking and harvesting. In many cases, an integrated approach to aquatic plant management is necessary.

Not all plant management alternatives can be used in a particular lake. What other states accept for aquatic plant management may not be acceptable in Wisconsin. What is acceptable and appropriate in southern Wisconsin lakes may not be acceptable and appropriate in northern Wisconsin lakes.

All existing APM Plans and the management permits (chemical or harvesting) that accompany them are undergoing greater scrutiny by the WDNR. It has become increasingly important for new and existing APM Plans to include at a minimum, yearly monitoring and assessment to document impacts on water quality, fish and wildlife, native plants, and control results for the targeted species. It is equally important for new APM Plans to at least evaluate the potential for restoring the lakes natural plant community by “shifting the plant community toward more natives with targeted aquatic invasive species reduction” rather than just routine maintenance.


8.1 WDNR Northern Region Aquatic Plant Management Strategy

The WDNR has a Northern Region Aquatic Plant Management Strategy (Appendix D) that went into effect in 2007. All aquatic plant management plans developed for northern Wisconsin lakes are evaluated according to the goals of this strategy which are as follows:

Preserve native species diversity which, in turn, fosters natural habitat for fish and other aquatic species, from frogs to birds.

Prevent openings for invasive species to become established in the absence of the native species.

Concentrate on a” whole-lake approach” for control of aquatic plants, thereby fostering systematic documentation of conditions and specific targeting of invasive species as they exist.

Prohibit removal of wild rice. WDNR-Northern Region will not issue permits to remove wild rice unless a request is subjected to the full consultation process via the Voigt Tribal Task Force. We intend to discourage applications for removal of this ecologically and culturally important native plant.

To be consistent with our WDNR Water Division Goals (work reduction/disinvestment), established in 2005, to “not issue permits for chemical or large scale mechanical control of native aquatic plants – develop general permits as appropriate or inform applicants of exempted activities.” This process is similar to work done in other WDNR Regions, although not formalized as such.

The management alternatives discussed in the following section of this plan are arranged in order of acceptable and appropriate use in Poskin Lake.

8.2 Hand Pulling/Manual Control

Except for wild rice, manual removal of aquatic plants by means of a hand-held rake or by pulling the plants from the lake bottom by hand is allowed by the WDNR without a permit provided the area of removal does not exceed 30 shoreland feet and all raked or pulled plant material is taken completely out of the lake (NR 109). If an aquatic invasive species like EWM or CLP is the target species, than removal by this means is unrestricted. Manual removal can be effective at controlling individual plants or small areas of plant growth. It limits disturbance to the lake bottom, is inexpensive, and can be practiced by many lake residents. In shallow, hard bottom areas of a lake, or where impacts to fish spawning habitat need to be minimized, this may be the best form of control. Pulling aquatic invasive species while snorkeling or scuba diving in deeper water is also allowable without a permit and can be effective at slowing the spread of a new aquatic invasive species infestation within a waterbody when done properly.

8.3 Chemical Control and Management

Chemical management techniques have changed dramatically in the past 20 years. Increased concern about the safety of pesticide use in the 1960’s and 1970’s changed the review process for all pesticides, particularly for products used in water. Currently, no product can be labeled for aquatic use if it poses more than a one in a million chance of causing significant damage to human health, the environment, or wildlife resources. In addition, it may not show evidence of bio-magnification, bioavailability, or persistence in the environment (Madsen, 2000). In 1976, 20 active ingredients were available for aquatic use. As of 1995, only six are available with one additional compound (Triclopyr) undergoing the registration process. The


six compounds have undergone rigorous testing to enable them to be approved by the U.S. Environmental Protection Agency (EPA) for use in aquatic settings.

The six or seven active ingredients that have been approved by the EPA not only are ensured safe for aquatic use but also have manufacturers committed to the aquatic market supporting them. These products are only considered safe when used according to the label accompanying the product. The EPA approved label provides guidelines for protecting the health of the environment, the humans using that environment, and the applicators of the herbicide. In most states, there exists additional permitting or regulatory restrictions on the use of these herbicides. A typical state restriction requires that these herbicides be applied only by licensed applicators. Annual updates from state regulatory and environmental agencies are necessary to check for changes in label restrictions and application policies or permit requirements, before developing or implementing any plans for applying herbicides (Madsen, 2000).

Herbicides labeled for aquatic use can be classified as either contact or systemic. Contact herbicides act immediately on the tissues they come in contact with. Typically, these herbicides are faster acting, but they do not have a sustained effect, in many cases not killing root crowns, roots, or rhizomes. In contrast, systemic herbicides are translocated throughout the plant. They are slower acting but often result in mortality of the entire plant (Madsen, 2000).

Herbicides are applied in either liquid or granular form directly to the water overlying the problem area. Most granular herbicides are activated through photo degradation of the granular structure, releasing the active chemical. These chemicals either elicit direct toxicity reactions or affect the photosynthetic ability of the target plant. The plants die and degrade within the lake. Some herbicide residuals sink to the lake sediment, providing some additional temporary control of vegetation (NYSDEC, 2005).

When properly applied, certain herbicides can control aquatic vegetation without harming fish and other wildlife. In some instances, herbicides can be used selectively to control certain plant species without killing others. Aquatic herbicides can be part of an integrated management plan where some areas are treated and others are left with vegetation or treated with another method. They can be particularly effective for controlling aggressive weed species such as EWM. Aquatic herbicides offer temporary solutions. None of the EPA approved products when properly used will eliminate plants from a body of water permanently. Plants will reappear, and re-treatment or application of another control method will usually be necessary.

Correct timing of the chemical application is important, since seeds can germinate and roots can sprout even when the parent plants are killed off. The specific time for the application will depend on the specific target weed, required dosage rate, water temperature, water chemistry characteristics of the lake, weather conditions, water movement and retention time, and recreational use of the lake. Herbicide applications must consider the timing of the growing season relative to the algae levels (since photo degradation of herbicides may be slower when algae reduces lake clarity), ice cover, and the effect the chemical application will have on the recreational use of the lake. Most herbicides have use restrictions immediately after treatment, sometimes lasting up to 30 days (NYSDEC, 2005).

Chemically-treated lakes may experience significant side effects. Non-target plants may not be resistant to the herbicide. Furthermore, if a wide variety of plant species are eradicated by


herbicide treatment, the fast-growing (“opportunistic”) exotic species that were the original target plants may re-colonize the treatment area and grow to levels greater than before treatment (NYSDEC, 2005).

Short-term impacts of aquatic herbicides have been fairly well studied for most of the inhabitants of lakes and the surrounding environment, and have been deemed to pose “acceptable risk” if applied in the appropriate manner. In general, humans and most animals have high tolerance to the toxic effects of herbicides presently approved for use in lakes. This is especially true of the newer generation herbicides that have been formulated to impact metabolic processes specific to chlorophyll-producing plants. However, the long-term impact of herbicides on humans and other plants and animals in the environment continues to be studied (NYSDEC, 2005).

When herbicides are applied in a lake environment, the affected plants drop to the bottom of the lake, die, and decompose. The resulting depletion of dissolved oxygen and release of nutrients could have detrimental effects on the health or survival of fish and other aquatic life as well as stimulating new plant growth (NYSDEC, 2005). This could also impact water quality in a given body of water.

Herbicide costs will vary with the chemical brand and form (liquid or granular), required dose rate, applicator fees, frequency of application, and the amount of pre and post treatment monitoring and assessment that is done. Typical costs for using herbicide range from $400-700 per acre of treated area (more if extensive post treatment monitoring is completed) with the majority of these costs associated with the raw materials.

Full disclosure of any negative impacts, good education, and making sure application is done properly by experienced people will help to reduce negative public opinion related to herbicide use. While there is some concern that target plants may develop a resistance to some herbicides, and that chemical residues may remain in the aquatic environment longer than is reported, there is little evidence of any build-up of herbicide residues or chronic toxicity in natural aquatic systems and fish populations appear not to be adversely affected (Murphy and Barrett ,1990).

One unconfirmed study by Lovato et al., 1996 from the Michigan Department of Environmental Quality, Drinking Water, and Radiological Protection Division, Ground Water Supply Section suggests that 2,4-D can migrate from surface water application to groundwater under certain hydro geologic conditions. Once in groundwater, a lack of oxygen may allow the compounds that make up 2,4-D to persist for longer periods of time. The authors conclude that shallow, near shore wells are at greatest risk for contamination. They also conclude that further study is needed.

8.3.1 Large-scale Herbicide Application

Large-scale herbicide application involves chemical treatment of more than 10 acres combined on a given body of water. Usually this is completed in the early-season for non-native invasive species like EWM and CLP. While not required by the WDNR at this time, chemical residual testing is suggested to track the fate of the chemical herbicide used. Water samples are taken prior to treatment, and then 1, 4, 7, 14, 21, and 28 days after chemical application. Sampling sites are within the treatment area, outside of the treatment area, in areas that may be sensitive to the herbicide used, in areas where chemical drift may have adverse impacts, and in areas where movement of water or some other characteristic may impact the effect of the chemical. Residual testing is completed to determine if target


concentrations are met, to see if the chemical moved outside its expected zone, and if it breaks down in the system as expected.

8.3.2 Small-scale Herbicide Application

Small-scale herbicide application involves treating smaller areas, usually less than 10 acres combined on a given body of water. This is most often completed in the early season, but not always. It may be used to follow up a large-scale treatment to retreat areas missed or not impacted by the first application. As with large-scale chemical application, residual testing is not required by the WDNR. It is however, suggested if it pushes the levels considered large-scale, is repeated more than once in any given year, or is in an area where there may be question as to its effectiveness on target species, or impacts on non-target species.

8.3.2.1 USEPA Approved Aquatic Herbicides in Wisconsin There are several aquatic herbicides approved for use in Wisconsin. They are summarized in the following paragraphs. Not all of these herbicides are appropriate for use in Poskin Lake. Follow-up monitoring should track the fate of any applied chemical through residual testing, changes in plant communities through plant surveys, and water quality conditions through water sampling. The effectiveness of any given herbicide treatment varies with the treatment design, and the conditions of the lake and treatment site.

8.3.2.1.1. Endothall

Endothall is a contact herbicide. Its common trade name is Aquathall K or Super K, or Hydrothall. Endothall is a broad spectrum herbicide most commonly used to kill pondweeds like curly-leaf. Because CLP is an annual plant not dependant on existing root structure to grow, a contact herbicide like Endothall can be very effective. It is also used to kill EWM, coontail, wild celery, and some species of algae. It is not effective on roots, rhizomes, or tubers. Unlike Diquat, another contact herbicide, it is not affected by particulates or dissolved organic material. It should not be used in tank mixtures with copper, as it can have an antagonistic reaction with chelated copper compounds. Combined early season treatments using 2,4-D and Endothall have been used with some success to control both EWM and CLP when present in the same area (Skogerboe and Getsinger, 2006).

8.3.2.1.2. Glyphosate

Glyphosate is a systemic herbicide not effective on submersed plants. It is used for control of emergent or floating leaf plants like purple loosestrife, cattails, phragmites, and lily pads. Glysophate is the herbicide found in the Round-Up (trade name) that is available over the counter for terrestrial weed control. A water-safe version of it called Rodeo is commercially available, but not from the average retail store. The Rodeo form of glysophate must be used when on or near water. It is not legal to use Round-Up on or near water. A surfactant and dye are usually added to it to make it stick to the target vegetation better and to make it more visible after application. Glysophate can be applied in a foliar spray or painted or dabbed onto cut stems. It is a systemic herbicide drawn into the plant and to the roots, so it will kill all parts of the target plant if applied correctly. Glyphosate will be recommended for control of purple loosestrife in isolated areas to big for physical removal and too small for beetle release.

8.3.2.1.3. 2,4-D

2,4-D is one of the most common systemic herbicides in use today. It is a relatively selective herbicide commonly used for treatment of EWM. A few of its most common trade names for use in an aquatic environment are Aqua-kleen, Aquacide or Navigate. In its liquid form it is known as Weedar 64. It effectively controls broadleaf plants (dicots) like EWM, coontail, and


northern watermilfoil with a relatively short contact time, but does not generally harm pondweeds or water celery. It is not effective against elodea or hydrilla. 2, 4-D can impact early season wild rice growth so should not be used in areas where the target species and wild rice cohabitate.

8.3.2.1.4. Triclopyr

Triclopyr is a systemic herbicide, similar to 2,4-D used for control of aquatic dicots. It common trade name is Garlon 3A or Renovate. Triclopyr degrades quickly in an aquatic environment making its use most effective in systems with low water-exchange where contact with target plants can be maintained for longer periods of time, though not as long as Fluridone. Low concentrations of this herbicide can be effective for EWM control when exposure time reaches 48 to 72 hours (Netherland and Getsinger, 1992). It does not appear to significantly affect pondweeds and coontail (Clayton & Clayton, 2001). As of 2005, Triclopyr was not a registered herbicide and can only be used under an experimental use permit in the United States (Cooke et al., 2005).

8.3.2.1.5. Diquat

Diquat is a non-selective, contact herbicide that will kill or injure a wide variety of plants by damaging cell tissues when absorbed by the foliage. It will not kill parts of the plant it does not come into direct contact with. Its common trade name is Reward. Diquat is not effective in lakes or ponds with muddy water or plants covered with silt because it is strongly attracted to clay particles in the water. Bottom sediments must not be disturbed when this herbicide is used. At approved application rates Diquat does not appear to have any long or short term effects on most aquatic organisms.

8.3.2.1.6. Fluridone

Fluridone is a non-selective systemic herbicide. It requires very long exposure times often three months or more, but may be effective at very low concentrations. Its common trade name is SONAR. Fluridone is gaining acceptance for control of EWM. It was just recently approved for use in Wisconsin lakes. It works best where the entire lake or flowage system can be managed, but not in spot treatments or high water exchange areas. Fluridone does not appear to have any long or short term adverse effects on fish or other aquatic invertebrates if label directions are followed.

8.4 Mechanical Control and Management

There are several mechanical means for controlling aquatic vegetation. The following summarizes what is available, but not necessarily applicable in Poskin Lake.

8.4.1 Large-scale Mechanical Harvesting

Harvesting assumes that vegetation is cut and removed from the system after cutting. Harvesters are driven by modified paddle wheels and include a cutter that can be raised and lowered, a conveyor system to capture and store the cut plants, and the ability to off-load the cut plants. The depth at which these harvesters cut generally ranges from skimming the surface to as much as five-feet deep.

Harvesters can remove thousands of pounds of vegetation in a relatively short time period. They are not, however, species specific. Everything in the path of the harvester will be removed including the target species, other plants, macro-invertebrates, semi-aquatic vertebrates, forage fishes, young-of-the-year fishes, and even adult game fish found in the littoral zone (Booms, 1999). Large-scale plant harvesting in a lake is similar to mowing the lawn. Plants are cut at a designated depth, but the root of the plant is often not disturbed. Cut


plants will usually grow back after time, just like the lawn grass. Re-cutting several times a season is often required to provide adequate annual control (Madsen, 2000). Harvesting activities in shallow water can re-suspend bottom sediments into the water column releasing nutrients and other accumulated compounds (Madsen, 2000). Some research indicates that after cutting, reduction in available plant cover causes declines in fish growth and zooplankton densities. Other research finds that creating deep lake channels by harvesting increases the growth rates of some age classes of bluegill and largemouth bass (Greenfield et al., 2004).

One benefit of large-scale aquatic plant harvesting is the removal of large amounts of plant biomass from a water body. Plants use up nutrients including phosphorous in the water and sediment. However, they often re-deposit that phosphorous back into the lake water and sediment when they die. Early season or cool water plants like CLP, that complete their life cycle, die, and senesce (decay) in early summer can be a source of significant phosphorous loading and may negatively affect dissolved oxygen levels.

8.4.2 Alternative Mechanical Management

Cutting without plant removal, grinding and returning the vegetation to the water body, and rotovating are also methods employed to control nuisance plant growth in some lakes. Cutting is just like harvesting except the plants are left in the waterbody. Grinding incorporates cutting and then grinding to minimize the biomass returned to the lake. Smaller particles disperse quicker and decay more rapidly. Rotovating works up bottom sediments dislodging and destroying plant root crowns and bottom growth. All three of these alternatives have major drawbacks and will not be used on the White Ash Lakes.

On a smaller scale, bottom rollers and surface sweepers exist that are usually attached to the end of a dock or pier and sweep through an area adjacent to the dock. Bottom rollers are usually driven by electric motors and run at least once a week. Continued disruption of the bottom area usually causes plants to disappear and light sediments to be swept out. The use of rollers may disturb bottom dwelling organisms and spawning fish. Plant fragmentation of nuisance weeds may also occur. In soft bottom areas, sediment disturbance can be significant. Concern has also been expressed about the use of weed rollers on sediments high in organic matter (Greenfield et al., 2004).

The Lake Sweeper or Lake Maid is an automatic weed control device that is used in similar areas to the weed roller. Like weed rollers, the Lake Sweeper is attached at one end to a dock or other fixed location and consists of a 24’-42’ metal pole that moves forward and reverse in a 270-degree arc. A pump provides the force to move the floating pole back and forth. Instead of rolling along the sediment, the Lake Sweeper floats along the lake surface, with a series of lightweight rakes dragging behind it. According to the manufacturer, these rakes can kill a variety of submerged aquatic plants within three to five days by gradually weakening the plants. Purchase costs for a Lake Sweeper is approximately $2,000. Installation is said to be simple and operating costs are reported by the manufacturer to be very low. The potential for the Lake Sweeper to increase the rate of release of viable plant fragments has not been independently evaluated (Greenfield et al., 2004).

Automated untended aquatic plant control devices as the Minnesota Department of Natural Resources (MDNR) has taken to calling these devices, have the potential to remove larger swaths of vegetation, displace more sediment, and eliminate plants for a longer period of time than many other devices used by homeowners to control aquatic plants. For these reasons, it is important to ensure that the device is used appropriately.


Weed Rollers and similar devices have been permitted by the MN DNR, assuming certain requirements have been met. Minnesota regulations state that:

A permit is required to use Crary WeedRollers, and similar devices, for aquatic plant control regardless of the size of the area. A permit will likely not be issued where operating this device is expected to "dredge" or excavate the lake bottom.

A permit valid for three years may be obtained if the device is operated in an area of submerged vegetation that is no larger than 2,500 square feet, and extends no more than 50 feet along the shore or one-half the property owner's frontage, whichever is less. An annual permit is required for larger areas.

These devices are generally not permitted in Wisconsin as is demonstrated by the following paragraph taken from the Crary WeedRoller webpage at www.weedroller.com.

“The state has no specific statute which governs mechanical weed control for Wisconsin riparians. They have however declared jurisdiction over the WeedRoller under statute #30.12 - 3 which governs the placement of certain "structures" in navigable waters. Form 3500-53 must be submitted with a $25 filing fee. The Wisconsin Dept. of Natural Resources has demonstrated to be adverse to the WeedRoller and the issuance of permits for its use.” 1995

Other states including Florida, Illinois, Indiana, Iowa, Michigan, New York, North Dakota, and Washington allow their use. In most cases a permit is required, but not all.

Another common, less sophisticated method for removing aquatic plants from a beach or dock area is for riparian owners to hook a bed spring, sickle mower blade, or other contraption to the back of a boat, lawn mower, or ATV and drag it back and forth across the bottom. This type of management is considered mechanical and is generally not permitted by the WDNR. Plant disruption by normal boat traffic is not considered illegal. One of the best ways for land owners to gain navigation relief near their docks is to use their watercraft on a regular basis.

8.4.3 Suction Harvesting and Suction Dredging

Another form of mechanical harvesting is using diver operated suction harvesting to remove aquatic plants. Diver-operated suction harvesting entails the use of barge-mounted pumps and strainer devices with hoses used by divers to “vacuum up” plants uprooted by hand. This management technique is called harvesting because even though a specialized small-scale dredge is used, sediments are not removed from the system. Sediments are re-suspended during the operation but use of a sediment curtain can mitigates these effects. Plants are removed directly from the sediments by divers operating this device.

8.5 Aquatic Plant Habitat Disruption

Aquatic plant habitat disruption involves management activities that alter the environment in which aquatic plants are growing. Several techniques are commonly used: drawdown or flooding, dredging, benthic barriers, shading or light attenuation, and nutrient inactivation. While not prohibited in Wisconsin, these plant management alternatives will undergo much greater scrutiny by the WDNR, and in most cases will not be permitted.

http://www.weedroller.com/


8.5.1 Dredging

Dredging is usually not performed solely for aquatic plant management but to restore lakes that have been filled in with sediments, have excess nutrients, have inadequate pelagic and hypolimnetic zones, need deepening, or require removal of toxic substances. Dredging typically creates an area of the lake too deep for plants to grow, thus opening an area for riparian use. By opening more diverse habitats and creating depth gradients, dredging may also create more diversity in the plant community. Results of dredging can be very long term. Biomass of Potamogeton crispus in Collins Lake, New York remained significantly lower than pre-dredging levels 10 years after dredging. However, due to the cost, environmental impacts, and the problem of disposal, dredging should not be performed for aquatic plant management alone. It is best used as a multi-purpose lake remediation technique (Madsen, 2000).

8.5.2 Water-level Manipulation

Drawdown is an effective aquatic plant management technique that alters the plant’s environment. Essentially, the water body has all of the water removed to a given depth. It is best if this depth includes the entire depth range of the target species. Drawdown, to be effective, needs to be at least one month long to ensure thorough drying. In northern areas, a drawdown in the winter that will ensure freezing of sediments is also effective. Drawdown requires that there be a mechanism to lower water levels. Although it is inexpensive and has long-term effects (two or more years), it also has significant environmental effects and may interfere with use and intended function (e.g., power generation or drinking water supply) of the water body during the drawdown period. Lastly, species respond in very different manners to drawdown and often not in a consistent fashion. Drawdown may provide an opportunity for the spread of highly weedy or adventitious species, particularly annuals (Madsen, 2000). Raising the water level, although not very common, can have a similar effect to dredging as the water depth can be made too great for aquatic plants to grow.

8.5.3 Benthic Barriers and Light Reduction

Benthic barriers or other bottom-covering approaches are another physical management technique that has been in use for a substantial period of time. The basic idea is that the plants are covered over with a layer of a growth-inhibiting substance. Many materials have been used, including sheets or screens of organic, inorganic and synthetic materials, sediments such as dredge sediment, sand, silt or clay, fly ash, and combinations of the above.

Benthic barriers will typically kill plants under them within one to two months, after which they may be removed. Sheet color is relatively unimportant; opaque (particularly black) barriers work best, but even clear plastic barriers will work effectively. Sites from which barriers are removed will be rapidly re-colonized. In addition, synthetic barriers may be left in place for multi-year control but will eventually become sediment-covered and allow re-colonization by plants. Benthic barriers, effective and fairly low-cost control techniques for limited areas (e.g., <1 acre), may be best suited to high-intensity use areas such as docks, boat launch areas, and swimming areas. However, they are too expensive to use over widespread areas, and heavily affect benthic communities (Madsen, 2000).

A basic environmental manipulation for plant control is light reduction or attenuation. Shading has been achieved by fertilization to produce algal growth, application of natural or synthetic dyes, shading fabric, or covers, and establishing shade trees. During natural or cultural eutrophication, phytoplankton growth alone can shade macrophytes. Although light


manipulation techniques may be useful for narrow streams or small ponds, in general these techniques are of only limited applicability in lakes (Madsen, 2000).

8.6 Biological Control and Management

Biological control (bio-control) involves using animals, fish, fungi, insects, other plants, or pathogens as a means to control another in the same environment. The goal of bio-control is to weaken, reduce the spread, or eliminate the unwanted population so that native or more desirable populations can make a comeback. Care must be taken however, to insure that the control species does not become as big a problem as the one that is being controlled. A special permit is required in Wisconsin before any bio-control measure can be introduced into a new area.

8.6.1 Native Plant Restoration and/or Enhancement

Restoring a native plant community is almost always the end goal of an aquatic plant management program. Lakes currently lacking a native plant community can have these communities reestablished. In communities that have only recently been invaded by non-native species, a propagule seed bank probably exists that will restore the native community after successful management of the non-native plant. However, in communities that have had mono-specific non-native plant dominance for a long period of time (e.g., greater than 10 years), native plants may have to be reintroduced after a successful management program has been instituted. A healthy native plant community might slow invasion or reinvasion by non-native species and will provide the environmental and habitat needs of an aquatic littoral zone. However, even healthy, well-developed native plant communities may eventually be invaded and dominated by non-native species (Madsen, 2000).

8.6.2 Insects, Animals, or Pathogens

Bio-control using other animals, insects, pathogens, or fungi for reduction of nuisance plants in aquatic systems has both positive and negative attributes. One positive is that control agents are often host specific, so effects to non-target species may be reduced. Control agents can also reproduce in response to increases in nuisance species density often without reapplication of the agent. Development and registration (where necessary) of bio-control agents is generally less expensive than chemical agents.

Bio-control can have many potential disadvantages. A substantial risk is involved when new species are introduced as bio-control agents. To be considered successful, these species are expected to persist indefinitely in the environment where they are used, and may spread to new locations. Therefore, if there are any adverse effects resulting from the bio-control agent, these effects may be difficult or impossible to control. Other drawbacks include unpredictable success and rates of control that are slower than with chemical methods. Resistance in host species is unlikely to develop but can occur. Finally, agents that work in one area may not be suitable in all ecosystems. Climate, interference from herbicidal application, hydrological conditions, and eutrophication of the system can influence the effectiveness of bio-control agents. The growth of nuisance weeds can be suppressed with the use of bio-control agents, but not fully eliminated (Greenfield et al., 2004).

8.6.2.1 Biological Controls Approved for Use in Wisconsin Many herbivorous insects have been and continue to be studied for their impacts on unwanted aquatic plant species. An herbivorous aquatic moth, Acentria ephemerella, two native herbivorous weevils, Euhrychiopsis lecontei and Phytobius sp., and a chironomid species Cricotopus have been associated with the decline of EWM in a waterbody. Several species of


insect are being used to control purple loosestrife infestations very effectively. Two Galerucella spp are easy to rear, can be extremely effective at reducing large populations of purple loosestrife, and after nearly 20 years of use seem to have no negative effect in the areas they are introduced.

To date, this researcher is not aware of any insect controls being studied specifically for the control of CLP. However, research into establishing bio-controls is on-going. Studying naturalized and native herbivores and pathogens that impact nuisance aquatic and wetland plants increases the number of potential bio-control agents that could be incorporated into invasive plant management programs. The groundwork has been laid for conducting future bio-control research and experimentation. Although not all of the native and naturalized organisms researched can be successful, the information and expertise is now available for potential insects and pathogens to be collected, analyzed, and studied. A continuation of the work that has been started is needed to make available for the future more successful native bio-control agents (Freedman et al., 2007).

There are several forms of biological control that have been used in other states, but are generally not approved for use in Wisconsin. The grass carp, also known as the white amur (Ctenopharyngodon idella), feeds on aquatic plants and has been used as a biological tool to control nuisance aquatic plant growth in other states. In addition to grass carp, common carp and tilapia (a fish species) have been added to ecosystems to reduce aquatic vegetation. Wisconsin does not permit the use of these fish for aquatic plant control.

Plant fungi and pathogens are currently still in the research phase. Certain species for control of hydrilla and EWM have shown promise but so far, only laboratory tests in aquariums and small ponds have been conducted. Methods are not available for widespread application. Whether these agents will be successful in flowing waters or large-scale applications remains to be tested (Greenfield et al., 2004).

8.6.3 Barley Straw

Organic materials, such as peat, and barley straw, have been used for control of rooted aquatic plants and algae. There are several theories for why barley straw, at least in small scale applications may work. One suggests that decomposing straw uses up nutrients in the water so they are not available for algae growth. Another suggests that decomposing straw gives off compounds toxic to algae (Scheffer, 1998). In general, research done to determine the effect of barley straw has not been consistent or very positive.

Questions still remain as to whether barley straw should be considered an algicidal (kills existing algae) or an algistatic (prevents new algae growth). This designation is an important one for if it is considered an algicidal agent then it is also considered a pesticide. As a pesticide, the EPA requires rigorous testing and a registration number before being “approved” for use in a public water body. No company has ever registered barley for use as a pesticide. It has not gone through the testing required for registration. Therefore, barley cannot be sold as a pesticide to control algae. This ruling has serious implications for certified commercial applicators (individuals who have been state certified to apply aquatic pesticides for hire) and lake management specialists. These individuals cannot recommend or apply barley for algae control; this application would be the same as distributing an unregistered pesticide (Lembi, 2002).

However, EPA acknowledges that some products have multiple uses and that it is legal to advertise, sell, and apply a product based on its non-pesticidal uses, even if the product also


has pesticidal uses. In this case, as long as someone does not claim algae control per se, they could sell or apply barley straw. The obvious alternative reason for the application of barley is that it might act as a water clarifier. Although there is little evidence that barley acts like typical clarifiers such as alum (which causes the precipitation of phosphorus or removes particles from the water), this is one way in which the direct claim or implication of “algae control” can be avoided (Lembi, 2002).

8.6.4 Other Algicides

Copper sulfate and chelated coppers have been widely used as non-selective, fast-acting, contact herbicides or algicides. Copper compounds are widely used for algae control but certain groups of phytoplanktonic algae are more tolerant to copper. Copper can build up in sediments, can be toxic to fish and invertebrates, and certain species of algae can build up a resistance (Charudattan 2001). A paper written by Hanson and Stefan in 1984 summarized the effects of 58 years of copper sulfate treatments to the Fairmont Lakes in Minnesota. They conclude that some of the intended algae was killed, however several short-term effects including dissolved oxygen depletion caused by decomposing dead algae resulted in fish kills and recycling of phosphorous from the lake bed. And, these treatments generally were only effective for a period of 7-21 days before algae concentrations returned to their pre-treatment concentrations. Several long-term effects resulted as well. Toxic levels of copper accumulated in the sediments, resistance in several plant species led to even greater dosages of copper, algae species present shifted from less problematic green algae to highly problematic blue-green algae, the fish population shifted from abundant game fish to rough fish, and aquatic macrophytes and benthic macroinvertebrates all but disappeared.

Chelated copper formulations tend to stay in solution longer, give better control, and are generally less toxic to fish species than traditional copper sulfate (Watson 1989). In some cases chelated copper compounds have been combined with other herbicides including Endothall to control certain aquatic plants and reduce algae concentrations (Pennington et al., 2001). The use of copper compounds to control algae was once widely accepted in WI, but in recent years it has not been supported as a viable control method because of the potential negative impacts inherent with its use.

9.0 Documentation of Plant Problems/Need for Management

Native plants are an important component to the Poskin Lake system in that they provide habitat for fish and wildlife, use up some of the available nutrients, protect shoreline, and hold sediment in place. Large-scale aquatic plant management recommendations are limited. Certain emergent species, like the abundant wild rice in Little Poskin, are extremely desirable and should be protected at all costs. On a small scale (individual property owners), re-establishing desirable native plants should be considered. Monitoring for the expansion of existing AIS, specifically CLP, and monitoring to identify new AIS introductions to Poskin Lake should be continued. Poskin Lake is downstream of another waterbody (Lower Vermillion Lake) that currently has EWM, so it is quite conceivable that EWM may come in through that vector. In-lake monitoring for AIS and watercraft inspection are important tools in preventing new AIS from entering the lake. Physical removal of offending plant material (native or invasive) by individual land owners is acceptable and reasonable. Hand-pulling or raking can and should be used to remove aquatic plants in areas where they might be a nuisance. Water quality monitoring of all three sites should be continued to particularly if the PLA applies for and receives a Lake Protection Grant to implement best management practices in the watershed and in the nearshore area of the lake.


10.0 Aquatic Plant Management Goals, Objectives, and Actions

Appendix E provides an outline of the aquatic plant and related management activities included in this APM Plan. There are six broad goals followed by the specific objectives and actions necessary to meet those goals over the course of the next five years. This five-year document is intended to be a fluent document able to be revised based on the results attained each year. Minor changes and adaptations are expected and will be made annually, but any major change in activities or management philosophy will be presented to the Lake residents, and the WDNR for approval. The six goals for this project are as follows:

AIS education and prevention planning AIS control and management Water quality monitoring Promotion of shoreland best management practices Native species preservation, enhancement, and protection Project assessment and evaluation

The goals and the objectives associated with them in this APM Plan will be completed by the PLA, their consultants, and through partnerships formed with the WDNR, Barron County Soil and Water Conservation Department, local Township authorities, and local clubs and organizations.

Funding for the activities in this APM Plan will be generated through PLA finances, contributions from partners, and through volunteer and donated services.

11.0 Five-year Time Line of Activities

The activities in this APM Plan are designed to be implemented over a 5-year period beginning in 2011. Appendix F provides an outline of the recommended activities and when they are to be implemented. Many activities in the timeline will require grant support to complete. If grant support is not garnered then a few of the activities will be modified or eliminated until more revenue can be arranged through Lake Association fund raising or state grant funding.


12.0 References

Author Unknown, 2005 Draft. A Primer on Aquatic Plant Management in New York State. New York State Department of Environmental Conservation, Division of Water, p. 63.

Berg, Matt 2009. Curly-leaf Pondweed P/I, Bed Mapping, and Warm Water Point/Intercept Macrophyte Surveys Poskin Lake (WBIC: 2098000) Barron County, Wisconsin. Endangered Resource Services, LLC. St. Croix Falls, Wisconsin, p. 96.

Booms, Travis, 1999. Vertebrates removed by mechanical weed harvesting in Lake Keesus, Wisconsin. Journal of Aquatic Plant Management, Vol. 37, pp. 34-36.

Charudattan, R. 2001. Are we on top of aquatic weeds? Weed problems, control options, and challenges. World’s Worst Weed International Symposium. Brittish Crop Protection Councinl, Brighton, England, pp. 27.

Clayton, Deborah E. and John S. 2001. Evaluation of Selected Herbicides for the Control of Exotic Submerged Weeds in New Zealand: I. The Use of Endothal, Triclopyr and Dichlobenil. J. Aqaut. Plant Manage. 39: 20-24.

Cooke, Dennis, Eugene Welch, Spencer Peterson, and Stanley Nichols, 2005. Restoration and Management of Lakes and Reservoirs, 3rd. Edition. CRC Press. Taylor and Francis Group. Boca Raton, Florida, p. 591.

Freedman, Jan, Michael Grodowitz, Robin Swindle, and Julie Nachtrieb, 2007. Potential Use of native and Naturalized Insect Herbivores and Fungal Pathogens of Aquatic and Wetland Plants. Army Corp ERDC Environmental Laboratory, Vicksburg, Mississippi, pp. 1-64.

Greenfield, Ben, Nicole David, Jennifer Hunt, Marion Wittmann, & Geoffrey Siemering, 2004. Aquatic Pesticide Monitoring Program - Review of Alternative Aquatic Pest Control Methods for California Waters. San Francisco Estuary Institute, Oakland, California, p. 109.

Hanson, Mark J. and H.G. Stefan, 1984. Side effects of 58 years of copper sulfate treatment of the Fairmont Lakes, Minnesota. Water Resources Bulletin, American Water Resources Association Volume 20, No. 6, pp. 889-900.

Langlade County Land Records and Regulations Department. http://lrrd.co.langlade.wi.us/shoreland/bufferblocker.asp

Lembi, Carol. A., 2002. Aquatic Plant Management, Barley Straw for Algae Control. Purdue university Publication APM-1-W. http://www.agcom.purdue.edu/AgCom/Pubs

Lovato J. L., B. O. Fisher, and W. E. Brown, 1996. Migration of Aquatically Applied Herbicides from Surface Water to Ground Water. Michigan Department of Environmental Quality, Drinking Water, and Radiological Protection Division, Ground Water Supply Section.

Madsen, John, 2000. Advantages and disadvantages of aquatic plant management techniques. Lakeline Vol. 20, No. 1, pp. 22-34.

Mares, Anna, S. Braun, and D. J. Heuschele, 2009. Aquatic invasive species survey of lakes with public access in Barron, Chippewa, Dunn, Eau Claire, and Rusk Counties. Beaver Creek Reserve Citizen Science Center, Fall Creek, Wisconsin, p 400.

http://lrrd.co.langlade.wi.us/shoreland/bufferblocker.asp

http://www.agcom.purdue.edu/AgCom/Pubs


Moss, Brian, Jane Madgwick, and Geoffrey Phillips, 1996. A Guide to the Restoration of Nutrient-enriched Shallow Lakes. WW Hawes, UK, pp. 180.

Murphy, K. J. and P. R. F. Barrett. 1990. Chemical Control of Aquatic Weeds, in A. Pieterse and K. Murphy (Eds.), Aquatic Weeds, the Ecology and management of Nuisance Aquatic Vegetation. Oxford University Press, Oxford, UK. Pp. 136-173.

Netherland, M. D. and K. D. Getsinger. 1992. Efficacy of Triclopyr on Eurasian Watermilfoil: Concentration and Exposure Time Effects. J. Aquat. Plant Manage. 30: 1-5.

Nichols, Stanley A. 1999. Floristic Quality Assessment of Wisconsin Lake Plant communities with Example Applications. Journal of Lake and Reservoir Management 15 (2): 133-141.

Pennington, Toni G., J. G. Skogerboe, and K. D. Getsinger, 2001. Herbicides/copper combinations for improved control of hydrilla verticillata. Journal of Aquatic Plant Management, Volume 39, pp. 56-58.

Roesler, Craig. 2008 Unpublished data. Wisconsin Department of Natural Resources, Hayward, Wisconsin.

Scheffer, Marten. 2004. Ecology of Shallow Lakes. Kluwer Academic Publishers, Norwell, MA. Pp 357.

Skogerboe, John and Kurt Getsinger, 2006. Selective control of Eurasian watermilfoil and curly-leaf pondweed using low doses of Endothall combined with 2,4-D. ERDC/TN APRCD-CC-05, pp. 1-15.

Smart, Michael, G. O. Dick, and R. D. Doyle, 1998. Techniques fro Establishing Native Aquatic Plants. Journal of Aquatic Plant Management Vol. 36, pp. 44-49.

Watson, C. 1989. Use of copper in aquaculture and farm ponds. IFAS Fact Sheet, FA-13. University of Florida, Gainsville, Florida, 2 pp.

WDNR Natural Heritage Inventory (NHI) Portal. http://dnr.wi.gov/org/land/er/nhi

http://dnr.wi.gov/org/land/er/nhi

Appendix A

2009 Beaver Creek Reserve Aquatic Plant Survey

Appendix B

Poskin Lake Property Owners Survey

Appendix C

Lake Property Owners Survey Results

Appendix D

WDNR NOR APM Strategy

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