Lake Operations

Current Topics of Importance




 Purple Loosestrife: It’s A Pretty Big Problem

Between July and September, you may notice a tall, bushy plant with very attractive magenta colored flowers growing along your shoreline, perhaps in a wetland, along a wet ditch area or maybe in your garden. This striking plant is tall enough to shield unwanted views and grows with little or no care so the uninformed might see it as a charming shrub. But once the facts are presented, it becomes very clear that this plant, Purple Loosestrife, Lythrum salicaria is nothing but trouble.

A native of Europe and Asia, Purple Loosestrife was introduced in the United States as a garden plant. It reproduces predominantly by seed however reproduction by roots and underground stems is also common.  Due to rapid reproduction (a mature plant can produce up to 3 million seeds), vigorous growth and lack of natural predators, Purple Loosestrife quickly escaped cultivation and has since invaded many of our valuable natural areas.

Purple Loosestrife can take over wetlands and lakeshore areas within a few years. These natural areas are important habitat for many native species of plants, birds, insects, amphibians, and animals, which often disappear when Purple Loosestrife outcompete the native plants in an area. Purple Loosestrife is so detrimental that is has been added to the Wisconsin’s Invasive Species law, Chapter NR 40 as a restricted species. As a restricted species, it is illegal to transport, transfer or introduce all cultivars, hybrids and varieties of Lythrum salicaria and L. virgatum.

In order to prevent new infestations it is important to identify and  eliminate large and small populations of Purple Loosestrife.  If care is taken to minimize soil disturbance, single plants or small populations can sometimes be carefully dug out and disposed of. It is important to make sure all of the root is removed or new shoots will grow. Once plants start to flower it is important to remove the flowering stalks carefully and dispose of them away from water. This is done by bending the flowering stalk into a bag and cutting it so that it falls into the bag. Allow the plants to dry and burn if possible so that seeds do not disperse. On large sites, chemical control may be an option. If the  Purple Loosestrife is growing near  water, a DNR permit may be required and the chemical may need to be one that is acceptable for use on water. For more information about aquatic plant management and control visit the WI. Department of Natural Resources (DNR) website at and/or contact Heidi Bunk, DNR Water Resources Management Specialist at (262) 574-2130. Using either control method will require continued monitoring and control efforts because seeds in the soil will continue to germinate for several years.

In larger, more severe infestations, manual and chemical control may be too expensive or labor intensive. However, the use of specially selected and highly tested insects that feed on Purple Loosestrife have been shown to be highly successful. This method is known as biological control (biocontrol) and research has shown that these specialized insects reduce both plant height, seed output and overall plant numbers. This allows other, native plants to regain control in a few years. Wisconsin DNR and UWEX have created a program in which hundreds of citizens have raised and released millions of beetles that feed on Purple Loosestrife. For more information about Purple Loosestrife biocontrol, contact Brock Woods, WI Purple Loosestrife & Wetland Invasive Plant Program Coordinator at (608) 266-2554, email at            

For those gardeners that enjoy the magenta flowers, there are several attractive alternatives, such as: Blazing star, Liatris pycnostachya. Foxglove, Digitalis purpurea, Obedient Plant, Physostegia virginiana and  Steeplebush, spiraea tomentosa. These, and a few other look-a like plants can sometimes make identification difficult. For assistance with identification of Purple Loosestrife in Walworth County, please feel free to contact Audrey Greene, Lake Specialist & Aquatic Invasive Species Coordinator at 262-741-7902 or                                                                                                                                                                                                                    

Citizen Lake Monitoring for the Future of Your Lake

The Citizen Lake Monitoring Network (CLMN), formerly Self-Help Lake Monitoring, is a collaboration between citizen volunteers and the Wisconsin Lakes Partnership (Wisconsin DNR and UW-Extension and Wisconsin Lakes) that began in 1986 as a means to involve citizens and increase lake protection.  There are currently over 1200 CLMN volunteers in Wisconsin collecting information about their lakes. The work is unpaid, but the results are invaluable. As monitors work on their lakes, they acquire knowledge that helps them become more effective at protecting their lakes. They also collect data that very likely would not be collected without them, because there is simply not enough DNR staff available.

CLMN volunteers may choose to monitor for water clarity using a Secchi disk or they might be interested in collecting water chemistry data.  Some monitors decide they would rather learn to identify and map native aquatic plants, while others prefer to look for one or more of the aquatic invasive species (AIS) that threaten their lake. The decision is totally up to the volunteer but whatever their choice, or choices, the DNR and UW-Extension CLMN staff provide the equipment and training.

There are currently 23 lakes in Walworth County that have water quality data on the DNR website thanks to volunteer monitors. Depending on the lake, this data may go back for more than 20 years. Anyone that is interested and has access to a computer can easily find all water quality monitoring data on the by visiting the DNR website lakes page at and then clicking on “Lakes A-Z”.

In recent years many CLMN volunteers have started monitoring their lake for new AIS introductions or tracking existing populations of AIS to protect their lakes.  It is well known that AIS can cause large problems on lakes. Aquatic invasive plants can clog boating lanes and diminish recreational opportunities Aquatic invasive plants and animals reduce essential habitat and out compete native species.  The economic damage to taxpayers for management of the AIS that are currently in Wisconsin waterways is currently several million dollars per year. New AIS will mean higher costs, however, finding new populations of AIS before they become established has been shown to lower control costs and provides a much higher possibility of eradication.

Through the CLMN training, volunteers are taught to monitor their lake for one or more of a variety of AIS. They will learn where and when to look for the species they decide to monitor and what steps to take if they discover a suspicious plant or animal. Volunteers do not need to have any previous experience or knowledge of AIS. They also do not have to devote a huge amount of time. An hour or two once a month through the boating season is more than enough for most species and several species require considerably less time than that. Some monitors look for AIS by checking at boat ramps and beaches. Others look in deeper water areas. It is entirely up to the volunteer to decide what they want to do. 

The lakes in this county are some of our most precious natural resources and they need the best protection we can give them. Educating lake users about AIS and prevention methods has increased protection but we can always go one step more. Please consider becoming a CLMN for AID monitor on your lake.  If you have questions or would like more information please contact Audrey Greene at (262) 741-7902 or

     New AIS Fact Sheets


Aquatic Invasive Species




Pier Pick-Up Dates:

Main Lake   -  June 13, 27 - July 11, 25 and August 1, 15

Inlet/Outlet  -  June 14, 28 - July  12, 26 and August 2, 16

                       Starting at 6:00 am. (all dates are weather permitting)

The request for Pier Pick-Up must be called into the office before 9:00 pm the Sunday before the pick-up date.  262-728-4100 (the recorded message will give you instructions) Your pier must be numbered or identified in such a manner that we can locate it.

Pier Pick-Up is for aquatic plants only and must be placed at the end of the pier and clearly visible to the Harvesting Crew.  We will not pick up plants mixed with rocks, lawn or garden debris, branches, garbage, etc.

Aquariums & Aquatic Invasive Species (AIS)
As fall winds down and winters cold temperatures freeze the lake, those of us that love the water look for other ways to experience the pleasure of it. Many people find that the underwater world of aquariums do provide the relaxation and beauty they crave.
Pet stores and internet sources make setting up and populating an aquarium easy and fun, but aquarium enthusiasts need to be aware that Chapter NR 40, Wisconsin’s Invasive Species Identification, Classification and Prevention law has resulted in the regulation of some popular, but highly invasive, aquarium plants.  Several of these prohibited and restricted plants are sold through the internet and out of state sources. They are often promoted as species that will beautify and oxygenate your tank, and while they may indeed be beautiful, they could cause huge problems for Wisconsin waterways.  Below is a list of popular aquarium plants that are prohibited or restricted. Prohibited species may not be transported, possessed, transferred or introduced in Wisconsin. Restricted species may not be transported, transferred, or introduced in Wisconsin.
There are many aquarium plants that are not listed as AIS in Wisconsin so there will be no shortage of attractive plants for aquatic gardeners to enjoy. Regardless of whether or not an aquarium species is regulated in Wisconsin, never dump any plants, fish or animals into any lake, pond or stream. Besides the fact that it is illegal and the fines are quite large, they could do immense harm to our waterways.
To further protect Wisconsin from AIS, verify the scientific names of any aquatic plants purchased and inspect all shipments/purchases to ensure that the plant ordered is indeed the plant received and that there are no ‘hitchhikers’ included. Dispose of unwanted aquarium species responsibly. Check with your retailer for possible returns or bag and throw in the trash.

Aquatic Invasive Plants sold for aquariums

Scientific name

& Synonyms

Common Name(s) Notes
Cabomba caroliniana Fanwort, Carolina fanwort Prohibited; submersed perennial; native to southeastern United States; often confused with water milfoils and water buttercup
Crassula helmsii Australian stonecrop, New Zealand pygmyweed Prohibited; sold as an oxygenator for ponds and aquariums
Egeria densa Brazilian waterweed; Brazilian elodea Prohibited; sold as an oxygenator for ponds and aquarium; native to South America; may be confused with Hydrilla verticillata and Elodea nuttallii
Hydrilla verticillata Hydrilla; water thyme; Florida elodea Prohibited; submersed perennial; native to Asia; introduced to Florida in 1958 as an aquarium plant; may be confused with Elodea canadensis, Egeria densa
Hydrocharis morsus-ranae European Frog-bit Prohibited; Free-floating perennial; can be confused with water lily and Limnobium spongia
Lagarosiphon major Oxygen weed; African elodea, African waterweed Prohibited; submersed perennial; may be confused with Elodea Canadensis and Elodea nuttallii
Myriophyllum  aquaticum Parrot feather Prohibited; submersed perennial; may be confused with other milfoils
Myriophyllum spicatum Eurasian water milfoil Restricted; submersed perennial; may be confused with other milfoils
Najas minor Brittle, lesser, bushy, slender, spiny and minor naiad; waternymph Prohibited; submersed annual, reproduces by seed and fragmentation; easily confused with native Najas spp.
Nymphoides peltata Yellow floating heart Prohibited; bottom rooted perennial with floating leaves;
Potamogeton Curly-leaf pondweed Restricted; submersed perennial; introduced as an aquarium plant
Trapa natans Water chestnut Prohibited; annual floating leaf emergent

 For more information see the Wisconsin Department of Natural Resources website at, or contact Audrey Greene, Walworth County Land Use & Resource Management at 262-741-7902 or


             LAKE SPRAYING PLANS 2014

We have again been granted a permit from the Department of Natural Resources for chemical treatments on Delavan Lake.  A copy of the permit is available by contacting the District office and on the Aquatic Plant Harvesting page of this website. 

Chemical spraying for nuisance aquatic plants is planned as follows:

Inlet Area - The first treatment will be in early May if conditions warrant.  Additional treatments as needed.  The treatment area will be around the piers and up to 150 feet from shore..

Outlet Area -The first treatment will be in early May if conditions warrant.   Additional treatments as needed.  The treatment area will be around the piers and up to 150 feet from shore.

Southwest Bay - This area goes from South Shore Manor west to the Island.  Treatment is planned for early June if conditions warrant.  The treatment area will be around the piers and up to 150 feet from shore.

Northwest Bay - This area goes from Chicago Club west to the Island.  Treatment is planned for early June if conditions warrant.  The treatment area will be around the piers and up to 150 feet from shore.

North Shore - This area extends from the Yacht Club to Assembly Park.  Treatment is planned for early June if conditions warrant.  The treatment area will be around the piers and up to 150 feet from shore.

We again plan to treat the entire developed shoreline for algae control.  The initial treatment is planned for a week to 10 days before the July 4th holiday.  Additional treatments may occur if conditions warrant.

All planned chemical treatments are subject to lake and weather conditions as well as Department of Natural Resources approval.


                  Aquatic Plant Management Map



Our plans for mechanical harvesting remain much the same as past years.  We intend to launch our harvesting equipment the week of May 19th and begin the initial harvesting of plants in the access channels at that time.  After June 15th we will harvest all areas of the lake as conditions warrant.  

For those of you who would like more information on zebra mussels here are some web sites to check:

 Blue-Green Algae In Wisconsin Waters


New regulations regarding the placement of Piers in Wisconsin waters has gone into effect and an overview of these regulations can be found at:


Town of Delavan has a new Bouys/Rafts Permit