This is an answer to Tracy Nordstrom and Terrill Brown - thought others of you might be interested, Annie Young citywide Par Commissioner
>From: "Lee, Jeffrey T." <[EMAIL PROTECTED]> >To: "Young, Annie" <[EMAIL PROTECTED]> >Cc: "Schmidt, Michael P." <[EMAIL PROTECTED]>, > "Aplikowski, Sara" <[EMAIL PROTECTED]>, > "Brown, Natalie" <[EMAIL PROTECTED]>, > "Doucette, Sharon" <[EMAIL PROTECTED]>, > "Janet, Amanda" <[EMAIL PROTECTED]>, > "Perniel, Michael" <[EMAIL PROTECTED]>, > "Rossing, Abigail" <[EMAIL PROTECTED]> >Subject: RE: [Mpls] Milfoil on Calhoun >Date: Tue, 23 Jul 2002 16:26:04 -0500 >X-Mailer: Internet Mail Service (5.5.2653.19) > >Current conditions: >Eurasian Water Milfoil growth is much more robust this year than it has been >the last few years >number of possible explanations - dry spring and thus better water clarity; >late ice out and milfoil grows under the ice and gets a jump on natives; >milfoil is cyclic and we may (especially in Harriet) be at the top of the >4-5 year cycle. What you see in the lake is indeed milfoil not algae - >milfoil grows to the surface in water that is 16 feet or less in depth. The >harvesters cut milfoil down to a four foot depth to allow use of the lakes >and the milfoil grows back at a rate of an inch a day. Given that all of >the littoral zone of the lake (areas with rooted aquatic vegetation ~16 feet >and less in depth) the fragments have little place to root that does not >already have milfoil. > >MPRB crews are harvesting 6 10-hour days per week with two harvesters and we >target the boat launches, beaches and fishing docks first and then general >recreational areas second, with some attention to aesthetics after that. >The harvester operations moved to Lake Harriet on Saturday June 22nd after >spending most of three weeks working on Lake of the Isles and Lake Calhoun. >We were working six 10 hour days up until the July Fourth weekend (no >Saturday work on July 6th or the holiday on the 4th). We are now back on >6/10s and moved back to Calhoun/Isles after working on Cedar Lake for a >couple of weeks. The harvesting operation includes two milfoil harvesters >and two flatbed trucks that are removing from 20 - 25 truck loads of milfoil >per day (up to 20 tons of milfoil a day). The harvesters start at 6:00 AM >and are off the lake around 2:30 in the afternoon before heavy use starts so >many people only see them anchored in the evening. The channels are areas >that are targeted for extra harvesting as they are areas of highly >concentrated use. > >Research results: >The University of Minnesota Milfoil researchers are sampling this summer and >stocked about 1000 weevils into Harriet last week. Weevils and weevil damage >has been very low at all of the lakes. There is no evidence of adequate >weevil densities in the four lakes and other research suggests that high >sunfish densities in these lakes may be limiting weevil and other herbivore >densities. Apparently the plants are starting to disappear in Isles due to >poor clarity as the summer algae growth proceeds. Among the lakes and over >time, water clarity appears to be influencing plant density and biomass. >Cedar has consistently had a high plant biomass since 1997 and improved >clarity in Isles in 2000 resulted in similar high biomasses. The relatively >poorer late season clarity in Calhoun was associated with low plant biomass >as was the low clarity at Isles in 1997-1998 and 2001. > >Harvesting Constraints: >The DNR rules allow that no more than 50% of the littoral zone - that area >of a lake less that is 16' deep or less - can be harvested for fish habitat >protection - in the absence of native vegetation which was the case in many >areas before milfoil there was little habitat. Definitely not a reason to >have milfoil but also a reason to not create an aquatic desert by killing or >removing all of the vegetation. MPRB spends $70-80,000 on weed harvesting >on the lakes per year. > >Many areas of the country have had milfoil much longer than Minnesota - >Madison area lakes since the 1960s - and have learned to cope with and >manage the weed. Unfortunately at this time there appears to be no reason >to believe that milfoil is going away, we will only be seeing more exotic >species introduced and more problems created by people who either do not >know about the movement of exotic invasive - or don't care. > >Treatment Options: >At this point in time MPRB has chosen not to chemically treat the lakes for >milfoil as we would have to treat all of the lake area and all of the chain >at once. Fuoridone is registered for the control of milfoil and if the >concentrations are held within a fairly narrow range for 30 days it is >possible to control milfoil and only a few other non-target species are >killed. Control is achieved 30 to 90 days following treatment and is >effective for up to 12 months. > >Treatment of the chain would require between an initial treatment of 160,000 >gallons of the herbicide in the spring (May) and follow-up treatments that >could be needed as frequently as every rain storm (of up to 110,000 gallons >of herbicide per additional treatment). Swimming is prohibited for 24 hours >after each treatment. At higher concentrations many other aquatic plant >species are killed. Multiple applications are required as the >concentrations are monitored through lab tests and the levels need to be >maintained above a minimum concentration (8 - 20 ppb range). This means >that every time it rains the concentration would have to be measured and >another application completed to keep the concentration above the minimum >levels needed for control. > > > >- _______________________________________ Minneapolis Issues Forum - A Civil City Civic Discussion - Mn E-Democracy Post messages to: [EMAIL PROTECTED] Subscribe, Unsubscribe, Digest option, and more: http://e-democracy.org/mpls
