09-24-2018 Council Packet - Laserfiche WebLink

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PEhCAN RIVEN watersh�dcristrict September 21, 2018 Gabriel Jabbour i onka Bay Marina RE: Flowering Rash – Detroit Cakes, mN chain of Cakes Dear Mr. Jabbour: 211 Holmes Street West, Suite 201 Detroit LaRes, PIN -sb5U1 (218) 846-0436 www.piwd.org Per your recent inquiry regarding tfie use of mechanical harvesting for control of Flowering rush, I will emphatically state, "Mechanical Harvesting WILL NOT WORK FOR CONTKOL and CONTRIBUTES 10 1 Rt 5PREAu and INCREA5E OF P1AIQ i DEM51 i y/ POPUGC i IONb of Flowering Rusfi". This statement is supported by peer-reviewed, published research. The District was unsuccessful in controlling Flowering rush using mechanical harvesters on three general develuNmCnt lakes, including a une-mile pa6lic Beacfi area on Detroit CaKe. Basea upon research tindings, tfie uistriLt sold its three mechanical harvesters and currently uses herbicides to manage Flowering rush and Curly leaf Nondweed. In 19/6, a Flowering rusfi intestation was first documented in Curfman Lake (Becker County, MN) and spread through the Pelican River chain inty Uciruit, IDluskrat, Sallie, IDIElissa, Plill Pond, and Bink lakes. By the mid-lygu's, Flowering rash reached nuisance conditions in the near sfiore areas and the first Flowering rush management efforts included hand -digging, deflowering, and limited chemical treatments- all failed tv curb the spread. Ouri, ig this time, the Pelican River watershed District, a local unit of guvernment, was petitioned by its citizens to set up projects, funded by assessments, to control aquatic plants on three lakes. i he District purLha�ed three mechanical harvester s and began To use mechanical harvesting as the principal management tout for controlling Flowering rush. However, by 2000, it became evident the use of mechanical harvesting was contributing towards the spread of Flowerinx rash. With only a few lakes in MN recreationally affected by Flowering rush, little was known about the biology, ecological impacts, yr effELtive control methods. Frostrated with the lack of research or knowledge base to effectively i-ontrul Flowering rusfi, the District reached out to various agencies and institutions to begin a 10 -year coordinated applied science research effort to anderstand the biology and eculugy of Flower ing rush, and built upon this knowledge base to further develop effective fier6iciae control measures. i ne District contracted witfi Mississippi -state Oniversity, LunLurdia College, and the Army corps of Engineers to conduct this multi-year research effort. 1. Phenology and Eiulugy study – vast majority of FR density is from shoreline to b ft water aeptfi (targeted herbicide application area); Flowering rush is mostly below ground (root rhizome) unlike other AIS plants, therefore mechanical Rarvesting will nut work and management efforts need to target Below ground Biomass redaction using herbicides. In addition, mechanical harvesting7hand pulling was contributing to the spread and increases in plant density because of its mode of reproduction. 2. Herbicide Mesocosm Study – Diquat and Endothall are promising herbicides. 3. In lake Field trial —Diquat is effective, not endothall. 4. Farther in -lake stadies—twice a year regimen of diyuat (injected into the water column) with first treatment in late Jane/ early July followed by a second treatment in late July/early August for a 3-5 year timeframe (95-99% below ground biomass redur-tion). 5. Bulrush and Flowering rush mixed stand study – Can safely treat mixed stands of Bulrush and Flowering rush by injecting Diquat into the water column, applying same methods and tinning as the in -lake study resuits. FKwD Ras treated 65 acres using this method. 6. Adaptive Management long Term Control Strategy— After 3-5 years of treatment, implemented adaptive management – twice year, once, or no application treatments in plotted areas depending upon, percentage of r egrowth. i wice-year herbicide applicatiuns result in aensity reauLtions; one application results in maintaining torrent density (sparse).