Comparison of hybrid and parental watermilfoil growth and phenology in Minnesota. Wesley J. Glisson and Daniel Larkin

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1 Comparison of hybrid and parental watermilfoil growth and phenology in Minnesota Wesley J. Glisson and Daniel Larkin

2 Eurasian watermilfoil (EWM) Long history of invasion and management Found in North America prior to 1950 Discovered in Lake Minnetonka in 1987

3 Northern watermilfoil (NWM) Native watermilfoil species Morphologically and genetically similar to Eurasian watermilfoil Moody and Les, 2002

4 Moody and Les, 2007 Hybrid watermilfoil (HWM) Cross between Eurasian and northern watermilfoil Shares characteristics of both parent species

5 Hybrid watermilfoil (HWM) Potentially more invasive than EWM, i.e., hybrid vigor Higher growth rates than EWM in lab trials (LaRue et al. 2013) Evidence of herbicide tolerance (LaRue et al. 2013; Berger et al. 2015; Netherland and Willey, 2017) LaRue et al. 2013

6 Objective Compare the growth and phenology of hybrid watermilfoil (HWM) to its parental species (EWM and NWM) by examining the timing and amount of:

7 Objective Compare the growth and phenology of hybrid watermilfoil (HWM) to its parental species (EWM and NWM) by examining the timing and amount of: 1. Surface matting

8 Objective Compare the growth and phenology of hybrid watermilfoil (HWM) to its parental species (EWM and NWM) by examining the timing and amount of: 1. Surface matting 2. Flowering

9 Objective Compare the growth and phenology of hybrid watermilfoil (HWM) to its parental species (EWM and NWM) by examining the timing and amount of: 1. Surface matting 2. Flowering 3. Stem growth

10 Study lakes Species Lake County Year(s) EWM Cedar Hennepin Phalen Ramsey Auburn Carver 2018 HWM Otter Anoka Thomas Dakota Cobblestone Dakota 2018 NWM Big Carnelian Washington Orchard Dakota Spectacle Isanti 2018

11 Sampling methods Surveyed lakes and recorded locations in watermilfoil beds Randomly selected 5 locations for repeated sampling ( 50 m apart) Sampled each location every 2-4 weeks during growing season May November 2017 May present 2018 Sampled each location once during winter January/February 2018

12 Sampling methods at the surface 5 locations within each lake 5-m radius from boat Surface matting Cover of plants floating at surface Flowers Number of flower heads (inflorescences)

13 Sampling methods below the surface Novel sampling device Underwater camera with live feed to tablet Camera aimed at a sampling board with 30 cm 70 cm frame 4 samples taken off the side of the boat at each location Counted stems at 0.5 m increments

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17 Results at the surface

18 Flowers

19 Flowers Number of flower heads EWM HWM NWM

20 Flowers Number of flower heads a a 0 EWM HWM NWM

21 70 b Flowers Number of flower heads a a 0 EWM HWM NWM

22 HWM EWM NWM 100 Number of flower heads 50 0 Jun Jul Aug Sep Oct Nov Dec

23 HWM EWM NWM 100 Number of flower heads 50 0 Jun Jul Aug Sep Oct Nov Dec

24 HWM EWM 5 NWM 4 Number of flower heads May Jun Jul Aug

25 HWM EWM NWM 200 Number of flower heads May Jun Jul Aug

26 Surface matting

27 4 3 Surface cover (cover class) Surface cover Surface matting >25-50% >5-25% >1-5% 2 >0-1% 1 0 EWM HWM NWM

28 4 3 Surface cover (cover class) Surface cover Surface matting >25-50% >5-25% b >1-5% 2 a >0-1% 1 b 0 EWM HWM NWM

29 4 3 Surface cover (cover class) Surface cover Surface matting >25-50% >5-25% c >1-5% 2 a >0-1% 1 b 0 EWM HWM NWM

30 >50-75% HWM EWM >25-50% NWM >5-25% Surface cover >1-5% >0-1% 0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

31 >50-75% HWM EWM >25-50% NWM >5-25% Surface cover >1-5% >0-1% 0 Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

32 Results below the surface

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35 HWM EWM 80 NWM 60 Stems / m Jul Aug Sep Oct Nov Dec Jan Feb

36 HWM EWM 80 NWM 60 Stems / m Jul Aug Sep Oct Nov Dec Jan Feb

37 Conclusions HWM produces more flowers and flowers earlier than EWM and NWM Varies by year HWM has greater surface matting than EWM and NWM Varies by year Consistently greater than NWM HWM produces an intermediate number of stems

38 Conclusions Field-based evidence of hybrid vigor HWM appears more invasive than parental EWM Earlier and increased flowering may increase HWM spread and provide a competitive advantage Increased surface matting may shade out natives more than EWM More aggressive management may be needed for HWM infested lakes Knowledge of which lakes have HWM is important Crucial to distinguish HWM from EWM and NWM

39 Acknowledgements UMN Carli Wagner Michael Verhoeven Rafael Contreras-Rangel Carolyn Kalinowski Noah Berg Ranjan Muthukrishnan Jasmine Eltawely Ray Newman MNDNR Keegan Lund Kylie Cattoor April Londo Mike Netherland, University of Florida Rachael Crabb, Minneapolis Parks and Recreation Board Eric MacBeth, City of Eagan Adam Robbins, City of Saint Paul