Eurasian and hybrid watermilfoil genotype distribution in Minnesota

Invasive Eurasian watermilfoil is known to hybridize with native Northern watermilfoil in some lakes in Minnesota. This hybrid watermilfoil is also invasive and some strains have shown resistance to management efforts including herbicide treatments. However, much is unknown about the genetic makeup, diversity, and distribution of hybrid watermilfoil throughout the state, making management efforts very difficult. 

In partnership with Montana State University, this project will quantify the genetic diversity of Eurasian, hybrid, and northern watermilfoil in sixty Minnesota lakes and will help answer questions such as:

  • Do different genotypes present increased invasiveness or tolerance to control techniques?
  • Are there patterns of hybrid watermilfoil invasion? Are plants hybridizing within a lake, or is one hybrid strain being moved among lakes?
  • How is hybrid watermilfoil interacting with native plant communities?

The collected watermilfoil samples will first be genetically identified as Eurasian, northern, or hybrid. Later, the hybrid samples will be genotyped using molecular genetic techniques to determine whether specific genotypes are widespread or have restricted distribution, related to management activities or environmental factors, or if they’re hybridizing within lakes.

Understanding the patterns of invasion as well as genetic diversity of this plant to help lake managers develop and refine management strategies.


Milfoil samples were collected from 33 lakes in 2017, and samples were sent to the Thum lab at Montana State University for genetic analysis. Eurasian watermilfoil was found in 19 lakes, hybrid watermilfoil was found in 18, northern watermilfoil in 10, and all three were found in one lake. In 2018, researchers selected and sampled 5 treatment and 5 control lakes with point-intercept surveys, in order to characterize the genetic composition and plant community structure. Treatment lakes were subjected to a range of herbicide treatments, and will be resampled in late summer 2018 to assess changes.

Project manager: Ray Newman

Funded by: Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources

Project start date: 2017

Estimated project end date: 2019

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