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Biological Control Research

Milfoil Weevil Mass Rearing Pilot Study
Biological control studies are currently underway in Wisconsin to improve the science of applied biological control of Eurasian watermilfoil (EWM) using the Milfoil Weevil (Euhrychiopsis lecontei).  Many lake groups are eagerly awaiting the results of those studies and are interested in applying biological control in their lake.  However, weevils are no longer available for purchase in Wisconsin.  As we move forward in our understanding of the biological control of EWM, our Mass Rearing Pilot Study aims to create an approachable option for volunteers to affordably raise their own milfoil weevils. 

Our pilot study worked with several volunteer groups in 2011-2014 to test whether volunteers could successfully raise their own weevils on a mass scale.  Volunteers used the mass rearing method developed by our Executive Director and Regional AIS Coordinator, Amy Thorstenson, during her graduate studies on biological control of EWM. The study has found volunteers quite capable of executing the methods correctly, and we learned a lot with our pilot groups to help us work the “bugs” out of the system.  

One of our pilot groups, Lake Holcombe Improvment Association successfully raised over 10K weevils for their lake, and discontinued their rearing program in 2014 due to no further need. EWM was under control!  Read about their pilot project in the Powerpoint presentation below, or check out this episode of Silent Invaders on You Tube!

One problem has come about; weevils are no longer commercially available in Wisconsin, so our volunteer groups have nowhere to order their starter stock from!  We are currently working on solving this problem by testing a variety of collection and culturing methods.  

Once this problem is solved, we hope to make the mass rearing program available to volunteers statewide, to make biological control a viable option for their lake. 


Amy Thorstenson,
May 12, 2015, 12:01 PM
Amy Thorstenson,
May 4, 2015, 10:58 AM