Conservation Minnesota

Bio-Control: Using Nature to Fight Nature


Invasive Leafy Spurge showing signs of Flea Beetle Larva damage. Caleb Ashling – Natural Resources Technician: City of Burnsville photo credit.

Often in our lives we hear the phrase, “Ignorance is bliss.” When it comes to invasive species, I think that truer words have never been uttered. Having worked with invasive species (by which I mean non-native vegetation) for much of my professional career, I can honestly tell you that I wish I did not know how to identify these terrorizing plants but there they are: every time I drive down the road, talk a walk in a park, or go out on the lake I see hundred if not thousands of them everywhere I turn. Once you start looking for them you see them everywhere. I made the mistake of pointing out Sweet Clover to my fiancé who then asked if it is a common invasive. I said, “No, I rarely see it around!” The next thing I know, we are driving to southern Minnesota from the metro area and I spot it constantly in the ditches of every highway we are on. If you notice a plant in the ditch of a major roadway, chances are it is an invasive species, especially if it is “pretty” and has purple or yellow flowers.

So, in this world of hopelessness, what is one to do? There are too many to pull by hand and spraying chemicals is nobody’s first choice if there is an alternative. What could possibly be the answer to this seemingly impossible problem? My answer, and the answer that many people are starting to preach, is biological control (or bio-control for short).

Bio-control has emerged in recent years as an answer to a challenging question: how do we naturally get rid of invasive species without resorting to time consuming hand weeding or dangerous chemicals. Bio-control relies on the idea that invasive vegetation is a nuisance because these plants where introduce without any natural pests or diseases and therefore can outcompete almost all of our native counterparts.  Classical bio-control is a fairly simple process: introduce natural pests to the exotic organism and let nature do what it does best: compete for resources.


Root Boring Weevil used to control the invasive Spotted Knapweed. Caleb Ashling – Natural Resources Technician: City of Burnsville photo credit.

In Minnesota, bio-control is used for a variety of invasive vegetation. Currently, there are bio-controls available in Minnesota for Purple Loosestrife, Leafy Spurge, Spotted Knapweed and in the development stages are Garlic Mustard, Common Buckthorn and Common Tansy. The most common bio-control target in Minnesota is Purple Loosestrife. There are four organisms that have been found effective in targeting this invasive wetland plant: two leaf-feeding beetles, one root-boring weevil and one flower-feeding weevil. These little bugs are proving quiet effective and have even started spreading to new sites to feast on Purple Loosestrife. All bio-control options in the United States are rigorously tested by the Department of Agriculture to ensure they themselves will not become a new pest.

More government agencies in Minnesota use bio-control than one might think. The City of Burnsville is a great example. I worked as a Natural Resources Intern with the city when they first started their bio-control program in 2011. Their target was a small patch of Leafy Spurge in one of their parks. It was a large enough area to be able to hand the experiment but if it didn’t pan out, it wasn’t a hot spot in the city.  Three years later and it seems like the Flea Beetles that were released are still thriving and doing their thing. Caleb Ashling, Burnsville’s Natural Resource Technician and all together Ecological Badass, has recently introduced two more bio-control projects in the city: one targeting Purple Loosestrife and one targeting Spotted Knapweed.

The downside of using bio-control is that it takes time to show results. Spray herbicide on a patch of land and you will see results in a few days but bio-control takes time and patience. The most successful bio-control users are the ones that release their predators then do nothing for the next 5-10 years. If you get too eager and do something that will harm your progress, such as spraying at the wrong time, you will hurt your chances of success.

Bio-control might not be a perfect solution but it is a natural solution. It is easy, cost-effective, and a viable long term solution. It does take time but is well worth the effort.  Invasive species are a major issue and now is the time to think outside the box and try something new. Who would have thought the answer to our invasive species problem would involve so much sitting by and doing nothing but letting nature do what it was designed to do? Sounds like a good plan to me.

About Whitney Thesing

Whitney Thesing
Whitney Thesing graduated in 2009 from the University of Minnesota - Morris with degrees in Economics and Environmental Studies.  After graduating, she has worked in many areas of natural resources including water quality, invasive species management, ecological experiments, phenology, and native ecosystem restoration. She volunteers her time as a member of St. Louis Park's Environment and Sustainability Commission, focusing on education and behavior change, and water resources, two causes near to her heart.
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