weeds on prop

Photos: Diane Deming

You have probably heard about nasty weed problems at other lakes—infestations that have forever changed their lakes for the worse and created problems that seem beyond solution. Are there similar dangers to Clark Lake? A good question. We enjoy a beautiful spring-fed lake, known for its pristine, clear water–without troubling weed growth. New information suggests that change is on the way and that a potentially vexing problem is already upon us.

Clark Lake is threatened.

The threat is a new invasive species—the Eurasian milfoil, and a hybrid version of it. The hybrid is the product of the Eurasian milfoil crossbreeding with a similar Clark Lake weed that previously was not a problem. Should we be alarmed? This hybrid tends to propagate wildly. It potentially spreads to any area less than 15-feet deep.

Early infestations have not gone unnoticed. Others have observed it, and I have written about it. You can see it for yourself around the County Park at the east end where the tops of the weeds extend to the surface. Other areas in the lake are less noticeable as boat traffic chops off the first couple feet of the plants. This, too, is bad news. The clippings find their way to other locations and start new colonies.

You may ask “how do we know that this is a real threat?” Recently samples from suspected areas in Clark Lake were sent to Grand Valley State University for DNA testing. Sadly the results indicate that the Eurasian milfoil and its hybrid are here. That it can be found in at least three different areas of the lake shows that it has successfully multiplied and spread.

It’s likely the Eurasian milfoil arrived in a manner similar to the zebra mussel. The plant fragments found their way into Clark Lake from the hull, prop, trailer or live well of boats that had previously been used in infected bodies of water.

all weeds

Invasive weeds at the County Park, Clark Lake

Clark Lake is not alone in facing this problem, so others have searched for effective solutions. Research reveals several options.

Do nothing and see what happens. Watchful-waiting could be the most perilous and costly approach. A more extensive infestation requires a more extensive treatment program.

Use a weed harvesting machine. This is only a temporary solution in that the weeds grow back in greater numbers. The chopping action creates clippings that then migrate to other areas where the plants establish new colonies.

Apply herbicides. The DNR and DEQ approve the application of chemicals when used within their strict guidelines.

Seek a natural solution. The Eurasian milfoil and its hybrid have an archenemy–the water weevil. This insect eats the outside edge of the stalk of the milfoil. As a result, the plant dies. The weevil seems to prefer the Eurasian milfoil over native plant species. Research has not uncovered any negative impacts.

Visit the area around the County Park to visualize the impact of doing nothing. Considering what we have to lose, inaction seems inexcusable. There is work to be done. Upon hearing of the threat to our lake, several have already volunteered to be part of a group dedicated to defeating the threat. Would you like to join us? Please contact me at 529-9117.

-John Deming