Brazilian Water Milfoil: A New Threat to Wisconsin Waters

While acquiring exotic plants is a pleasing pursuit, when these plants leave a contained area and enter into the wild, big problems can arise. In this case, the plant newly causing troubles in the state of Wisconsin is Brazilian Water Milfoil also referred to as Parrotfeather.

Recently the plant was found by the Wisconsin Department of Natural Resources in pool 5 of the Winona District of the Upper Mississippi River National Wildlife and Fish Refuge. Though this isn’t the first finding of the plant in the state, it is the most alarming — it is the first time that Brazilian water milfoil has been found in a non-isolated body of water, making extensive spreading into other bodies of water possible.

This South American plant is prized in aquariums and backyard water features because of its bright green color and attractive whorled leaves. The problem is that when this plant leaves a confined area and is released into the wilderness it quickly takes over, choking out native plant life forms. This plant is known to be even more aggressive than the troublesome Eurasian watermilfoil and even more challenging to eliminate.

As an emergent plant, the underwater and above water foliage of a Parrotfeather makes herbicides difficult to deliver effectively, and the plant’s leaves and stems are covered in a waxy cuticle that inhibits herbicide uptake. Plant-eating sterile grass carp are useless against Parrotfeather due to their woody stems.

Since all Brazilian water milfoil plants in the U.S. are female they do not produce seeds. They do, however, reproduce through fragmentation and can break apart and spread by trying to remove them mechanically. Currently, Lake Restoration is using a combination of diquat and “2, 4-D” to treat this recent invasion, and time will tell how many treatments will be required.

Though Parrotfeather proliferation is a newer concern to Wisconsin, boaters and fishing enthusiasts should follow the same practices they follow for the prevention of the spread of other invasive species:

  • Be diligent in efforts to not transport invasive and / or exotic species
  • Remove vegetation from boat trailers
  • Empty bait buckets on land
  • Pull drain plugs.
  • For those of you with exotic species of any variety, please remember to never release anything from your home into the wild.

If you notice this invasive plant in your body of water, please contact the DNR or Lake Restoration immediately.