Tom's Blog

Monday, May 26, 2008

Ugly area of roadside garlic mustard

Garlic mustard is by now famous in southern Wisconsin as our worst invasive plant. People everywhere are working to eradicate it. Roadsides are major eradication targets because this is the most common mode of transmission from one place to another. At Pleasant Valley Conservancy, we have been at the forefront of efforts to remove it from roads in the Town of Vermont. Fortunately, there are only a few serious patches, and the Town Board has been very receptive to these efforts, even providing some money to get a contractor involved.

Imagine my dismay when Kathie and I took a drive on several roads in the Towns of Arena and Ridgefield, Iowa County, passing the worst roadside infestations of garlic mustard we have ever seen. Miles and miles of flowering garlic mustard plants that had taken over and would be making seeds soon. This area, along Ray Hollow and Knights Hollow Roads (and probably others), is a disaster. All native plants have been wiped out. If these roadsides are mowed seeds will be transported far and wide.

The situation is so bad in these areas that herbicide spraying is the only option. Garlic mustard is very sensitive to the common weed killer 2,4-D, which has the advantage that it is only active against broad-leafed plants. Grasses are not affected. However, spraying the named roadsides is far beyond a hand-held or backpack sprayer. Gallons of spray are going to be needed, from a boom sprayer.

The Invasive Plants Association of Wisconsin has a very useful web site with important information on the control (among others) of garlic mustard. I have added links to their pages on community weed control and on the use of herbicides.

Roadside spraying with herbicides received a "bad press" about 35 years ago. The objection then was that spraying would wipe out "good" native vegetation. This may have been true, but when major infestations of such bad plants as garlic mustard are allowed to develop, there is no other option.

Citizen input is needed, not only in Iowa County, but wherever major infestations occur.

The Wisconsin Department of Transportation manages weed control on state and federal highways and uses herbicides judiciously. However, they do not work on county or town roads.


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