As pesticide dealers and applicators and crop farmers may know, rules about using herbicides containing isoxaflutole have been changing in the past couple of years. Let’s try to clarify where you stand with regard to these products.

First, a little background. When the Environmental Protection Agency registered these products in 1998, there were concerns about the potential to contaminate both surface and groundwater, and potential effects on non-target crops, including vegetables. Wisconsin, Minnesota and Michigan opted to require the manufacturer, Aventis CropScience, to perform additional studies to demonstrate these products could be used without causing unintended harm.  Ultimately, Aventis chose not to register the products in those states.

The current manufacturer, Bayer CropScience, approached the Department of Agriculture, Trade and Consumer Protection in 2013 to revisit the issue.  Considering use histories in other states and some additional research, DATCP agreed to allow use of isoxaflutole in eight counties in 2016, with some added restrictions and water monitoring. This year, the list has been expanded to 12, due to difficulties in finding suitable groundwater monitoring sites in the original eight counties.

While the product may be sold by licensed pesticide dealers anywhere in Wisconsin, it can be applied only in these 12 counties.  Additional restrictions are required within these 12 counties, so be sure to follow both the product label and the Wisconsin product bulletin:

Columbia                             Fond du Lac                                        Jefferson                                          Sauk
Dane                                     Grant                                                    Lafayette                                          Walworth
Dodge                                   Green                                                   Rock                                                 Waukesha

The only isoxaflutole products registered for use in Wisconsin are Corvus Herbicide® and Balance Flexx®. Other isoxaflutole products cannot be used in Wisconsin.  A copy of the product labels including the Wisconsin product bulletin is available at https://www.kellysolutions.com/wi/, where you can search for pesticide product information.

These are the restrictions on use in the 12 counties:

• No application on sites classified as coarse-textured soil (sand, loamy sand and sandy loam) if the depth to groundwater is less than 25 feet, or is unknown.
• Application only from April 1 through July 31.
• No application within 66 feet of points where field runoff enters perennial streams and rivers. If the land is highly erodible, this 66-foot buffer must be planted to crop or seeded to grass.
• No application within 200 feet of natural or impounded lakes and reservoirs.

Additional studies are also occurring in Minnesota and Michigan. For more information, call 608-224-4503 or email stan.senger@wi.gov.

Source: Mike Murray, DATCP – Wisconsin Pesticide Program Manager