Follow setbacks when applying pesticides

Tana Haugen-Brown, Extension educator and Co-coordinator - Pesticide Safety and Environmental Education, Lizabeth Stahl and Angie Peltier, Extension educators – crops, and Larry VanLieshout, Minnesota Department of Agriculture

Photo: Larry VanLieshout, Minnesota
Department of Agriculture

As producers and applicators work in the fields this spring and summer, it’s important to remember that a number of pesticides require a setback between the application area and water resources. This is in order to protect water quality and it is important to remember that setbacks listed on the label are a legal requirement too. These setbacks may be for mixing/loading, application, or both. Be sure to check each pesticide label for more details.

Herbicides of particular concern in Minnesota due to detections in surface water include atrazine and acetochlor (e.g. the active ingredients in Harness, Calisto, Resicor, Tripleflex, and Warrant). Herbicides that have been detected in groundwater include atrazine, acetochlor, metolachlor, and metribuzin (metolachlor and metribuzin products include Boundary, Matador-S, Me-too-lachlor, and Stalwart). These herbicides can be found in numerous products as single active ingredients or as part of a pre-mix.

Herbicides of concern

Atrazine

Atrazine has the potential to leach into groundwater and run off to surface water. Leaching concerns are greatest on coarse-textured soils such as sands, loamy sands, and sandy loams. Be sure to check the label as recommended application rates can vary by soil type. Limit atrazine rates in fields with features such as sinkholes that allow the rapid movement of surface water and chemicals into groundwater. Do not mix, load, or apply within 50 feet of wells (active or abandoned) or sinkholes.

To protect surface water from atrazine runoff, labels specify the following practices:

• Do not apply within 66 feet of points where runoff enters perennial or intermittent streams and rivers.
• Do not apply within 200 feet of natural or impounded lakes and reservoirs.
• Do not mix or load within 50 feet of streams, lakes, or reservoirs.

Acetochlor

Acetochlor label setbacks include the following restrictions:

• For groundwater protection, do not apply within 50 feet of any well if the depth to groundwater is 30 feet or less for the following soil types:
• sands with less than 3% organic matter or
• loamy sands with less than 2% organic matter or
• sandy loams with less than 1% organic matter.
• For surface water protection, do not mix or load this product within 50 feet of perennial or intermittent streams and rivers and natural or impounded lakes and reservoirs.

Metolachlor

Metolachlor setbacks include the following restrictions:

• Do not mix or load within 50 feet of perennial or intermittent streams and rivers, and natural or impounded lakes and reservoirs.
• Do not mix, load, or apply within 50 feet of wells (active or abandoned), drainage wells, and sinkholes.

Metribuzin

The metribuzin label does not have setback requirements, but this product can be prone to leaching. Be sure to follow label application rates based on soil type and organic matter content.

Pre-mixes

In a pre-mix, setbacks must be followed for the most restrictive active ingredient. Regardless if a product is applied preemergence or postemergence to the crop, setback requirements must be followed in order to comply with pesticide laws.

Note: There are many other products besides the ones mentioned here that require a setback, so be sure to review all product labels before application.

For more information

Pesticide best management practices can be found at: https://www.mda.state.mn.us/pesticide-fertilizer/pesticide-best-management-practices

For more detailed herbicide best management practices to protect water quality, go to:
https://www.mda.state.mn.us/herbicide-best-management-practices-protect-water-quality

Products are mentioned for illustrative purposes only. Their inclusion does not mean endorsement and their absence does not imply disapproval.