By Naworaj Acharya, Research Scientist, Minnesota Department of Agriculture and Tana Haugen-Brown, Extension Educator and Private Pesticide Applicator Program Manager, PSEE.
High acetochlor levels can harm aquatic organisms, including plants, which disrupts aquatic ecosystems. These elevated acetochlor levels, typically observed in May and June, occur at the same time as early-season applications and subsequent rain events that cause surface runoff. The Minnesota Department of Agriculture (MDA) advises using Best Management Practices (BMPs) to help protect Minnesota’s water quality and tackle high surface water detections of acetochlor.
The herbicide acetochlor, found in products like Tripleflex, SureStart, Warrant, and Harness, is widely used in Minnesota to control weeds in crops like corn and soybeans. As sales continue to rise, acetochlor is increasingly detected at levels above the state’s chronic water quality standard (≈ 3.6 parts per billion) in many southern rivers and streams (Figure 1).
If acetochlor levels repeatedly exceed the state’s chronic water quality standard, the waterbody may be designated as impaired. This triggers the development of a response plan to promote responsible pesticide use and may lead to restrictions on acetochlor use. Currently, Silver Creek in Carver County is the only waterway impaired for acetochlor.
To keep using acetochlor while protecting water quality, the MDA suggests following acetochlor BMPs and general agricultural herbicide BMPs. Key BMPs that could help keep acetochlor out of waterways include:
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| Figure 1. Watershed map for acetochlor detections from 2017 to 2023. |
The herbicide acetochlor, found in products like Tripleflex, SureStart, Warrant, and Harness, is widely used in Minnesota to control weeds in crops like corn and soybeans. As sales continue to rise, acetochlor is increasingly detected at levels above the state’s chronic water quality standard (≈ 3.6 parts per billion) in many southern rivers and streams (Figure 1).
If acetochlor levels repeatedly exceed the state’s chronic water quality standard, the waterbody may be designated as impaired. This triggers the development of a response plan to promote responsible pesticide use and may lead to restrictions on acetochlor use. Currently, Silver Creek in Carver County is the only waterway impaired for acetochlor.
To keep using acetochlor while protecting water quality, the MDA suggests following acetochlor BMPs and general agricultural herbicide BMPs. Key BMPs that could help keep acetochlor out of waterways include:
- Rotate acetochlor with other herbicides or use more non-acetochlor herbicides. Talk to your dealer or agronomist to find the best non-acetochlor options for your farm.
- Use non-acetochlor herbicides early in the season when acetochlor runoff risks are high, and save acetochlor for later, especially for early post-crop emergence applications. Be sure to follow label guidelines for crop growth stage or height restrictions.
- Incorporate pre-plant acetochlor applications into the soil. Consider moving pre-crop emergence surface applications to pre-plant incorporated applications.
- Avoid applying acetochlor before rain events that could cause runoff. Specifically, refrain from applications when rainfall is expected within the next 48 hours.
- Maintain vegetative buffers along waterways, including in areas where rainwater and runoff collect before flowing into nearby surface waters like lakes, rivers, and streams.
- Consider acetochlor premixes over standalone acetochlor products when possible. Premixes usually contain less acetochlor, reducing the overall amount applied.
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