Monitoring
History
In 1987, the Minnesota Legislature amended the Minnesota Pesticide Control Law (MN Statute 18B.04). It directed the MDA to determine the impact of pesticides on the environment, including the impacts on surface water and groundwater.
In response to this charge, the MDA initiated a pesticide groundwater monitoring program in 1987. In 1991, surface water monitoring began. The MDA also conducts edge-of-field water quality monitoring for nutrients and sediment. The MDA has one of the most comprehensive pesticide monitoring programs in the country.
Surface Water Monitoring Results
In 2025, the MDA collected 1,090 pesticide samples from 57 rivers and streams, 52 samples from 4 rainfall monitoring locations, and 6 samples from 1 lake. The MDA analyzed for up to 185 pesticide analytes during each sample collection event. Seventy-seven different pesticide analytes were detected. The most frequently detected parent pesticides included 2,4-D (88%), metolachlor (83%), clothianidin (79%), atrazine (74%), and sulfentrazone (53%). Cyanazine acid and flufenacet OXA were detected for the first time by MDA in a river or stream.
A total of 163 pesticide detections in the ambient river and stream monitoring network were above the numeric component of the Minnesota water quality standard or United States Environmental Pollution Agency (USEPA) aquatic life benchmark (ALB) in 2025. Two neonicotinoid insecticides, clothianidin (87 detections greater than the numeric component of the USEPA ALB) and imidacloprid (56 detections greater than the numeric component of the USEPA ALB), accounted for 88% of the pesticide detections greater than a reference value. The insecticides, chlorpyrifos, fipronil and malathion accounted for 8% of the pesticide detections greater than a reference value. Herbicides, acetochlor and pyroxasulfone accounted for 4% of the pesticide detections greater than a reference value.
Clothianidin and imidacloprid detections were widespread in agricultural regions of western and southern Minnesota and concentrations exceeded the numeric component of the USEPA ALB. Clothianidin was detected in 67% to 100% of the samples and was greater than the numeric component of the USEPA ALB in 6% to 38% of the samples. Imidacloprid was detected in 19% to 51% of the samples and was greater than the numeric component of the EPA ALB in 6% to 26% of the samples.
All pesticide detections in Double Lake were very low compared to the applicable reference value, and 21 pesticide compounds were detected in rainfall in 2025.
Surface Water Pesticides of Concern
Following guidance in the Pesticide Management Plan, the MDA has designated 5 pesticides as a “surface water pesticide of concern”. This designation is made by the Commissioner of Agriculture following detection(s) of a pesticide in a surface waterbody at a concentration of concern relative to a water quality reference value, and that the detection(s) is not the result of misuse or unusual or unique circumstances. The designation prompts actions to address the pollutant including the development and promotion of BMPs, additional monitoring, and increased data analysis.
| Active Ingredient | Type | Example Trade Name* |
|---|---|---|
| Acetochlor | Herbicide | Harness, Confidence, Volley NXT |
| Atrazine | Herbicide | Astrex, Acuron, Callisto Xtra |
| Chlorpyrifos | Insecticide | Duraguard, Pyrofos |
| Clothianidin | Insecticide | Arena, Belay, Poncho |
| Imidacloprid | Insecticide | Admire, Gaucho, Skyraide |
*Reference to commercial products or trade names is made with the understanding that no discrimination is intended, and no endorsement is implied.
For more information on this designation and the supporting resources for the determination to designate clothianidin and imidacloprid, visit the surface water pesticides of concern page.
Surface Water Pesticide Impairments
There were 7 Minnesota waterbodies that were designated by the MPCA as impaired for a currently registered pesticide on the draft 2026 USEPA 303(d) Impaired Waters List after failing to meet a water quality standard. Additionally, 8 waterbodies that were included on a previous USEPA 303(d) Impaired Waters List have been removed from the list after meeting the water quality standard. Inclusion and removal from the USEPA 303(d) Impaired Waters List resulted from the MPCA assessment of the MDA surface water pesticide data in comparison to Minnesota water quality standards.
Minnesota pesticide impairments for currently registered pesticides
Currently designated as impaired on the USEPA 303(d) Impaired Waters List
| Analyte | Impaired Waters List Addition Year | Waterbody | Monitoring Location County | Minnesota Water Quality Standard Violation that Resulted in Impairment |
|---|---|---|---|---|
| Acetochlor | 2016 | Silver Creek | Carver | chronic (3,600 ng/L) |
| Chlorpyrifos | 2022 | Bevens Creek | Carver | maximum (83 ng/L) |
| Chlorpyrifos | 2026 (draft) | Hazel Creek | Yellow Medicine | maximum (83 ng/L) |
| Chlorpyrifos | 2018 | Jack Creek | Jackson | maximum (83 ng/L) |
| Chlorpyrifos | 2024 | Shakopee Creek | Swift | maximum (83 ng/L) |
| Chlorpyrifos | 2020 | Three Mile Creek | Lyon | maximum (83 ng/L) |
| Chlorpyrifos | 2020 | Yellow Medicine River | Yellow Medicine | maximum (83 ng/L) |
Historic impairments removed from the USEPA 303(d) Impaired Waters List
| Analyte | Impaired Waters List Addition Year | Impaired Waters List Removal Year | Waterbody | Monitoring Location County | Minnesota Water Quality Standard Violation that Resulted in Impairment |
|---|---|---|---|---|---|
| Acetochlor | 2008 | 2014 | Beauford Ditch | Blue Earth | chronic (3,600 ng/L) |
| Acetochlor | 2008 | 2014 | Le Sueur River | Blue Earth | chronic (3,600 ng/L) |
| Chlorpyrifos | 2018 | 2024 | Beauford Ditch | Blue Earth | maximum (83 ng/L) |
| Chlorpyrifos | 2018 | 2024 | Beaver Creek | Murray | maximum (83 ng/L) |
| Chlorpyrifos | 2020 | 2026 (draft) | Double Lake | Cottonwood | chronic (41 ng/L) |
| Chlorpyrifos | 2016 | 2026 (draft) | Dry Weather Creek | Chippewa | maximum (83 ng/L) |
| Chlorpyrifos | 2020 | 2026 (draft) | Dutch Creek | Martin | maximum (83 ng/L) |
| Chlorpyrifos | 2018 | 2024 | Chetomba Creek | Renville | maximum (83 ng/L) |
| Chlorpyrifos | 2014 | 2022 | Grand Marais Creek | Polk | maximum (83 ng/L) |
| Chlorpyrifos | 2018 | 2026 (draft) | Lac qui Parle River | Lac qui Parle | maximum (83 ng/L) |
| Chlorpyrifos | 2012 | 2018 | Seven Mile Creek | Nicollet | maximum (83 ng/L) |
| Chlorpyrifos | 2018 | 2024 | Sleepy Eye Creek | Redwood | maximum (83 ng/L) |
| Chlorpyrifos | 2014 | 2026 (draft) | Tamarac River | Marshall | maximum (83 ng/L) |
Visit the MPCA Minnesota Impaired Waters List for more information.
Chlorpyrifos Response Plan was developed in response to continued detections of chlorpyrifos in rivers, streams and lakes and the determination of chlorpyrifos water quality impairments of rivers and streams in agricultural areas of Minnesota.
Data Availability and Future Work
All of the pesticide data collected as part of the MDA's ambient monitoring program is publicly available through the Water Quality Portal or by contacting the MDA. The MDA will continue to improve its program to expand monitoring to new locations and to include additional pesticide analytes, as resources and needs permit. The MDA is committed to maintaining its long-term data record to allow for continued assessment of the impacts of pesticides on surface water from routine use.
