The primary goal of the MDA's surface water monitoring program is to provide detailed information on the occurrence and concentrations of agricultural chemicals, including pesticides and nutrients, in Minnesota's surface waters. Protection of Minnesota's citizens and water resources from agricultural chemicals is the fundamental purpose of this goal. The program focus is monitoring of streams and rivers in the agricultural and urban areas of the state.

NEW: Notice of Preliminary Decision to Designate Clothianidin, Imidacloprid, and Thiamethoxam Neonicotinoid Insecticides as “Surface Water Pesticides of Concern” in Minnesota.

The MDA is seeking public input on the Commissioner’s preliminary decision to designate neonicotinoid insecticides clothianidin, imidacloprid, and thiamethoxam, as “Surface Water Pesticides of Concern”. “Surface Water Pesticide of Concern” means the detection of a pesticide in surface water at concentrations of concern relative to a water quality “Reference Value” not due to misuse or unusual or unique circumstances, but likely to be the result of normal use of a product or practice.

The proposed decision is based on the following guidelines as recommended in the Pesticide Management Plan (PMP):

  • In 2018, the Environmental Protection Agency (EPA) lowered the Aquatic Life Benchmark (ALB) for clothianidin, imidacloprid, and thiamethoxam.
  • The MDA monitoring results from 2010 through 2018 show clothianidin, imidacloprid, and thiamethoxam detections in several state rivers and streams approached or exceeded the EPA’s updated ALBs for these pesticides.
  • The Pesticide Management Planning Committee members provided comments to the Commissioner to designate these three neonicotinoids, as “surface water pesticide of concern”. 

As a part of the proposed designation as “Surface Water Pesticide of Concern”, the MDA may reformat previously developed pollinator-focused BMPs for Neonicotinoids to have a water quality focus.

Full announcement of the notice can be viewed at the Minnesota State Register website (Volume 44, Number 33) or by contacting Trisha Leaf.

The comment period is open for 60 days until April 9th, 2020.

Comments should be submitted by letter or e-mail to Trisha Leaf.

Trisha Leaf
Minnesota Department of Agriculture
625 Robert Street North
St. Paul, MN 55155

In 2017 the MDA’s ambient monitoring program sampled over 200 river, stream and lake locations throughout the state for pesticides and/or nutrients.

Map showing surface water monitoring locations


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. 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 for 2017

  • 1,218 pesticide samples were collected from 208 river, stream, or lake monitoring locations.
    • 150 pesticide compounds were analyzed; 70 pesticide compounds were detected.
      • 48 of the 70 detected pesticide compounds were detected in less than 10% of the samples.
      • Nine of the 70 detected pesticide compounds were detected in greater than 50% of the samples.
    • A degradate of atrazine (hydroxyatrazine) was detected in 89% of samples collected and was the most frequently detected pesticide compound in Minnesota surface waters.
    • The three most frequently detected pesticide parent compounds were 2,4-D (74%), atrazine (63%), and metolachlor (63%).
    • The MDA detected the insecticide chlorpyrifos more times in 2017 than any previous year, including the first detection in a lake.
    • Twenty-two percent of river and stream samples had glyphosate detected, and no detections occurred in lakes. The maximum glyphosate detection was less than one percent of the lowest water quality reference value.
    • Eleven, one, and nine percent of river and stream samples had clothianidin, imidacloprid, and thiamethoxam (neonicotinoid insecticides) detected, respectively.
      • All three imidacloprid detections were greater than the USEPA chronic water quality reference value
      • All clothianidin and thiamethoxam detections were below the USEPA water quality reference values
    • Thirty-nine detections were above the numeric applicable water quality reference value including detections of acetochlor (13 detections), atrazine (2 detections), bifenthrin (4 detections), carbendazim (1 detections),
      chlorpyrifos (15 detections), dichlorvos (1 detection), and imidacloprid (3 detections). The MPCA will assess these detections, including the duration of concentration, for violation of water quality standards, if applicable.

Surface Water Pesticides of Concern

Three pesticides have been designated as "surface water pesticides of concern" by the Commissioner of Agriculture. Acetochlor and atrazine (herbicides) were designated in 2002, and chlorpyrifos (insecticide) was designated in 2012. Designation as a "surface water pesticide of concern" initiates chemical specific best management practices (BMP's) and increased water quality analysis. The designation as a "surface water pesticide of concern" evaluates both detection of the pesticide in Minnesota surface waters and the concentration relative to water quality standards and/or reference values.

Chlorpyrifos Response Plan: This 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. 

Surface Water Pesticide Impairments

There are ten waterbodies in Minnesota that are either designated, or proposed, by the MPCA as impaired on the USEPA 303(d) Impaired Waters List for currently registered pesticides. These listings are a result of the MPCA assessment of the MDA collected surface water pesticide data. The 2017 and 2018 MDA pesticide water quality data will be reviewed by MPCA as part of the 2020 USEPA 303(d) Impaired Waters List assessment process.
Pesticide Impairment map through 2017 for MN.


Table 1. Minnesota pesticide impairments for currently registered pesticides.

Pesticide Impaired Waters List Year Stream County Violation that Resulted in Impairment
Acetochlor 2016 Silver Creek Carver chronic (3,600 ng/L) Minnesota water quality standard
Chlorpyrifos 2018 Beauford Ditch Blue Earth maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2018 Beaver Creek Murray maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2018 Chetomba Creek Renville maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2016 Dry Weather Creek Chippewa maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2014/2016 Grand Marais Creek Polk maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2018 Jack Creek Jackson maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2018 Lac qui Parle River Lac qui Parle maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2018 Sleepy Eye Creek Redwood maximum (83 ng/L) Minnesota water quality standard
Chlorpyrifos 2014 Tamarac River Marshall maximum (83 ng/L) Minnesota water quality standard


Three waterbodies have been removed from the USEPA 303(d) Impaired Waters List for currently registered pesticides. The Le Sueur River and Beauford Ditch were designated as impaired for acetochlor in 2008 and were removed from the USEPA 303(d) Impaired Waters List in 2014. Seven Mile Creek was designated as impaired on the 2012 Impaired Waters List for chlorpyrifos and has been proposed for removal from the proposed 2018 Impaired Waters List. Removal from the USEPA 303(d) Impaired Waters List followed several years of water quality monitoring without elevated pesticide detections.

Visit the MPCA Minnesota Impaired Waters List for more information.

Data Availability and Future Work

All of the pesticide data collected as part of MDAs ambient monitoring program is publicly available through the Water Quality Portal or by contacting 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.