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Josh Stamper, MDA, welcomed participants to the meeting, emphasized the importance of discussion and member feedback, encouraged members to reapply, and touched on revisions to the Pesticide Management Plan and MDA’s recent comments to the Environmental Protection Agency (EPA). PMPC Members and MDA leadership introduced themselves.

Kate Hall (meeting facilitator), MDA, went through housekeeping items and presented background slides on PMPC. The presentation provided an overview of the MDA’s Pesticide Management Plan, “common detection” and “surface water pesticide of concern” designations, and select comments received from members the previous year. The MDA’s Indigenous Land Acknowledgement statement was read. 

MDA Presenter: Bill VanRyswyk

The presentation provided an overview of the MDA’s monitoring program and introduced the main sections of the 2023 report. Changes to the 2023 analyte list were highlighted along with groundwater and surface water program design elements.

MDA Presenter: Kim Kaiser

The presentation focused on the groundwater results from the 2023 monitoring season. Current common detection pesticides were reviewed, and trend maps were presented showing changes in detection frequency and concentration for individual pesticide monitoring regions (PMRs). Highlighted topics included: pesticides detected in PMR 4, detections of 4-hydroxychlororthalonil and neonicotinoids, detections of cyanazine degradates in private wells, and urban groundwater results.

Following the main presentation, Kate Hall briefly shared additional background on chlorothalonil and the actions being taken by MDA to better understand and address detections of its degradate (4-hydroxychlorothalonil) in groundwater including, considering common detection status, expanding monitoring, and developing best management practices.

Discussion focused on:

• Chlorothalonil and its degradate, 4-hydroxychlorothalonil
  • Detections of 4-hydroxychlorothalonil in private wells and crop use in the area, particularly use on potatoes, were discussed. The MDA has been evaluating potential chlorothalonil use sites near wells with detections in Minnesota.
  • The development of a Health Risk Limit (HRL) for 4-hydroxychlorothalonil which currently uses Risk Assessment Advice (RAA) as a reference value was discussed. The MDA previously requested that the MN Department of Health (MDH) develop an HRL for the chemical; however, due to limited toxicological data, only an RAA could be developed. The MDA is continuing to work with MDH regarding human health-based reference values for 4-hydroxychlorothalonil.
  • Chlorothalonil use patterns were discussed along with EPA proposed federal label changes to reduce maximum allowable rates on various crops and turf as part of its ongoing chlorothalonil registration review.
  • Potential best management practices (BMPs) for chlorothalonil were discussed. Challenges related to its use as a protectant were noted and the importance of predictive modeling and data from weather stations to guide applications was discussed. It was also noted that the MDA is working to expand the collection of weather data to use for modeling.
• Common detection status
  • The history of designated common detection pesticides was discussed along with why there haven’t been new designations in recent years compared to 20 years ago. The previously designated pesticides are some of the most widely used pesticides and were an important focus when the MDA first began monitoring groundwater. The common detection pesticides were heavily relied upon and frequently detected at the time of designation.
  • Additional discussion around the number historical vs. recent common detection designations noted changes in pesticide use patterns over time (e.g., rotating modes of action, lower application rates) and the focus on education and outreach for pesticides such as atrazine which has also helped to stabilize and/or decrease detections in groundwater over time.
  • Two herbicides that have more recently been detected in groundwater, fomesafen and sulfentrazone, were further discussed. The MDA is carefully tracking these herbicides in groundwater and a Health Risk Limit is currently being developed by MDH for sulfentrazone and its degradate.
• Additive effects of multiple pesticides/degradates
  • The total load of pesticides being used per acre vs. the rate of individual pesticides was discussed along with the challenges of accounting for potential additive effects from mixtures of chemicals. It was noted that the MDH has an additivity calculator for human health to consider mixtures. Use the following link to download the Excel file: MDH Additivity Calculator.

MDA Presenter: Dave Tollefson

The presentation focused on the surface water results from the 2023 monitoring season. Pesticide waterbody impairments were presented along with an overview of how Minnesota water quality standards are used to evaluate data. Current surface water pesticides of concern were reviewed, and trend maps were presented showing changes in detection frequency and concentration for individual PMRs. Comparisons of detected concentrations to relevant standards or guidance values (i.e., reference values) were also presented, focusing on pesticides detected at concentrations >10% and >50% of relevant reference values.

Discussion focused on:

• Pyrethroid insecticides
  • Testing of sediments and the potential additive effects of pyrethroid insecticides were discussed. The MDA does not sample sediments for pesticide residues, and pyrethroids are evaluated individually because only individual chemical aquatic life benchmarks are available. The potential importance of evaluating additive effects from pesticides with similar modes of action was further discussed along with the challenges of doing so.
• Neonicotinoid use
  • The percentage of corn and soybean seed treated with neonics was discussed. The MDA noted that an estimated 40% of soybean seed is treated with a neonic and 99% of corn seed is treated with a neonic.
  • Imidacloprid urban detections were also discussed in relation to its non-agricultural uses including residential lawn grub treatments and emerald ash borer management.
•  Toxicological basis for reference values
  • The toxicity data used to determine reference value concentrations was discussed with respect to the test species used, consideration for plants like wild rice and treaty protected resources, and the limitations of toxicity data for single chemicals. 
• Unspecified reference values for degradates
  • The lack of a chemical specific reference value was discussed in relation to pyroxasulfone M1, a degradate of pyroxasulfone. When a degradate-specific reference value is not available, the MDA will typically use the parent reference value. The EPA does not provide an aquatic life benchmark for pyroxasulfone M1, and data was not available through the EPA’s ecological risk assessment for the MDA to calculate a chemical-specific value.

MDA Presenter: Neal Kittelson

The presentation introduced a new MDA project developing interactive maps based on the MDA’s pesticide water quality monitoring data. The project aims to present monitoring data in an interactive format and to improve access to site-specific data while acting as a companion to the PDF annual report. An overview of the ArcGIS stories was presented along with demonstrations of various interactive maps and tables.

Discussion focused on:

• Additional features to consider
  • Inclusion of groundwater data from pre-2000 was discussed. All data is being taken directly from the Water Quality Portal which does not currently include pre-2000 groundwater data.
  • Adding the USDA crop layer to the maps was discussed. It was noted that this was initially included; however, it slowed the program down and was removed. There is potential to add the layer back in.
  • How to account for additivity in comparisons of detected concentrations to reference values was discussed. The MDA plans to explore ways to allow for this comparison, and, at a minimum, additivity for atrazine and cyanazine with their degradates will be noted in the text.
• Potential for misinterpretation of data

All maps/graphs/tables will be accompanied by text, directions, and appropriate disclaimers. Use of ArcGIS stories also allows for the inclusion of key background information about the program, analysis, and evaluation of data.

Raj provided an update on treated seeds and MDA’s authority to take action to prevent unreasonable adverse effects. He explained that while MDA now has this authority, treated seeds will not be handled the same as pesticides. The MDA also received money for pollinator research which may be used to study pesticide treated seed.

Discussion focused on:

• Pesticides in precipitation
  • A member expressed concerns over the presence of pesticides in rain and requested the report focus more on these results.
• Aquatic life benchmarks and water quality standards for neonicotinoids
  • It was explained that MDA does not develop reference values and uses guidance from the MN Pollution Control Agency.
  • Currently, there are no promulgated standards for neonics in surface water. The neonics are on the MPCA’s list of standards to develop; however, they have not been prioritized.