Discussion topics included:
- The MDA’s investigation into potential propazine sources.
- Detections in surface water are likely the result of impurities in atrazine products. Propazine has not been sold in MN in over 30 years and detections correlated well with atrazine detections.
- This relationship between atrazine and propazine is unique and similar trends with other chemicals (particularly triazines) have not been observed.
- Sources of metribuzin detections outside of PMR 4 and method reporting limits (MRLs) for its main degradates.
- Detections have been limited and occur in different areas throughout the state. Because detections are erratic, the source has not been fully investigated by the MDA.
- Metribuzin has been making a reappearance as part of pre-emergence tank mixes to address resistant weeds in soybean.
- The MDA is not able to lower the MRLs for metribuzin and its degradates at this time.
- Availability of raw data for 4-hydroxychlorothalonil (report table only shows a single maximum concentration).
- Requested data was sent after the meeting. Raw data is also available through the Water Quality Portal.
- The MDA’s actions regarding increasing metolachlor trends in groundwater.
- The MDA is continuing to promote Water Quality Best Management Practices for Metolachlor (PDF).
- While some PMRs do show increasing trends, concentrations remain well below human health reference values in groundwater. The MDA will continue to carefully monitor metolachlor and its degradates.
- Increased metolachlor use is anticipated due to resistance issues with glyphosate and other herbicides.
- The continued use of Roundup-Ready crops despite the development of glyphosate-resistance.
- Growers are continuing to use Roundup-Ready crops and glyphosate is still an important part of weed management programs from corn and soybean.
- The new addition of piperonyl butoxide to the monitoring list and the lack of detections.
- Piperonyl butoxide is a synergist often used with pyrethroid insecticides. It has been detected by other monitoring programs, but it was not detected in 2020 by the MDA.
General Discussion
Discussion topics included:
- The MDA’s investigation into potential propazine sources.
- Detections in surface water are likely the result of impurities in atrazine products. Propazine has not been sold in MN in over 30 years and detections correlated well with atrazine detections.
- This relationship between atrazine and propazine is unique and similar trends with other chemicals (particularly triazines) have not been observed.
- Sources of metribuzin detections outside of PMR 4 and method reporting limits (MRLs) for its main degradates.
- Detections have been limited and occur in different areas throughout the state. Because detections are erratic, the source has not been fully investigated by the MDA.
- Metribuzin has been making a reappearance as part of pre-emergence tank mixes to address resistant weeds in soybean.
- The MDA is not able to lower the MRLs for metribuzin and its degradates at this time.
- Availability of raw data for 4-hydroxychlorothalonil (report table only shows a single maximum concentration).
- Requested data was sent after the meeting. Raw data is also available through the Water Quality Portal.
- The MDA’s actions regarding increasing metolachlor trends in groundwater.
- The MDA is continuing to promote Water Quality Best Management Practices for Metolachlor (PDF).
- While some PMRs do show increasing trends, concentrations remain well below human health reference values in groundwater. The MDA will continue to carefully monitor metolachlor and its degradates.
- Increased metolachlor use is anticipated due to resistance issues with glyphosate and other herbicides.
- The continued use of Roundup-Ready crops despite the development of glyphosate-resistance.
- Growers are continuing to use Roundup-Ready crops and glyphosate is still an important part of weed management programs from corn and soybean.
- The new addition of piperonyl butoxide to the monitoring list and the lack of detections.
- Piperonyl butoxide is a synergist often used with pyrethroid insecticides. It has been detected by other monitoring programs, but it was not detected in 2020 by the MDA.
