The publicly available monitoring data for dimethenamid-P in Belgium (from the Flemish and Walloon authorities and from the EEA Water Base) in surface water for the period 2010-2021 were tested against the acute and chronic water quality standards (MAC-EQS and AA-EQS). Based on these data, the main emission routes and vulnerable regions were identified and a plan for reducing emissions to surface water was drawn up.

Dimethenamid-P is used as an herbicide in the cultivation of corn, sugar beet, rapeseed and in vegetable crops, mainly in cabbages, leeks, onion and chicory, and in addition, in a number of smaller vegetable crops. Application takes place from April to September depending on the crop. In most arable crops, it is from April to June, and in vegetable crops from May to July. A somewhat later application is from July to September, for the cultivation of leeks and rapeseed.

In 635 monitoring sites (452 in Flanders and 183 in Wallonia), 10,444 samples (9,180 in Flanders and 1,264 in Wallonia) were analyzed for dimethenamid-P.

In Flanders, 26 samples (0.3%) exceeded the MAC and at 12 locations with a connection to agriculture, the AA EQS was exceeded. 10 of these 12 locations are in the Yser basin in West Flanders. Some very high concentrations were also measured there. There has been no downward trend in these exceedances in recent years. The number of sites exceeding the AA EQS per year is between 0 and 3. The highest values are found in May to July.

In Wallonia, the MAC was exceeded in 1 sample (0.08%). Due to the high concentration found and the fact that few measurements were made there in that year, the AA EQS was also exceeded at that location. The highest concentrations are found in May and June.

Monitoring sites with catchment areas where the AA EQS has been exceeded

The emission routes were studied based on the characteristics of the most critical locations. Given the properties of the substance dimethenamid-P, the expected routes are mainly spray drift and/or surface run-off.

The analysis of the locations in Flanders shows that dimethenamid-P could reach the surface water mainly via spray drift after an application in corn or via run-offs from plots mainly grown with corn but also with sugar beet or vegetables. These routes (with the exception of vegetables) also seem to be relevant for Wallonia. The indication that the route runs via spray drift is supported by the fact that critical water bodies also show a high percentage of fields with minimal distance from surface water.

Point emissions cannot be excluded because high to very high concentrations were measured several times in the period 2013-2020 and no significant precipitation was present at that time.

The emission reduction plan therefore proposes the following specific measures:

Labels of all dimethenamid-P containing products will bear the following information:

• A buffer zone of at least 10 m together with 50 % drift reduction technique should be applied.
  This also applies to new authorisations that have yet to be applied for.
  For products where a larger buffer zone or higher drift reduction is already prescribed in the authorisation, this will remain in place.
• Following recommendations will also appear on the labels of dimethenamid-P containing products:
  • Do not spray if there is a risk of drift
  • When filling and cleaning the tank, always keep a distance from watercourses and ditches. 
  • Always respect the prescribed buffer zones. The recommendation is to always maintain a minimum buffer zone of 5 meters (with 75% drift reduction technique), even if the use of higher drift reduction caps allows a narrower buffer zone.
  • In addition to the buffer zones listed on the label, regional buffer zones also apply. Always maintain the widest buffer zone. Attention will also be paid to the presence of permanent vegetation cover in specific circumstances.
  • Do not spray within 24 hours in case of a weather forecast of ≥ 5 mm of precipitation.

Authorisation holders of dimethenamid-P will also focus on general measures in their product stewardship program:

• Supporting farmers' awareness of the consequences of incorrect application of plant protection products including dimethenamid-P containing products
• Cooperating with external parties involved and Belplant to set up a regional action for West Flanders (foremost for the Yser basin) regarding emission reduction to surface water.
• Providing strong support in the development/introduction of the Closed Transfer System (“CTS”) for filling the spray tank without contact to plant protection products for the user.