Herbicides and water quality

By Kieran Kenny, Teagasc Soils and Environment Adviser, Castlerea

In recent years, there have been frequent detections of herbicides in streams, rivers and lakes throughout the country, including some water bodies used for the supply of drinking water (examples Lough O’Gara in Roscommon and Lough Forbes in Longford). These persistent cases are a continuous concern and clearly indicate that a small number of farmers are not handling products with sufficient care. The two herbicides causing the greatest problems are MCPA (sold as Agritox, Agroxone 50, Mortone etc) and 2,4-D (sold as Bandock, Mortox 50). These chemicals are commonly used on grassland farms to control rushes, docks, ragwort and other weeds.

We must all take greater care and adhere to the following best practices when spraying:

• Ensure the sprayer is fit for purpose and recently calibrated and inspected.
• NEVER fill the sprayer directly from a water course.
• Spray at the right time: a young healthy growing crop of weeds, suitable weather conditions and when land is reasonably dry (no surface water in field).
• ALWAYS read and follow the label instructions.
• Take great care to avoid spills.
• Be aware of all water bodies and leave the required Buffer Zone (unsprayed area of 5m for MCPA).
• Comply with Safeguard Zones (up to 200m) if located near drinking water abstraction points. 
• Tank washings must be sprayed in the field and not emptied in the farmyard.
• Avoid spraying for rushes from 1st October - 1st March.
• Consider other options for rush control, such as topping, sward improvement, drainage works and weed wiping with glyphosate.

It is important to note that if the situation with MCPA does not improve the product could be prohibited for use and a cost effective control measure for rushes will be lost.