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Thursday March 25th 2021

Protecting water from pesticide losses and Environment Schemes

Today's focus is on pesticide use on farms and how these can impact streams and rivers and also drinking water supplies. The roles that agro forestry and wetlands can play in helping to protect and improve water quality are also addressed.

Pesticides and losses to water

What happens to pesticides after application? TEAGASC researchers have monitored the concentrations of commonly used herbicides in two agricultural river catchments as a part of the EU Horizon 2020-funded WaterProtect. Per-Erik Mellander, Catchment Scientist, has details of this on-going monitoring

Monitoring in the Agricultural Catchments Programme

Modern agriculture uses many agrochemicals such as pesticides, yet we know very little of what happens to pesticides following application. To address this knowledge gap TEAGASC researchers have monitored the concentrations of a suite of commonly used herbicides in two agricultural river catchments as a part of the EU Horizon 2020-funded WaterProtect. The monitoring is on-going within the Agricultural Catchments Programme and uses passive samplers for continuous monitoring of the rivers. These provide time weighted mean concentrations over 14-day periods. We combine this data with sub-hourly monitoring of water flow.


One of the most commonly used pesticide in Ireland is the acid herbicide MCPA which is used to control rushes, and have recently been more frequently detected in water. This is not only reflecting a more frequent use but also that we are finding better methods to detect them in water. MCPA is highly soluble in water and does not stick to soil so it is easily lost to water. While it degrades quickly in the sun and open air, it and can be lost to water shortly after or during application by wind drift or by surface runoff if rain occurs. If MCPA reaches an environment with little oxygen it can be leached to groundwater with a slow transfer to rivers from belowground pathways and it can also be released from oxygen-poor environments such as stores in the sediments of the river beds.

The Findings

To identify suitable methods to mitigate the loss of herbicides to water we need more knowledge on when, where and how such compounds are lost. Even if the two monitored catchments were not areas associated with pollution of herbicides in water, there were detections in both rivers all year round. Herbicides were also detected in private drinking water wells indicating leaching of the compounds. In the rivers the concentrations peaked in summer, associated with application and low river flow during good weather conditions. But since herbicides were present in the river all year there were higher mass loads in the winter due to higher river flow. There appeared to have been a restricted degradation with a slow release from below surface and from sediments in the rivers.

In summary:

  1. Pesticides were present in the water of two agricultural catchments that are normally not associated with pesticide pollution
  2. The concentrations peaked in summer but pesticides were present in the river all year round resulting in higher mass loads in the winter
  3. Pesticides can be lost to water during or shortly after application, via wind drift or surface runoff, and can leach to groundwater with a slow transfer to rivers from belowground pathways and from sediments in the rivers.

In this short video below Per-Erik Mellander, Teagasc Catchment Scientist with the Agricultural Catchments Programme discusses pesticides and losses to water

More information can be found in:

Khan AK, Barros Costa F, Fenton O, Jordan P, Fennell C, Mellander P-E (2020). Using a multi-dimensional approach for catchment scale herbicide pollution assessments. Science of the Total Environment, 747, 141232.

For more information on protecting water quality visit the water quality section of the website here

Best practice use of pesticides 

Monitoring of drinking water in Ireland continues to detect exceedances above the standard for certain herbicides. The chemicals causing greatest problems are MCPA (Agritox, Mortone, etc) and 2,4-D (Bandock EW, Mortox 50 etc). They are highly soluble in water. Kieran Kenny ASSAP Advisor has more

The chemicals causing the greatest problems are MCPA (Agritox, Mortone, etc) and 2, 4-D    (Bandock EW, Mortox 50 etc). They are highly soluble in water, more persistent in the environment and widely used. Two other herbicides with high usage and causing increasing concern are Glyphosate (Roundup, Gallup etc) and Triclopyr (Grazon Pro, Garlon Ultra etc). These four herbicides accounted for 78% of the total exceedances in 2020.

How to minimise the impact on water bodies

Implementing best management practice is the best mitigation advice:

1. Storage and Preparation for Spraying:

  • The store should be secure, warning sign at entrance, potential leakages retained and labels still attached on original containers.
  • The applicator must be a trained Professional Pesticide User.
  • Application equipment must be well maintained, calibrated and tested every 3 years.
  • Discuss with your adviser alternative methods of control such as, topping, drainage, soil fertility and sward improvement.

2. Handling Herbicides

  • Use appropriate Personal Protective Equipment (PPE) - Check safety data sheet.
  • Minimise risks during transport as accidents can happen.
  • Always read and follow label instructions (correct use, correct rate, correct time).
  • Always use the approved application method for the chemical. Where appropriate the safest option is spot spraying as it reduces the volume of chemical used.
  • Take care to avoid spills, especially when handling the concentrated product. Useful to have a containment system in place to catch spills.
  • Sprayers should be filled where losses to water bodies cannot occur. NEVER fill the sprayer directly from a watercourse.

3. Spraying Herbicides

  • Be aware of the location of water bodies on the farm. Take note of the Buffer Zone on the chemical label (generally 5m for grassland herbicides).
  • Comply with Safeguard Zones for the protection of drinking water abstractions.
  • Do not apply close to vulnerable areas such as karst bedrock, swallow holes or field drains filled towards the surface with stone.
  • Spray when conditions are suitable: calm day, vegetation dry, no heavy rainfall for >2 days, land dry (no tyre marks) and a young crop of healthy weeds.
  • Triple rinse the container and add the rinsate to the sprayer.
  • In the field, spray off the tank washings and clean down the external parts of the sprayer. Do not discard sprayer washings on a yard or gravel area as it can potentially enter a water body.

In the video below, Kieran Kenny, Teagasc ASSAP Advisor goes through how to minimise the impact of pesticides on water bodies.

MCPA and rushes

In 2020 MCPA commonly used to control rushes was responsible for 46 out of 91 detected pesticide breeches. MCPA is water soluble, it does not bind to soil particles and therefore more prone to leaching and run-off to nearby waterbodies. Mary Roache, ASSAP Advisor Mayo, talks about Rush Spraying here

Add to this the fact that rushes thrive in poorly drained areas with a water table near the surface and you can see why run-off can potentially occur. Remember a single drop of pesticide lost to a water body such as a typical small stream (1 meter wide, 0.3 meters deep), for example, can be enough to breach the legal limit for pesticides along 30km of its length. It is not necessary or indeed sustainable to be constantly applying sprays and they should not be looked on as the main method to control weeds. The presence of rushes in a field do not make the field ineligible for payment once it is being grazed.

Some Non- Chemical methods of control

  • Good grazing management and appropriate stocking rates.
  • Taking a soil test and applying nutrients required.
  • Appropriate drainage if required.
  • Use of a topper/mower for weed control.

To minimise spray drift with MCPA products consider using low drift nozzles or switch to using Glyphosate products in a weedlicker instead.

Always Ensure That

  • There is no heavy rain forecast for 48 hours
  • Ground conditions are good, no standing water in the field
  • Rates of application are not exceeded
  • The correct method of application is used (e.g. only boom sprayer for MCPA)
  • There are calm conditions if applying product using a boom sprayer
  • Buffer zones are observed (e.g. a 5m buffer zone for MCPA)
  • Empty containers are triple rinsed before being disposed of properly
  • You never fill your sprayer from a watercourse
  • MCPA shall not be used from 30th September to 1st

This brief video clip (30 secs), gives an overview of MCPA and Rushes as Mary Roache, Teagasc advised 

Sheep dip and footbaths

The practice of sheep dipping in summer or winter or both, is an important annual practice on sheep farms. Sheep dips, such as Organophosphates and Pryrethroids, are extremely effective but must be safely disposed of afterwards to protect aquatic life, as Shaun Roarty, ASSAP Advisor, Donegal advises

Sheep dips such as Organophosphates (active ingredient = diazinon) and Pryrethroids (active ingredient = cypermethrin) are extremely effective in their jobs of eliminating and preventing a number of serious sheep ectoparasites, namely blow fly (bluebottle) strike, lice, keds, ticks and sheep scab. Parasites such as bluebottles are insects and the sheep dipping products used are called insecticides, which effectively target and kill their target organism.

Best practice when using sheep dips have gained increased attention in recent times, primarily due to active ingredients (a.i.) such as cypermethrin been detected in our waterways. When cypermethrin is detected in our streams and rivers, we can quite confidently confirm and conclude that the aquatic living insects will have been eliminated. This has serious consequences for the health of other species (fish, birds, small mammals, humans) that are reliant on aquatic insects as part of the overall food chain.

Water quality in Ireland is under the spotlight from a National and EU perspective. The insects in our streams are part storytellers in that they are used to inform us, on how healthy the state of the water actually is. This is further backed up by chemical analyses, by confirming the presence of sheep dipping active ingredients. So before you go organising your next sheep dipping day, please follow the best practice sheep dipping guidelines with the protection of water in mind.

  1. Make sure you choose a cool, dry day, with relatively good drying conditions.
  2. Identify your holding field/ paddock for your sheep after dipping, there should be no open drain or watercourse within or adjacent to this area. 
  3. Check that your dipping tank is sound and leak-proof, with no structural cracks or defects and has no outlet pipe or valve at the base of the tank. 
  4. Sheep should be allowed to stand for 10-15 mins. in the adjoining drip pen standing area (concreted) when they emerge from the dipping tank, to allow dripping solution funnel back to the tank.
  5. Sheep should be kept in the holding field/paddock for at least 24 hours to make sure that they dry effectively, to prevent any chance of any sheep accessing or crossing watercourses and product ending up in a drain or watercourse.
  6. After dipping - wash and brush the dung from the adjoining drip pen stand thoroughly to ensure that no debris including wool enter any drain or waterbody. The brush used should be soaked in water a number of times and rinsed well. 
  7. Empty dip containers and opening caps/ foil should be safely disposed of after use, following the manufacturer’s instructions on the data sheet.
  8. Spent sheep dip should be mixed 1:3 parts either with slurry or water and land spread by a tanker at a rate not exceeding 5,000 litres/ha (440 gallons per acre) of spent dip, equivalent to 20,000 litres/ha (1760 gallons per acre) of diluted dip [1].
  9. In no circumstances should spent dip be disposed of if there is no facility or slurry tanker available to hold or spread the dip safely. In hill areas some farmers may not have access to a slurry tank on the farm, however, sheep dip must be disposed of to a tank for dilution and spreading.
  10. These recommendations also relate to pour-ons which use active ingredients such as cypermethrin. Pour-ons when sprayed on fleece should be allowed to dry effectively before allowing sheep go back to open hill or mountainous areas or any lowland areas where watercourses are present. As with dipping, sheep should be kept in the holding field/paddock for at least 24 hours before return to hill or lowland areas containing watercourses.
  11. Injectable products to control ectoparasites should be considered where dipping is not feasible. Please check and consult with your local veterinary practitioner for advice.
  12. Mobile showers or dipping is also an option and the same principles above apply.
  13. Please read manufacturer’s instructions on the data sheet carefully regarding health and safety procedures when using and disposing of foot bath products.
  14. Products such as Formalin may cause cancer, whereas Copper Sulphate are toxic to plants and animals at high levels and also impact on soil microorganisms. Zinc sulphate is a heavy metal and very toxic to aquatic life.
  15. Overflow of foot bath solution must be collected and the bath should be covered when not in use.
  16. Spent footbath solution from portable footbath trays should be emptied into a tank and not emptied directly to a soakaway or on sacrifice land.
  17. Used solution may be spread to land if it is very dilute (1:3) and if it is spread at a very low rate and only on land areas having a low water pollution risk. Some animals and birds may be susceptible to the toxicity of foot bath solution and so livestock must be kept away from areas that have been sprayed. Do not let livestock graze on these areas for at least 1 month.
  18. Unwanted concentrate must be disposed of to a licensed specialist waste disposal contractor. Contact your local authority for more information on licensed contractors.



In this video, John Cannon, Teagasc sheep advisor goes through best practice with using and disposing of sheep dip and Sean Gallanagh, Catchment Officer of CatchmentCare Project talks about the work being done to investigate pesticides and their effect on water quality.

This video is the result of close collaboration between Teagasc in Donegal and those bodies involved in the CatchmentCare Programme. CatchmentCARE is an EU-funded project that aims to improve freshwater quality within the North Western and Neagh Bann international river basins. The project partners include the following organisations: Donegal County Council (Lead Partner) and Armagh City, Banbridge & Craigavon Borough Council, Ulster University, The Agri-Food and Biosciences Institute (AFBI), British Geological Survey, Loughs Agency, Geological Survey Ireland and Inland Fisheries Ireland.

Agro Forestry/Native Woodland

Ireland's waterways evolved in tandem with our native woodlands. Of the 16,000 townlands in Ireland 14,000 have names related to trees, forests and water. Farm forests are known to reduce the leaching of nutrients from agricultural soils

Ireland’s relationship with trees run over millennia. From the great oak woodlands of the southern plains to the majestic pines of the midlands rising into the juniper and scrub like woodlands of our hills and mountains this cherished relationship between native trees and our cultural heritage run deep into the physic our countryside’s memory.

Our waterways evolved in tandem with these native woodlands. Of the 16,000 townlands in Ireland 14,000 have names related to trees, forests and water. Over time these trees left the landscape because of clearcutting and no planting reduced our woodlands to approximately 1 % land cover.

Today like the phoenix raising from the ashes our native woodlands are slowly reappearing in our country side. The rivers and waterways have never forgot this relationship. Planting new native forests offer many benefits to our waterways. The Native Woodland Establishment Scheme provides opportunities to protect and expand Ireland’s native woodlands and support and enhance our water quality, landscape and cultural heritage.

These forests will minimise soil erosion, reducing the run off of sediment such as silt into our waterways. They absorb and store polluting chemicals. New trees along with the fallen leaves and underground roots fighting for space, light and nutrients in a forests can trap sediments and chemicals and keep them from flowing into waterways. As these trees grow they shade and cool the river itself. They capture the rainwater in the trees canopy and reduces and slow down flood flow into rivers.

Trees are anchored to the ground by its roots. These roots grow into each other. As they do they bind the soil together and allows the soil by the river’s edge to stabilise the rivers bank. New native forest allow unplanted field margins. These unplanted strips follow the rivers course and are colonised by many grass and shrub species which are filled with an abundance wild life. Riparian margins can be as basic as unfenced or fenced grass margins along the watercourse. Some margins will contain hedgerows and trees while others can be wider larger areas, devoted to woodland / scrub or natural habitat. Despite the differences in what they contain, all riparian margins have the potential to protect the rivers and streams they are adjacent to them while enhancing the habitat and biodiversity living along them. It can offer an effective means of breaking the pathway of nutrients or sediments (sources) that can arise from a range of adjoining land uses to watercourses

Forests and benefits to water

Farm forests are known to reduce the leaching of nutrients from agricultural soils and in turn this may affect water quality in adjacent watercourses and aquifers. Research confirms that mature conifer and broadleaf farm forests can reduce both the concentrations of nitrate and the quantity of water draining to groundwater compared to arable and intensively managed pasture.

Along major watercourses and streams within or adjoining farm forests the retention and enhancement of the existing scrub and vegetation cover will help to lessen bank erosion and slow floodwater thereby reducing its impact on the surrounding land. This also maintains wildlife habitats and their role as wildlife corridors.

The Department of Agriculture, Food & the Marine (DAFM) is responsible for ensuring the development of forestry within Ireland in a manner and to a scale that maximise its contribution to national socio-economic well-being on a sustainable basis compatible with the protection of the environment. Its strategic objectives are to: 

  • foster the efficient and sustainable development of forestry
  • increase quality planting
  • promote the planting of diverse tree species
  • improve the level of farmer participation in forestry
  • promote research and training in the sector
  • encourage increased employment in the sector

Water-related benefits

A wide range of a range of significant water-related ecosystem services can be realised under the Woodland for Water measure. These include:  

  • reduction in sediment mobilisation and runoff into watercourses
  • interception of nutrient runoff into watercourses
  • bank stabilisation
  • food input into the aquatic ecosystem
  • shading / cooling
  • regulation of floodwater
  • riparian restoration

These are in addition to other ecosystem services such as native woodland biodiversity, habitat linkage within the wider landscape, carbon sequestration, amenity and environmental interpretation.


Pearl Mussel Project 

The freshwater pearl mussel (Margaritifera margaritifera) is a large filter-feeding bivalve. European freshwater pearl mussel populations have declined by 90% over the past century. Mary McAndrew, Catchment Officer Pearl Mussel Project gives information on this long lived creature.

Freshwater pearl mussels are extremely long lived and are capable of surviving for up to 140 years.This makes them Ireland’s longest living animal. 

Adult freshwater pearl mussels can reach lengths of 12-15 cm. They live buried, or partially buried in the river bed. Freshwater pearl mussels are filter feeders, inhaling and expelling up to 50 L of water per day through siphons, while retaining food particles. This filtering activity means that pearl mussels can help to maintain and improve water quality, where they are present in high numbers.

Lifecycle of Freshwater Pearl Mussel

European freshwater pearl mussel populations have declined by 90 % over the past century. In Ireland, 27 freshwater pearl mussel populations are protected within Special Areas of Conservation (SACs). Eight of these populations contain 80 % of the total Irish freshwater pearl mussel population and occupy what are known as the ‘Top 8 catchments'. While the ‘Top 8 catchments’ support the highest remaining numbers of freshwater pearl mussels in Ireland, these populations are also undergoing a slow decline, and face extinction unless action is taken. The Pearl Mussel Project EIP was set up to support farmers in these Catchments to improve and protect water quality through a result based payment system.

Threats to Freshwater Pearl Mussel

The main reason for decline is the low survival rate of juvenile mussels, which are extremely sensitive to slight changes in environmental conditions. This is leading to an ageing population, not capable of replenishing itself. Juvenile survival is dependent on a clean, well oxygenated river bed, with little silt, sediment, or algal growth.

Any activities that result in changes in river flow, increased levels of silt, and increased levels of nutrients are contributing to the decline of freshwater pearl mussels. In addition drainage and increased intensification of land use in river catchment areas can contribute to inadequate conditions for freshwater pearl mussel survival.

The Pearl Mussel Project are currently working with over 450 farmers throughout the Top 8 Catchments. With the help trained farm advisors the project assesses each farm annually using habitat and whole-farm scorecards. Farmers are financially rewarded according the scores achieved. Through this results-based payment approach farmers are incentivised to improve the habitat condition and water quality throughout their farms. Ultimately the project pays farmers to produce clean water and the delivery of other benefits to biodiversity and climate.

The main agricultural pressures to water courses within the top 8 catchments include:

  • Changes in flow and hydrology due to land drainage and habitat conversion.
  • Sediment losses to watercourses due to excessive poaching and animal access to rivers and streams.
  • Nutrient run-off to watercourses due to inappropriate use of fertilisers.

The Pearl Mussel project encourages farmers to manage their habitats for the benefit of water, carbon, and biodiversity. A major part of the programme involves raising awareness amongst participant farmers through ongoing training and engagement. 

This video gives more detail on the Freshwater Pearl Mussel project 

Wetlands for water quality

A combination of geology and abundant rain has endowed Ireland with an extraordinary array of wetlands covering some 20% of the country. Functional wetlands are among our most productive environments providing a vast array of eco-system services. ASSAP advisor Mary Roache has more information

Most of our wetlands occur naturally but they may also be artificially created. Naturally occurring wetlands include lakes, rivers, bogs, turloughs, fens, saltmarshes, swamps and wet woodlands, produced as a result of environmental processes. Artificial wetlands include fishponds, farm ponds, reservoirs, quarry ponds, constructed wetlands, drainage ditches and canals.

Many wetlands are protected under EU environmental legislation and forty five of Ireland’s wetlands are Ramsar sites.  These sites are internationally important and are part of a global network of wetland sites. Functional wetlands are productive environments they provide a vast array of eco-system services

  • Wetlands support biodiversity; 40% of all species live or breed in wetlands
  • Wetlands store 30% of land – based carbon; vital for climate change mitigation
  • Wetlands remove pollutants from circulation.
  • Wetlands provide protection from flooding and storms
  • Wetlands absorb and store water
  • Wetlands provide employment, food and energy.
  • Wetlands are places for recreation, culture and leisure.

The biodiversity of wetlands in Ireland has been estimated to be worth €385 million per year to the Irish economy. The vast amount of wetlands occur on farmland and so we must manage these correctly. Farmers should identify such areas on the farm and avoid any drainage that may affect them. Maintain buffer zones adjacent to wetlands from nutrients and pesticides and keep grazing to a sustainable level. Some may need fencing off to protect them while other wetlands need active appropriate management such as controlling invasive species or letting light into neglected ponds. Farmers play a key role in this conservation and “wise use of wetlands” so that these unique areas exist and continue to be enjoyed by future generations.