Teagasc has confirmed that pesticide usage within the tillage sector is not impacting on Irish water quality.

But with the autumn planting season about to start in earnest, growers are being reminded of the need to ensure that all sprayers used in the application of herbicides and aphicides over the coming weeks are fully fit-for-purpose.

Recent days have seen the National Pesticides and Drinking Water Action Group (NPDWAG) urging all users of pesticides to remain vigilant as the main grassland spraying window for 2026 comes to a close.

Communities are again reminded that it only takes one drop to impact a drinking water source.

And this is messaging that has very much hit home with Irish farmers across the board.

In recent years, Ireland has made significant progress in reducing pesticide detections in drinking water supplies.

Pesticides

Since the establishment of the NPDWAG in 2017, pesticide exceedances have reduced by more than 50%, demonstrating the positive impact of local collaboration, awareness raising and responsible pesticide use.

However, continued vigilance remains essential, particularly during the autumn months when wetter conditions can increase the risk of pesticides entering rivers, streams and other drinking water sources.

Significantly, sprayer testing was introduced in Ireland as part of the Sustainable Use Directive (SUD) in 2015.

This sets out to regulate the use of pesticides and to put controls in place to make the use of plant protection products more sustainable.

Sprayer checks

There are a number of steps that farmers can take to ensure their sprayers continue to operate efficiently.

All nozzles should be replaced as a complete set when there is any indication of wear, such as increased flow rate or uneven spray patterns.

An accurate and easy to read pressure gauge is essential for accurate spraying.

While full testing is best, if a new nozzle gives an incorrect output, it often indicates an inaccurate gauge or transducer.

In addition, accurate forward speed indication is also essential and it should be checked: many simple GPS guidance monitors give an accurate speed output.

Many modern sprayers will have a flow transducer fitted which allows the application rate per hectare to be calculated and controlled, but they depend on the accuracy of the forward speed and flow transducers which should be checked.

These control systems use system pressure to keep the output constant if forward speed changes, so this can impact on spray drift and spray quality. The correct forward speed must still be chosen for the nozzle size and application rate.

Filling, filtration, and cleaning

Sprayers have suction, pressure, (possibly in-line) and nozzle filters fitted to prevent suspended material blocking nozzles.

Some air-induction nozzles are prone to blockage and need correctly sized filters particularly at the nozzle to avoid blockages. 

Meanwhile, some filter types, often in nozzle bodies, have a much greater filter area than others and are less easily blocked.

Cleaning the sprayer is essential to avoid contaminating the environment.

Accurate calibration will avoid the need for excessive disposal as the sprayer should be emptied in the field.

Internal sprayer washing systems should then be used to clean the residues from the sprayer, which in very dilute form can again be sprayed out in the field.

The level of cleaning required beyond this rinsing will depend on the products used.