The Department of Agriculture has said that it is working on legislation to allow for the spraying of problem grass weeds in arable margins in tillage.

However, it is unclear why this should take so long. Under ACRES, all farmers can control noxious or invasive weeds in field margins where necessary, and the practice was encouraged to advisers at training.

Under the new CAP, which started in 2023 and saw farmers leave 3m margins beside watercourses in 2022 in winter cereal and oilseed rape crops, tillage farmers are required to leave a 3m margin beside a watercourse that is uncultivated and does not receive fertiliser or pesticides.


However, this can create an issue, as problem weeds can flourish in these margins – particularly grass weeds like sterile brome, canary grass, Italian ryegrass and, of course, blackgrass. Teagasc refers to blackgrass as a highly invasive weed.

These weeds are often very difficult to completely control by rogueing, and topping can increase the problem.

Spot-spraying is a good control option, which if carried out for a few years may lead to full control of the problem, or make it more manageable so that weeds can be pulled.

Here are some of the measures under ACRES where spot-spraying of noxious and invasive weeds is allowed:

Measure: grass margins – arable

What the rules state: Pesticides and herbicides are not permitted, except for the spot treatment of noxious/invasive weeds.

Measure: management of intensive grassland next to a watercourse

What the rules state: Pesticides and herbicides are not permitted, except for the spot treatment of noxious/invasive weeds. Invasive weeds can also be controlled by topping, but this is only permitted after 1 July in localised areas.

Measure: Planting trees in riparian buffer zones

What the rules state: Unmanaged riparian areas are very susceptible to non-native invasive species, eg, Himalayan balsam, giant hogweed. Monitor the riparian buffer and carry out appropriate management/removal of non-native, invasive species where necessary.

Measure: Riparian buffers strips/zones – arable and grassland

What the rules state: Pesticides and herbicides are not permitted, except for the spot treatment of noxious/invasive weeds.

Measure: Unharvested cereal headlands

What the rules state: Do not select the margin where problem weeds may be an issue, eg, sterile brome, blackgrass, wild oats.

Once the crop is sown, no herbicides, pesticides or pre-harvest desiccants are permitted on the headland(s) selected for this action. Only the spot treatment of noxious and invasive weeds with herbicides is allowed.

It should be noted that many arable farms have problems with one or all of the grass weeds outlined above, so this rules out the measure for these farmers.

Noxious weeds (as outlined in the Department’s ACRES specifications)

A noxious weed is a plant species that has been designated by a statutory authority as one that is injurious to agriculture, horticulture, habitats/ ecosystems and humans or livestock.

They are usually injurious to human or animal health. Noxious weeds can be native or introduced.

A native species may not pose a threat when growing in a natural forest type situation, but it becomes a problem with a changing landscape, eg, clearance to cultivation.

They are usually plants which multiply aggressively without any natural control, such as herbivores, soil or climatic conditions.

Examples of noxious species include: Ragwort, thistle, Dock, common barberry, male wild hop, spring wild oat.

Alien invasive species (as outlined in the Department’s ACRES specifications)

‘Alien invasive’ species are species that have been introduced (deliberately or accidentally) by humans and that have a negative impact on the economy, wildlife or habitats of Ireland and Northern Ireland.

After habitat loss, invasive species are the second biggest threat to biodiversity worldwide, and the biggest threat on islands.

Examples of invasive species include New Zealand burr, great maple, daisies, Montbretia, European Rabbit, reedgrass, common pitcher plant, Canada goldenrod, cotoneaster, Himalayan knotweed, evergreen oak and holm oak.

Official list of noxious weeds:

  • Thistle
  • Ragwort
  • Dock
  • Common barberry
  • Male wild hop plant
  • Wild oat
  • Making blackgrass a noxious weed

    In June, the Department of Agriculture told the Irish Farmers Journal that work was underway to make blackgrass a noxious weed. The Department stated that it was “examining the list of noxious weeds already provided for in legislation, as well as potential amendments to the list”.

    Water quality

    Water quality is one of the reasons that this 3m buffer beside watercourses is in place, and of course, it is right to prevent pesticides entering watercourses. This has to be at the top of people’s minds.

    If allowed, spot-spraying should only be used as a last resort and where there is already a weed problem in place. Remember, this buffer is mandatory, so it is not like ACRES where farmers are advised to choose a field without a grass weed problem for the unharvested headlands measure.

    A farmer could already have a grassweed problem in the field where the buffer is required. Tillage has a good track record with water quality.

    Most pesticide exceedances do not occur with tillage-specific products or in areas traditionally associated with tillage farming. Bentazone in the Clonroche area of Co Wexford is an exception to this.

    Tillage farmers have embraced precision technology and low-drift spraying nozzles to prevent contamination and this should continue and be encouraged.

    Grassweed issues in tillage

    Grassweeds are now a huge problem on tillage farms. They can render farms unviable, but also put our native seed supply at risk and, very importantly, they add huge costs to crop production.

    Many of the chemicals used to control them are now failing. There are no herbicides available in Ireland that can guarantee the control of blackgrass in a sown crop.

    Glyphosate is the only herbicide which will give full control.

    Other grassweeds are extremely hard to control in spring cereal crops, and resistance is emerging against numerous herbicides.

    If these grassweeds get out of control in the field margins, then they will gradually creep into the field, creating quality issues for crops that can result in rejection, income reduction and problems for neighbouring farmers, as the weed could spread.

    This is the first year that Teagasc will hold a conference dedicated to grassweeds in tillage farming.

    The conference will take place on 8 November in the Killashee Hotel, Naas, Co Kildare.