MCPA herbicide Ireland: labels, application rates and rush control

What is MCPA weed killer, and what does “MCPA 500” mean on an Irish label?

Agritox 500, PCS 05499, is an MCPA weed killer: a soluble concentrate containing 500 g/l (44.25% w/w) MCPA as the dimethylamine salt, a selective herbicide for many broad-leaved weeds in established grassland. Its specimen carries the code 510007487_102022.

Nufarm markets Agritox for cereals and grassland. The DAFM specimen for Agritox 500 (2022 to date) lists only established grassland and grass seed crop.

Before you ask an adviser or supplier anything, photograph the pack and write down its full marketed name, PCS number, formulation, concentration and supplier. Keep the quantity you bought separate from the concentration printed on the container. “MCPA 500” in a search result does not identify every pack or mixture that contains MCPA, so quote the name and PCS from your own pack.

If a supplier’s description differs from the DAFM document, note both and ask which one applies to your product and your field.

Is every MCPA product still legal to use?

No. Mastercrop MCPA 50 (Hygeia Chemicals, PCS 05510) is on DAFM’s list of products whose registration expired on 31/12/2025; its use becomes illegal from 30/06/2027.

Registration expiry and the last legal use date are two different dates, so check both for any older stock. Look the product up by name and PCS in the official product search, and compare the current entry with the job you plan. If that does not settle a stock question, DAFM’s products page gives pcs@agriculture.gov.ie for named-product enquiries; send the actual name, PCS and the proposed use. Do not carry one product’s status over to every MCPA formulation, and do not treat a file’s presence in the label directory as a status decision.

MCPA application rates on Agritox 500

Read each row together with its restrictions, and keep the product quantity with its area unit (l/ha). Only then work out a batch: give the tank calculator the product rate and treated area in compatible units, and keep the result with the product and crop row it came from. Do not turn the concentration on the pack into a per-tank recipe: concentration, product dose per hectare and water volume are three different numbers, so write each down with its unit. If only part of a paddock was sprayed, record the area it covered and mark the treated boundary.

The label allows an interval of 4–6 weeks between successive applications if weeds persist, and grass for hay or silage is sprayed 3–4 weeks before cutting.

Does Agritox spray work on rushes, and when do you apply it?

The Agritox 500 specimen lists compact rush and soft rush as moderately susceptible: the weed is suppressed and its top growth is usually killed. Hard rush is listed one category lower, as moderately resistant, where only top growth may be killed. Soft and hard rush are treated as compact rush.

Before choosing a product, identify the weed from whole plants. Take clear photographs, describe the paddock, and say whether you have a dense infestation, scattered plants or an advancing boundary. A search phrase such as “agritox spray for rushes” does not mean every rush species responds the same way, so compare the weed-table entry with your situation and what you want from the treatment.

The timing for compact rush is April to June, with the stems cut and removed either four weeks before or four weeks after treatment.

Should you spray rushes at all: containment or suppression?

DAFM sets two strategies. Containment prevents the situation getting worse and stops rushes entering adjoining fields; it is limited to actions such as letting stock graze or trample the vegetation, or cutting or mulching when machinery can get in. DAFM states there is no justification for applying herbicides under containment.

Suppression expects better sward productivity in the long term and a return on the investment; herbicides may have a role in an integrated rush strategy, with the label followed to the letter of the law.

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DAFM states that farmers no longer need to use herbicides based on MCPA or 2,4-D to be seen to be tackling rushes. Land is not penalised for rushes where there is evidence of grazing, such as trampled vegetation or dung, but payment reductions can follow if it becomes overgrown with scrub, gorse or brambles because it was not managed.

High rainfall, poor drainage and low pH favour rushes. Liming is a relatively cheap way to improve the growing environment for grass; drainage is very expensive, and reseeding gives no permanent gain unless drainage and pH are also addressed.

Participation in an agri-environmental scheme may limit control options, such as the use of pesticides. Check your scheme conditions before linking rush work to a payment claim.

Prepare a short paddock assessment for your adviser: ground condition, access, grass cover, livestock system, water features and previous management. Say what improvement you expect and what problems will remain after a spray. If you choose cutting, grazing or another non-chemical action, record it under its own name and who did it; do not log it as a pesticide application.

Does MCPA spray harm water?

Yes. Uisce Éireann says MCPA can be harmful to water sources and the environment, and lists integrated weed management among the measures that protect them. DAFM calls it a high-risk strategy to apply MCPA or 2,4-D herbicides at any time near water courses, particularly if there is water in field drains and ditches and no dry window for uptake. Land in a drinking water catchment raises the risk further.

Give your adviser a sketch showing drains, ditches, surface water, wells and where you plan to fill the sprayer, and describe standing water or runoff routes as you saw them, with the date. Compare the weather conditions on the label with the forecast and with what you see: wet foliage or saturated soil. The rain guide covers that question. Keep the label wording with the job instruction instead of relying on a remembered waiting period.

Where Agritox 500 cannot be applied

The label bans hand-held equipment, application between the end of September and the beginning of March, and water volumes below 200 litres per hectare.

MCPA-based products are not approved for weed wipers, and that use is illegal; only glyphosate-based products are approved for weed wipers.

Before the work starts, give the contractor the final product name and the method, and ask them to confirm that their equipment and operator match the label. Ask about weed wiping separately from a boom-spraying plan: a shared aim of rush control does not make products interchangeable between methods. Keep the application report under the same paddock names you used on the order.

If you want to tank-mix Agritox 500, ask Nufarm or its distributor and name every proposed partner, such as 2,4-D, fluroxypyr or clopyralid, with the actual formulation and intended use. Say whether it is a ready-made multi-active product or a mix assembled on the farm, and ask what evidence covers the whole combination, crop and method. Keep the reply with the component list; if a component changes later, treat it as a new question. The tank-mix guide covers physical compatibility, crop safety and performance.

After spraying, pass the instructions from the product actually used to whoever grazes the stock and whoever cuts the silage, and list stock access, cutting and machinery work separately instead of one line called “waiting time”. Record the real application date first; if a contractor corrects the report, tell everyone who relied on the old date.

Which weeds does Agritox 500 control?

The specimen rates these as moderately susceptible (suppressed, top growth usually killed): meadow buttercup, cat’s ear, hoary cress, common daisy, autumn hawkbit, common knapweed, common ragwort, self heal, creeping thistle and spear thistle. Creeping thistle is treated at the early flower bud stage.

Tell your adviser the exact species you see rather than “broadleaves”; the table lists creeping and bulbous buttercup separately. For a mixed infestation, ask which weeds the treatment covers and which need another decision, and mark their spread on the paddock sketch, separating a boundary patch from a problem across the whole sward. Do not expect eradication where the label describes suppression or top-growth kill.

Moderately resistant (top growth only may be killed): bulbous buttercup, creeping buttercup, coltsfoot, dandelion, meadowsweet and hard rush. Bulbous buttercup is treated in autumn on new leaf or in spring; creeping buttercup in spring or early summer.

Next step

Check the pack’s PCS number against the Irish register; mixing and recording are covered in the tank-mix guide and the grassland-records guide.