Italian ryegrass as forage: where it fits
Italian ryegrass is best suited to short-term leys of 2–3 years. It has early spring growth but is difficult to manage in mid-season because of stemmy regrowth.
It suits intensive silage production and gives useful grazing in spring and late autumn. Grazing Italian ryegrass is limited by its low sward density and its susceptibility to poaching under adverse conditions.
Before ordering seed, decide what the ley is for (conserved forage, grazing or both), how long it will stay and how it will end, so the next crop can be established without a gap.
Hybrid ryegrass is a cross between Italian and perennial types. Hybrids yield more than the intermediate and late perennial groups but less than the Italians, and they are stemmier in summer than the perennials but less stemmy than the Italians.
Italian ryegrass varieties: the list, diploid or tetraploid
When you compare offers, ask the merchant for the species, variety and ploidy (diploid or tetraploid) of every component of a mixture. If a variety is substituted, ask for the same information before you accept the seed.
The 2022 Irish Recommended List names three Italian ryegrass varieties: Davinci (diploid, first listed 2011), Fabio (tetraploid, 1998) and Nabucco (tetraploid, 2007). Heading dates are 18 May for Fabio, 20 May for Nabucco and 22 May for Davinci.
The 2026 list has tables for intermediate and late perennial ryegrass, hybrid ryegrass and white clover. The Italian ryegrass table is in the 2022 list. If a merchant calls a mixture “recommended”, ask which list, which year and which named varieties support that, and do not assume a perennial variety's listing covers an Italian or hybrid one.
Tetraploid varieties generally have higher quality, are more palatable to livestock (higher intake) and are more tolerant to drought than diploids. They have considerably lower tiller densities, which gives more open swards, and lower dry matter content. On heavy soils subject to poaching their persistence may suffer.
Seeding rates for tetraploid grasses need to be higher because of their larger seed size, so Italian grass seed of a tetraploid variety is sown at a higher rate. In the list, (T) marks a tetraploid and every other variety is diploid.
The two hybrid tables of the 2026 list come from two different trial protocols, because hybrid varieties were included in intermediate perennial ryegrass trials and compared with those controls, so the data in the two tables is not directly comparable. Compare a score only with other varieties in the same table.
The Pasture Profit Index (PPI) expresses the relative differences between varieties for spring, summer and autumn herbage yield, herbage quality, silage yield and grazing utilisation. Each trait is a € value, and the total PPI is the additional net profit expected from sowing the variety compared with the average sward in Ireland. The data comes from DAFM and Teagasc plot trials. When a merchant quotes a figure, ask what it measures (total-year yield, silage, quality or grazing) and in what units, and ask for the trial's location, seasons and comparison varieties rather than the best line of a chart.
Italian ryegrass as green manure or cover crop
Resistance is suspected in both wild types and cultivated varieties of Italian ryegrass, so Italian ryegrass sown as green manure is not exempt from the weed risk described below.
Purchased seed, cover-crop seed included, must be certified by a competent authority, and additional proof of the highest seed standards is requested particularly for cover crops. If the seed is doubtful, do not bring it onto the farm.
Identify Italian ryegrass in a cereal field
Italian ryegrass is present on a small number of Irish farms, and growers who have it find it extremely difficult to control. It is treated as seriously as blackgrass because both have similar biology and a high risk of developing herbicide resistance.
Identification features: flattened spike heads with the spikelets arranged alternately on opposite sides of the stem. If you are not sure, ask your adviser to identify the whole plant and its seed head rather than a photograph from a distance. Mark the patch and note its location and the crop history, and keep a confirmed finding apart from a suspicion.
Biology: it emerges in autumn between September and November, seeds have a short dormancy (under 7 years), seed numbers fall by 80% a year when buried and seeds do not emerge from below 5 cm. Left uncontrolled it produces up to 200 seeds per plant, isolated plants up to 1,000. It is an obligate cross-pollinator, with a high risk of developing herbicide resistance.
Keep your spray records in one place. Free to start.
Herbicide resistance in Italian ryegrass and wild oats
Resistance is confirmed in Ireland to ACCase herbicides (Axial, Falcon, Stratos Ultra) and ALS herbicides (Pacifica, Broadway, Monolith). In tests since 2019, 79% of Italian ryegrass populations were resistant to ACCase and/or ALS herbicides.
Glyphosate resistance in Italian ryegrass has been confirmed in three cases. The first population was resistant to ACCase, ALS and glyphosate. The second (IRG-19, 2025) is resistant to ALS herbicides and to glyphosate, with an EPSPS Pro-106 mutation.
When survivors appear after a spray, photograph them and mark the patch before anything else is done to it, and write down the product, the date and the rate used. Italian ryegrass has been identified in 67 Irish fields, and 53 of them (79%) are confirmed resistant. In the 2025 tests of 18 suspect populations, 13 were resistant to ACCase and/or ALS herbicides. Centurion still controlled populations IRG-06 to IRG-08, Stratos and Centurion still controlled IRG-09, and all ACCase herbicides controlled IRG-10 to IRG-12, which were resistant only to ALS.
Wild oats: 55% of tested wild oat populations were ACCase-resistant, and one population showed multiple resistance to ALS herbicides. Annual ploughing mixes weed seeds through the soil profile, which makes wild oats and Italian ryegrass harder to control. Narrow row spacing (125 mm) increases crop competition and helps suppress wild oats and blackgrass. Fallow, with glyphosate on regrowth and no cultivation until the next crop is drilled, suits wild oats because seeds need light to break dormancy.
Controlling Italian ryegrass
Zero tolerance is the policy for every farm. Hand-rogue plants entering the farm before seed set; where hand rogueing is not possible, destroy the crop before seed set and take the area out of crop production for 4–5 years.
- Hand rogueing: pull the entire plant before seeds fall from the head and take the plants away from the field for disposal. It works best on small populations.
- Crop destruction: on moderate to heavy infestations, kill crop and weed with a total herbicide or cut and remove both before the seeds ripen.
- Stale seedbed: cultivate shallow, up to 5 cm, to encourage germination, then apply glyphosate at the 1–2 leaf stage of the weeds.
- Rotation: an autumn non-cereal break crop allows a change of herbicide mode of action, and a short-term ley of 3 to 5 years lets short-lived weed seeds disappear.
- Hygiene: harvest and bale fields with grass weed problems last, and clean the combine or baler before entering and leaving them. Run a cleaned machine for 10 minutes with sieves and fans open.
- Straw for farmyard manure: check its origin; ideally use only straw from your own farm.
Walk every field from May to the end of June, map the weed (type, density, size or area, on a sketch or an old DAFM LPIS map) and record each year which herbicides worked. Using herbicides with the same mode of action in successive seasons on the same field is one of the factors that raise the grass weed challenge. Check the active substance of each product in your plan, because a different brand name does not mean a different mode of action. Anti-resistance strategies are part of integrated pest management.
Integrated weed management (IWM) combines non-herbicide or cultural techniques, which are applied first, with herbicide when needed. It includes rotations, crop establishment, targeted work and monitoring over sequential seasons, and it aims to reduce the weed seed bank and stop weed movement between areas. Keep the history in a field record.
Resistance testing
Teagasc Oak Park tests suspect weed seed for free as part of the DAFM-funded EVOLVE project. Harvest 2026 is the final opportunity for widespread testing. For a later season, ask Teagasc for the current route before you collect seed. When the result comes back, read which products were tested and apply it to that sampled population, not automatically to every field.
- Collect ripe seeds, fully dry, and store them in a paper envelope. For grass weeds the sample is two cups full of ripe seeds.
- Complete the resistance testing form, including the crop management information.
- Send form and seeds to Vijaya Bhaskar, Teagasc Crops Research Centre, Oak Park, Carlow.
Sample live plants where the appropriate herbicide was applied correctly at the label-recommended rate.
Next step
Check which herbicide products are authorised with the Irish product-register guide.