Ryegrass can remain in the soil for up to 20 years, though the majority of seed usually persist for up to 7 years. Mature plants typically produce 250 seeds/head and with 20 heads per plant.
Ryegrass
What is ryegrass?
Two species of ryegrass, Perennial ryegrass (Lolium perenne) and Italian ryegrass (Lolium multiflorum). Ryegrass is widespread throughout the UK. Italian ryegrass causes the greater problems, with populations of just 5 plants/m2 causing a yield loss of at least 5%.
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Biology
Ryegrasses have a competitive index of 0.85, compared with 1.0 for wild oats and 0.4 for blackgrass, so even moderate populations can have severe effects on crop yield. Italian ryegrass can be annual or biennial and can be very well tillered or not depending on crop competition. Italian ryegrass has a protracted germination period, with the majority germinating in the autumn and lesser amounts in the spring. Ryegrass responds well to nitrogen fertiliser spread for the crop and hence it is very aggressive in its spring growth pattern.
Flowering time is much more variable and later types may not have shed before harvest. Seed can become dormant in the soil and persist for two years and exceptionally for four years.
Flowering occurs in May-August and seed is shed before harvest and can persist in the soil for up to seven years.
Perennial ryegrass is a competitive weed, but less so than Italian ryegrass. As the name indicates it is a perennial plant 30-60 cm tall and will tiller as much as conditions allow.
How can I identify ryegrass?
Italian ryegrass leaves are hairless with a glossy underside and tend to be wider than perennial ryegrass. When the stem is cut horizontally the leaves can be seen to be rolled in the sheath. The stems are round (perennial ryegrass is flattened) and auricles are present and without hairs.
The seedhead is a flattened spike with spikelets arranged alternately on opposite sides of the stem. The spikelets are awned and stalkless and have their rounded face next to the stem. It must be noted that the spikes of couch are similar but have the flattened face of the spikelets next to the stem.
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Italian ryegrass
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Perennial ryegrass
Why is ryegrass a problem?
Italian ryegrass can remain in the soil for up to 20 years, though the majority of seed usually persist for up to 7 years. Mature plants typically produce 250 seeds/head and with 20 heads per plant not uncommon, seed production can be 5000 seeds/plant. With 5 plants/m2 reducing yield by 5% it causes marked economic losses.
Additionally, there is widespread resistance to a range of chemistry, with resistance reported to ALS, fops and dim and flufenacet chemistry. Much of the resistance is Enhanced Metabolic Resistance (EMR), so these products will provide some activity, with control better on smaller plants.
How do I control ryegrass?
Delayed autumn drilling of winter wheat has some benefits or introducing a spring crop to allow ryegrass germination and the use of glyphosate prior to drilling.
Within the autumn drilled crop a robust spray programme of pre-emergence products (i.e. cinmethylin, prosulfocarb or pendimethalin+flufenacet) is required and a follow-up autumn treatment of diflufenican + flufenacet may be appropriate. ALS containing products (Broadway® Star, Memphis®, Avocet® or mesosulfuron+iodosulfuron) can be applied in the autumn in tank mixture with a residual acting product where temperatures and ground conditions all. Where Broadway Star, Memphis, Avocet are used in the spring, a residual tank mixture should be considered before the ryegrass plants get too large (>tillering).
Avocet Herbicide
Avocet®, a post-emergence ALS inhibitor for use on winter wheat, rye and triticale for the control of blackgrass and other grasses and broad-leaved weeds.
Broadway Star Herbicide
Broadway® Star delivers an outstanding performance in winter wheat against yield robbing grassweeds including wild oats, ryegrasses and bromes PLUS the bonus of controlling an extensive range of broad-leaved weeds.
Memphis Herbicide
Memphis® provides a robust solution for control of key grassweeds and broad-leaved weeds in winter wheat, winter rye, winter spelt and winter triticale.
Palio Herbicide
Palio® delivers outstanding performance in winter wheat against yield robbing grassweeds including wild oats, ryegrasses and bromes.