- Italian ryegrass (Lolium multiflorum) is becoming an increasing problem in many areas of the country
- Dr Paul Fogg, Frontier crop production technical lead, believes growers can learn lessons from controlling black-grass (Alopecurus myosuroides) and adopt an integrated strategy
One of the issues is that ryegrass is more competitive than black-grass; just five plants per sq.m. will reduce yields by five per cent,” Paul warns. “It tillers more than black-grass and while most ryegrass seed germinates in the autumn, germination can also occur throughout the year.”
Hygiene and a zero-tolerance approach can help stop weeds spreading, but due to the movement of contracting equipment and straw, this is often easier said than done.
With seed surviving in the soil for more than five years, cultivations can play an important role and deep inversion ploughing of fields which have not seen a plough recently can effectively bury seeds. However, Paul warns that annual ploughing will simply mix viable seed near the surface.
“In the worst-case scenarios, it may be best to simply take fields out of production,” he notes.
Delaying autumn drilling and increasing the seed rate will help. However, because ryegrass seed can germinate year-round, he explains a move to spring sowing may be less effective as a control technique.
“Spring drilling has a role to play if conditions are just right, although in my experience it’s likely to be less effective than for black-grass control,” says Paul.
Higher seed rates and moving to hybrid barley varieties can help crops compete with weed pressure. However, it is important not to increase seed rates to the point that crops compete with themselves.
“SOYL’s soil and weed mapping services through MyFarm can facilitate a variable rate drilling approach to provide strong competition from the crop in those patches where ryegrass is present,” he adds.
Paul notes that herbicides remain a key part of an integrated strategy. But with evidence of different resistance mechanisms to different active ingredients, he stresses growers must test their ryegrass populations in order to make the most of the available chemistry.
“In some places contact herbicides will still work well, whereas some populations may show resistance,” he says. “Don’t assume that just because, for example, mesosulfuron-methyl is not effective, that pinoxaden won’t work, or vice versa.”
Another issue is that resistance to flufenacet has also been found in some areas; although it is not widespread.
“To add to this, glyphosate stewardship is also necessary to prevent resistance building up when creating stale seedbeds,” he notes. “Historically, control has centred around the use of flufenacet and prosulfocarb, although recently aclonifen has played a more important role.”
A new active is now available in the form of Luximo™, active ingredient cinmethylin, and is likely to prove useful, although Paul warns there are ‘no silver bullets’.
“Looking forward, further new herbicide products and novel techniques such as destroying weed seed at harvest with seed destructors are also likely to become a part of control strategies.”
