Developing an effective strategy for the sustainable control of Italian rye-grass (Lolium multiflorum)

Abstract

The aim of the project was to identify specific aspects of crop and herbicide management that would optimise control of Italian rye-grass (Lolium multiflorum) in wheat with a range of herbicides. This would reduce reliance on one specific mode of action, leading to the more sustainable herbicide use.

The information generated has enabled a more effective strategy for the sustainable control of Italian ryegrass to be developed which should help to avoid resistance to the mode of action of iodosulfuron + mesosulfuron (Atlantis), the dominant herbicide used for rye-grass control.

This project has contributed to a sustainable strategy for controlling Italian rye-grass in the following ways: 
• Alternatives to Atlantis and its mode of action, such as chlorotoluron, Axial (pinoxaden), Crystal (flufenacet + pendimethalin), Ingot (diflufenican + flurtamone + isoproturon), Grasp (tralkoxydim) when applied at the optimum growth stage of the weed can provide effective control of rye-grass where herbicide resistance does not significantly reduce efficacy. However, these may not provide adequate control of moderate to high populations of black-grass (Alopecurus mysosuroides) that may also be present.
• There is little innate dormancy in Italian rye-grass at the time when winter cereals are sown and there is likely to be significant emergence soon after the seedbed has become thoroughly moist. The lack of dormancy results in reduced numbers of Italian rye-grass emerging in later-drilled winter wheat.
• Contrary to farming folklore, there appears to be no secondary peak of emergence in the spring of Italian rye-grass in winter wheat. Similar numbers appear to emerge after mid-November in crops drilled from mid-September to mid-October. The lack of a ‘spring flush’, together with a similar emergence from mid-November, may explain why applications of herbicides in the autumn provide effective season-long control. There can be an advantage from applying post-emergence herbicides at the one-leaf stage of the weed rather than the three-leaf stage. The extent of the advantage will depend on the herbicide in question and the resistance status of the weed.
• Typically, the moisture content of the surface layers of the soil will not significantly affect the level of control of non herbicide-resistant populations. When the soil is very dry the control achieved by Atlantis may be reduced.