The trials at Syngentas Innovation Centre in Stafford shire, on difficult to control ryegrass with RRR target site resistance to ALS (sulfonylureas) and ACCase (‘fop and ‘den) herbicides, assessed surviving ryegrass head numbers in five varieties of hybrid barley, two varieties of conventional two-row winter barley, two varieties of conventional six-row winter barley and two varieties of winter wheat.

All varieties were drilled early, in mid-September, to purposely exacerbate the ryegrass pressure.

Each variety was then either left untreated or received a pre-emergence application of five litres/hectare Defy (prosulfocarb) + 0.6 litres/ha flufenacet+diflufenican, a peri-emergence application of two litres/ha flufenacet+pendimethalin, or these same herbicides in a combined pre and peri-emergence programme.

At the end of March, each of these treated and untreated plots was then either oversprayed with 0.82 litres/ha of the contact-acting graminicide, Axial Pro (pinoxaden), or left without a spring graminicide.

Commenting on the findings, Syngenta area manager Peter Hawkins says: Unsurprisingly, the greatest ryegrass reductions tended to be in the plots where the full pre-emergence plus peri-emergence plus spring herbicide programme was applied.

Robust However, what was particularly interesting was, even with this robust programme, and despite this being an extremely high-pressure site with more than 300 ryegrass heads/sq.m, clear differences between the levels of ryegrass reduction were still apparent between the different crop types.

While 85% ryegrass control was achieved with the full programme in winter wheat and in the conventional two-row winter barley and 90% was achieved in the conventional six-row winter barley, this increased to between 95% and 98% control in the hybrid barley.

This was with the winter wheat drilled at 350 seeds/sq.m and the conventional winter barleys drilled at 325 seeds/sq.m.

By comparison, the hybrids were drilled mainly at 200 or a maximum of 250 seeds/sq.m.

Even where one of the hybrids, SY Kingsbarn, was drilled at a purposely low 100 seeds/sq.m to simulate poor crop establishment, this still gave 90% ryegrass reduction.

With lower weed pressure, we have seen previously that hybrids can have a greater impact in terms of percentage reduction.

Mr Hawkins adds, as this trial indicated, when dealing with a tough ryegrass population, it is important to use every management method available including cultural, varietal and chemical with delayed drilling being critical.