French Study Tests Autumn Strategies Against Perennial Ryegrass in Cereals
France's Arvalis institute has spent two seasons testing autumn herbicide programmes against perennial ryegrass in wheat. The best results came from combining a pre-emergence treatment with a follow-up at the first-leaf stage.
The French agricultural research institute Arvalis tested autumn herbicide programmes against perennial ryegrass (Lolium perenne) in wheat in 2025 and 2026. The issue also matters in Poland, where flufenacet, the active substance that has kept this weed in check, is due to be withdrawn at the end of this year. The French researchers have been looking for an alternative for several years.
New substances in the trials
Arvalis tested a new two-component herbicide coded H2103. It contains beflubutamid, already known in Poland from existing products, and bixlozone, a compound not yet listed in the Polish register. Bixlozone blocks the formation of carotenoids, plant pigments, and belongs to HRAC group 13. Also tested was H2501, a post-emergence product containing cinmethylin, which Poland has temporarily authorised in limited quantities this year as Luximo.
Results
With a single pre-emergence application, efficacy ranged from 71% to 88%, the highest being H2103 combined with Defi. With a single post-emergence application at the first-leaf stage of wheat, Constel plus Defi reached 87%, and H2501 alone 78%.
Two autumn applications performed better. In seven trials in 2026, H2103 plus Codix before emergence followed by Defi at BBCH 11 gave about 95%. Other programmes scored between 86% and 94%. The researchers note that at high weed densities even 88% control leaves plants that compete with the crop.
Adding a spring correction to the autumn treatment is technically sound but expensive when resistant weeds are not an issue. Of four sites, only one saw a gain comparable to the autumn-only strategy.
The French conclude there is no cause for concern for now, but costs will be higher than with flufenacet.
