Influence of Sowing Date of Winter Cereals on the Efficacy of Cinmethylin on Alopecurus myosuroides (Huds.)

Cinmethylin, a pre-emergent applied active ingredient, inhibits the fatty acid thioesterase and offers a new option in the chemical control of Alopecurus myosuroides, one of the most problematic weeds in arable farming in Europe. It was assumed that with the delayed sowing of winter wheat and winter barley due to more humid and cooler conditions, the efficacy of cinmethylin against A. myosuroides increases. Four field trials were conducted in Southwestern Germany from 2019 to 2022. From mid-September until early November, winter wheat and winter barley were sown in at four dates each year, with intervals of fourteen days. After each sowing, 500 and 250 g cinmethylin ha(-1) were applied subsequently to winter wheat and winter barley, respectively. Flufenacet (240 g ha(-1)) served as a comparison in both crops. A herbicide efficacy of over 90% was achieved for winter wheat sown in mid-October, while it was only 70% for winter wheat sown in mid-September. Similar results were observed for winter barley. On average, cinmethylin achieved a significantly higher efficacy in winter wheat than flufenacet. The presented approach with cinmethylin and delayed sowing date provides a basis for the comprehensive control of A. myosuroides. However, further measures of integrated weed management (crop rotation, situational ploughing, and stale seedbed) need to be applied for 100% control.