Investigations on Apera spica-venti (L.) P. Beauv. (loose silky-bent grass) resistance against herbicides from different HRAC-classes in Hessen

Abstract

In the summer of 2014, panicles from loose silky-bent grass (Apera spica-venti) were collected at 109 sites across the federal state Hessen, to analyze the level of loose silky-bent grass resistance against herbicides from HRAC-class A, B and F1/K3. Panicles from established spraying windows as well as panicles from A. spica-venti patches, which were identified at time of harvest within cereal fields, were included into the monitoring. In December 2014 the loose silky-bent grass seeds were seeded into pots and placed in the greenhouse of plant protection service Hessen in Wetzlar. The young seedlings were sprayed (repeated) with herbicides from HRAC group A, B and F1/K3 at BBCH-stages which provided optimal efficacy for each individual herbicide. Efficacy was rated. Each biotype was tested for well-known mutations, which modify the amino acid sequence of acetolactate-synthase (ALS). Biotypes, in which the herbicide from HRAC group A reached low efficacy, were tested for well-known mutations in the acetyl coenzyme a carboxylase (ACCase) gene. The treatments with the herbicide from HRAC group F1/K3 reached very high efficacy up to 100% in nearly all biotypes. The herbicide treatment with an herbicide from HRAC group A reached high efficacy in most cases. However, all herbicides from HRAC group B showed very low efficacy. Only 12 biotypes could be controlled with an efficacy of more than 90%. 45 biotypes contained several mutations in the ALS gene, which cause ALS-resistance. Only one biotype contained a mutation, which can cause ACCase resistance. These results will be used to study reasons for development of resistance in order to develop guidance information to prevent further increase of resistance.

Keywords

• ALS inhibitor
• herbicides
• loose silky-bent grass
• resistance monitoring
• target-site resistance