Mark VanGessel, Extension Weed Specialist, University of Delaware; mjv@udel.edu, Kurt M. Vollmer, Extension Weed Management Specialist, University of Maryland; kvollmer@umd.edu, Caio Brunharo, Assistant Professor of Weed Science, Pennsylvania State University; brunharo@psu.edu, Adrian Veron, Pennsylvania State University; eav5256@psu.edu
Each year there seems to be more questions about Italian ryegrass control in the region. So last spring, Kurt Vollmer (Univ. of MD, Weed Extension) and I gathered ryegrass seeds across the eastern shore. Big thank you to a number of you who supplied us with samples as well. We had viable seeds from forty-one fields. This was not a systematic survey, but rather a collection of ryegrass plants that were seen growing in small grains, corn fields, or soybean fields as we drove around the countryside. Dr. Bruharo and Adrian Veron tested these samples for potential resistance to glyphosate, PowerFlex, Accent Q, Axial XL, and clethodim (Select).
None of the samples were resistant to glyphosate. However, all were resistant to PowerFlex. Over half were resistant to Accent Q, and five sites were resistant to Axial XL. Finally, none were resistant to clethodim. It is important to know that two widely used herbicides for winter wheat have resistance in the area (PowerFlex and Axial XL); and these herbicides represent two different modes of action. If you have had issues with ryegrass control in your area and are planning on planting winter wheat, it’s important that you start clean and use Zidua or Anthem Flex at planting. Using Zidua or Anthem requires that you seed with a drill; do not spin on wheat seed. Axial use should not be the first line of control due to presence of resistance in the region.