Impact of post-anthesis glyphosate on woolly cupgrass seed production, seed weight and seed viability

Abstract

Nurse, R. E., Darbyshire, S. J. and Simard, M.-J. 2015. Impact of post-anthesis glyphosate on woolly cupgrass seed production, seed weight and seed viability. Can. J. Plant Sci. 95: 1193–1197. Herbicides are generally applied at early stages of crop and weed growth to protect crop yield. Few studies have evaluated the effect of late (post-anthesis) applications of glyphosate as a management option to limit the seed production of weed escapes, such as woolly cupgrass (Eriochloa villosa). We propagated woolly cupgrass under greenhouse conditions and then applied three glyphosate treatments post-anthesis including: (1) an untreated control; (2) 900 g a.e. ha−1; and (3) 1800 g a.e. ha−1. Terminal inflorescences were collected 21 d after glyphosate application, and seed production, seed weight and embryo viability were assessed. Post-anthesis glyphosate applications did not influence seed production, but reduced seed weight and viability by 50 and 96%, respectively. Therefore, glyphosate applied just before the woolly cupgrass inflorescence begins to emerge from the leaf sheath (as late as the R1 stage in soybeans) is an effective strategy to manage woolly cupgrass reproduction and stop viable seeds from entering the soil seed bank or other dispersal pathways.