Effects of soil-borne Rhizoctonia solani on canola seedlings after application of glyphosate herbicide

Abstract

Rashid, A., Hwang, S. F., Ahmed, H. U., Turnbull, G. D., Strelkov, S. E. and Gossen, B. D. 2013. Effects of soil-borne Rhizoctonia solani on canola seedlings after application of glyphosate herbicide. Can. J. Plant Sci. 93: 97–107. Application of glyphosate (N-phosphonomethyl glycine) prior to seeding is a common weed management practice in many agricultural systems. However, there are concerns that this practice may increase the impact of soil-borne diseases on the crop, even in cultivars that are resistant to glyphosate. In the current study, the effects of pre-plant applications of glyphosate on seedling blight of canola caused by Rhizoctonia solani and subsequent crop growth were examined under field and greenhouse conditions. Under greenhouse conditions in soil inoculated with R. solani, glyphosate application 15 d before seeding reduced seedling emergence, increased damping-off, and decreased plant height and shoot dry weight of canola relative to a glyphosate-free control. However, the adverse effects were substantially reduced when the crop was seeded 33 d after glyphosate application. This indicates that glyphosate application prior to planting may increase the impact of R. solani on canola seedlings, but that this effect diminishes quite rapidly. Soil populations of R. solani declined over the 33-d period regardless of glyphosate treatment. Glyphosate application 10 d before seeding increased seedling emergence and seed yield (1 of 2 yr) of canola in field trials inoculated with R. solani.