Hwang, S. F., Ahmed, H. U., Turnbull, G. D., Gossen, B. D. and Strelkov, S. E. 2014. The effect of seed size, seed treatment, seeding date and depth on Rhizoctonia seedling blight of canola. Can. J. Plant Sci. 94: 311-321. Rhizoctonia solani can have a substantial impact on seedling establishment and productivity of canola (Brassica napus). The effects of seeding date, seeding depth, seed size, and seed treatment on seedling blight of canola were evaluated under greenhouse and field conditions. Early seeding resulted in higher seedling emergence in one trial year and higher seed yield in all trial years relative to a late-seeded treatment. Mid-sized seed (range 0.7-2.0 mm diam.) had greater seedling emergence in R. solani-inoculated growth medium in a greenhouse trial and higher seed yield in one of two field trials compared with smaller seed (<0.7 mm). In the greenhouse study, sowing of large seed resulted in greater plant height and shoot weight compared with sowing of smaller seed. The effect of seeding depth was significant only on shoot dry weight, which increased at a seeding depth of 2.6 cm. Seed treatment with Helix Xtra (thiamethoxam difenconazole metalaxyl fludioxonil), and Prosper FX (clothianidin carboxin trifloxystrobin metalaxyl) resulted in a significant increase in seedling emergence and yield compared with the inoculated control. These results indicate that fungicidal seed treatment can minimize the impact of R. solani on canola.