Evaluation of Fall and Spring Lime Applications for the Management of Clubroot of Canola in Western Canada

Clubroot, a soilborne disease caused by <i>Plasmodiophora brassicae</i>, poses a significant threat to canola (<i>Brassica napus</i>) production. The use of lime to elevate soil pH shows promise for clubroot management. In this study, limestone and hydrated lime (HL) were evaluated for their effectiveness in controlling clubroot across four field sites in 2019 to 2020 and 2021 to 2022, and in greenhouse trials conducted in 2019 to 2020 and 2020 to 2021. The treatments included an untreated control (UTC), limestone applied at rates of 5 and 10 t ha^-1 in either fall or spring, spring application of HL at 5.0 and 10 t ha^-1, and a combination of fall limestone application with spring HL application at rates of 2.5 or 5.0 t ha^-1 each. The canola hybrids '45H31' (susceptible) and 'CS2000' (moderately resistant) were included in the greenhouse experiments, while '45H31' was used in the field. Significant reductions (<i>P</i> < 0.05) in clubroot severity relative to the UTCs were observed in all lime treatments in the field or greenhouse, except for the 5.0 t ha^-1 spring limestone application at one field site in 2021 to 2022. Increases in soil pH and reductions in soil inoculum density were recorded for all lime treatments. The most consistent reductions in clubroot severity across sites and years were obtained with fall limestone or spring HL application at 10 t ha^-1, or the combination of fall limestone and spring HL at 5 t ha^-1 each. Applying limestone in the fall may present a viable option for managing clubroot in canola.[Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.