Evaluation of Amisulbrom Products for the Management of Clubroot of Canola (<i>Brassica napus</i>)

Clubroot, caused by <i>Plasmodiophora brassicae</i>, is an important disease of canola (<i>Brassica napus</i>). Amisulbrom, a quinone inside inhibitor (QiI), was evaluated for its effectiveness in clubroot management in Alberta, Canada. Resting spores of <i>P. brassicae</i> were treated in vitro with 0, 0.01, 0.1, 1, and 10% (<i>w</i>/<i>v</i>) amisulbrom to determine its effect on spore germination and viability. Amisulbrom inhibited resting spore germination by up to 79% and reduced viable spores by 31% relative to the control. Applications of a liquid solution (AL1000, 1000 g active ingredient (ai) ha⁻¹) and granular formulations (AF700, 700 g ai ha⁻¹; AF1000, 1000 g ai ha⁻¹; AF1500, 1500 g ai ha⁻¹) of amisulbrom were tested on the canola cultivars ‘45H31’ (clubroot-susceptible) and ‘CS2000’ (moderately resistant) under greenhouse conditions and in field experiments in 2019 and 2020. In the greenhouse, the treatments were evaluated at inoculum concentrations of 1 × 10⁵ or 1 × 10⁷ resting spores g⁻¹ soil. A trend of decreasing clubroot severity with an increasing amisulbrom rate was observed. At the lower spore concentration, treatment with AF1500 resulted in a clubroot disease severity index (DSI) <20% for both cultivars, while the lowest DSI under both low and high spore concentrations was obtained with AL1000. The field results indicated a significant reduction in DSI, with varied effects of rates and liquid vs. granular formulations. The greatest reductions (up to 58.3%) in DSI were obtained with AF1500 and AL1000 in 2020. These findings suggest that amisulbrom holds promise as part of an integrated clubroot management approach.