Oilseed rape crop debris and potential spread of Leptosphaeria maculans (phoma stem canker) into China
Bruce Fitt: University of Hertfordshire
<div>Quarantine regulations are designed to prevent establishment of pathogens in new countries. Phoma stem canker, which causes global losses in oilseed rape worth >£1000m per annum, is caused by <em>Leptosphaeria maculans</em> and the less damaging <em>L. biglobosa</em>. Chinese surveys provided evidence that only <em>L. biglobosa</em> is currently present in China but that <em>L. maculans</em> is present in crop debris associated with cargoes of oilseed rape seed imported into China. Following our work, which applied models of the spread of <em>L. maculans</em> across Canada to assess potential spread across China, in November 2009 the Chinese quarantine agency imposed restrictions on the import of oilseed rape seed into China. Canadian exports to China decreased in 2010 but then returned to previous levels when it was agreed that they could enter China through ports in regions where oilseed rape is not grown. A debate about the amount of crop debris (dockage) permitted in seed cargoes was resolved until 2020, when a memorandum of understanding was signed between China and Canada during a visit by Chinese prime minister Keqiang Li to Canada in 2016. Current modelling work will assess the risks of spread of <em>Leptosphaeria maculans</em> associated with different amounts of debris in cargoes. This work will establish principles that can be applied to help restrict the spread of pathogens to new countries in seed cargoes.</div>
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