Clubroot of cruciferous crops - new perspectives on an old disease

Clubroot, caused by the obligate parasite Plasmodiophora brassicae, is an economically important disease affecting plants in the family Brassicaceae worldwide. In Canada, it has mainly been a problem on cruciferous vegetables in the traditional production areas of Ontario, Quebec, British Columbia and the Atlantic Provinces. In the Prairie Provinces, clubroot has been reported sporadically in a few home gardens and commercial vegetable fields in Alberta and Manitoba over the past 80 years; however, this situation changed dramatically with the discovery of 12 infected canola (Brassica napus) fields near Edmonton, AB in 2003. Annual surveys carried out since 2003 have revealed that clubroot is a much more widespread and serious disease in Alberta than initially thought. By 2008, it had been detected in about 410 canola, mustard and vegetable fields in central and southern areas of the province. The Alberta Clubroot Management Plan was developed to guide farmers, agribusinesses, oil and gas companies, contractors, and the general public in adopting good growing practices or taking measures to prevent further spread of this disease. An unprecedented research effort is underway in western Canada to develop a better understanding of the biology and management of clubroot, especially in the canola production systems on the Prairies. These studies are broadly based and include activities such as the improvement of diagnostic tests, determination of P. brassicae pathotypes, investigation of modes of seed and soil transmission, evaluation of fungicide efficacy, soil amendments, biological control agents and equipment sanitation protocols, and modelling disease distribution and risk. Through these efforts, new information is being generated that will give the agricultural industry and other stakeholders some new perspectives on this old disease threat.