According to government officials in Alberta, the most worrying rapeseed rhizobia spread faster than expected in 2009, leading to a decline in the planting area in Alberta, Canada.
On the whole, nearly 500 farmland in Alberta are infected with root nodule disease, which can make the roots of rapeseed unable to absorb soil nutrients and water, and can live in the soil for up to 20 years. The local government has banned the infected farmland from planting rapeseed for three to six years.
Officials confirmed that more than 50 fields in western Alberta were infected with rhizobia last year, slightly lower than the level in previous years.
Alberta government oilseed experts said that the drought in Alberta in early 2009 affected the growth of rapeseed and other crops, but also restricted the spread of root nodule disease. But July's rainfall improved two things.
Canada is the world's largest rapeseed exporter. Last year, farmers harvested 11.8 million tons of rapeseed, a record high.