When a field is confirmed infected with clubroot, it’s recommended that producers implement (or continue) strict sanitation protocols, crop rotations, and the responsible use of Plasmodiophora brassicae-resistant canola varieties. There may be further options, however, like the use of fumigants traditionally used in horticulture.
“The first fumigant I look at is Vapam, and the Vapam is widely used for vegetable production,” says Sheau-Fang Hwang, plant pathologist with Alberta Agriculture and Forestry, in this Canola School video. “It is a very broad-spectrum fumigant.”
Hwang’s team published findings on the efficacy of Vapam in 2014, after preliminary trials showed a 12-16 fold reduction in primary and secondary infection, and clubroot severity at application rates of 0.4-1.6mL/L of soil.
But there are challenges to using the product, cautions Hwang.
First, it can be cost-prohibitive for large-scale applications.
“I did a little bit of calculation, and it could cost you about $2,000 per hectare — that’s almost like you don’t get any profits at all,” she says, adding that some farmers have seen a number closer to $300 per hectare with better deals, and lower rates.
The other challenge is Vapam handling and application requires special training, and can be a rather difficult product to deal with.
But, for farmers looking to treat small areas like field entrances and hot spots, fumigation might be a good option.
Canola School videos are produced by Real Agriculture.
You can find all of the episodes on Real Agriculture's Canola School page