Identifying that you have blackleg in your canola and it is a problem is a critical first step.
If you have had canola in tight rotation (canola every year or every other year in same field) for a number of years, that will have helped to slowly build up the level of disease inoculum in your field. As well, potentially allowing for selection of blackleg races that your past variety did not have resistance to.
1. Increase the time between canola in the same field by adding another crop for additional break year (instead of canola-wheat-canola, try canola-wheat-pea-canola or canola-wheat-flax-canola).
2. Grow an R-rated blackleg tolerant variety. If you have already been growing a variety with the R rating and still have high levels of blackleg, consider changing to another variety. R-rating is a blackleg tolerance rating, and does not mean immunity. Your affected field, may have blackleg races that are different than the races your current variety has tolerance to.
3. Control volunteers from the past crop in break years. Also control weeds like wild mustard, stinkweed, flixweed and shepherd’s purse, which are all hosts and sustain blackleg in non-canola years.
4. Consider a fungicide. Using a fungicide on high pressure fields can assist in reducing the incidence and severity of blackleg infection. But, using a fungicide to control blackleg on fields where no blackleg has been seen in the past is not economical. Save this option for when you need it.
Keep record and continue to track the level of blackleg in those fields when planted back to canola. As well, watch other fields on your farm in 2013 and onwards for the signs of blackleg infection.