b'If blackleg severity is increasing in your field over time, then the races in your field are likely adapting to overcome the genetic resistance in your cultivar.PHOTO: JUSTINE CORNELSEN, CANOLA COUNCIL OF CANADAthe Agricultural Research and Extension Council of AlbertaHarding summarizes. Overall, our surveys show blackleg is (ARECA). Last year, and in 2018, they partnered with thewidespread in the province, but we generally only see 10 to 20 per agricultural fieldmen again. These surveys include blackleg,cent of the plants with symptoms, and the severity on average is sclerotinia and clubroot. very low in most fieldsless than one out of five. Meaning, the This has been a really big step forward for us in Alberta toresistance in our canola varieties is working very effectively. have a consistent, long-term, annual disease survey in canola,Harding states the 2019 blackleg results could be quite says Harding. And it is thanks to partnering with groups likedifferent in various areas of the province. In 2019, some parts the agricultural fieldmen and ARECA. Were going to continueof Alberta had almost no rain, and in other parts it wouldnt with this partnering approach.stop raining. For southern Alberta, Im guessing that the 2019 They try to survey about one per cent of the canola fields inblackleg numbers will be quite similar to those in 2017 and 2018. each county, collecting data on blackleg prevalence, incidenceBut in the central part of the province, where they essentially and severity. The table below summarizes the results from thehad rain all season long, we could have much higher levels.2015 to 2018 surveys. The blackleg levels were a little higher inTo try to draw more information from the survey data, 2016 due to wet conditions that favoured the disease.Harding and his group have started conducting a hot spot analysis. The data points in the survey have a precise GPS RESULTS FROM ALBERTA BLACKLEG SURVEYS, 2015 TO 2018 location attached to them so we can map them. One of the tools Parameter 2015 2016 2017 2018 in the mapping software can look around each individual point that has a high severity to see how many points nearby also Number of fields surveyed 208 480 421 339 have a high severity. If it reaches a certain threshold, it will tell you there might be a little hot spot there, he explains.Prevalence: percentage of This analysis is one way we can distil down an enormous surveyed fields that have70.70% 90% 82.20% 80.50% amount of survey data and say, here are some areas we may blackleg symptomsneed to look at a little closer. Incidence: percentage of13.10% 21.20% 14% 13.25% They first conducted the hot spot analysis in 2018. stems with blackleg symptoms We found a few spots with a little higher severity and maybe a little higher incidence. We dont yet know what causes the hot Severity: rated on a scale fromspots, whether they might be due perhaps to the appearance 0 (no disease) to 5 (completely0.39 0.42 0.26 0.24 of a new virulent race that is overcoming the resistance in our diseased) varieties, or maybe the local weather conditions pushed the Courtesy of Michael Harding, Alberta Agriculture and Forestry severity a little higher. Spring 2020 23'