The map shows positive clubroot findings by Rural Municipality (RM), discovered through visual field symptoms and/or presence of clubroot spores in soil through laboratory testing for DNA. Testing completed from 2009-2016 is still considered limited. Positive findings have been at low concentrations, usually below 5,000 spores/gram soil and throughout the province. As more fields are sampled, the map will be updated.
RMs have been highlighted to show the highest concentration of clubroot spores found. This does not mean all fields in the specific RM have these concentrations. As clubroot spore concentrations can be highly variable within a field, the RM classification indicates only the maximum spore concentration found in any field in the RM. Further explanation on the concentration categories are as follows:
RED = Symptoms Observed - Clubroot symptoms have been observed in fields in this RM. Management to prevent continued build-up or spread of this pest should be implemented on farms.
ORANGE = 10,001 to 80,000 spores/gram soil - Clubroot spores have been found in fields in this RM at concentrations approaching levels known to cause field symptoms. Without management, concentrations may increase to where symptoms are visible in the field within one crop cycle.
YELLOW = 1,001 to 10,000 spores/gram soil - Clubroot spores have been found in this RM at low to intermediate levels. With proper management, spore concentrations can decline over time.
GREEN = 0 to 1,000 spores/gram soil - Clubroot spores have not been detected, or detected at very low levels. At this concentration, clubroot is not a major concern, but fields should be monitored over time. Re-testing is recommended within the next five years to determine if concentrations are increasing.
It is generally reported that 100,000 spores/gram of soil are required to see symptoms under field conditions, but under favourable conditions, lower concentration can cause field symptoms of clubroot.
Annual surveys for clubroot started in 2009, testing 80 - 100 fields annually. Since 2015, soil sampling and laboratory testing increased, as part of expanded efforts to better understand clubroot distribution in Manitoba. From the culmulative survey efforts, 270 individual fields were found positive for clubroot through soil analysis and 8 fields were confirmed to have symptoms.
As less than 10% of farms in Manitoba have been sampled, it is recommended that all fields be tested to determine if clubroot spores are present, regardless of RM classification.
Clubroot is a soil-borne pest that can move from field to field on both agricultural and non-agricultural equipment. Specific biosecurity activities to minimize the spread of clubroot will differ by the known levels of clubroot DNA found within the field. Manitoba Agriculture has a series of suggestions for all industries operating on agricultural land to minimize the potential of spread on the Crop Biosecurity page.