This map shows positive clubroot findings by Rural Municipality (RM), discovered through laboratory testing for presence of clubroot spores in soil and/or positive confirmation of clubroot symptomatic plants. Testing was done from 2009-2014 and is still considered limited. Positive findings have been at low spore concentrations and sporadic throughout the province. As more fields are sampled, the map will be updated.
A number of fields in an RM may have been tested and 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 and in some fields, clubroot may not have been detected. As clubroot spore concentrations can be highly variable within a field, use the RM classifications to indicate only that clubroot has been found in the RM and the maximum severity of the spore concentration. More explanation on the concentrations are as follows:
RED = >80,000 spores/gram soil or symptoms observed - Clubroot symptoms have been observed in fields in this RM or fields have tested positive for clubroot spores at concentrations known to cause disease symptoms in field. 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 symptoms in field. Without management, concentrations may increase to levels 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 has only been detected in this RM 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.
Note: In Alberta, clubroot concentrations are known to reach more than 10 million spores/gram of soil in some fields. It is generally reported that 100,000 spores/gram of soil are required in order to see clubroot symptoms under field conditions. Under favourable conditions, lower concentration of spores could lead to clubroot symptomatic plants.
Biosecurity Implications
As less than 5% of farms in Manitoba have been tested, it is recommended that all fields be tested to determine if clubroot spores are present, regardless of RM classification. To date, clubroot has been confirmed in 48 Manitoba fields.
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. MAFRD has a series of suggestions for all industries operating on agricultural land to minimize the potential of spread on the Crop Biosecurity page.
Source : Manitoba Agriculture, Food and Rural Development