Clark Brenzil, Weed Control Specialist with Sask. It is located in Saskatchewan mostly in the northeast corner. It does not tolerate tillage. Even minimum tillage with one pass a year with sweeps will probably provide adequate control. However, others suggest that it may be more susceptible at the seedling stage.
Competition can certainly reduce the vigor of common tansy.
Dan Cole weed specialist with Alberta Agriculture suggests that cropping practises such as fertilizing to soil test recommendations, using competitive crops, and using high seeding rates should all be effective in suppressing common tansy in low disturbance production of annual crops. Cole's research has been done with common tansy in pasture land where he has tried several different herbicides in conjunction with mowing and fertilizing. One of his suggestions to control the spread of common tansy is to mow the ditches where it is prevalent while the flowers are still yellow. The seed will not be viable at this stage. Escort, an industrial herbicide with the same active ingredient as Ally, has a registration for controlling common tansy in ditches.