Biosecurity and clubroot: How it spreads

Here are the main ways that clubroot spreads, in order from most to least spores:

1. Soil on tillage and seeding equipment openers and frames. This is worse in wet conditions.
2. Soil on tires (tractors, sprayer, truck, ATV, etc.). This is worse in wet conditions.
3. Soil inside combines and swathers. Soil movement with these tools will be greater with pick-up headers or flex headers that often contact the ground.

For each of these first three points, the risk is higher for custom operators that visit many farms. Farmers can ask that vehicles and machines be disinfected before coming to their farm. If this is not possible, doing the job yourself might be lower risk. Renting machinery or implements can also increase the risk of moving infested soil. As does purchasing used machinery.

4. Other non-agricultural machinery. Oil patch, utility company, recreational, and personal vehicles.
5. Soil erosion by wind and water. This is often worse in tilled soils, but soil will blow and wash off no-till fields.
6. Soil on boots. This risk increases for crop tours and agronomist visits where people are coming in from other farms.
7. Animals tracking soil from farm to farm. Livestock grazing on infested soil is a greater risk than wild animals (including deer, geese and others) in most cases.
8. Earth tag on common seed.
9. Hay bales grown on infested soil.
10. Manure from livestock feeding on infested soil.

With clubroot, biosecurity has become (or should become) a fact of life across the Prairies. The pathogen has proven to move faster than anticipated. Keeping clubroot out of the farm for as long as possible is a good thing because even CR varieties are not completely resistant. Biosecurity is even more important in areas that already have clubroot because these areas now have pathotypes that can overcome CR in current varieties. More soil movement increases the chance of bringing these pathotypes onto the farm.

Where is clubroot confirmed? Alberta map. Districts 9A and 9B in Saskatchewan. Manitoba map. NOTE: When clubroot is confirmed in a county, district or municipality, it is likely present in adjacent jurisdictions as well.

Further reading:

Managing clubroot: Equipment sanitation guide
Clubroot: Scouting and CR seed decisions section on controlling clubroot