Clubroot: Management steps for infested land

Clubroot has been found in 18 Alberta counties and it spreads every year. See the 2010 clubroot map at the bottom of this article. Growers have clubroot-resistant varieties to choose from, but this resistance could be lost quickly if not supported by a combination of the following practices:

1. Use resistant varieties. Six clubroot-resistant hybrids are on the market for 2011. They are D3152 from DuPont, Dekalb 73-67 and 73-77 from Monsanto, Proven 9558C from Viterra, 1960 from Canterra, and 45H29 from Pioneer Hi-Bred. While these varieties can provide a significant drop in clubroot infection and severity, growers using them can expect some clubroot infection in the field. Host canola plants will most likely be susceptible volunteers in the field and susceptible off-types from the seed bag.

2. Use a minimum four-year rotation. Clubroot resting spores are long lived. Four years is considered a minimum rotation between canola in fields known to have the disease.

3. Rotate between resistant varieties. Because resistance likely comes from a single gene, that resistance can fail if used frequently on the same field. Rotating varieties may help, but we don’t know if current resistant hybrids have the same resistance gene.

4. Minimize traffic in and out of infested fields. Once clubroot is found in a field, the goal is to prevent the introduction of the long-lived resting spores into new fields. Minimize all equipment traffic into infested fields. Service and nurse trucks, for example, should remain on the road and field equipment should be brought to them. Equipment leaving an infested field should be thoroughly cleaned and disinfected. Click here for tips on how to clean machinery.

5. Limit tillage. Whenever practical, do not work infested fields when they are wet because more mud will stick to equipment and could be transported to clean fields. Reduced tillage or direct seeding also may help combat a clubroot infestation by reducing the movement of contaminated soil.

6. Control weeds. Volunteer canola and susceptible weeds (mustard family, dock, and hoary cress) must be controlled in the rotational crops. These volunteers and weeds host clubroot in non-canola years, reducing the effectiveness of rotation as a management tool.

7. Scout. When using resistant varieties, continue to scout for gall formation on plant roots. Low-level infection is normal for these hybrids, as noted in point No.1 above. Higher incidence levels could signal the start of a breakdown of resistance.

No fungicides. Some Group-14 fungicides are registered to control clubroot in other brassica vegetable crops, but they are not registered for use on canola. Do not use non-registered products on canola. Residues of unregistered products found on exported seed could jeopardize canola markets.

Click here for more details on the clubroot situation in Western Canada. Clubroot maps are updated often. Click herefor the latest version.

Published on January 5, 2011