Clubroot resistance breakdown confirmed over a wide area in Alberta

May 13, 2015 - Issue 9

Erosion of clubroot resistance is showing up in fields across central Alberta. Recent research by Alberta Agriculture and Rural Development (AARD) and the University of Alberta (U of A) has confirmed the continued spread, with multiple virulent pathotypes suspected.

Some fields risk losing their ability to grow canola profitably until new genetic solutions or other management options become commercially available. Follow these steps to keep erosion of clubroot resistance from showing up or getting worse:

—Equipment contaminated with clubroot-infested soil is the key mechanism for clubroot spread, so good sanitation on equipment during all field operations — including seeding and spraying — is recommended. At least 90% of clubroot spores that move from field to field can be stopped by just taking a few minutes to scrape off most (90%) of the soil before leaving the field.

—Longer rotations and the use of resistant varieties will prevent the buildup of spores on land with little or no clubroot present. If growers wait for clubroot to show up before choosing resistant varieties, the selection pressure for new virulent pathotypes and total number of spores is literally millions of times higher than if growers begin using these varieties before the disease shows up.

—Scout canola fields with extra effort on clubroot identification. The best time to scout for clubroot symptoms on roots is late in the season, approximately two weeks before swathing, when root galls should be easy to identify. Soil samples can be collected as well at any time of year and from non-canola fields to determine if the clubroot pathogen is present.

—Scout resistant varieties grown on land known to have clubroot, or suspected to have clubroot, for patches of higher than expected infection. This will help with early detection of new pathotypes, and have an impact on future management decisions.

If resistance breakdown is suspected, contact your CCC agronomy specialist.

More information:

Clubroot: When genetic resistance no longer works
Check out Clubroot.ca for more details on clubroot identification and best management practices including sanitation, long rotations, weed management and minimizing tillage.

Canola Watch