Understanding and Applying Canola Disease Diagnostic Results

Disease testing through Canola Diagnostic Services can confirm which diseases are present in a field, but knowing how to act on them can be challenging. The real value of diagnostic testing is understanding what those results mean and using that information to make informed management decisions to protect future canola crops.

Blackleg and Verticillium
In Manitoba Canola Growers’ Diagnostic Testing, blackleg and verticillium stripe results are combined into a single report. For each stem analyzed, the report indicates whether blackleg and verticillium stripe were detected. 

For verticillium stripe, the report includes an estimated DNA load and an infection category. DNA load reflects the amount of pathogen DNA detected in the sample and can vary depending on plant maturity at sampling. The infection category provides a general indication of disease presence, but it cannot be linked directly to yield loss as the relationship between infection and yield loss is still being researched.

For blackleg, the inferred race profile detected is reported. This is the mix of the blackleg pathogen populations that are present across all stems provided.

Using Your Blackleg and Verticillium Results 
Start by reviewing the field’s history. Where were symptoms observed during the season? What variety was grown, and how did its disease ratings align with what was found in the field?

For verticillium stripe, management options are currently limited. Some seed companies provide internal tolerance ratings based on field observations, which can help direct future variety selection.

For blackleg, use the inferred race profile to select a variety with resistance to the blackleg races present in your field. Look for a variety that has the Resistance Group that contains a Major Gene that matches one of the Avr genes identified in your results.