Each Prairie province does its own disease survey most years. The Manitoba Canola Disease Survey has been happening for over 15 years and tracks a variety of diseases. Alberta’s survey the past few years has mainly been focused around monitoring the spread of clubroot. Blackleg results are based on prevalence, incidence and severity — but what do these words mean?
Results from the disease survey show increases in sclerotinia stem rot incidence. Blackleg incidence is down from 2015 in Manitoba and Saskatchewan and up in Alberta.
Disease scouting long after swathing is not usually the most accurate, as saprophytic organisms — those that feed on and break down dead material — move in fast and cloud the identification process. Verticillium is one disease that can be more obvious and easier to identify after cutting a canola crop.
Harvest is a great time to assess the incidence and severity of canola diseases, an important step in management for next year.
We know that tillage will spread clubroot as well as weed seeds and verticillium, but ruts can create headaches for combining, fall spraying and seeding next spring. Working wet fields can also cause compaction.
Keep a look out for clubroot, and take care to slow the spread of soil away from these infested areas. This quiz gives you a few numbers to think about….
After a moist spring and summer in many areas, disease levels in harvest canola could be high this year — even for fields that received a fungicide.
More than 10 clubroot pathotypes have been identified in Alberta, and clubroot-resistant (CR) varieties will not protect against all of them. CR varieties with the same source of resistance grown in a short rotation will quickly select for those pathotypes that are virulent to those varieties. With good moisture for clubroot this year, many fields of CR canola are showing high levels of clubroot infection.
Test your disease ID knowledge. Match the disease to these four images…
With blackleg, sclerotinia stem rot and clubroot, base the swath timing decision on healthy plants that will contribute to yield. One exception where early swathing could provide an economic benefit is the case of severe alternaria black spot (shown).