When you see the stem rot in the field, it’s too late.
And that’s just one of the reasons why managing sclerotinia is a challenge, as exerienced in 2016, a severe year for the disease in canola fields in Western Canada.
In this Canola School episode, we talk to Michael Harding, plant pathologist with Alberta Agriculture and Forestry about scouting for sclerotinia.
“For the people who aren’t faint at heart you can scout for signs that the fungus is sporulating, but you have to crawl around on your hands and knees, looking for tiny little mushroom structures that are formed,” explains Harding, discussing sclerotinia at CanolaPalooza in Lacombe, Alberta.
Beyond scouting for these tiny structures, Harding suggests using a checklist or a decision-making tool to assess risk and make the call on whether or not too spray (such as this sclerotinia tool from SaskCanola.)
“You go through a series of questions and you end up with a score that helps you make a decision as to whether or not you should spray,” he explains.
Harding emphasizes once you start to see symptoms of sclerotinia, it is too late to intervene.
“We have to use these predictive systems before the symptoms show up, because the fungicides only work to protect green tissue. And once we have lesions forming on the stems, it’s too late, we can’t cure them.”
He explains that “using sclerotinia tolerant varieties and fungicides at the right time when the risk is there will help, but because of the nature of sclerotinia, we probably won’t ever eradicate it.”
“We don’t have complete genetic resistance and because it can complete its life cycle on so many other crops, it’s probably something we are going to have to do our best with. As new tools and new products become available, hopefully we can get better at managing it. But once we start to see the symptoms it will be too late, the damage will be done.”
Harding discussed the timeline for sclerotinia infection, risk factors and why multiple tools must be put to use to manage sclerotinia at CanolaPalooza in Lacombe on June 27, 2017: