Prairie canola growers urged to be on sclerotinia alert (July 8, 2005)

July 8, 2005: Wet soils, warm weather and a rapidly closing canopy of leaves could be setting prairie canola crops up for a major outbreak of the fungal disease sclerotinia.


Saskatchewan Canola Council agronomist Jim Bessel says most growers are well aware of the possible problem but they “want to get the most for their control buck and they’re not sure when they need to step in to fight the fungus this year".


Bessel urges growers to get into their canola fields in the early stages of flowering to check possible infection levels. He says most growers look for “mushrooms”, known scientifically as apothecia, that grow like little golf tees out of the black sclerotia in the soil. When they find enough of them, they use fungicide to prevent the spread of spores.


“But even after plants are infected”, Bessel says, “the severity of stem rot symptoms and the resulting effect on yield will be affected by temperature, rainfall, crop density and especially the stage of crop growth at the time of infection. That makes it tough to know just when or even if to spray.”


“Unfortunately,“ Bessel says, “too many growers just guess – and they could be wasting their money.” He says the only reliable way to know for certain that spraying will be worthwhile is to pick up a petal test kit, follow the simple instructions and find out the answer in a couple of days.


These kits are available commercially from only one source – Discovery Seed Labs in Saskatoon. Bessel says the kits are based on sound science. “There’s really no other way to be sure you need to spray”, he says. “You can look at all the photos in the world, but you'll still be left without a clear answer.”


He suggests that growers contact Discovery Seed Labs at (306)249-4484 to get more information about the kits and the tests. Meanwhile, Bessel does recommend reading up on the enemy at http://www.canola-council.org/PDF/summaryofapotheciaresearchpaper.doc . This link will pull up a summary on apothecia developed by Penny Pearse of Saskatchewan Agriculture and Food from a paper published by McLaren, et al in the Canadian Journal of Plant Pathology.


There are some new photos taken by Pearse on the Canola Council website at http://www.canola-council.org/sclerotiniaforecast.aspx showing apothecia and sclerotinia development on canola leaves. Bessel says the same site contains more information on forecasting and scouting for sclerotinia, including a copy of the sclerotinia stem rot checklist from the Canola Growers Manual.