Early signs point to lower levels of sclerotinia stem rot in Saskatchewan canola fields this year, but ideal conditions for infection are being linked to the unusual appearance of the disease in some parts of Alberta.
The Canola Council of Canada recently alerted growers that in some fields the symptoms of the disease are appearing lower down on the plant than typical, even near ground level and sometimes causing lodging.
Clint Jurke, agronomy specialist with Canola Council of Canada in Saskatchewan, says sclerotinia levels may be up in northern Alberta this year because of increased moisture.
Officials said it’s not commonplace and indicates a more severe infection. In these cases, the symptoms of sclerotinia infection remain the same and growers can identify it in the usual way at swathing.
The plant will show bleached or brown lesions and the stem will easily shred apart.
Jurke said it could be the sign of an early infection.
“The other one, which we saw last year for the first time out in the Wat-rous (Sask.,) area, was the infected petals were falling onto the leaves that were already decaying on the soil surface — the leaf litter layer — and was actually able to go through that leaf litter layer and infect stems directly that way, which is a little bit unusual.… But it does happen under conditions of very high levels of humidity and moisture, like what we had last year (in Sask.).”
The appearance of the disease is highly influenced by the weather.
Harry Brook, a crop specialist with the Alberta government, said reports of disease in Alberta are to be expected following a growing season with high humidity and plenty of moisture.
“Those are ideal conditions for a good crop but also for the disease development, and we’re seeing it. Not just sclerotinia, but we’re also seeing stripe rust. We’re seeing fusarium,” he said.
“Those that did not spray, there are going to be producers that get some nasty surprises as far as affecting the grade.”
Fungicide applications were common across the Prairies, said Jurke. The canola council recommends applications be made at 20 to 50 percent bloom.
“Because those are the first petals that drop, and where do they usually drop? They usually drop low on the plant, which can produce those big yield losses in the main stem,” said Jurke.
“If the infection comes in later in the season, those petals usually will stay up high in the canopy and might only affect one branch or maybe a couple of branches.”
Dan Orchard, a canola council agronomy specialist in Alberta, said growers who sprayed in northern Alberta will see benefits, although the disease’s appearance is variable.
He’s seen some fields this year with 50 percent infection.
Officials are also observing the likely spread of clubroot in Alberta.
“Areas that were known to have clubroot just have a little bit more, it seems, and some areas that were kind of on the fringe, that had only found a few fields here and there, I think they’re finding it a lot more easily now this year, just with the conditions,” said Orchard.