Published on Tue, 03/06/2018 by BASF Canada

Sclerotinia management still important in dry conditions

The 2016 season broke all records for Sclerotinia across the Prairies, with provincial disease surveys claiming that prevalence was at 93 percent in Manitoba, 92 percent in Saskatchewan, and 80 percent in Alberta. The heavy disease pressure felt then is still an issue for canola growers today.

Despite 2017 being a dry year, Sclerotinia was observed in 51.3 percent of canola surveyed in Saskatchewan, according to the 2017 Canola Disease Survey conducted by the Saskatchewan Ministry of Agriculture.

Sclerotinia stem rot occurs in all canola growing areas of Canada, aggravated by tight rotations, increasing broadleaf acres, and moisture. The inoculum can also overwinter and remain in fields for up to five years – even in dry conditions.

“We need to be more innovative when we think about Sclerotinia management. Perhaps the old way of thinking about Sclerotinia as a disease that’s only a concern in wet years in canola needs to be retired,” said Colleen Redlick, Senior Technical Service Specialist with BASF Canada. “When you think of moisture, it is usually about rainfall, but heavy morning dews and dense canopies can still harbour enough moisture to start the Sclerotinia disease cycle.”

Growers know that soil moisture is necessary to establish a healthy, high-yielding crop. However, increasing canola acres and larger, denser canopies are creating ideal environments for disease development, even despite low rainfall.

“If growers want to protect their crop and investment in dry years, it is best to plan a preventative fungicide application from the start, then assess moisture closer to the most effective spray timing,” said Redlick. BASF Canada and the Canola Council of Canada recommend 20 to 50 percent flowering as an ideal spray window for a Sclerotinia fungicide.

An integrated approach to disease management is also recommended to control Sclerotinia and achieve the best return on investment.

Proactive scouting, seeding at recommended rates to avoid lodging, controlling weed pressure, and a preventative fungicide application with multiple modes of action all make up an integrated disease management plan for Sclerotinia.

First task: get out there and scout. “Scouting during the season involves checking canola fields for apothecia, little golf tee-like fungal structures, concentrating on lower spots that may be wetter,” Redlick said. “Another way to assess the moisture in your field, even in years with low rainfall, is head out to your crop at the 10 to 20 percent bloom stage around midday. If your pants are wet, there is enough moisture for disease development, and growers should consider a Sclerotinia fungicide application.”

Throughout the dry 2017 season, BASF Canada conducted more than 60 field-scale trials across the Prairies with their latest multiple mode of action fungicide, Cotegra. It is currently the only fungicide on the market that has the two leading active ingredients for Sclerotinia control.

Despite what appeared to be low levels of infection during early disease assessments, the Cotegra field trials saw an added yield bump of 3.5 bu/ac over the untreated check. “Given the increasing number of canola and broadleaved crop acres, we are seeing higher Sclerotinia pressure across the Prairies - using a fungicide with multiple modes of action will be the most beneficial management tool in the long run,” said Redlick about the new Cotegra.

Murray Schaefer, a canola grower from Stonewall, Manitoba, was involved in a field-scale trial with Cotegra. “One of the main things I saw in the trial was the benefit of using multiple modes of action to control the disease,” he said. “Based on the results we saw, it looks like it will be a good fit on our farm.”

According to Statistics Canada, canola acres have increased 10 percent since 2016, meaning that growers will need to have a good disease management strategy in place to combat Sclerotinia and other canola diseases. “Being ready to apply a fungicide is vital; be aware, plan ahead and start thinking about your fungicide choices now,” concluded Redlick.