Agronomy •  2021-03-27

White Mould & Sclerotinia: Same Disease. Big Problem for Soybean and Canola Farmers

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Soybeans and canola plants

Canadian farmers have never been one to stand idly by. Faced with new opportunities every season, they “grab the bull by the horns” so to speak, outworking, outthinking and outmaneuvering whatever insect, pest or problem that stands between them and record yields.

Given their proactive approach to farming and life, it is surprising when growers take a more passive approach to disease management - especially when it comes to protecting their soybeans and canola from white mould or sclerotinia stem rot.

While farmers can manage the problem effectively by reacting quickly to a disease outbreak in their field, the best way to protect their crop and their profits is through making proactive disease management decisions.

What is white mould and sclerotinia?

Sclerotinia stem rot in canola and white mould in soybeans are both caused by the fungus Sclerotinia sclerotiorum. Weather and field history are two significant factors that put your crops at risk of developing the disease, which shows symptoms late in the season as grey to white lesions on the stems. The characteristic black sclerotia appear inside the stems, and in the seed pods in canola as well.

The disease infects the crop at flowering under cool and moist conditions. Dense plant canopies can also be more disease-prone than canopies that are not as closely knit.

Once white mould or sclerotinia occurs in a field, it is nearly impossible to eradicate. Long-term survival structures of this organism (sclerotia) ensure that inoculum is always available to attack the next canola or soybean crop should conditions allow. This is why growers with previously infected fields must treat the disease as a perennial threat.

Because white mould or sclerotinia can cause a significant yield reduction in both canola and soybeans, it is vital that growers take a proactive approach to managing the disease. Here are six recommended proactive strategies to follow:

  • Variety/Hybrid Selection: There is no absolute resistance available to white mould/sclerotinia (all varieties/hybrids can get the disease under severe pressure), but differences in tolerance exist between varieties/hybrids. Choosing canola hybrids, such as Pioneer Protector® brand 45CS40 and P505MSL, and soybean varieties that reduce sclerotinia incidence as well as overall severity of the disease is important.
  • Crop Rotation: Rotation with non-host crops is an effective means of reducing disease pressure in a field. Non-host crops include corn, sorghum and small grains. However, because sclerotia survive for up to ten years in the soil, rotation is only a partial solution.
  • Weed Management: White mould’s 400+ plant hosts include many broadleaf weeds. In addition to acting as host to the disease, weeds can also increase canopy density, which favours disease development. Stay on top of tough weeds with advanced crop protection solutions from Corteva Agriscience™.
  • Zero Tillage May Minimize Disease: Sclerotia germinate from the top two inches of soil. Below that depth, they can remain dormant for up to ten years. Research studies have shown that zero tillage is generally superior to other tillage systems in limiting white mould.
  • Limiting Dense Canopy Formation: In areas of high risk, cultural practices that encourage early, dense canopy development may need to be avoided. This includes early planting, narrow rows and excessive plant populations.
  • Foliar Applications for Proactive Management: Acapela is a Group 11 fungicide that provides reliable protection against white mould/sclerotinia. Control depends on both application timing and coverage. In soybeans, make the initial application at R1 to R2 (beginning to full bloom) and follow up with your second application seven to 10 days later, if needed. For sclerotinia in canola, apply prior to disease development at 20 to 50 per cent flower.
  • Acapela has one-of-a-kind movement properties that help provide complete coverage, consistent performance and superior protection. Rapid absorption moves the fungicide quickly and efficiently into and within each plant, allowing application to occur even when field conditions are challenging, so farmers get healthier crops and higher yield potential.

    For more information on Acapela and proactive fungicide applications, download our infographic, or visit your retailer or or

    This article was written in partnership with agronomist Laura Sharpe.