To spray or not to spray? Making the sclerotinia fungicide decision.

Written by Stacy Pritchard on May 26 2017

Category: Grow Grain

Due to the popularity of growing canola, sclerotinia has the chance to thrive in tight rotations. See the reasons to spray your crop against this disease.

Do you struggle with deciding whether or not to spray fungicide to manage sclerotinia on your farm? This yield-robbing disease isn’t easy to manage in the field or financially, but as canola is showing up more frequently in our rotations, it’s increasingly important to think about how to proactively control sclerotinia.

Fungicide is your best defense against in-season diseases.

Canola diseases have the potential to significantly reduce yield if not managed. Yield loss from sclerotinia in canola is typically associated with a lack of moisture and nutrients reaching the pods. This causes premature ripening and uneven maturity of the field. The toughest part about managing sclerotinia is that fungicide usually needs to be applied before any symptoms appear.   

Spraying for sclerotinia may not provide an economic return at the same frequency as other fungicide applications, such as for cereal and pulse diseases. However, when it does infect, sclerotinia can cause enough yield loss to make you rethink your spray decisions.

To spray or not to spray? Ask yourself these questions. 

Here are a few things to consider:

  • Have you seen evidence of disease in the past? Going into this growing season, think about past canola crops on this year’s canola fields. If there is a history of disease, then you can expect to have a disease issue in the coming year.
  • How are this year’s growing conditions shaping up? Great growing conditions plus high disease pressure typically results in yield loss.
  • What are the moisture levels in your crop? When your crop is at about 10% bloom, usually in June or July, walk your fields. If your pants are still wet from dew in the afternoon, that suggests conditions are perfect for the development of sclerotinia.
  • Timing and location are important. If you find evidence of sclerotinia, the location of the disease on the plant and the timing of the infection will dictate the losses caused by sclerotinia. The earlier in the season and the closer to the base of the plant, the higher the potential for loss.
  • What is your potential yield impact? Yield loss is variable dependent on the time of year and severity of infection. It can be 50% or higher under extreme cases of infection. A simple calculation is to take the percentage of infection and multiply it by 0.5 to determine potential yield loss.

Spraying for sclerotinia.

The majority of sclerotinia infection occurs from ascospores settling on canola petals, which drop onto the branches of the plant. As the petals fall off, they brush the stem and branches on their way to the ground, infecting on contact. Even the slightest bit of moisture can lead to the infection of those branches. This is why fungicide for the control of sclerotinia is applied to as many canola flowers as possible.  

  • The ideal timing for a one-pass application of fungicide is in the 30-40% bloom stage. That’s typically when we start to see petals start to drop off and can get fungicide on the most petals possible.
  • In a two-pass fungicide system, we typically aim for between 20% and 50% bloom to maximize the number of petals we hit with fungicide. 
  • Fungicides available to manage sclerotinia include Proline®, Lance® / Lance® AG or BASF’s new fungicide Cotegra ™.
  • Spray fungicides at the 20-50% bloom stage for best control of the disease.
  • If you’re not sure what kind of sclerotinia pressure is in your area, or want to see what kind of impact a fungicide application will make, try spraying and leaving a test strip to see the difference for yourself.

Fungicide applications in canola can increase harvest ease.

Because sclerotinia can cause uneven maturity in the field, a fungicide application can not only help reduce yield loss, it can also make those swathing or pre-harvesting decisions easier, while reducing shattering caused by overripe plants.

Help your crops perform at their best and talk to your Cargill agronomist about getting ahead of diseases in the field.

Proline® is a registered trademark of Bayer. Cotegra ™, Lance®, and Lance® AG are trademarks of BASF.
Always read and follow label directions.


Tags: Fungicide, Canola, sclerotinia, crop scouting

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