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Sclerotinia Mythbusters

There are several common beliefs about how and when to treat for sclerotinia, but you might be surprised to learn the background behind the myths and facts.

We asked growers from Alberta, Manitoba and Saskatchewan to relay some of their thoughts and concerns about the disease. We’ve worked with experts to address questions, unveil the truth, and ultimately help you make the best treatment decision for your operation.



Last year’s sclerotinia pressure was low. So this year it will be low again.

Each field and every year is different and needs to be handled differently. When determining whether to spray, growers should consider a variety of factors including: is everything else there for the disease to thrive? Does the crop have a good canopy? Has the weather been conducive to disease development? Does the crop have a high yield potential (which makes the return on investment easier)?

The right thing to do is assess your field in that critical time frame prior to flowering and pay specific attention to the moisture and environment. External factors like these can turn quickly, so if you’ve seen sclerotinia out in the field in previous years, that should be your first warning sign. With this disease, you should plan for it every season - even if you can’t see it building, but it’s been there in the past.

Calculate your potential return on investment »

Sclerotinia is in your area but not on your farm; therefore, it is not a problem.

Sclerotinia is present across the prairies, exposing growers to it over longer periods. Because spores move in the wind and can infect adjacent fields, it is recommended to begin a scouting process early. This will allow growers to get a sense of the levels of infection in their field and to give a them some insight into the risk for future planning. It’s always recommended that growers have a proactive plan. If you feel there is an increased risk, or you do have sclerotinia and want to correct it, there is no doubt that the use of a fungicide is part of the solution in managing the disease - especially during very damaging years. Remember, an application over a longer-term strategy and dollar/cost over a longer term is still warranted.

Proactively protect your profits with Proline® »

It’s better to apply fungicide before optimal spray timing, than after.

We recommend that growers spray earlier in that window (in the 20-30% flower range) even if the stand is a little less consistent. The reason behind this is that the main stem will be flowering, which is the biggest contributor to yield success. If you have success in the main stem you’ll have a better yield overall. If you get early infection, the damage is more severe as infection on the main stem can kill the entire plant. If infection comes later, it tends to be a branch infection, which will still affect yield, but not as significantly.

Learn more about canola bloom stages »

Tighter canola rotations mean you don’t have to worry more about sclerotinia.

White mould in pulse crops are one of the many examples of how sclerotinia can build up in the soil, depending on what type of rotations growers are using. Anything in a four-year rotation where one crop is the only one susceptible to the disease is ideal.

Spraying for sclerotinia this year doesn’t reduce the risk in future years.

Sclerotia bodies can survive in the soil for years, so there is no guarantee that spraying in one year will give you control for multiple seasons. A long-term proactive integrated pest management approach including fungicides is a viable solution for reducing sclerotinia inoculum in your field. Looking at the weather when approaching the time to spray is a good indicator of what might be happening in the field. You can see the benefits of it—what’s done is done at that point in time but leaving a little untreated area of the field will give you a pretty good assessment. If there has been an untreated or susceptible spot in the field, growers will be able to spot the dying plant material in the field.

Sclerotinia bodies can survive in the soil for three or more years.

Sclerotinia can remain inactive in the soil for lengthy periods of time, including over the winter months. If you identify sclerotinia in your field, it is important to keep it top of mind for seasons to come, to ensure protection of your crop.

Quickly reacting to sclerotinia is better than spraying in advance.

Once you see sclerotinia symptoms on your plants, it’s already too late. Spray between 20% and 50% bloom to ensure you’re proactively protecting your crop.

Learn more about optimal spray timing »

Ascospores of sclerotinia don’t travel more than 15-20 metres.

Apothecia (the gold tee like structure) will release ascospores into the air and become wind borne. Most travel between 100-150 metres from their launch site and have been known to travel several kilometres in stronger winds.

Yield loss from sclerotinia is generally half the infection level.

Here is a quick way to estimate your potential yield loss:

How to quantify your yield loss potential


Growers should expect about 5% yield loss from sclerotinia infections.

Yield loss from sclerotinia can actually range from 5% to 100% in extreme cases, where the disease could cost you your entire crop.

Proactively protect your profits. Calculate your potential return on investment »

Sclerotinia stem rot, white mold, sclerotinia wilt, and timber rot are all caused by the same pathogen

All of these diseases are caused by the same pathogen, Sclerotinia sclerotiorum. Depending on the crop they often have different common names.