Fighting sclerotinia with fungicides

July 9, 2020

As flowering begins in soybean fields, it’s time to apply a fungicide proactively to protect
the quality of your soybean plants and potential yield. In Québec and Ontario,
sclerotinia (or white mould) is the most common disease among soybean plants, and it
also causes the most economic damage. Whether it comes from your machinery, poorly
composted manure, animals or a previous year’s infestation, sclerotinia can be
stubborn! In this article, we’ll go over the benefits of using fungicides to reduce any
negative economic impacts.

The sclerotinia cycle

First, you need to understand that sclerotia are the dormant resting bodies of fungi.
They hibernate in the soil and can live for 7 years, with a strong fungal structure that can
withstand freezing and thawing. In the spring, sclerotia germinate in the top centimetre
of the soil and propagate spores that can contaminate flowers. That’s how white mould
appears on plants and weakens stems. Contaminated plants then produce sclerotia that
increase the quantity of spores in the soil.

Favourable management conditions

Unfortunately, the recommended conditions to increase soybean yields are also
favourable to sclerotinia! Fertile soil, early seeding, narrow rows, high populations and
high-yield varieties with branches are all factors that contribute to sclerotinia. Cool and
humid conditions can also increase the risk of infection and disease.

Reducing sclerotinia’s impact

Of course, fungicides can help control sclerotinia. But this is a preventive measure, not a
treatment. To eliminate seasonal sclerotinia, we recommend spraying twice at the R1
and R3 stages to maximize the effect of the fungicide. You can also give your crops the
best possible odds by:

  • Using resistant varieties
  • Using varieties with good standability
  • Opting for a longer rotation with a non-host crop
  • Favor wider rows for improved aeration
  • Managing crop waste
  • Using certified and treated seeds

Your trusted Prograin representative can help you implement a monitoring system and
apply recommendations to fight sclerotinia. Give them a call!