The Agronomists, Ep 75: White mould and sclerotinia management with David Kaminski and Rob Miller

Photo: OMAFRA

White mould of soybeans, dry beans and sunflowers is the same disease as sclerotinia of canola and sunflowers. What’s more, it’s a disease that can infect a multitude of broadleaf weeds. The endemic nature and soil survivability of the pathogen make it a tough disease to keep on top of.

To tackle management of this disease, we go to David Kaminiski, plant pathologist with Manitoba Agriculture, and Rob Miller, technical development manager with BASF.

This episode of The Agronomists is brought to you by ADAMA Canada, the Mind Your Farm Business podcast, and our July 19th webinar on infrastructure investment (register here).

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SUMMARY

  • Ontario could use a rain; Manitoba doesn’t need it, thanks
  • We’re talking sclerotinia/white mould. Fun fact, it’s the same pathogen! And it isn’t terribly picky on what crop it lives on. Most broadleaf crops are a host
  • Plenty of weeds are too, Miller adds. Good weed control matters.
  • Is it dry beans or edible beans? You decide.
  • White mould/sclerotinia is difficult to control for several reasons, including the length of time the resting bodies (sclerotia) can live in the soil, even in dry conditions
  • Tillage can bring new sclerotia to the surface
  • You’re looking for small mushroom like structures — but don’t confuse the apothecia (the wee mushroom) with bird’s nest fungi!
  • Management is key: rotation, row spacing, plant populations, but also, when the risk is high, you’ve got to protect the flower petals, regardless of the crop
  • Ideal timing on soybeans is R1.5 to R2
  • The disease is likely always present, but that doesn’t mean the environment or field conditions are conducive to disease development — a spray is not a foregone conclusion
  • It depends on the year, depends on the field, and the field history
  • No-till lowers risk
  • Higher plant population and tighter rows equals more risk (think air movement in the canopy)
  • Manage the crop, not the weather
  • In July, if the grass is green, white mold is keen! Grass is brown, white mold is down
  • Sclerotia do die in the soil. What about other soil pathogens and fungi that feed on sclerotia? So do we have some biological help in the fields? There is some
  • Trying to find apothecia? Look on canola stubble, sunflower stubble
  • Chuffing ascospores (Lyndsey’s new band name) really project the spores — which means they can blow in from some distance away
  • Clip 1: Alberta Tenuta and too-late to spray timing
  • Revenge spraying, what is it?
  • Once you start to see white mold, it’s too late
  • On canola, the range is 20 to 30 per cent bloom
  • The reason is two fold: one, it’s the petals that are the food source for the ascospores, and, earlier infection is more detrimental to the plant and thus has a higher impact on yield
  • Soybean petals don’t drop, canola petals do
  • What about row spacing? Miller says pick one that works for your farm overall, not just for white mould control
  • A little bit of white mould means higher yield potential because it means good growing conditions!
  • Why is the disease so patchy at times? Likely microclimate in the canopy, and plant-to-plant spread
  • Is there enough value in the crop or in going in at two stages because staging the crop can be difficult? Stagey canola: are the earliest worth protecting, or will they add to disease pressure?
  • Humidity or rain — is humidity enough to start a disease outbreak? Chances are, no. Need an initial rain to start; humidity drives it after
  • Scout for phomopsis at the same time/later in the season and learn the difference. It’s also called pod and stem blight
  • In Manitoba, sclerotinia/white mould is the biggest risk for dry beans
  • Clip 2: Holly Derksen and staging canola 
  • What about apps, such as Sporecaster? Are they reliable?
  • Blackleg vs. sclerotinia: symptoms can look similar and happen at the same depth in the canopy. Learn to ID each. Picnidia in blackleg lesions are a good clue
  • Genetics play a role, but in surprising ways
  • Plant architecture is perhaps the biggest driver or “resistance”
  • Poor sunflowers don’t even have a chance
  • Sclerotinia/white mould can infect two ways, at three different times, including through mycelium in the soil