The number of tools in the white mould management toolbox continues to increase as growers look to reduce the impact the yield-robbing disease could have on their 2019 crop.
Syngenta Soybean Product Development Agronomist Bryce Rampton says white mould can have its greatest effect when growing conditions are cool, cloudy, wet and humid during flowering. The disease is most problematic in soybean fields with high plant populations, narrow row spacing and an early-closing canopy. Depending on severity, white mould can lead to reduced yields, standability and seed quality.
Genetics is the first tool that growers can use to defend their crop against the disease. Rampton says growers with fields prone to this disease should always look for soybean varieties with a high level of tolerance to white mould. He notes that fields with a history of white mould should be candidates for reduced plant populations and potentially wider row spacings that will open up the crop canopy and promote air movement.
Target R1 growth stage for fungicides
Fungicides are also a key defense against white mould. Rampton says it’s important for growers to “go early” and time fungicide application for when they can still see the soil. Specifically, he recommends growers to be ready to apply fungicide at the R1 growth stage (beginning bloom) if conditions are conducive to the development of this disease.
“It’s critical to protect the primary infection site,” says Rampton who notes that Syngenta’s Allegro® fungicide is labelled to control white mould in soybeans. He advises growers to pay close attention to water volumes and nozzle choice for optimal control. “When you use flat fan nozzles we get fine to medium droplets that give us better coverage deep into the canopy. When using Allegro water is also key — go with 20 gallons per acre or more.” If conditions remain favourable for disease development a second fungicide application may be needed. TrivaproTM (registered for suppression of white mould), or another fungicide with activity on white mould, may be applied 10 to 14 days after the application of Allegro.
Sporecaster forecasts white mould risk
This year, Rampton is also testing the Sporecaster smartphone app — a new tool growers can use in their fight against white mould. The purpose of the app is to help growers predict the need for a fungicide application to control white mould in their crop. The best time for spraying fungicides to control the disease is during flowering (R1 and R3 growth stages) when apothecia (small mushroom-like structures) are present on the soil. Apothecia release spores that infect senescing soybean flowers, leading to the development of white mould.
The app was developed by the University of Wisconsin-Madison Nutrient and Pest Management Program with support from the Wisconsin Soybean Association and Wisconsin Soybean Marketing Board. Sporecaster uses university research to turn a few simple taps on a smartphone screen into an instant forecast of the risk of apothecia being present in a soybean field.
Download the app to your smartphone
Apple and Android versions of the app can be downloaded for free. When installed, growers can create multiple fields to determine their apothecial risk. The app will prompt the user for information, such as field name, row spacing, if the field is irrigated and the field location. Then the risk of apothecial presence can be calculated.
Always read and follow label directions. Allegro® is a registered trademark of ISK Biosciences Corporation. Trivapro is a co-pack of Trivapro A fungicide and Trivapro B fungicide. TrivaproTM is a trademark of a Syngenta Group Company. © 2019 Syngenta.