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Soybean Fungicide Treatment

When do foliar fungicides pay off in soybeans?

 

Foliar fungicides have proven effective in helping to manage several common foliar diseases. Strobilurin fungicides have generated increased interest because of the possibility that these products may provide physiological benefits to the plant.

Before using a foliar fungicide, growers should scout fields and determine the type of disease or diseases present. These products only work on fungal diseases such as anthracnose, Septoria brown spot, Cercospora leaf blight, frogeye leaf spot, pod and stem blight, and soybean rust.

However, they've been less effective on stem canker as well as two diseases that involve infection of soybean roots - charcoal rot and sudden death syndrome. Likewise, foliar fungicides can't control bacterial diseases such as bacterial blight or bacterial pustule or viral diseases like soybean vein necrosis virus.

Trials show benefits

DuPont Pioneer has conducted extensive on-farm and small-plot trials to better understand the potential value of foliar fungicides in soybeans, both alone and combined with an insecticide. Here are highlights of these studies:

  • Across 148 on-farm trials from 2007 and 2011, the average yield response to a foliar fungicide application was 2.5 bushels per acre. In trials where an insecticide was included, the average gain was 5.3 bushels per acre.
  • In small-plot research trials from 2004 to 2008, fungicides increased soybean yields by 2.9 to 5.5 bushels per acre on average.
  • Despite considerable variation in growing conditions across years and locations, the trials demonstrated a consistent positive yield response to treatments that included a strobilurin fungicide.
  • The economic viability of a fungicide or fungicide-and-insecticide application can vary greatly according to the price of soybeans and cost of the treatment and application.

Does yield response cover costs?

The economic viability of a fungicide application or fungicide-and-insecticide application can vary greatly depending on the price of soybeans and cost of the treatment and application. Higher soybean prices and lower treatment costs both reduce the breakeven yield response.

On the other hand, as soybean prices drop and treatment costs rise, growers will need a greater yield response to justify applications from an economic perspective.

This table offers a look at treatment costs, soybean prices and yield responses needed to break even.

Yield response needed to break even

Yield response needed to break even