Foliar Health Basics: Fungicide Decisions

Grower and agronomist scout for disease in soybeans

Deciding Which and When to Apply

The decision to apply a fungicide should be a calculated, proactive choice, based on management and environmental factors, not a reaction to damage that has already occurred.

“Fungicides work by inhibiting growth or reproduction of a fungus. They will always be more effective when applied before disease can develop,” explains Bond McInnes, fungicide technical manager, DuPont Crop Protection.

Are Your Fields at Risk for Disease?

These five risk factors affect disease development in corn, soybeans and wheat.

Fungicide Decision Tree for Corn and Soybeans

Weighing these three factors will help determine the need for fungicide application in corn and soybeans.

Aproach® Prima Protects Yield Potential, Increases Revenue

In multi-year comparisons, applying Aproach® Prima helped increase yield and revenue in corn, soybeans and wheat.

Determining when disease is likely to develop is the challenge. To simplify the decision making process, McInnes recommends using a decision tree, which helps analyze risk factors, weighing them against possible outcomes. He has developed the following series of questions to help corn and soybean growers determine when a fungicide treatment should be planned.

What’s your crop and field history?

  • Multiple years of continuous corn or soybeans increase a field’s odds of facing yield loss due to disease.
  • Signs of disease observed the previous year means pathogens are likely to still be lingering in the field.
  • High levels of crop residue provide the ideal environment for overwintering disease inoculum.

Have you chosen hybrids or varieties with disease resistance?

  • A hybrid or variety chosen for excellent yield potential may not carry the disease resistance of a defensive hybrid or variety.
  • Hybrids or varieties with only some or moderate levels of disease resistance will benefit the most from fungicide protection.

What are expected environmental conditions during the growing season?

  • Favorable field environments for fungal diseases include heavy dews, frequent rainfall, high humidity and moderate temperatures.
  • When these conditions occur early and repeatedly, they create opportunity for prolonged disease impact.

What are your yield goals?

  • To preserve corn yields with one fungicide application, research shows the greatest return on investment occurs by applying at VT (tassel) to R2.
  • In years with continued significant disease pressure in corn, apply a first fungicide application at V10, followed by a second application at VT to R2.
  • To protect soybeans from foliar diseases, make the first application at R2 to R3, followed by a second application, if needed, at R4 to R5.
  • To control soybean white mold, make the first fungicide treatment at R1 (bloom), followed by another application 10 to 14 days later, if needed.

DuPont™ Aproach® Prima is the best choice for foliar diseases such as common rust, northern corn leaf blight and frogeye leaf spot.  With two modes of action, Aproach® Prima offers broad-spectrum, long-lasting, preventive and curative control of many damaging diseases.

DuPont™ Aproach® fungicide provides effective early season control of diseases in corn and is recommended for control of soybean white mold.

DuPont Aproach® and Aproach® Prima fungicides are not registered in all states. See your DuPont retailer or representative for availability in your state.
The information provided on this website is for reference only. Always refer to the product labels for complete details and directions for use.