On the farm, where maximizing crop health and productivity is of utmost importance, one crucial factor cannot be overlooked: fungicide timing.

Fungal diseases can pose a significant threat to crops, and put yields and quality at risk. But by strategically applying fungicides at optimal growth stages, farmers can enhance disease control measures, safeguard their crops, and ultimately secure high yields.

Why Fungicide Timing Matters

Fungal diseases can wreak havoc on valuable crops. Gray leaf spot (GLS), northern corn leaf blight (NCLB), soybean rust, and frogeye leaf spot are just a few examples of yield-robbing diseases. But with the right approach to fungicide timing, farmers can protect their corn and soybean crops from these threats.

To achieve the most efficient fungicide timing, several factors come into play, including hybrid susceptibility, weather conditions, and field history.

Hybrid susceptibility:

Not all hybrids are created equal when it comes to fungal disease resistance. By selecting AgriGold hybrids and varieties with better resistance, farmers can reduce the need for frequent fungicide applications.

Weather conditions:

Environmental factors such as humidity and temperature can either promote or suppress fungal growth. Monitoring weather patterns and disease forecasts can help farmers determine the ideal timing for fungicide application. They should aim to take advantage of conditions that lessen disease development.

Field history:

Past experiences provide valuable insights into disease occurrences. By considering the history of fungal diseases in their fields, farmers can make proactive decisions and adjust fungicide timing accordingly.

How to Achieve Optimal Fungicide Timing 

For corn, farmers should apply fungicide alongside crucial growth stages such as tassel emergence (VT), silking (R1), and blister (R2) stages. The highest ROI on corn fungicide applications occurs at or shortly after tasseling when most diseases start to spread. These stages represent corn plants’ peak vulnerability to fungal diseases like gray leaf spot and northern corn leaf blight.

If field disease history or high early-season disease pressure warrants an early fungicide application, we recommend an application during the V5-V8 growth stages.

Similarly, for soybeans, the beginning pod (R3), full pod (R4), and full seed (R6) stages mark critical periods. These are when the crop is most susceptible to diseases such as soybean rust and frogeye leaf spot. To achieve the highest ROI, the main window of application is around the R3 growth stage. Here, insecticides can be tank mixed with a fungicide application if conditions and pest pressure warrant a mixed application.

While the recommended timing serves as a valuable guideline, it’s important to remember ideal timing may vary based on geographic location, hybrid susceptibility, and specific disease pressures. 

To determine appropriate timing for fungicide applications with corn and soybeans, regularly scout fields to monitor for disease symptoms, and utilize disease forecasting systems and maps.

The bottom line

• Fungicide timing is crucial to maximize crop health and productivity.
• Factors such as hybrid susceptibility, weather conditions, and field history influence fungicide effectiveness.
• Ideal application timing varies based on location, hybrid susceptibility, and disease pressures. To choose the best timing for a fungicide application, use scouting observations, disease forecasting systems, and maps.

Always carefully read and follow application instructions on fungicide product labels. For questions or concerns, work with your local AgriGold agronomist for further instruction or disease identification and control.