Optimizing Cercospora Leaf Spot Control in Table Beet Using Action Thresholds and Disease Forecasting.

Area of Science:

• Plant Pathology
• Agricultural Science
• Fungal Disease Management

Background:

• Cercospora leaf spot (CLS), caused by *Cercospora beticola*, is a major foliar disease impacting table beet production.
• Uncontrolled CLS leads to rapid defoliation, crucial for harvest in broad-acre farming.
• Current fungicide applications rely on a fixed action threshold and calendar scheduling, potentially leading to overuse.

Purpose of the Study:

• To evaluate the efficacy of current fungicides and action thresholds for CLS control.
• To assess the utility of weather-based risk scheduling versus calendar applications for fungicides.
• To determine optimal risk thresholds for specific fungicide combinations.

Main Methods:

• Two replicated field trials assessed fungicides initiated at the 1 CLS lesion/leaf threshold.
• Six replicated field trials compared weather-based risk scheduling (moderate and high thresholds) with calendar applications.
• Fungicide efficacy and spray frequency were recorded.

Main Results:

• Pydiflumetofen + difenoconazole and propiconazole demonstrated significant CLS control.
• Weather-based scheduling with pydiflumetofen + difenoconazole reduced applications from three to two without compromising control.
• Propiconazole with a moderate risk threshold achieved equivalent control to calendar applications, saving one spray.

Conclusions:

• Scheduling fungicide applications based on weather-based risk significantly reduces spray frequency for CLS management in table beets.
• Optimal risk thresholds vary by fungicide, with high risk for pydiflumetofen + difenoconazole and moderate for propiconazole.
• This approach offers substantial scope for reduced fungicide applications while maintaining effective disease control.