New Aspects of In Situ Measurements for Downy Mildew Forecasting

Area of Science:

• Agricultural Science
• Plant Pathology
• Viticulture

Background:

• Downy mildew is a major threat to global grape production, primarily managed with fungicides.
• Increasing regulatory and environmental pressures necessitate improved forecasting models to minimize fungicide application.
• Current forecasting relies on weather station data, which may not accurately reflect microclimatic conditions within grape canopies.

Purpose of the Study:

• To compare climatic parameters (temperature, relative humidity, leaf wetness) measured by weather stations with those recorded inside a grape canopy.
• To assess the impact of these measurement differences on the precision of downy mildew forecasting models.
• To evaluate the potential for reducing fungicide applications through enhanced forecasting accuracy.

Main Methods:

• Simultaneous measurement of temperature, relative humidity, and leaf wetness using a weather station and sensors placed inside a grape canopy.
• Statistical analysis to compare data sets and identify significant differences between the two measurement locations.
• Evaluation of the implications of these differences for established infection potential calculations (e.g., 50 h-degree).

Main Results:

• Temperature showed daytime but not nighttime differences between weather station and canopy measurements.
• Relative humidity exhibited significant differences during both day and night.
• Leaf wetness displayed the most substantial and statistically significant differences, occurring during both daytime and nighttime.

Conclusions:

• Discrepancies in climatic data between weather stations and grape canopies significantly affect the precision of downy mildew forecasting models.
• Incorporating in-canopy microclimate data into forecasting models is crucial for accurate prediction of infection risk.
• Utilizing canopy-specific data holds the potential to optimize fungicide application strategies, leading to reduced chemical use in viticulture.