Fighting Barley’s Hidden Threat: Weather and Timing Are Key to Protecting Barley Crops in Argentina

Scientists unveil critical insights into Ramularia leaf spot, a disease threatening barley yields worldwide. Through field trials and predictive models, they identify optimal fungicide application timing and establish links between disease severity and weather conditions.

Barley farmers in Argentina and across the globe are confronting an escalating challenge from Ramularia leaf spot (RLS), a disease caused by the fungus Ramularia collo-cygni. Known for its long latency period (from pathogen infection until visible symptoms), the pathogen often goes undetected until significant damage has occurred, leading to reductions in grain yield and quality. Its development is closely tied to environmental factors, making it notoriously difficult to predict and control.

This research quantified RLS-related yield losses, which can reach up to 16%, mainly due to a 20% decrease in grain size and an 8.7% reduction in grain weight. The study identified the flag leaf fully emerged stage (GS39) as the most efficient timing for fungicide application (mixtures with carboxamides), falling within a critical protection period (GS33-GS49).

Furthermore, the researchers developed four forecast models correlating disease severity with key environmental variables (multiple regression models). These include cumulative daily average temperatures combined with rainfall, soil water availability or leaf wetness duration from early tillering to flag leaf emergence (before RLS symptoms onset). Such models could help growers anticipate outbreaks and optimize fungicide use, enhancing both crop protection and sustainability.

By integrating precise fungicide timing with weather-based forecasting, this research offers a practical framework to mitigate the impact of one of barley’s most persistent threats.