What does the FRAC group number indicate?

The FRAC group number is a classification system established by the Fungicide Resistance Action Committee (FRAC) to identify the site of action of fungicides. This classification helps to understand how different fungicides work against fungal pathogens and is essential for effective disease management strategies. By grouping fungicides based on their mechanisms, it enables users to rotate different fungicides with varying sites of action to manage resistance development in target diseases. This is crucial for prolonging the efficacy of fungicides and ensuring sustainable pest management practices.

The other options do not align with the function of the FRAC group number. The potency of a fungicide refers to its effectiveness, while the region of effectiveness and the type of plant absorption are not related to the classification provided by the FRAC system.