Citrus melanose, a serious fungal disease affecting citrus crops, is increasingly difficult to control due to the development of fungicide-resistant fungal strains. This study examined how resistant and susceptible Diaporthe citri strains respond to two common fungicides. The researchers found that resistant strains have genetic mutations that allow them to overcome fungicide treatments, particularly a specific change in the β-tubulin gene. Understanding these resistance mechanisms is crucial for developing better strategies to manage citrus diseases.