Scientists discovered that Fusarium oxysporum, a fungus that causes plant diseases, uses an internal clock system to time its attacks on plants. The fungus is most dangerous at dawn, when it activates special genes to survive the plant’s defenses and produce toxins. By disrupting the fungus’s clock genes, researchers found they could make it harmless. This discovery could lead to new ways to protect crops by targeting the pathogen’s timing system rather than using traditional fungicides.