Researchers in Egypt identified a fungus called Lasiodiplodia theobromae as the cause of a serious disease affecting grapevines in the southern region. Using both microscopic examination and genetic analysis, they confirmed the fungus causes dark streaking in grape vine trunks, leading to branch death and decline. When they tested the fungus on grape tissues in the laboratory, it successfully infected all tested samples, showing it is a highly virulent pathogen. The findings suggest farmers need to use disease-resistant grape varieties and implement management strategies to prevent losses.