Angular Leaf Spot
Angular leaf spot is caused by the bacterium Xanthomonas fragariae, which causes a water-soaked lesion on the lower leaf surface. Under moist conditions, the bacterium produces an exudate that appears as a whitish, scaly film when dry. The pathogen not only infects the foliage but also can invade the vascular system of the plant, causing decline. Important commercial varieties have not been found to exhibit resistance to angular leaf spot. Antibiotics are applied for the control of this disease. The bacterium that causes angular leaf spot is systemic, which means it exists throughout the plant. This bacterium overwinters in infected plants and dead leaves. Exudate from infected leaves can be splashed to uninfected plants by water. Young tissue is most easily infected. Temperatures just above freezing and moist conditions favor disease development.
Varieties vary in susceptibility, but none are resistant. Because this disease is caused by a bacterium rather than a fungus, fungicides have no effect. Since the bacterium prefers cool temperatures and wet conditions, any practice that minimizes the amount of frost protection needed (site and variety selection) is recommended, as are practices that maximize drying of the foliage