Angular Brown Spots Are Appearing on My Strawberry Leaves

Strawberry leaves developing distinctive angular dark spots — spots that follow the veins and leaf structure rather than forming round circles — are affected by angular leaf spot, caused by the bacterium Xanthomonas fragariae. This bacterial disease is separate from common strawberry leaf spot (Mycosphaerella fragariae), which produces round, purple-centred spots with white-grey centres. Angular leaf spot is a less common but more damaging problem, particularly in cool, wet conditions and on plants grown under cover where moisture on leaves is persistent.

Identifying angular leaf spot

Angular leaf spot (Xanthomonas fragariae) produces water-soaked, angular lesions on leaves — visible first on the underside as pale, oily-looking patches bounded by the leaf veins. As they dry, the lesions become reddish-brown on the upper surface and are clearly angular (following the lines between veins) rather than round. In humid conditions, a bacterial ooze may be visible on lesions. The disease can also infect calyx tissue of fruits, causing dark spots that reduce marketability. Severe infection defoliates plants significantly.

Common strawberry leaf spot for comparison

The much more common strawberry leaf spot (Mycosphaerella fragariae) produces round or oval spots with a distinctive dark purple border and a white, grey, or tan centre. These spots have no specific relationship to the leaf veins and are found across the leaf surface. They look quite different from the angular, vein-bounded lesions of angular leaf spot. Leaf spot is generally cosmetic and does not threaten plant health or yield unless very severe; it is most significant on old, crowded beds where it accumulates through the season.

Management

Remove and dispose of heavily infected leaves to reduce the source of inoculum. Avoid overhead watering — irrigate at the base of plants to keep foliage dry. Increase plant spacing to improve air movement. Angular leaf spot is a bacterial disease and fungicide sprays are not effective against it; copper-based bactericides may be applied in severe cases (check label approval). The most effective long-term management is replanting on a fresh site with healthy, certified clean stock and ensuring good growing conditions from the start.