Mycosphaerella blight can produce yield losses of more than 30% in field peas and 50% in processing peas. The pathogens attack leaves, stems, flowers and pods:
- On leaves, early symptoms of infection are small, purplish spots with irregular, indefinite margins. Lesions on the stem may extend 10 mm (3/8 in.) above and below the point of leaf attachment.
- On older leaves or under moist conditions, the lesions enlarge, causing the tissues to dry up. Lesions on petals are small, but infected blossoms may drop.
- On pods, lesions are initially small, and are typically lighter in colour. Lesions may expand on ripe pods and produce extensive purplish brown discolouration.
Infected seeds from diseased pods may show no visible symptoms, or may be shrunken and discoloured. Seedlings from infected seed often develop disease symptoms, but the lesions are confined to the stem base where the cotyledons are attached to the stem.