Septoria Leaf Spot Disease Research Articles

Septoria drummondiiEll. et Ev., A common seed-borne pathogen in European lines ofPhlox drummondiiHook. Seed imported to New Zealand

Abstract Septoria leaf-spot disease caused by Septoria drummondii Ell. et Ev. has for several seasons severely limited production of Phlox drummondii seedlings in commercial nurseries of the Manawatu. The disease is most severe during periods of prolonged cool humid weather. First symptoms are apparent approximately thirty-five days from sowing as diffuse chlorotic blotches on one or both cotyledons. Within three days these develop as distinct light-brown lesions covered with pyenidia (Fig. 1). On true leaves, first lesions may occur within fifteen days of first appearance of pyenidia on cotyledons. All seedlings from a seed box initially containing less than ten seedlings with cotyledonary lesions may be heavily infected within thirty days of pricking out. The disease has been located on established plants throughout summer and autumn but is then less spectacular. Leaves are mainly attacked but lesions with pycnidia have also been observed on stems, petioles, peduncles, and sepals (Fig. 2).