| Popis: |
Green needles of 7-9-year-old Pinus radiata trees at a plantation in Sunny Corner, New South Wales, have been infected primarily by two species of fungi, Cyclaneusma minus and Lophodermium pinastri. Needles emerged from fascicle sheaths in October and November and persisted on the trees for about 2 years before developing symptoms of Cyclaneusma minus infection during summer and autumn. Immature current year's needles were infected by both C. minus and L. pinastri before they were fully elongated. Ascospores of C. minus were released from cast needles in very large numbers in spring (September-November) and most new infections occurred during this period. Infection by L. pinastri lagged behind that by C. minus by about 2 months. There was significant between-tree variation in disease levels of each of these fungi. Susceptibility to C. minus was not linked with susceptibility to L. pinastri. Nitrogen levels in P. radiata foliage and symptom expression are correlated. |
