Abstract
Seasonal development of symptoms and production and dispersal of conidia of Lecanosticta acicola, the causal fungus of the brown spot needle blight, were examined in Pinus thunbergii in Shimane Prefecture, Japan. In February 1999, infected 5-yr-old seedlings, as an infection source, were transplanted to a nursery where sound 3-yr-old seedlings were being raised. Conidia were produced from late March through late September on the needles of the 5-yr-old seedlings, and were abundantly dispersed in late June as the primary infection source. Symptoms were first evident on current-year needles in early August and the infection severity rapidly increased in September and October. No progress in symptoms was observed in winter and the infection severity slightly increased in the next April through June. Conidia were produced on the 3-yr-old seedlings from mid-August through late December and were abundantly dispersed from late September through mid-October. The conidia dispersed only during rainfall, but a large number of conidia dispersed even during a slight rainfall.
