Slash pine (Pinus elliottii) is severely damaged by brown spot disease fungus (Lecanosticta acicola) in southeast China. Observations in northern region of Fujian province show that the fungus passes winter on affected needles and died needles hanging on branches or fallen to the ground. Spore traping with slids indicate that conidia release only in raining days but won’t release days on when rainfall is less than 1.7mm. Examinations of rainwater collected under diseasetrees show the same result. Washing sporulated needles of slash pine with artificial rainfall (2.6 or 12mm/h.) indicated that maxium conidia releasing occurs during the first 15~30 min. of washing. Washing diseased slash pine needles collected from a plantation with artificial rainfall (6mm/h.) for 30 min. to ex amine sporulations of the fungus in nature from March to November in 1983 with 5℃ days intervals showed that conidia develop all the time with the maxium appearing from late April to middle May. The longivity of conidia on slids is not more than 70 days at 5. and 45 days at room temperature.