. De récentes recherches sur les maladies du feuillage : conference proceedings : Carlisle, Pennsylvanie, du 29 mai au 2 juin 1989. Maladies et ravageurs des feuilles United States Congrès. Weir (20) ont indiqué qu'hysterothecia sur les aiguilles de pin ponderosa infectées l'année précédente dans l'alésage du Nord-Ouest du Pacifique avec l'asci à maturité des spores bien développé au début du printemps. Cependant, il a indiqué qu'hys- terothecia et spores mûres peuvent être trouvés à n'importe quelle saison de l'année, et que les organes de fructification résister à sécher et libèrent des spores uniquement pendant les périodes d'abondance- dant l'humidité. Plus grand nombre de spores ont été libérés durant

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. Recent research on foliage diseases : conference proceedings : Carlisle, Pennsylvania, May 29-June 2, 1989. Leaves Diseases and pests United States Congresses. Weir (20) reported that hysterothecia on needles of ponderosa pine infected the previous year in the Pacific Northwest bore fully mature asci with well developed spores in early spring. However, he reported that hys- terothecia and mature spores could be found at any season of the year, and that the fruiting bodies resist drying and release spores only during periods of abun- dant moisture. Greatest numbers of spores were released during the May-June rainy season, however, when early vegetative growth of the host was present. Weir (20) also found that temperature regulated spore release. After 4 hours at 5 C no spores were released, whereas at 27 C abundant spores were discharged. Weir (20) concluded that warm summer rains stimulated spore release. Waters (19) found mature ascospores in hysterothecia from July to April in Montana. Maximum spore dis- charge occurred from fall to early April. On the other hand, Waters (19) found that "greenhouse" conditions prevented development of hysterothecia in infected needles and he concluded that hot, dry weather in spring and fall might be important in preventing infection. Lightle (9) found mature hysterothecia and ascospores on needles only from September through December. He trapped spores mostly during rains in September and October, some in November and December and a few in January, March, April and May. Laurent (8) suggested that hot, dry weather or other variations in local and regional weather are responsible for time of hysterothe- cial development and maturity. My investigations, although somewhat limited, showed maturation of hysterothecia to be much earlier in several locations in California than Lightle (9) reported (figs. 2 and 3). However, no mature hysterothecia were found in early spring as reported by Weir (20). July 28 was the earliest sp

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