Gymnosporangium asiaticum Miyabe et Yamada에 의해서 발생되는 배나무 붉은별무늬병(赤星病)의 感染과 관련되는 몇가지 要因에 대하여 調査하였다. 향나무(品種 : 가이즈가)에서 冬胞子의 50% 成熟時期는 배나무(品種 : 長十郞)의 滿開花日 3-6日前이었고, 冬胞子堆의 成熟度와 배나무의 滿開花時期는 그 해의 氣象條件에 따라 달랐다. 冬胞子의 發芽와 小生子의 形成은 多濕條件에서 15~20℃일때 가장 많았고, 4月24日에는 同胞子堆를 24時間 多濕狀態에 두었을 때 小生子가 형성되었으나 4月29日 이후에는 水浸 5시간 후부터 形成되었다. 小生子는 耐乾性이 대단히 낮아서 室內에 放置했을 때 1時間 후에는 완전히 發芽力을 상실하였다. 또한 小生子가 發芽하여 잎을 侵入하고 發病하는데 필요한 多濕狀態는 적어도 8시간 이상 持續되어야 하는 것으로 나타났다. 冬胞子堆의 小生子 形成能力은 1985年 4月 22日부터 5月27日까지 계속되었다. 배나무 잎의 葉位別 感受性 4月末의 接種에서는 下位葉에서, 5月15日頃까지는 中位葉쪽에서, 5月下旬에는 上位葉 또는 徒長枝葉에서 높아 發病이 많았다. 따라서 서울地方에서의 배나무 붉은별무늬병의 發生時期는 4月末로부터 5月末까지 약 1개월간으로 추정된다.
The study has been carried out to investigate the effect of several factors on pear rust infection caused by Gymnosporangium asiaticum Miyabe et Yamada. Fifty percent of telia on Juniperus chinensis(cv. Kaizuka) were matured at 3-6 days before the full blooming of oriental pear trees(cv. Jangsiprang). The maturity of telia and flowering period of pear trees were variable according to weather conditions of the year. Teliospore germination and sporidial formation of G. asiaticum were maximum under the conditions of higher humidity and temperature between 15 and 20℃. On April 24, sporidial formation from telia started 24 hours after water soaking, but water soaking of telia reconized for sporidial formation was at least 5 hours after April 29. The drought resistance of sporidia was very low ; their germinating ability was lost after one hour exposure to the room condition. Duration of leaf wetness period required for rust infection was at least 8 hours when inoculated with sporidia of G. asiaticum on leaves of pear trees. In 1985, the sporidial formation from telia on juniper started from April 22 and continued to May 27. The number of pycnial lesions developed on leaves was highest in younger leaf age when inoculated with sporidia, but older leaves were not susceptible to rust fungi and no lesions appeared in older leaf age. The results indicate that critical period for pear rust infections covers about one month, ordinarily from late April to late May in the Seoul district.