梨树疫病病原经鉴定为恶疫霉(Phytophthora cactorum),田间寄主只限于梨树和草毒。人工接菌,可侵染西瓜、白兰瓜、黄瓜、西葫芦、番茄、豇豆、梨树、草毒、马铃薯块茎、苹果果实,而不侵染茄子、辣椒、桃树、杏树、酸梨树、苹果树。病菌在梨树树干和果实上形成的孢子囊,明显地较菌丝在皮氏液中形成的大。病菌在CMA、OMA培养基上单独培养能形成大量的卵孢子,而在小麦芽、V-8汁、PSA培养基上不形成。5月下旬-6月份高温以及降雨(或灌水)是病害流行的主要因素。 The pathogen of pear blight was identified as Phytophthora cactorum, and the field host was confined to pear and grass. The artificial inoculation can infect watermelon, white melon, cucumber, zucchini, tomato, cowpea, pear, grass virus, potato tuber, apple fruit without infringing eggplant, pepper, peach tree, apricot tree, Apple tree. Sporangia formed on the stems and fruits of pear trees were significantly larger than the mycelium formed in Peel’s solution. Pathogenic bacteria in CMA, OMA medium alone can form a large number of oospores, but not in wheat germ, V-8 juice, PSA medium is not formed. Late May-June high temperatures and rainfall (or irrigation) are the major factors contributing to the epidemic.