山楂锈病,由Gymnosporangiumharaeanum　Syd引起,叶片、新梢、幼果均可受害、转株寄主为龙柏。经调查,该病在泰安零星分布为10亩左右。 山楂被害症状:叶片受害时,开始正面发生黄褐色小斑点,后展为圆形,中部黄褐色,边缘淡黄色,表面密生黄褐色针头大的小粒点,后为黑褐色,即为病菌 Hawthorn rust, caused by Gymnosporangiumharaeanum Syd, leaves, shoots, young fruit can be affected, the transposon host Cypress. After investigation, the disease sporadically distributed in Taian about 10 acres. Hawthorn victimization symptoms: leaf damage, began positive brown small spots, after the exhibition for the round, the middle of yellow-brown, the edge of the yellow, the surface of dense brown needle large small particles, after the dark brown, that is, bacteria