广东桑花叶病的研究

桑花叶病的症状有花叶、环状叶、丝状叶和网状叶（沿脉绿叶）４种：在２５—２８℃温度下分离花叶、丝叶症状的病原是线状病毒，花叶症状病毒粒体长约１０００ｎｍ、宽约１６ｎｍ，最短的长约４００ｎｍ；丝叶症状粒体大小长约５００ｎｍ，宽约１２ｎｍ；传染试验结果表明昆虫可能传染桑花叶病；田间消长规律表明环斑症状发病适温为２０—２４℃左右，而花叶、丝状叶和网状叶（沿脉绿叶）症状最适宜的发病温度是２５—２８℃；连续用病桑叶养蚕，蚕的体质变弱，蔟中死亡率增高，容易诱发蚕病。

A STUDY ON MULBERRY MOSAIC DISEASE

There are four types of symptoms of mulberry mosaic disease,i.e.mosaic leaf ,ringspot leaf,filamentous leaf and network leaf(The leaf veins are in network pattern andgreen in colour).At 25 28℃,the pathogens were isolated from the mosaic leaf and fila-mentous leaf.The virion of the former is approximately 1,000 nm in length and 16 nm inwidth.The shortest is only about 400 nm. That of the latter is approximately 500 nm inlength and 12 nm in width.The result of infection experiment shows that insects maypossibly serve as the vectors of the disease.The developing and decline regularity of thedisease in fields shows that the optimum temperature for the occurring of ring spot leafis 20 24℃,and that for the mosaic and filamentous leaf is 25 28℃。If silkworms arefed with the diseased leaves continuously ,they would become weak ,the death rate dur-ing mounting is increased,and the silkworms are easily infected with diseases.