Abstract
1. Dwarf-diseased mulberry trees which had been infected by viruliferous leafhoppers in the previous year developed healthy leaves in April, but gradually showed symptom on new shoots from May to July, under natural conditions.
2. When diseased trees having healthy leaves in April were placed in a constant temperature chamber at 30±1°C, symptom developed in one to two weeks.
3. When diseased trees showing severe symptom were kept at 37±1°C, the symptom entirely disappeared from newly emerging leaves in one to two weeks.
