1. When mulberry trees affected with dwarf disease sprout in April, typically crinkled leaves are not seen but normal or smaller subnormal leaves are produced in the beginning. Subsequently, typical crinkled leaves appear gradually.
2. At Taimei village in Kumamoto Prefecture, the symptom of this disease showing crinkled leaves appears before the cutting back of mulberry trees in June. At Kikuchi city, on the other hand, the symptom does not appear before the cutting back but on the newly grown shoots after cutting back in June.
3. At Taimei village, the symptom always makes its appearance in May irrespective of the time of cutting back. At Kikuchi city, on the other hand, when diseased trees are cut back in winter the symptom begins to appear in May, but when mulberry trees are cut back in June and July, the symptom appears in these months.