Studies on the dwarf disease of mulberry tree

(XIV), On the suppression of newly developed symptoms by the cutting back in winter and no cutting back in summer

Abstract

When mulberry trees, which had been severely infected with the dwarf virus in the previous year, were cut from the basal part of trunk in winter or were allowed to remain unpruned throughout the growing stages, most of these trees developed normal shoots and leaves, although some trees showed only slight symptoms in summer. When the cuttings obtained from these apparently normal trees were grown in field or in greenhouse, most of them remained to be free from the disease, not only at the time of sprouting, but also at their growing stages.
When the affected trees with apparently normal shoots or those showing slight symptoms were cut from the base of trunk in summer season, the typical or sometimes severe symptoms appeared.
It is considered that the recovery from the disease by the cutting back of affected mulberry trees in winter or no cutting back throughout the year is not attributable to masking of the symptoms, but to the retardation of movement of the virus from the roots, which is accelerated by the cutting back in summer.