Abstract
As has presiously been reported, when mulberry trees which had been infected with Kikuchi mild strain in previous year were cut from the basal part of the trunk in winter or were allowed to remain unpruned throughout the growing season, most of these trees developed normal shoots and leaves in summer. And it has been 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 attributable to the retardation of movement of the pathogen from the roots. Results in line with these findings, this experiment was carried out at Kikuchi city in order to establish the economical protection counterplan from damage of the disease.
From one of the results of this experiment, it was discovered that the cutting back of mulberry trees from 1 meter above the stump in June (cutting back 1m above) is efficient to protect from the damage as well as the cutting back of trees in winter or no cutting back throughout the year and moreover increase a leaf yield at the same time.
Using two methods of the cutting back in winter and of the cutting back 1m above, these experiments were carried out. Experiment A were performed the cutting back in winter in 1964, the cutting back 1m above in 1965, and the cutting back in winter in 1966. Experiment B were the cutting back 1m above in 1964, the cutting back in winter in 1965, and the cutting back 1m above in 1966. Experiment C were the cutting back in winter in 1964, the cutting back 1m above in 1965, and the cutting back 1m above in 1966. Experiment D were cut back, leaving the stubs in June from 1964 to 1966 as to control. The results of A, B, C were excellent in respectively compared with D.
Therefore, it seemed to the author that the best economical protection counterplan is the three-year rotation of the method of experiment C is carried out in the field.
