Causes of tree vigor weakening and occurrence of deformed fruit in 'Hongro' apple trees

This study was conducted to investigate the causes of tree vigor weakening and occurrence of deformed fruit in problem of cultivation in 'Hongro' apple trees (Malus domestica). 'Hongro' apple, compared to 'Tsugaru' apple, had more flower buds including axillary flower buds. Therefore, the vigor weakening in 'Hongro' apple trees was due to extremely a lot of flowers and could be prevented with blossom thinning and N fertilizer by twice supply. Occurrence of deformed fruit was not different between terminal fruits and axillary fruits, but fruits set on lateral fruiting branch and weak vigor tree occurred a few deformed fruit.