Effect of fruit shape on core rot caused by Phomopsis sp. in Japanese pear cv. ‘Kosui’

The effect of fruit shape on the incidence of core rot caused by Phomopsis sp. in Japanese pear cv. ‘ Kosui’ was investigated in 3 field experiments during 1999-2000. One finding was that fruit where the diameter of the calyx tube at harvest was bigger than 1 mm had an incidence of core rot twice (41.3%) as high as fruit (22.1%) with a tube diameter smaller than 1 mm. Moreover the rate in fruit with a calyx hole bigger than 1mm when measured 52 days after full bloom stage was remarkably higher for flattened fruit compared to those with an oval shape. I estimated that it would be possible to greatly reduce the incidence of core rot if flattened fruit were selectively removed within 2 months after full bloom stage.