Epidemiological Studies on Bacterial Blossom Blight of Kiwifruit

2. Relationship between Occurrence of Bacterial Blossom Blight and the Rate of Bud Development

Abstract

During the 5 years from 1989 to 1994 (except 1993), calyx splitting and flowering date and occurrence of bacterial blossom blight of kiwifruit were investigated on a total of 89 trees (100 to 200 flower buds per a tree). While the date of calyx splitting negatively correlated with the disease occurrence, a positive correlation was found between disease occurrence and the number of days from calyx splitting to flowering. Although new canes were deliberately infected with Pseudomonas syringae, a causal pathogen of bacterial blossom blight of kiwifruit, flowers on the shoot tips were more resistant to the disease than those on the bottom. No difference was observed in the population density of P. syringae among the flowers on the new canes. These results lead to the conclusion that decrease of disease incidence on new canes might result from the number of days between calyx splitting and flowering, suggesting that the later rate of bud development, the more disease occurrence increased.