5. Conclusion
In conclusion, this study indicates that P. syringae pv. syringae was isolated from all symptomatic plants. A poor plant physiological status exposed the plants to early attacks even in presence of weak environmental in oculum. The improvement of soil quality could largely contribute to keep the risk of apple blister bark caused by P. syringae pv. syringae at a minimum. Conversely a vigorous vegetative growth exposed plants to higher risk of spring attacks in the location with strong in oculum. In the latter case, appropriate plant management would be required to promote tissue hardening. Further more the physical protection of the trunk during winter fromextreme thermal excursions would seem to be important in order to reduce the susceptibility of young apple trees to the blister bark disease.