Aspects still to solve for the management of kiwifruit bacterial canker caused by Pseudomonas syringae pv. actinidiae biovar 3

The pandemic wave of kiwifruit bacterial canker, caused by Pseudomonas syringae pv. actinidiae biovar 3, has caused, in recent years, severe economic losses in all major areas of kiwifruit production. After the initial discouragement, each country affected by the disease promptly reacted trying to establish and promote phytosanitary and agronomic measures aiming at reducing the incidence and severity of the disease and the risk for further spreading. Within this context, public and private research groups, strongly supported by ad hoc projects funded by international, national and local political and commercial Institutions, have made considerable efforts. After about 10 years since the initial outbreak of May 2008 in central Italy (i.e., Latina province), the management of the disease has reached in many areas of cultivation worldwide a rather satisfactory level, despite the endemic presence of the pathogen in the orchards. However, if the coexistence has been successfully obtained in some circumstances, some aspects of disease control still require particular attention. Among the others, there are: a) the rapid occurrence of copper-resistant P.s. pv. actinidiae and P.s. pv. syringae strains in New Zealand and Italy, respectively; b) the winter and spring frost promoting an increase in the aggressiveness of the pathogen; c) the susceptibility of the new gold and red cultivars; d) the control measures to perform during the plant dormancy season; e) the upgrade of some agronomical techniques to prevent the multiplication and spread of the pathogen within and between the orchards.