FIELD EFFICACY OF A ZINCCOPPERHYDRACID OF CITRIC ACID BIOCOMPLEX COMPOUND TO REDUCE OOZING FROM WINTER CANKERS CAUSED BY PSEUDOMONAS SYRINGAE pv ACTINIDIAE TO ACTINIDIA spp
Pseudomonas syringae pv. actinidiae (Psa) is the causal agent of bacterial canker of green-fleshed (Actinidia deliciosa) and yellow-fleshed (A. chinensis) kiwifruit and is causing severe economic losses worldwide. In Italy, a combined strategy that takes into consideration timely spray treatments to the plant canopy, a correct pruning management including the disinfection of the tools and the protection of the pruning cuts, the avoidance of excessive nitrogen fertilization and water stress, and training systems favoring a better air circulation, are giving satisfactory results in controlling the pathogen severity in the field. However, despite these efforts, the dormant phase of the plant still represents a main problem, especially in the areas where winter frosts regularly occur. During winter 2013-14 and 2014-15 in four sites, spanning from Northern to Southern Italy, the field efficacy of a zinc (4.7%)-copper (2.6%)-hydracid of citric acid (21.4%) biocomplex compound has been tested on Actinidia deliciosa and A. chinensis orchards. The biocomplex compound was applied three times, at a dose of 1.0%, to reduce the occurrence of bacterial exudates oozing out from the main trunk and leaders in early spring. During the trial, winter frosts were recorded in all sites. The biocomplex compound was more effective than a 1% Bordeaux mixture used under the same conditions. This biocomplex formulation could be used to effectively reduce the amount of exudates caused by Psa in areas where winter frost occurs regularly.