RELATIONSHIPS BETWEEN THE INCIDENCE OF FIRE BLIGHT AND NUTRITIONAL-STATUS OF PEAR TREES

This study was carried out to investigate the relationships between in cidence (strikes per tree) of fire blight caused by Erwinia amylovora and nutritional status of Santa Maria pear trees in the Korkuteli, Ant alya region of Turkey. The macro- and micro-nutrient contents of dried leaf and shoot samples were analyzed. Following natural infection the relationship between nitrogen (N), phosphorus (P), potassium (K), cal cium (Ca), magnesium (Mg), iron (Fe), zinc (Zn), manganese (Mn), and c opper (Cu) content of leaves and shoots and the number of fire blight strikes per tree was examined by correlation and regression analysis. There were statistically significant relationships between the inciden ce of fire blight and the K content and N/K ratio of leaves and shoots , and the Mn content of shoots. Concentrations of K above 1.7 g/100 g dried leaf and Mn above 33 mu g/g dried shoot were correlated with low incidence of shoot infection. Fewest strikes per tree were observed, when the leaf-N/K ratio was 1.2 and rose to its highest level at a rat io of 1.8. Based on a step-wise regression procedure, 82.3% of the tot al variation in the incidence of fire blight was explained by the N, K , and Mn contents of leaves.