NUTRIENT STATUS OF CHESTNUT ORCHARDS. I. RELATIONSHIP WITH INCIDENCE OF BLIGHT

This study investigated the relationship between the incidence of chestnut blight, caused by Cryphonectria parasitica and the nutritional status of chestnut orchards. One hundred chestnut orchards were classified according to blight incidence and aggregated into two groups: H-orchards (<10% blight incidence) and D-orchards (>10% blight incidence). Some soil fertility parameters were also determined. The nutrient concentration of leaves and phloem tissue were measured in 40 chestnut orchards. Bark samples were collected in June from eight trees in both groups of orchards. In the H-orchards only healthy trees were sampled, while in the D-orchards both diseased (D-trees) and healthy trees (H-trees) were sampled. The leaves of five H-trees were sampled in September in D-orchards as well as in H-orchards. Multiregression analysis revealed that the age of the chestnut orchard, soil organic matter (OM), extractable P and exchangeable Ca was responsible for 22% of the variation of blight incidence. While the age of the orchard and P were positively correlated with disease incidence, OM and Ca were negatively correlated. Multiregression analysis carried out for H-trees (in H-orchards) and D-trees (in D-orchards) showed that the most significant variables to explain blight incidence were P, Ca/N ratio, Mn, Cu and the age of chestnut trees. The foliar analysis carried out for H-trees both in H-orchards and in D-orchards did not give consistent results with soil analysis or phloem analysis.