Biological control of chestnut diseases in Italy: effectiveness of blight and ink disease management

In Italy, chestnut stands and orchards suffered from blight and ink disease. After severe damage caused by blight, a spontaneous re-growing of chestnut trees has been observed in relation to the natural spread of hypovirulence, which is caused by the hypovirulent isolates of Cryphonectria parasitica, the causal agent of blight. Field investigations on unmanaged chestnut stands and coppices have emphasised a widespread but variable presence of chestnut blight in the plots visited. Limited levels of mortality due to blight have been recorded on the study sites. Observations have highlighted the effectiveness of the natural spread of hypovirulence, with a clear prevalence of healed and healing cankers in almost all the stands surveyed. Inocula produced in healing cankers collected on the study sites were investigated by means of laboratory and field tests. Differing percentages of C. parasitica morphotypes (normal, intermediate, white, and pigmented) were detected. Artificial inoculations using these inocula produced healing cankers, while strains obtained from single conidia isolations produced different infections and cankers. Intermediate strains even without dsRNA produced non-lethal infections. Ink disease has been causing severe damage to Italian chestnut orchards and stands. Although the attacks of Phytophthora cambivora are limited, each year they still cause the death of trees in many areas. The antagonistic activity of Trichoderma viride and T. harzianum was assayed in laboratory tests, and proved of perspectives for biological control. This was achieved by using organic manure in orchards: the treatments were efficient, and suffering trees recovered. The use of natural and biological controls makes it possible to limit the damage caused to chestnut trees by these two main diseases.