Death of the pear tree
The pear's death is caused by a single-celled organism genetically correlated with the phytoplasmas that cause apple sweeps and stone fruit yellows. This phytoplasma settles in the phloematic tubes also infecting the body of the psyllas, or insects that live on the leaves and shoots of the pear tree. The activity of phytoplasma is harmful because it stagnates the substances processed in the leaves and prevents their transfer to the roots: this causes the degeneration of vital tissues and the progressive drying of the plant. Contamination of other plants occurs through the psylls: in this way, the disease is transmitted to the entire orchard and can cause the death of thousands of trees, as happened in Trentino Alto Adige in the 1940s. On that occasion, the phytoplasma of the disease killed 50,000 pear trees. In addition to the various species of Pyrus, the death can also affect other shrubs, such as quince and nashi.
How it manifests itself
This pathology appears especially in the autumn season, manifesting itself through three different syndromes: rapid decay, slow decay and leaf curl. In rapid decay there is a withering of the leaves and fruits a few days after the appearance of the first symptoms: the dried parts remain attached to the rapidly dying plant. The slow decay is manifested by a reddening of the leaves followed by shoots, flowers and small and small fruits: the roots and branches dry slowly until the tree dies. In the leaf curl, the foliage progressively changes its appearance: the leaves, in fact, turn red and wrap around themselves. This last variant of the syndrome can resolve itself with definitive recovery or open the way to more serious forms of the disease.