Dieback syndrome

A decline is a progressive phenomenon resulting from multifactorial biotic and/or abiotic causes that leads to a general and gradual deterioration leading ultimately to tree mortality.

The decline process can be represented by a "spiral of decline" composed of predisposing, triggering and aggravating factors that are partly interchangeable.

Decline results in a reduction in leaf mass. The crown then becomes progressively transparent.

Chestnut trees have often been planted in unfavourable sites (predisposing factors) such as calcareous, shallow or hydromorphic soils, which can lead to dieback following sudden climatic stresses (triggering factors) and a series of secondary pests (aggravating factors).