Le dendroctone de l’Épicéa en France : situation et mesures de lutte en cours

The spruce beetle entered north-eastern France at the end of the 19th century. By relentlessly expanding its distribution area, it has gradually colonized practically all French spruce forests. This beetle is exceptionally resistant to the constituent defences of spruce and as such is one of the few species of bark beetles capable of attacking perfectly healthy trees. The damage is more serious in areas located at the outer limits of the beetle’s range, where the pest settles in the absence of its own particular predator, Rhizophagus grandis. Following this infestation stage, which sometimes lasts several years, the predator generally catches up with the pest and its population level is rapidly cut back to the endemic state. At this stage, damage to stands is practically imperceptible. The life cycle of this beetle is unusual and has been studied under dedicated research programmes that have developed a biological control method never previously applied to the forestry sector. To reduce the time lag between arrival of the beetle and that of its predator beetle to a minimum, reared populations of Rhizophagus grandis have been released in France for some twenty years. In addition, a number of promising techniques for monitoring the geographical progression of the species and its predator are currently being developed.