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International audienceThe pine scale Matsucoccus feytaudi was accidentally introduced into the maritime pine stands of the Maure and Estérel Forests. It is the primary cause of the dieback of 120 000 ha stands and its specialist predator Elatophilus nigricornis has been studied. It is possible to maintain and raise it in laboratory conditions but its output is not prolific enough to envisage propagation which would allow it to be released in natural conditions. When raised in laboratory conditions the time required for its development (table II) and fecundity have been determined. In natural conditions, nymphs develop in trunk bark cracks, adults mate, but females insert eggs in needles. The population of the eggs is distributed according to two gradients: a decreasing gradient from the bottom to the top of the trees and a decreasing gradient from the trunk to the extremities of the branches (figures 3 and 4). The distribution of its nymph populations on the trunk and branches is different before (figure 5) and after (figures 6 and 7) the invasion of M. feytaudi. In reality, the distribution of the predator nymph populations always coincides with that of its host even when that of the latter changes. E. nigricornis produces at least three generations a year (one for M. feytaudi) and overwinters at the fertilized female stage (figures 1 and 2). Two sampling methods have allowed us to estimate the population levels which have developed during (figure 8 ; table III ; IV) and after the pine scale invasion (figures 9 and 10, table V). Even when there was widespread destruction of the trees attacked due to the action of the xylophagous, there is a link between the size of the E. nigricornis populations on the trees and the capacity of the tree to survive. In stands where more than half the trees survived it was found that in 6 years the level of weekly captures was multiplied by 26 (figure 9). Finally, on regeneration trees which replaced the old stands that had been destroyed or felled, the population levels are 3 times greater (figure 10).Biologie et écologie d'Elatophilus nigricornis Zetterstedt (Hemiptera Anthocoridae) prédateur de Matsucoccus feytaudi Ducasse (Homoptera Matsucoccidae) dans le Sud-Est de la France. Les pullulations de la cochenille Matsucoccus feytaudi, introduite accidentellement dans les peuplements de pins maritimes des Maures et l'Estérel, ont entraîné le développement de son prédateur Elatophilus nigricornis. Il est possible de maintenir E. nigricornis en élevage au laboratoire mais son rendement ne permet pas d'envisager sa multiplication pour effectuer des enrichissements dans les conditions naturelles. La durée de son développement et sa fécondité ont été précisées. Sur le terrain, il vit dans les fissures des écorces des troncs et des branches. Les femelles déposent ses œufs dans les aiguilles. La répartition de ses pontes est décrite et interprétée. Il présente trois générations par an, alors que M. feytaudi n'en a qu'une, et passe l'hiver au stade de femelle fécondée. Deux méthodes d'échantillonnage ont permis d'estimer ses populations : elles sont en très bonne coïncidence spatiale avec celles de son hôte ; même quand la répartition de ce dernier sur l'arbre change ; elles sont plus élevées sur les arbres survivants et surtout sur les arbres issus de régénérations naturelles qui se sont développés après la destruction des peuplements initiaux. En définitive E. nigricornis est un prédateur sur les pins très spécialisé sur Matsucoccus

annals of forest science

Biology and ecology of <i>Elatophilus nigricornis</i> Zetterstedt (Hemiptera Anthocoridae) predator of <i>Matsucoccus feytaudi</i> Ducasse (Homoptera Matsucoccidae) in the South-East of France

Biology and ecology of Elatophilus nigricornis Zetterstedt (Hemiptera Anthocoridae) predator of Matsucoccus feytaudi Ducasse (Homoptera Matsucoccidae) in the South-East of France