Inter-relationships between the pear psylla Psylla pyri (L.) populations (Hom., Psyllidae) and its parasitoid complex in a sprayed orchard of southeastern France The parasitoid fauna of the pear psylla Psylla pyri (L.) is relatively well known. However, little information concerns its quantitative evolution. We have therefore estimated the host population prevalence (parasitism rate) by a caging method of P. p ri old nymphs (L4, L5) in the laboratory. The pest populations are estimated by visual assessment ortwigs.In orchards sprayed against psyllids, Trechnites psyllae (Ruschka) (Hym., Encyrtidae) is the only primary parasitoid which takes part in the pest regulation from the 1st generation. Sy hophagus mamitus (Walker) (Hym., Encyrtidae) is the main hyperparasitoid. Psylla pyrisuga Foester YP avours the settlement of S. mamitus pioneers and acts as a relay species for primary parasitoids between the 1st and 2nd generation of P. pyri. Highest populations of 5. mamitus are observed in autumn (5th generation of P. pyri). Concerning psyllidsparasitoids functional relationships, the prevalence and the host population level vary in hase opposition.This study shows the action oPthe primary parasitoids and their interest, more particularly in the early control of the pest populations at a period of scarcity of predators in orchards.Par ses caractiristiques biologiques et les digits qu'il entraine, P. pyri est un ravageur d'importance iconomique contre lequel il convient de se prkmunir. Dans I'optique de mettre au point une lutte intigrke, les travaux prisentis ici visent i priciser le r d e des antagonistes naturels, plus particulikrement des parasites, dans la regulation des populations d e P. pyri. La faune parasitaire (tableau) actuellement connue, infiodie aux psylles d u poirier, est U.S. Copyright Clearance Center Code Statement: 093 1 -2048/90/1003-0242 $ 02.50/0 Inter-relations psylles-parasitoides 243 essentiellement constituie de micro-hyrninoptkres s'attaquant aux larves Pgies (L4 et L5) de l'h6te. Des dipttres sont igalement cites parmi les parasites du stade imaginal des psylles. Aucun auteur ne signale pour le moment chez les psylles la prisence de parasites

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