Analysis of parasite and predator populations observed in pear orchards infested by Psylla pyri (L.) (Hom. : Psyllidae) in France

Abstract

Activity periods of the main natural enemies of Psylla pyri (L.), and their succession in pear orchards during the year at Avignon and at Toulouse (France) were determined. Their relative abundance at each sampling date was analyzed using Shannon's formula, which measures the degree of diversity of dominant species. A small number of rather specific beneficial arthropods, Anthocoris nemoralis (F.), Orius spp., Prionomitus mitratus (Dalman) and Trechnites psyllae (Ruschka), was essential to reduce populations of pear psylla notably but not sufficient to control the pest. Their action was enhanced by minor enemies, Orthotylus nassatus (F.). Heterotoma meriopterum (Scopoli), Campyloneura virgula (Herrich-Schaeffer), in June and July.