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

Abstract

The activity periods, and the succession during the year, of the main natural enemies of Psylla pyri [Cacopsylla pyri] were determined in pear orchards in Avignon and Toulouse, France. The relative abundance of these insects at each sampling date was analysed using the dominance diversity index devised by Shannon and described by J. Wilhm. A small number of fairly host-specific beneficial arthropods (the anthocorid predators Anthocoris nemoralis and Orius spp. and the encyrtid parasitoids Prionomitus mitratus and Trechnites psyllae) was essential to reduce psyllid populations but did not eradicate them. Their activity was supplemented in June and July by that of minor predators, the mirids Orthotylus nassatus, Heterotoma meriopterum and Campyloneura virgula.