The pear tree is a main economical orchard crops under temperate climate with more than twenty-five million tons of fruit produced each year. The psylla Cacopsylla pyri is the most important pest, as it infests all commercial pear tree varieties, it sucks the phloem sap and it cause damages to the trees by nutrient subtraction and disease transmission (sooty molds and phytoplasm). The management of this insect is mainly based on integrated pest management with a mix of natural and chemical controls. However, with the ban of a growing number of plant protection products and the increasing public interest in an “organic” mode of consumption, it is important to develop innovative ways of pest managements respectful of the environment. Trechnites insidiosus is the most abundant parasitoid of C. pyri but it has been poorly studied. The aim of this study is to evaluate the parasitism behaviour of T. insidiosus toward the different larval stages of C. pyri, and to evaluate the quality of the next generation individuals. We observed that stage 3 and 4 larvae are the most interesting hosts for T. insidiosus in order to produce individuals in quantity and in quality. This provides a basis for further studies and fulfill the lack of data concerning this insect in the literature, particularly with regard to its biology, its behaviour and its use in biological management.

Improved methods of integrated pest management of the pear psyllid Cacopsylla pyri (L.), the primary pest of pear in Europe and North America, are needed. Trechnites insidiosus (Crawford) is the most abundant parasitoid of C. pyri in pear orchards, where it is present early in the psyllid infestation period. However, little is known about its general biology, interaction with its host and potential as a control agent. The objective of this laboratory study was to evaluate the behaviour of a specialist parasitoid when presented with different larval instars of C. pyri, and assess the quality of the next generation of parasitoids. T. insidiosus was able to insert its ovipositor into all host instars. However, the fourth instar of the host appeared to be the most suitable in terms of behavioural acceptance, time spent walking, antennal activity and progeny development (mummy formation, development time and tibial length). In addition, we report a low frequency of host-feeding behaviour by this parasitoid. From a biological control perspective, we suggest that favouring T. insidiosus, either through mass releases or conservation of naturally present populations, when the fi rst generation of psyllids reach the fourth instar, would maximize the chance of controlling psyllid populations in pear orchards.