Abstract
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 first generation of psyllids reach the fourth instar, would maximize the chance of controlling psyllid populations in pear orchards.
Highlights
Pear (Pyrus communis L.) is one of the major fruit crops in temperate climates, it is ranked second in terms of fruit production in Europe with more than 100 000 hectares dedicated to its cultivation and approximately 2 million tons of pears produced in orchards in 2019 (Tougeron et al, 2021; FAOSTAT, 2021)
According to Armand et al (1990, 1991) and Booth (1992), T. insidiosus mainly oviposit in the fourth and fifth instar of the pear psyllid C. pyri, whereas for C. pyricola, the studies of McMullen (1966), Guttierez (1966) and Booth (1992) suggest that this parasitoid oviposit in all instars. We observed this parasitoid inserting its ovipositor in all host instars and that higher mummy productions were recorded when eggs were laid in third and fourth instars, as in the study of Gutierrez (1966)
Our results indicate that attraction and acceptance of fifth instar psyllids by T. insidiosus was low as there were few antennal contacts and ovipositor insertions and no mummies were produced
Summary
Pear (Pyrus communis L.) is one of the major fruit crops in temperate climates, it is ranked second in terms of fruit production in Europe with more than 100 000 hectares dedicated to its cultivation and approximately 2 million tons of pears produced in orchards in 2019 (Tougeron et al, 2021; FAOSTAT, 2021). Honeydew excretions produced by C. pyri immatures are colonized by sooty moulds, which results in marked fruit and reductions in marketable fruit (Civolani, 2012; Sanchez & Ortin-Angulo, 2012). Spiders, ants or anthocorid bugs may help in the management of pear psyllid populations (Sanchez & Ortin-Angulo, 2012; Sanchez et al, 2020; Gajski & Pekár, 2021) and mass releases of anthocorids into orchards can effectively reduce pear psyllid populations (Sigsgaard et al, 2006a, b) Their abundance in pear orchards is not always sufficient to regulate psyllid populations below sustainable levels (Booth, 1992; Erler, 2004; Civolani, 2012). That is why it is crucial to study other natural enemies of the pear psyllid and develop new biological control solutions for use by pear growers
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