The granary weevil Sitophilus granarius is a stored product pest found worldwide. Environmental damages, human health issues and the emergence of resistance are driving scientists to seeks alternatives to synthetic insecticides for its control. With low mammal toxicity and low persistence, essential oils are more and more being considered a potential alternative. In this study, we compare the toxicity of 25 essential oils, representing a large array of chemical compositions, on adult granary weevils. Bioassays indicated that Allium sativum was the most toxic essential oil, with the lowest calculated lethal concentration 90 (LC90) both after 24 h and 7 days. Gaultheria procumbens, Mentha arvensis and Eucalyptus dives oils appeared to have a good potential in terms of toxicity/cost ratio for further development of a plant-derived biocide. Low influence of exposure time was observed for most of essential oils. The methodology developed here offers the possibility to test a large array of essential oils in the same experimental bioassay and in a standardized way. It is a first step to the development of new biocide for alternative management strategies of stored product pests.

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.

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Although synthetic pesticides are still used to control insect pests, greater efforts have been made to develop healthier and more environmentally friendly pesticides. Because of their insecticidal properties, botanical essential oils (EOs) are considered as promising alternatives to the use of synthetic insecticides. However, little is known about mechanisms underlying the insecticidal activity of most these natural compounds. In the present study, we evaluated the contact toxicity and the modes of action of the EO from Mentha arvensis against the granary weevil, Sitophilus granarius L. (Coleoptera: Curculionidae), a cosmopolitan insect pest that causes extensive damage to stored cereals. M. arvensis EO caused high contact toxicity in S. granarius adults, resulting in a rapid paralysis and rapid alteration of walking behavior. Our label-free quantitative proteomics approach revealed that M. arvensis EO induced dramatic physiological changes in exposed insects. The majority of the differentially expressed proteins (DEPs) were upregulated and are related to the development and functioning of the muscular and nervous systems, cellular respiration, protein synthesis, and detoxification. These results suggest that M. arvensis essential oil is capable of affecting a variety of biological processes, and shed light on the repair mechanisms put in place in surviving insects to counter the damage inflicted. This work opens new perspectives on the proposed mechanisms of insecticidal activity of a promising EO for controlling pests of stored cereals and may represent a first step in the development of novel bio-rational insecticides.

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.