Search

Apple orchards are highly treated crops, in which organophosphorus (OP) are among the most heavily sprayed insecticides. These pesticides are toxic to non-target arthropods and their repeated use increases the risk of resistance. We studied mechanisms involved in tolerance and resistance to OP insecticides in the earwig Forficula auricularia, an effective generalist predator in pomefruit orchards. Adult earwigs were sampled in three apple orchards managed under contrasting strategies: conventional, Integrated Pest Management, and organic. The threshold activities of enzyme families involved in pesticides tolerance: Glutathione-S-transferases (GSTs) and Carboxylesterases (CbEs) were measured in earwig extracts. Acetylcholinesterase (AChE) was monitored as a toxicological endpoint. Variations in these activities were assessed prior to and after exposure to chlorpyrifos-ethyl at the normal application rate. We observed that the mortality of earwigs exposed to chlorpyrifos-ethyl depended on the management strategy of orchards. Significantly lower mortality was seen in individuals sampled from conventional orchard. The basal activities of CbEs and GSTs of collected organisms were higher in conventional orchard. After in vivo exposure, AChE activity appeared to be inhibited in surviving males with no difference between orchards. However an in vitro inhibition trial with chlorpyrifos-oxon showed that AChE from earwigs collected in organic and IPM orchards were more sensitive than from conventional ones. These observations support the hypothesis of a molecular target modification in AChE and highlight the possible role of CbEs in effective protection of AChE. Our findings suggest that the earwigs with a high historic level of insecticide exposure could acquire resistance to chlorpyrifos-ethyl. • Chlorpyrifos-ethyl exposure killed fewer earwigs from conventional orchard. • High carboxylesterases/glutathione-S-transferases found in pre-exposed earwigs. • Acetylcholinesterase was less sensitive in earwigs from conventional orchard. • Chlorpyrifos-induced inhibition of acetylcholinesterase was higher in males. [ABSTRACT FROM AUTHOR]

The codling moth, Cydia pomonella, is a major pest of apple and pear orchards. However, with intensive use of pesticide, an increasing number of resistances has been reported. Detoxification is one of the main mechanisms involved in resistance in Lepidoptera, and there is still much to discover about the molecular mechanisms underlying it. This study was conducted to decipher the molecular mechanisms involved in the insecticide resistance of C. pomonella and to identify genetic markers associated with resistance upon exposure to several pesticides. To that aim, an experimental evolution was carried out from a wild population resistant to several active substances. We generated three lines by combining genetic crosses and experimental selection using chlorantraniliprole, deltamethrin and spinosad. High throughput RNA-sequencing (RNA-seq) was performed on the three lines to verify whether similar mechanisms were involved in pesticide resistance across lines and to assess the role of detoxification and other mechanisms in resistance. In total, we found 592 mutations and 157 differentially expressed genes. Of the candidate genes identified as involved in resistance, a very limited number were shared between lines. We found in total 20 genes belonging to already known candidate genes, with 2 of them known to be involved in C. pomonella resistance (CYP4C1 and CYP6B2) and identified several genes that have never been linked with resistance before (mainly associated with odorant perception and stress). [ABSTRACT FROM AUTHOR]

The utilization of insect pest pathogens as biocontrol agents can serve as an effective alternative to chemical pesticides. However, pests can develop resistance to these pathogens, similar to resistance observed with chemicals. Identifying the genetic bases of resistance is a crucial step in comprehending the co-evolution mechanisms between insect hosts and their pathogens, thereby enhancing the durability of these biocontrol methods. Cydia pomonella, a major pest of apple and pear trees found across all continents, can be effectively controlled in commercial orchards through the use of the granulovirus, CpGV. However, since 2005, resistance to the CpGV-M isolate has been reported in Europe, leading to significant challenges in managing C. pomonella in organic orchards. Studies conducted on CPGV-M resistance have revealed that viral replication is blocked in resistant phenotypes, and resistance is linked to a major gene located on the Z sex chromosome. Nevertheless, this major gene appears to be insufficient in explaining resistance to CPGV-M, as other forms of resistance involving autosomal genes have been identified subsequently. The objective of this study was to gain insights into the genetic architecture of C. pomonella resistance to CpGV-M by conducting a genome-wide association study using newly generated whole-genome resequencing data from pools of individuals (Pool-Seq) sampled from 13 susceptible and resistant populations across four regions in France and Italy. Through this analysis, eight candidate regions were identified, including one located on the Z sex chromosome. These eight regions encompass a total of 27 lncRNAs (long non-coding RNAs) and 40 genes, of which three are known to be involved in insects immune pathways. [ABSTRACT FROM AUTHOR]

As temperature is expected to strongly increase in the future, understanding temperature-mediated toxicity of insecticides is determinant to assess pest management efficiency in a warming world. Investigating molecular and biochemical mechanisms associated with cross mechanisms of temperature and insecticides on pests' tolerance would also be useful in this context. This study aimed to investigate cross effects between temperature and insecticides on the survival of a major pest, the codling moth Cydia pomonella , and their underlying mechanisms. The effect of three insecticidal active ingredients, i.e. chlorantraniliprole, emamectin and spinosad, was assessed at different temperatures on: (i) C. pomonella larval survival; (ii) detoxification enzymes activities (cytochrome P450 multi-function oxygenases, carboxylesterases and glutathione S-transferases) and (iii) genes expression of some detoxification enzymes, heat shock proteins and receptors targeted by the insecticides. We observed a decreased efficiency of emamectin and spinosad at high temperature to control the codling moth while no influence of temperature on chlorantraniliprole efficacy was observed. Detoxification enzymes activities were improved by heat stress alone but not by double stress (temperature + insecticides). Moreover, two detoxification genes (Cyp9A61 and Gst1) were over-expressed by a single stress but not by two stresses while Hsp70 and Cyp6B2 genes may be involved in tolerance to two stresses in C. pomonella. These results confirmed the cross effects of temperature and insecticides on C. pomonella for emamectin and spinosad and provided clues to understand how temperature affects the susceptibility of C. pomonella to insecticides. They illustrate however the complexity of molecular and biochemical responses of individuals facing multiple stresses. [Display omitted] • Evidence of cross effects of temperature and insecticides on C. pomonella mortality. • Some active ingredients efficiency on C. pomonella are affected by high temperature. • Molecular and biochemical responses of codling moth facing one or two stresses. [ABSTRACT FROM AUTHOR]

Insecticide-based management programmes targeting codling moth, Cydia pomonella L. ( Lepidoptera: Tortricidae: Olethreutinae), in apple orchards in southern France have incurred increasing levels of fruit injury in recent years. An alternative programme incorporating the use of exclusion netting named Alt'carpo has been developed. This study aimed at studying its efficiency and gaining more insight into its mode of action. This was achieved through laboratory and field behavioural tests and observations in a network of commercial orchards in southern France. The moths were able to lay eggs through the nets and escape from net cages in the laboratory. Male moths released in the netted rows were poorly recaptured using sexual pheromone trapping, whereas over 20% of the released males were recaptured in unprotected rows. The netting reduced fruit injury by up to 91% compared to the unprotected rows in the experimental orchard. The efficacy of this netting was even higher in commercial orchards in which fruit injury did not exceed 0.1% without any application of specific insecticide. These results lead us to assume that netting alters the reproduction of the pest, mainly by preventing it from flying over the canopy to find mates. [ABSTRACT FROM AUTHOR]

Neonicotinoids are the most important class of insecticides used as pest management tools during several decades. Exposition of insect to sublethal dose of insecticide induces physiological and cellular changes that could contribute to the adaptation of the insects in order to loss their sensitivity to insecticides. The aim of our study is to demonstrate that a subchronic exposure to a sublethal dose of a neonicotinoid imidacloprid is sufficient to induce molecular changes leading to a loss of imidacloprid sensitivity. We report that in the cockroach, Periplaneta americana , subchronic exposure to a sublethal dose of imidacloprid induced weak changes in detoxification enzyme activity and a significant decrease of the nicotinic acetylcholine α2 mRNA. This molecular effect is correlated to a decrease of imidacloprid sensitivity of cockroaches. Using RNA interference, we shown the key role of nicotinic acetylcholine α2 subunit in imidacloprid sensitivity. Thus, quantitative changes in insecticide targets lead to decreased sensitivity to insecticides. This parameter needs to be considered in order to develop sustainable insect resistance management strategies. [Display omitted] • Exposure to a sublethal dose of imidacloprid induces acclimation of cockroaches. • This acclimation persists overtime in absence of imidacloprid exposure. • Acclimation results in decreased sensitivity of cockroaches to imidacloprid. • Decrease of α2 nAChR subunit expression contributes to this phenomenon. [ABSTRACT FROM AUTHOR]