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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]

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]

Simple Summary: Apples are among the most heavily treated fruits against pests. Finding new, more environmentally friendly solutions for pest control is essential. Biological control is one of these, and can involve the use of predatory insects to eliminate pests. The earwig is one such predatory insect. We set out to determine whether earwigs had developed resistance mechanisms to the molecules to which they are exposed in orchards. A single population of earwigs was sampled in three types of orchard (organic, conventional and integrated pest management) and compared with each other. Mutations and higher expression levels in genes known to confer resistance were identified. These results highlight the effect of pesticide use on beneficial organisms and the resulting effect on the biodiversity of natural enemies in orchards. To date, apple orchards are among the most treated crops in Europe with up to 35 chemical treatments per year. Combining control methods that reduce the number of pesticide treatments is essential for agriculture and more respectful of the environment, and the use of predatory insects such as earwigs may be valuable to achieve this goal. European earwigs, Forficula auricularia (Dermaptera: Forficulidae) are considered beneficial insects in apple orchards where they can feed on many pests like aphids. The aim of this study was to investigate the potential impact of orchards' insecticide treatments on resistance-associated molecular processes in natural populations of earwigs. Because very few molecular data are presently available on earwigs, our first goal was to identify earwig resistance-associated genes and potential mutations. Using earwigs from organic, integrated pest management or conventional orchards, we identified mutations in acetylcholinesterase 2, α1 and β2 nicotinic acetylcholine receptors. In addition, the expression level of these targets and of some essential detoxification genes were monitored using RT-qPCR. Unexpectedly, earwigs collected in organic orchards showed the highest expression for acetylcholinesterase 2. Four cytochromes P450, one esterase and one glutathione S-transferases were over-expressed in earwigs exposed to various management strategies in orchards. This first study on resistance-associated genes in Forficula auricularia paves the way for future experimental studies aimed at better understanding the potential competition between natural enemies in apple orchards in order to optimize the efficiency of biocontrol. [ABSTRACT FROM AUTHOR]

Resistance to insecticides is one interesting example of a rapid current evolutionary change. DNA variability in the voltage-gated sodium channel gene (trans-membrane segments 5 and 6 in domain II) was investigated in order to estimate resistance evolution to pyrethroid in codling moth populations at the World level. DNA variation among 38 sequences revealed a unique kdr mutation (L1014F) involved in pyrethroid resistance in this gene region, which likely resulted from several convergent substitutions. The analysis of codling moth samples from 52 apple orchards in 19 countries using a simple PCR-RFLP confirmed that this kdr mutation is almost worldwide distributed. The proportions of kdr mutation were negatively correlated with the annual temperatures in the sampled regions. Homozygous kdr genotypes in the French apple orchards showed lower P450 cytochrome oxidase activities than other genotypes. The most plausible interpretation of the geographic distribution of kdr in codling moth populations is that it has both multiple independent origins and a spreading limited by low temperature and negative interaction with the presence of alternative resistance mechanisms to pyrethroid in the populations. [ABSTRACT FROM AUTHOR]

• Satiation varied from 17.8 aphids/day (1st instar, ladybird) to 84.3 (4th, earwig). • There was little evidence of intraguild predation (2.9% mortality/disappearance). • Intraguild predation was on the ladybird (1st-2nd instars) at low aphid densities. • Two predators consumed significantly more aphids than only one. • At non-limiting aphid density, two predators showed a slight agonistic interaction. A good knowledge of interactions between natural enemy species is necessary for effective implementation of biological control programmes. This laboratory study aimed at assessing the outcome of intraguild interactions between two generalist predators frequently observed in the colonies of the rosy apple aphid (RAA), Dysaphis plantaginea Passerini (Hemiptera: Aphididae). The level of complementarity between these two species was estimated by the comparison of their individual and combined predation on RAA. Predation by 1st (H1) to 4th (H4) instar larvae of Harmonia axyridis Pallas (Coleoptera: Coccinellidae) and 3rd (F3) and 4th (F4) instar nymphs of Forficula auricularia L. (Dermaptera: Forficulidae) was evaluated for 24 h in Petri dishes using seven different densities (5, 10, 25, 50, 75, 100 and 200) of 3rd instar nymphs of RAA. Both predator species were more voracious as their age increased. The satiation level, i.e. the highest number of consumed RAA, reached on average of 17.8, 36.3, 49.4, 79.6, 62.9 and 84.3 aphids per day for H1, H2, H3, H4, F3 and F4, respectively. In the combined treatments, there was little evidence of intraguild predation. Only 2.9% of H1 and H2 died or disappeared at low RAA densities (≤25 aphids). At the non-limiting RAA density of 200, we observed a slight agonistic interaction with 7.9% less RAA consumption when the two predators were in the same arena than the sum of their individual consumptions. However, this effect was very small and was largely outweighed by the benefits of using these two predators in combination to increase prey consumption. For the other six RAA densities, predators in combination consumed a high proportion (>90%) of RAA. Our results point to the use of combinations of these two predator species, especially of their oldest instars, as promising aphidophagous candidates in early spring against RAA. [ABSTRACT FROM AUTHOR]

Insecticide toxicity may strongly vary with temperature, and interspecific differences have been commonly reported for this relationship. A differential influence of temperature on insecticide toxicity between pests and their natural enemies may have important consequences on biological control in a global warming context. This study aimed to investigate cross effects between temperature and three insecticides—i.e., chlorantraniliprole, emamectin and spinosad—on the mortality of a major pest in orchards, Cydia pomonella L., and two of its natural enemies in southern France, the predatory earwig Forficula auricularia L. and the introduced parasitoid Mastrus ridens Horstmann. We observed a decreased efficiency of emamectin and spinosad with increasing temperature on mortality of codling moth, while no influence of temperature on chlorantraniliprole efficacy was observed. Increasing temperatures increased the toxicity of spinosad and chlorantraniliprole against M. ridens and only for emamectin on F. auricularia. This study provides essential insight to make recommendations for using these insecticides in combination with two natural enemies to control the codling moth in prevision of global warming. Our results suggest that the use of spinosad may become sub-optimal under higher temperatures. In contrast, chlorantraniliprole should be suitable under warmer climatic conditions to control C. pomonella and the less detrimental against F. auricularia and M. ridens. To conserve the use of biological control strategies relying on F. auricularia, alternating use of emamectin during early spring, when its toxicity is the lowest on this natural enemy, chlorantraniliprole during summer could limit resistance risks in codling moth populations and reduce the insecticides' impact on the populations of natural enemies. [ABSTRACT FROM AUTHOR]

Neonicotinoid insecticides have made possible, for three decades, to protect sugar beet crops against aphids and the viruses they transmit. However, they have been accused of reducing biodiversity, leading the European Union to ban the use of neonicotinoid-coated seeds. The requests for exemptions of use, submitted annually by different member states, might soon no longer be granted. Here, we performed a comprehensive analysis of the available alternatives to neonicotinoids for aphid control in sugar beets, following the PICO framework. The abstracts of 3878 references were consulted to evaluate alternative control methods. Of these, we selected 301 scientific publications, keeping only those which provided indications of treatment efficacy against sugar beet aphids. We identified 75 control strategies (products or methods) as possible alternatives to neonicotinoids. Each control strategy was evaluated based on four criteria: efficacy, durability, applicability and practicability. Using these criteria, we highlight 20 methods or products that have both potential as alternative to neonicotinoids and whose short-term use is feasible. These alternative methods include five synthetic and three natural insecticides, two entomopathogenic fungi, two arthropod natural enemies, organic and mineral oils, two plant defense elicitors, three farming practices and the potential of resistant varieties. Most of them provide important, but arguably insufficient, control of aphids if used alone. However, most of them appear to be complementary and compatible with each other. Therefore, integrating strategies will be needed to maintain beet yields while limiting unintended effects on environment and biodiversity. [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]

Monitoring pesticide resistance is essential for effective and sustainable agricultural practices. Bioassays are the basis for pesticide-resistance testing, but devising a reliable and reproducible method can be challenging because these tests are carried out on living organisms. Here, we investigated five critical parameters and how they affected the evaluation of resistance to the organophosphate phosmet or the pyrethroid lambda-cyhalothrin using a tarsal-contact protocol on Drosophila suzukii, a worldwide invasive pest. Three of the parameters were related to insect biology: (i) sex, (ii) age of the imago (adult stage) and (iii) genetic diversity of the tested population. The two remaining parameters were linked to the experimental setup: (iv) the number of individuals tested per dose and (v) the duration of exposure to the active ingredient. Results showed that response to insecticide differed depending on sex, males being twice as susceptible to phosmet as females. Age principally affected young females' susceptibility to phosmet, because 0–24 hour-old flies were twice as susceptible as 24–48 hour-old and 72–96 hour-old females. Genetic diversity had no observable effect on resistance levels. The precision and accuracy of the median lethal dose (LD50) were greatly affected by the number of individuals tested per dose with a threshold effect. Finally, optimal duration of exposure to the active ingredient was 24 h, as we found an underestimation of mortality when assessed between 1 and 5 h after exposure to lambda-cyhalothrin. None of the main known point mutations on the para sodium channel gene associated with a knockdown effect were observed. Our study demonstrates the importance of calibrating the various parameters of a bioassay to develop a reliable method. It also provides a valuable and transferable protocol for monitoring D. suzukii resistance worldwide. [ABSTRACT FROM AUTHOR]

The NPP-R1 isolate of CpGV is able to replicate on CpGV-M-resistant codling moths. However, its efficacy is not sufficient to provide acceptable levels of control in natural (orchard) conditions. A laboratory colony derived from resistant codling moths was established, which exhibited a homogeneous genetic background and a resistance level more than 7000 fold. By successive cycles of replication of NPP-R1 in this colony, we observed a progressive increase in efficacy. After 16 cycles (isolate 2016-r16), the efficacy of the virus isolate was equivalent to that of CpGV-M on susceptible insects. This isolate was able to control both CpGV-M-susceptible and CpGV-M-resistant insects with similar efficacy. No reduction in the levels of occlusion body production in susceptible larvae was observed for 2016-r16 compared to CpGV-M. [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]

Abstract: Tuta absoluta (Meyrick) resistance to insecticides has become a significant problem in many tomato production areas in South America. New insecticides are now available for the management of this pest (i.e. spinosad), however there is scarce information about their efficacy on field populations. With the aim of determining the susceptibility of T. absoluta to spinosad we evaluated the response of second instar larvae, from five field populations (Azapa 1, Azapa 2, Lluta, Colín and Valdivia) and a laboratory reference strain (S), to a diagnostic concentration of the insecticide. We also determined the activity of the detoxifying enzymes mixed-function oxidases (MFO), glutathione-S-transferases (GST) and esterases (EST) in the same larval stage. Larval mortality in field populations was significantly lower in Azapa 1 (50.0%), Azapa 2 (44.9%), Lluta (39.9%) and Colín (53.5%) when compared to the laboratory strain (91.7%). MFO activities in field populations were between 1.8 and 4.6 times higher than those observed in the S strain, while for EST, the ratio varied from 1.7 to 14.7. The lowest ratios were observed for the GST (0.5–2.7), however, significant differences were detected for the three enzyme systems. We conclude that the evaluated mechanisms would be involved in spinosad resistance of populations of T. absoluta, presenting an increased MFO activity in all populations. [Copyright &y& Elsevier]

To test the importance of the host genotype in maintaining virus genetic diversity, five experimental populations were constructed by mixing two Cydia pomonella granulovirus isolates, the Mexican isolate CpGV-M and the CpGV-R5, in ratios of 99% M + 1% R, 95% M + 5% R, 90% M + 10% R, 50% M + 50% R, and 10% M + 90% R. CpGV-M and CpGV-R5 differ in their ability to replicate in codling moth larvae carrying the type I resistance. This ability is associated with a genetic marker located in the virus pe38 gene. Six successive cycles of replication were carried out with each virus population on a fully-permissive codling moth colony (CpNPP), as well as on a host colony (RGV) that carries the type I resistance, and thus blocks CpGV-M replication. The infectivity of offspring viruses was tested on both hosts. Replication on the CpNPP leads to virus lineages preserving the pe38 markers characteristic of both isolates, while replication on the RGV colony drastically reduces the frequency of the CpGV-M pe38 marker. Virus progeny obtained after replication on CpNPP show consistently higher pathogenicity than that of progeny viruses obtained by replication on RGV, independently of the host used for testing. [ABSTRACT FROM AUTHOR]