Insecticides Chlorantraniliprole Research Articles

Toxicity and effects on anuran tadpole metamorphosis of the anthranilic diamide insecticides chlorantraniliprole and cyantraniliprole

ABSTRACT The present study examined the acute and chronic toxicity attributed to commercial formulations of the anthranilic diamide insecticides chlorantraniliprole (CHLO) and cyantraniliprole (CYAN) on the neotropical amphibian species Rhinella arenarum, Rhinella fernandezae and Scinax granulatus. The median lethal concentrations obtained after 96 hr exposure (96 hr-LC50) were generally greater than 100 mg/L, except for stage 25 S. Granulatus, which were the most sensitive animals tested with a 96 hr-LC50 value of 46.78 mg/L. In subchronic exposures of R. arenarum, the 21day-LC50 were 151.4 mg/L for CHLO and >160 mg/L for CYAN, the weight gain of the tadpoles during this period not being markedly affected in both cases. Finally, when tadpoles of R. arenarum were exposed to CHLO throughout the metamorphic process, an inverted U-shaped non-monotonic dose-response relationship was observed between exposure concentrations and both % of individuals transiting between stage 39 and 42 and the time required to accomplish this. Data obtained raise the hypothesis of an effect of CHLO on the hypothalamic-pituitary-thyroid (HPT) axis, either directly or through an interaction with the stress-hormone system, as metamorphic progression from stage 39 to S42 occurs under the strict control of thyroid hormones. These observations are important as the anthranilic diamide insecticides are not currently known as endocrine disruptors. Further investigations are needed to clarify the pathways leading to these effects and examine whether environmentally-relevant aquatic concentrations of anthranilic diamides might be impacting amphibian populations in the wild.

Coprecipitation-based synchronous chlorantraniliprole encapsulation with chitosan: carrier-pesticide interactions and release behavior.

Controlled-release pesticide formulations have emerged as a promising approach towards sustainable pest control. Herein, an environment-friendly formulation of insecticide chlorantraniliprole (CAP) was fabricated through a simple approach of coprecipitation-based synchronous encapsulation by chitosan (CTS), with carrier-pesticide interaction mechanism and release behavior investigated. The resulting CAP/CTS controlled-release formulation (CCF) showed a good loading content of 28.1% and a high encapsulation efficiency of 75.6%. Instrument determination in combination with molecular dynamics (MD) simulations displayed that the primary interactions between CAP and CTS were physical adsorption and complicated hydrogen (H)-bonds, which formed dominantly between NH in amides [or nitrogen (N) in ring structures] of CAP and hydroxyl (or amino) groups of CTS, as well as oxygen (O) in CAP with hydrogen in CTS or H2 O molecules. The in vitro release tests exhibited obvious pH/temperature sensitivity, with release dynamics following the first-order or Ritger-Peppas model. As the temperature increased, the CAP release process of the Ritger-Peppas model changed from Case-II to anomalous transport, and ultimately to a Fickian diffusion mechanism. The control effect against Plutella xylostella larvae also was evaluated by toxicity tests, where comparable efficacy of CCF to the commercial suspension concentrate was obtained. The innovative, easy-to-prepare CCF can be used as a formulation with obvious pH/temperature sensitivity and good efficacy on target pests. This work contributes to the development of efficient and safe pesticide delivery systems, especially using the natural polymer materials as carriers. © 2023 Society of Chemical Industry.

Uncovering the Dissipation of Chlorantraniliprole in Tomatoes: Identifying Transformation Products (TPs) and Coformulants in Greenhouse and Laboratory Studies by UHPLC-Q-Orbitrap-MS and GC-Q-Orbitrap-MS.

The present study addressed the dissipation of the insecticide chlorantraniliprole in tomatoes treated with Altacor 35 WG under laboratory and greenhouse conditions, as well as the identification of transformation products (TPs) and coformulants, performing suspect screening analysis. Analyses were performed by ultra-high-performance liquid and gas chromatography coupled to quadrupole-Orbitrap high-resolution mass spectrometry (UHPLC-Q-Orbitrap-MS and GC-Q-Orbitrap-MS). In all cases, chlorantraniliprole was fitted to a biphasic kinetic model, with R2 values greater than 0.99. Dissipation was noticeably faster in greenhouse studies, in which even 96% dissipation was achieved over 53 days. One TP, IN-F6L99, was tentatively identified in both greenhouse and laboratory studies and was semiquantified by using chlorantraniliprole as the analytical standard, yielding a top value of 354 μg/kg for laboratory studies, whereas values for greenhouse studies fell under the limit of quantitation (LOQ). Finally, a total of 15 volatile coformulants were identified by GC-Q-Orbitrap-MS.

Dissipation kinetics, effect of household processing, and dietary risk assessment of the insecticide chlorantraniliprole residue in bitter gourd and soil

A single quadrupole liquid chromatography-mass spectrometry (LC-MS) method was validated to determine the insecticide chlorantraniliprole residues in bitter gourd fruit, juice, and soil, according to the SANTE guidelines. A linear curve was obtained (R2 > 0.99) with LOD and LOQ at 0.003 mg kg-1 and 0.01 mg kg-1. The accuracy (87–102%) and precision (RSD <5%) of the method was found to be satisfactory. The dissipation pattern of chlorantraniliprole 18.5% SC was studied by spraying twice at ten days intervals, at the recommended dose (X) (25 g a.i. ha-1), and double the recommended dose (2X) (50 g a.i. ha-1). The initial deposit on bitter gourd was 0.72 and 1.41 mg kg-1 and residues persisted up to 15 and 20 days with a half-life of 2.44 and 2.79 days at X and 2X doses, respectively. Simple decontamination techniques were found to reduce residues to the extent of 30 to 80 per cent. The reduction of chlorantraniliprole residues in bitter gourd juice was 40-50 per cent by different washing techniques. The estimated level of Risk quotient indicated (<1) chlorantraniliprole residues pose no dietary risk to consumers at the level detected.

Evaluation of Botanicals Insecticide against Stem Borer Scirpophaga incertulas (Walker) Leaf Folder (Cnaphalocrosis medinalis) and Green Leafhopper and in Rice

A field experiment was conducted during the kharif season of 2020-21 and 2021-22 at Crop Research station, Masodha, Ayodhya, India to evaluate the efficacy of insecticide-botanicals against rice stem borer, green leafhopper and leaf folder. The experiment was comprising Four combination modules/treatments consisting of three insecticides Chlorantraniliprole 20% SC, Cartap hydrochloride 50% SC and Triflumezopyrim 10% SC, one commercial neem formulation - Neemazal and two plant oils - Neem and Eucalyptus oil procured were compared along with untreated control (only water spray). The lowest stem borers incidence (1 %) of in all insecticides treatment module recorded as compared to 14.8% in untreated control. Among modules, all insecticides module was found to be the best with 1.0% mean white ear damage followed by neemazal, eucalyptus oil and cartap hydrochloride module with 5.3% WE. Green leafhopper infestation was all insecticides combination was the most effective treatment showing mean population of 110.7/10 hills followed by all botanical combination (120.7) and were superior to control (158.7/10 hills). The mean leaf Folder damage (1.8%) was recorded from all insecticides module followed by treatment with neemazl (? %), Eucalyptus oil (? %), and Triflumezopyrim 10% SC (3.9% DL) when compared to untreated control (14.5% )4. Grain yield all insecticides treatment - Chlorantraniliprole, Cartap hydrochloride, Triflumezopyrim recorded the highest grain yield of 5212.0 kg/ha with 95.79% increase over control (IOC) followed by neemazal, neem oil and cartap hydrochloride with 4500 kg/ha (69.04% IOC). All the treatments were significantly superior to control plot which showed a yield of 2662 kg/ha.

Multicompartmental monitoring of legacy and currently used pesticides in a subtropical lake used as a drinking water source (Laguna del Cisne, Uruguay)

A pilot annual monitoring survey (April 2018–March 2019) was conducted to investigate the presence of pesticides in superficial water and fish in Laguna del Cisne, one of the most critical drinking water sources in Uruguay. A total of 25 pesticide residues were detected in superficial water (89.3 % of the samples). Pesticide's temporal distribution was associated with crops and livestock practices, with higher occurrences in spring and summer than in autumn and winter. The most frequent compounds in superficial water were the insecticide chlorantraniliprole, and the herbicides glyphosate (including its metabolite AMPA) and metolachlor. The levels of Organochlorine pesticide, p,p′-DDT, was in some cases two order of magnitude above the international water quality guidelines for Ambient Water Criteria. In fishes, eight different pesticides were detected, at concentrations from 1000 to 453,000 ng·kg−1. The most frequent pesticides found were propiconazole, chlorpyrifos, and p,p′-DDE. The widespread occurrence of pesticides in fish suggests potential exposure effects on fish populations and the aquatic ecosystem. The sampling approach of this work allowed monitoring the continuous concentrations of several pesticides in surface waters and fishes to establish the influence from past and current agriculture practices in Laguna del Cisne basin. For safety measures, continuous monitoring programs must be performed in this system to prevent toxicity impacts on aquatic organisms and human health.

Nutritional resources modulate the responses of three bee species to pesticide exposure.

The response of bee species to various stressors is assumed to depend on the availability of sufficient nutrients in their environment. We compare the response of three bee species (Apis mellifera, Bombus terrestris, Osmia bicornis) under laboratory conditions. Survival, physiology, and sensitivity, after exposure to the fungicide prochloraz, the insecticide chlorantraniliprole, and their mixture with different nutritional resources (sugar only, sugar with amino acids or pollen) were observed. Prochloraz reduced the bee survival of A. mellifera and O. bicornis fed with pollen, but not with other diets. Chlorantraniliprole impaired the survival of A. mellifera fed with sugar or pollen diet, but not with amino acid diet. The mixture impaired survival of A. mellifera and O. bicornis in association with every diet. B. terrestris was only affected by chlorantraniliprole and its mixture with prochloraz fed with sugar diet. The activity of P450 reductase was higher in A. mellifera fed with amino acids in all treatments, whereas no effect emerged in O. bicornis and B. terrestris. Our results indicate that the sensitivity of bee species after exposure to agrochemicals is affected by diet. Thus, balanced and species-dependent nutrition ameliorated the effects. Further field studies are necessary to evaluate the potential effects of such mixtures on bee populations.

Mechanisms underlying the effects of low concentrations of chlorantraniliprole on development and reproduction of the fall armyworm, Spodoptera frugiperda

It is well known that sublethal dose of insecticides induces life history trait changes of both target and non-target insect species, however, the underlying mechanisms remain not well understood. In this study, the effects of low concentrations of the anthranilic diamide insecticide chlorantraniliprole on the development and reproduction of the fall armyworm (FAW), Spodoptera frugiperda, were evaluated, and the underlying mechanisms were explored. The results showed that exposure of FAW to LC10 and LC30 chlorantraniliprole prolonged the larvae duration, decreased the mean weight of the larvae and pupae, and lowered the pupation rate as well as emergence rate. The fecundity of female adults was also negatively affected by treatment with low concentrations of chlorantraniliprole. Consistently, we found that exposure of FAW to LC30 chlorantraniliprole downregulated the mRNA expression of juvenile hormone (JH) esterase (SfJHE), leading to the increase of JH titer in larvae. We also found that treatment with low concentrations of chlorantraniliprole suppressed the expression of ribosomal protein S6 kinase1 (SfS6K1) in female adults, resulting in the downregulation of the gene encoding vitellogenin (SfVg). These results provided insights into the mechanisms underlying the effects of low concentrations of insecticides on insect pests, and had applied implications for the control of FAW.

<i>Euborellia annulipes</i> Mortality and Predation on <i>Diatraea saccharalis</i> Eggs after Application of Chemical and Biological Insecticides

Chemical and biological insecticides have been frequently used in sugarcane fields to control insects-pests, including the sugarcane borer, Diatraea saccharalis. Among the products used, those based on chlorantraniliprole and Metarhizium anisopliae entomopathogenic fungus, stand out. Euborellia annulipes is an insect of the order Dermaptera considered a potential predator of sugarcane borer eggs. This study aimed to evaluate the direct and indirect effects of the bioinsecticide based on M. anisopliae (Metarril®) and the chemical insecticide chlorantraniliprole (Altacor®) on the mortality of E. annulipes nymphs and adults, the predation and feeding preference of earwigs in eggs treated with the formulated products. Predator mortality was evaluated for seven days after treatment, while the effect on predation was analyzed by preference tests with and without choice, using prey eggs. The products tested were selective to the predator, causing ≤ 2% mortality and not affecting predation. The application of M. anisopliae on sugarcane borer eggs favored the food preference of fourth-instar nymphs, males, and females of the predator. Our results show that Metarril® and Altacor® can be used to control D. saccharalis when associated with the predator E. annulipes.

Neurotoxicity and behavioral disorders induced in mice by acute exposure to the diamide insecticide chlorantraniliprole.

Diamide insecticides activate ryanodine receptors expressed in lepidopteran skeletal muscle and promote Ca2+ release in the sarcoplasmic reticulum, causing abnormal contractions and paralysis, leading to death of the pest. Although they had been thought not to act on nontarget organisms, including mammals, adverse effects on vertebrates were recently reported, raising concerns about their safety in humans. We investigated the neurotoxicity of the acute no-observed-adverse-effect level of chlorantraniliprole (CAP), a diamide insecticide, in mice using clothianidin (CLO), a neonicotinoid insecticide, as a positive control. The CLO-administered group showed decreased locomotor activities, increased anxiety-like behaviors, and abnormal human-audible vocalizations, while the CAP-administered group showed anxiety-like behaviors but no change in locomotor activities. The CAP-administered group had greater numbers of c-fos-immunoreactive cells in the hippocampal dentate gyrus, and similar to the results in a CLO-administered group in our previous study. Blood corticosterone levels increased in the CLO-administered group but did not change in the CAP-administered group. Additionally, CAP was found to decreased 3-Methoxytyramine and histamine in mice at the time to maximum concentration. These results suggest that CAP-administered mice are less vulnerable to stress than CLO-administered mice, and the first evidence that CAP exposure increases neuronal activity and induces anxiety-like behavior as well as neurotransmitter disturbances in mammals.

Calmodulin Modulation of Insect Ryanodine Receptors

Ryanodine receptor (RyR) is a giant calcium release channel located on the membrane of the endoplasmic reticulum (ER). Here, we report the regulation of RyRs from two major agricultural pests, diamondback moth and fall armyworm, by insect calmodulin (CaM). The recombinantly expressed full-length insect RyR could be pulled down by insect CaM in the presence of Ca2+, but the efficiency is lower compared to rabbit RyR1 and insect RyR with the CaM-binding domain (CaMBD) replaced by rabbit RyR1 sequence. Interestingly, the enhanced binding of CaM in the mutant insect RyR resulted in an increased sensitivity to the diamide insecticide chlorantraniliprole (CHL), suggesting that this CaM-CaMBD interface could be targeted by potential synergists acting as molecular glue. The thermodynamics of the binding between insect CaM and CaMBD was characterized by isothermal titration calorimetry, and the key residues responsible for the insect-specific regulation were identified through mutagenesis studies.

Potential exposure and risk assessment of agricultural workers to the insecticide chlorantraniliprole in rice paddies.

Exposure of agricultural workers in rice paddies to the insecticide chlorantraniliprole and its subsequent potential health risks were investigated during two scenarios (mixing/loading and hand-held spraying). The exposure factors, such as the outer dosimeter, inner dosimeter, gauze, and nitrile gloves, were calculated using whole-body dosimetry to measure dermal exposure. The inhalation exposure was determined using a fiberglass filter which is set with an Institute of Occupational Medicine (IOM) sampler. A recovery test was performed to evaluate the accuracy of the analytical method. The exposure amounts of various matrices were calculated from extraction volume and concentration of the target compound. The dermal exposure to chlorantraniliprole was 0.6mg [0.001% of the total active ingredient (a.i.)] for mixing and loading, and 28.6mg (0.066% of the total a.i.) for application. The inhalation exposure to chlorantraniliprole was 7.2μg (1.3%, 1.2 × 10-5 % of the total applied a.i.) for mixing and loading, and 1.9μg (0.006%, 4.4 × 10-6 % of the total applied a.i.) for application. The most exposed part of the body was the hand (90.4%) during mixing and loading, whereas the primary sites during application were the thighs (32.8%) and shins (22.6%). For mixing and loading, the amount of actual dermal exposure was 5.5μg day-1 and that of actual inhalation exposure was 21.9μg day-1 . By contrast, in the application, the amounts of actual dermal and actual inhalation exposures were 34 178.7 and 5.9μg day-1 , respectively. The risk assessment results demonstrated that the risk of chlorantraniliprole exposure in rice paddies was low during application than during mixing and loading. © 2022 Society of Chemical Industry.

Determination of Chlorantraniliprole Residue in Soil by Gas Chromatography-Mass Spectrometry

Gas chromatography-mass spectrometry method was developed and validated for the quantification of anthranilic diamide insecticide chlorantraniliprole residues in soil. The soil samples were extracted with acetonitrile and dispersive solid phase extraction clean up. The average recoveries of chlorantraniliprole were in the range of 94.10-96.82% with reproducibility and repeatability was ranged between 0.17 to 1.90 and 0.97 to 1.22%, respectively. The limit of quantification of the analytical method was 0.01 μg g-1 and the matrix effect was less than 1%.

Toxicity of Chlorantraniliprole and it's Formulated Product, Altacor®, to Individuals and Populations of Ceriodaphnia Dubia Richard.

The toxicity of the insecticide chlorantraniliprole and its formulated product Altacor® was determined for the Cladoceran, Ceriodaphnia dubia Richard. Acute toxicity (48h) and 21 d population studies were conducted. The hypothesis of this study was that these two compounds would have different toxicities. We conducted acute and chronic toxicity studies for each compound and compared the results to test this hypothesis. 48h LC50s (95% CL) for chlorantraniliprole and Altacor® were 8.5 (6.6-11.5) and 6.0 (3.7-9.0) µg chlorantraniliprole/L water, respectively. Therefore, chlorantraniliprole and Altacor® were equitoxic to C. dubia at LC50 based on overlap of the 95% CL. In the population study, chlorantraniliprole and Altacor® concentrations equivalent to the acute LC5, 10, 25, and 50 for each product were evaluated on populations of C. dubia. Number of individuals after 21 d was the endpoint evaluated. T-tests conducted at each LC value indicated that there was no significant difference in population size between these two products at each LC value evaluated. Previous studies show that toxicity can vary greatly between formulated and technical grade pesticides. However, our results show that chlorantraniliprole and its formulated product, Altacor® were equally toxic to C. dubia. Therefore, making assumptions about the toxicity of formulated and unformulated products is ill advised.

Novel Fluorinated Aniline Anthranilic Diamides Improved Insecticidal Activity Targeting the Ryanodine Receptor.

The diamide insecticides show exceptional activity against Lepidoptera insects via activation of ryanodine receptors (RyRs). In the present study, a series of anthranilic diamides containing a fluoroaniline moiety were designed, synthesized, and evaluated for insecticidal potency. Most titled compounds exerted moderate to remarkably high activity against Mythimna separata, Plutella xylostella, and Spodoptera frugiperda. The insecticidal activity of compound II l and II ac against M. separata was 26.7 and 26.7% at 0.1 mg L-1, respectively, equivalent to that of chlorantraniliprole (0.1 mg L-1, 30.0%). Compounds II l, II y, and II z exhibited 8.0-, 1.8-, and 4.7-fold higher potency than chlorantraniliprole against P. xylostella, respectively, as compared with their LC50s. Compounds II k and II aa showed good insecticidal activity against S. frugiperda with LC50 of 0.56 and 0.46 mg L-1, respectively, comparable to that of the commercial insecticide chlorantraniliprole with LC50 of 0.31 mg L-1. Calcium imaging experiments indicated RyRs as the action target. Molecular docking suggested a higher binding energy of 8.647 kcal/mol between II l and the M. separata RyR than the 7.820 kcal/mol between chlorantraniliprole and the M. separata RyR. Meanwhile, the docking results of II l with mutated P. xylostella RyR at site G4946E showed that II l could have a good inhibition effect on the resistant P. xylostella. The density functional theory calculations suggested the importance of the fluoroaniline moiety in potency. Those novel anthranilic diamides containing a fluorinated aniline moiety are good insecticidal candidates.

Microbes, Dodonaea viscosa and Chlorantraniliprole as Components of Helicoverpa armigera IPM Program: A Three Region Open-Field Study

Field trials were conducted on the efficacy of different control options against Helicoverpa armigera on tomato. We evaluated and compared pest control, safety to natural enemies, crop yield and economics of application for various treatments including: a mycoinsecticide based on Beauveria bassiana; a baculovirus, H. armigera nucleopolyhedrovirus (HaNPV); a plant extract from Dodonaea viscosa; and the insecticide chlorantraniliprole (Coragen®). Trial sites were located in the Bahawalpur, Faisalabad and Rawalpindi regions in Punjab, Pakistan. A combined application of HaNPV + chlorantraniliprole was better than all other treatments in reducing pest larval populations and fruit damage, and in increasing crop yield. The least effective control was with D. viscosa, but plots treated with this plant extract also had the greatest number of natural enemies. Treatment with HaNPV + chlorantraniliprole resulted in the fewest natural enemies at all observation times and in all field sites, but the highest yields, varying from 42.8–46.6 tons ha−1, and the highest cost:benefit ratios of 1:1.74–1:1.81. Our findings suggest that a combined application of a specific microbial agent and an insecticide effectively controls H. armigera, increases tomato yield, reduces costs and maximizes economic returns. This open-field study concludes that all of the microorganisms and other treatments have the potential to combat H. armigera populations and could be used in successful integrated pest management programs.

Possible changes in trade-off strategy in female lizards (Eremias argus) during hibernation following exposure to chlorantraniliprole: Impact on the HPG axis and the energy mobilization

Hibernation is a short-term survival strategy for ectotherms to cope with cold weather and food shortages. The energy sources stored before hibernation are used not only in the winter, but also in preparation for reproduction. Reproductive physiology and behavior are primarily regulated by the hypothalamus-pituitary-gonad (HPG) axis. In this study, we examined endocrine hormone changes in the HPG axis of female lizards (Eremias argus) after chlorantraniliprole insecticide (CAP) exposure during hibernation. The levels of gonadotropin-releasing hormone, luteinizing hormone, follicle-stimulating hormone and progesterone were significantly decreased and the level of testosterone (T) was significantly increased after 135d experiment. This study verified the possible endocrine disrupting effects of CAP. More energy material consumption was observed in CAP treated group. Female E. argus preferred to invest energy to present survival when exposed to CAP, rather than to reserve material for following reproductive activity.

Dissipation, decontamination, dietary, and ecological risk assessment of chlorantraniliprole in chilli fields

For quantification of the insecticide chlorantraniliprole in chilli and soil, an optimized gas chromatographic-mass spectrometric method is presented, with recoveries of 92–96%, and relative standard deviations of 1.4–2.7%. The limit of quantification is 0.01 mg/kg. Degradation of chlorantraniliprole follows first-order kinetics with half-lives between 1.6 and 1.8 days for chilli and soil. For earthworms and arthropods in the chilli field, the calculated risk quotient is found to be <1, as well as for consumers of chilli just after application of chlorantraniliprole. Residue concentrations in chilli fruit can be further reduced by 6–63% using different decontamination methods.

Characterizing the exposure of streams in southern Ontario to agricultural pesticides

Aquatic communities can be exposed to pesticides transported from land. Characterizing this exposure is key to predicting potential toxic effects. In this study, samples of streamwater from 21 sites were used to characterize pesticide exposure to aquatic communities. Sites were in agricultural areas of southwestern Ontario, Canada and were sampled monthly from 2012 to 2019 from April to November. Samples were analyzed for a suite of hundreds of pesticides and pesticide degradation products and other water quality indicators (e.g., nutrients). Frequently detected pesticides included herbicides (2,4-D; bentazon; MCPP; metolachlor) and neonicotinoid insecticides (NNIs) (clothianidin; thiamethoxam) which were detected in >50% of samples collected between 2015 and 2019. Non-metric multidimensional scaling (NMDS) was used to explore connections between pesticide concentrations and upstream land use and crop type. Detectable concentrations of the NNI clothianidin and many herbicides were related to corn, soybean, and grain/cereal crops while concentrations of the NNI imidacloprid, insecticide flonicamid, and fungicide boscalid were related to greenhouse/nursery land use. Potential toxicity to aquatic communities was assessed by comparing pesticide concentrations to Pesticide Toxicity Index (PTI) values. Few samples exceeded levels where acute (1% of samples) or chronic toxicity (10.5%) would be expected. The diamide insecticide chlorantraniliprole was detected in several streamwater samples at levels that may cause toxicity to aquatic invertebrates, highlighting the need for continued toxicity research into this pesticide class. The number of pesticides detected was positively correlated with nutrient and total suspended solids levels, underscoring the multiple stressors aquatic communities are exposed to in these habitats.

Exposure to Temperature and Insecticides Modulates the Expression of Small Noncoding RNA-Associated Transcripts in the Colorado Potato Beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae).

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) is an insect that can adapt to various challenges, including temperature fluctuations or select insecticide treatments. This pest is also an ongoing threat to the potato industry. Small noncoding RNAs such as miRNAs, which can control posttranscriptionally the expression of various genes, and piRNAs, which can notably impact mRNA turnover, are modulated in insects under different conditions. Unfortunately, information regarding the expression status of key players involved in their synthesis and function is for the most part lacking. The current study thus aims at assessing the levels of such targets in L. decemlineata exposed to hot and cold temperatures as well as treated to the insecticides chlorantraniliprole, clothianidin, imidacloprid, and spinosad. Transcript expression levels of Ago1, Ago2, Ago3, Dcr2a, Dcr2b, Expo-5, Siwi-1, and Siwi-2, components of pathways associated with small noncoding RNA production or function, were measured by qRT-PCR and revealed modulation of select transcripts in response to temperature challenges and to select insecticides. RNAi-mediated reduction of Ago2 transcript levels in L. decemlineata injected with Ago2-targeting dsRNA and exposed to cold and warm temperatures was also conducted. Changes in survival rates were observed for the latter condition in dsRNA- versus saline-injected insects. These results showcase the differential expression of select targets involved in small noncoding RNA homeostasis and provide leads for the subsequent assessment of their involvement during stress response in L. decemlineata using RNAi-based approaches.