Influence of lethal and sublethal exposure to clothianidin on the seven-spotted lady beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Sublethal toxicity of sulfoxaflor to parasitoid Binodoxys communis Gahan

Integrated pest management is focused on combining biological and chemical controls. There is evidence of a negative impact of neonicotinoids on biological control, however, sulfoxaflor (SFX), a novel insecticide, its impact on parasitoid natural predator remain limited. Binodoxys communis is an important parasitic natural enemy of Aphis gossypii, which may have direct and indirect toxicity from the insecticides and aphids. Understanding the potential threat of SFX to B. communis is therefore essential to integrated pest management and the conservation of parasitoids. Here, the effects of sublethal doses of SFX on B. communis larvae and adults are presented for the first time. Sublethal SFX doses had a significant negative effect on the survival rate, adult life span, duration of development, and rate of parasitism. Moreover, exposure to sublethal SFX doses also had adverse effects on the biological performance of the next generation of B. communis. Based on the transcriptome analysis, the expression of genes involved in fatty acid metabolism, glycerolipid metabolism, glycerophospholipid metabolism, peroxidase, lysosomes, glutathione metabolism, drug metabolism, and CYP450 were significantly shifted by sublethal SFX exposure. These results indicate that sublethal SFX doses might adversely affect the biological performance of B. communis by altering gene expression related to the function of detoxification systems and energy metabolism. In conclusion, considering the beneficial ecological services of provided by parasitoids and the negative effects of sulfoxaflor across a greater usage scale, we emphasize the importance to optimize pesticide applications in IPM packages, in order to ensure the safety and survival of natural pest parasitoids.

Toxicity and Influence of Sublethal Exposure to Sulfoxaflor on the Aphidophagous Predator Hippodamia variegata (Coleoptera: Coccinellidae)

Hippodamia variegata (Goeze), the variegated ladybug, is a predator of many insect pests, especially aphids. Sulfoxaflor is a chemical insecticide that can be used to control many sap-feeding insect pests, for instance, plant bugs and aphids, as an alternative to neonicotinoids in different crops. To improve the combination of the H. variegata and sulfoxaflor in an IPM (integrated pest management) program, we studied the ecological toxicity of the insecticide to the coccinellid predator at sublethal and lethal doses. We examined the influence of sulfoxaflor on larvae of H. variegata using exposure doses of 3, 6, 12, 24, 48 (maximum recommended field rate (MRFR)), and 96 ng a.i. per insect. In a 15-day toxicity test, we observed decreased adult emergence percentage and survival, as well as an increased hazard quotient. The LD₅₀ (dose causing 50% mortality) of H. variegata due to sulfoxaflor decreased from 97.03 to 35.97 ng a.i. per insect. The total effect assessment indicated that sulfoxaflor could be grouped as slightly harmful for H. variegata. Additionally, most of the life table parameters were significantly decreased after exposure to sulfoxaflor. Overall, the results present a negative influence of sulfoxaflor on H. variegata when applied at the recommended field dose for controlling aphids in Greece, which demonstrates that this insecticide may only be employed with care when used in IPM programs.

Sulfoxaflor adversely influences the biological characteristics of Coccinella septempunctata by suppressing vitellogenin expression and predation activity

Sulfoxaflor is a widely used sulfoximine insecticide that has been regarded as an important alternative insecticide for IPM strategies, but a comprehensive study of its potential ecological toxicity is still lacking. In the present work, the growth, longevity, predation and reproduction toxicity of Coccinella septempunctata caused by sulfoxaflor were evaluated. In addition, the potential mechanisms of decreased fecundity in C. septempunctata were investigated by analyzing the transcriptional and protein levels of reproduction-related gene vitellogenin (Vg). In a 20-day acute contact toxicity test, decreased survival proportion, pupation rate, adult emergence ratio, and increased hazard quotient (HQ) values were observed. Moreover, sublethal dosages of sulfoxaflor significantly inhibited the predation, longevity, fecundity and net reproduction rate of progeny. In addition, LR₃₀ of sulfoxaflor dramatically down-regulate the mRNA-expression (F₀: 65.38-fold, F₁: 2.24-fold) and protein content (F₀: 1.35-fold, F₁: 1.36-fold) of Vg in the F₀ and F₁ generations. These results suggested that sulfoxaflor could inhibit the gene and protein content of Vg, thereby reducing the fecundity of C. septempunctata. Our study indicated that sulfoxaflor has potential risks to parent and progeny generations of C. septempunctata. These results provide valuable reference for optimal usage of sulfoxaflor in IPM systems.

Impact of Sulfoxaflor Exposure on Bacterial Community and Developmental Performance of the Predatory Ladybeetle Propylea japonica

Insects maintain a vast number of symbiotic bacteria, and these symbionts play key roles in the hosts' life processes. Propylea japonica (Coleoptera: Coccinellidae) is an abundant and widespread ladybeetle in agricultural fields in Asia. Both larvae and adults of P. japonica are likely to be exposed to insecticide residue in the field during their predatory activity. Sulfoxaflor is a highly powerful insecticide that has strong efficacy in controlling sap-sucking pests. To date, there have been several studies on the acute and long-term toxicity of sulfoxaflor to insects, but few studies have reported the impact of sulfoxaflor on the predators' micro-ecosystems. This study was to determine the impact of sulfoxaflor on the symbiotic bacteria and developmental performance of P. japonica. In the present study, two concentrations (1 mg/L and 5 mg/L) and two exposure periods (1 day and 5 days) were set for P. japonica under sulfoxaflor exposure. The survival rate, developmental duration, pupation rate, emergence rate, and body weight of P. japonica were examined. Moreover, the bacterial community of P. japonica was investigated by high-throughput 16S ribosomal RNA gene sequencing. Our results indicated that bacterial community of P. japonica was mainly composed of Staphylococcus, Pantoea, Acinetobacter, Rhodococcus, and Ralstonia at the genus level. The bacterial community of P. japonica in 1 mg/L and 5 mg/L sulfoxaflor groups was significantly altered on day 1, compared with that in control group. The results also showed that the larval duration was significantly prolonged but the pupal duration was significantly shortened in both sulfoxaflor groups. Meanwhile, the pupation and emergence rate was not significantly changed, but the body weights of adults were significantly decreased in both sulfoxaflor groups. Our study will provide a new perspective for evaluating the safety of pesticides to beneficial arthropods.

Sublethal toxicity, transgenerational effects, and transcriptome expression of the neonicotinoid pesticide cycloxaprid on demographic fitness of Coccinella septempunctata

Evaluating side effects of new neonicotinoids in terms of sublethal doses and transcriptome expression is a crucial but challenging part of integrated pest management (IPM) approaches. To this end, a study of lethal and sublethal effects on Coccinella septempunctata larvae was conducted, and an age-stage, two-sex life table procedure was performed to investigate life-table parameters. Cycloxaprid (CYC) was shown to have adverse effects on survival, development, total longevity, reproductive capacity, and predation ability in C. septempunctata. In addition, demographic growth parameters of the F1 generation such as net reproductive rate, and the intrinsic and finite rates of increase were significantly decreased under sublethal dosage LR₃₀ (1.91 g ai/hm²). These results demonstrated that the population growth of C. septempunctata was impacted by a sublethal dosage of CYC. For transcriptome expression, 544 up- and 338 down-regulated significantly differentially expressed genes (DEGs), were observed between LR₃₀ treatment and control groups. Moreover, pathways related to metabolism of retinol, carcinogenesis, biosynthesis of steroid hormone, P450 metabolism, and metabolism of xenobiotics were identified in KEGG pathway analysis. Ten DEGs were chosen and confirmed with quantitative real-time PCR analysis. Based on these findings, CYC should be considered as a component of IPM strategies in the field.

Sublethal and transgenerational effects of exposures to the thiamethoxam on the seven-spotted lady beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae)

The seven-spot ladybird beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae) has been used as the major natural enemy insect against many kinds of aphids in environment. Thiamethoxam is a second-generation neonicotinoid insecticide and commonly used to control various aphids, but it also has adverse effects on natural enemies. Therefore, the sublethal effects of thiamethoxam on the offspring of C. septempunctata were studied. For the adults of C. septempunctata, the LD₃₀ of F₀, F₅, F₁₀ and F₁₅ generations were 0.039, 0.136, 0.243, 0.417 μg adult^-1, respectively. The LD₅₀ of F₀, F₅, F₁₀ and F₁₅ generations were 0.072, 0.275, 0.435, 0.819 μg adult^-1, respectively. The resistance ratio of the F₁₅ generation was 11.4-fold higher than that of the F₀ generation. The preadult duration ( F₀ = 17.4 d, F₅ = 20.0 d, F₁₀ = 19.1 d, F₁₅ = 18.0 d) and adult preoviposition period ( F₀ = 7.39 d, F₅ = 8.07 d, F₁₀ = 9.32 d, F₁₅ = 8.03 d) of C. septempunctata were prolonged, and the fecundity ( F₀ = 1690.10, F₅ =1686.93, F₁₀ = 1119.40, F₁₅ = 752.87), oviposition period ( F₀ = 42.84 d, F₅ =40.33 d, F₁₀ = 40.72 d, F₁₅ = 30.84 d) and total longevity ( F₀ = 86.7 d, F₅ =81.3 d, F₁₀ = 82.0 d, F₁₅ = 74.0 d) were reduced by long-term exposure to sublethal dosage (LD₃₀) of thiamethoxam. Population parameters (r, λ, R₀, and T) were significantly reduced in F₅, F₁₀ and F₁₅ generation. In addition, the predation function of F₁₅ generation was reduced by sublethal dosage exposure of thiamethoxam. These results showed the negative impacts of sublethal thiamethoxam on the offspring of predators.

Evaluation of the Toxicity and Sublethal Effects of Acetamiprid and Dinotefuran on the Predator Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae)

Neonicotinoid insecticides affect the physiology or behavior of insects, posing risks to non-target organisms. In this study, the effects of sublethal doses of two neonicotinoid insecticides, acetamiprid and dinotefuran, against Chrysopa pallens (Rambur) (Neuroptera: Chrysopidae) were determined and compared. The results showed that acetamiprid and dinotefuran at LD₁₀ (8.18 ng a.i. per insect and 9.36 ng a.i. per insect, respectively) and LD₃₀ (16.84 ng a.i. per insect and 15.01 ng a.i. per insect, respectively) significantly prolonged the larval stages and pupal stages (except acetamiprid LD₁₀), compared to control. In addition, acetamiprid and dinotefuran at LD₃₀ significantly prolonged the adult preoviposition period (APOP) and total preoviposition period (TPOP). In contrast, the two insecticides at LD₁₀ and LD₃₀ had no significant effect on the longevity, fecundity, reproductive days, preadult survival rate (%), intrinsic rate of increase (r), net reproductive rate (R₀), and finite rate of increase (λ). These results provide a theoretical basis for the rational use of these two insecticides and the utilization and protection of C. pallens.

Sublethal effects of tolfenpyrad on the development, reproduction, and predatory ability of Chrysoperla sinica

The lacewing, Chrysoperla sinica, is a predaceous insect that is important in crop pest management. Chemical pesticides have adversely impacted predaceous insect species. Here we studied the effect of tolfenpyrad on C. sinica. The acute toxicity of tolfenpyrad to the second-instar larvae was determined and indicated that tolfenpyrad is a medium-risk insecticide. Sublethal concentrations (LC₁₀, LC₂₀, and LC₃₀) of tolfenpyrad had effects on the development, reproduction, and predatory ability of C. sinica. When the second-instar larvae of C. sinica were exposed to sublethal concentrations of tolfenpyrad, the activities of protective enzymes, such as superoxide dismutase, peroxidase, and catalase, and detoxification enzymes, including carboxylesterase, glutathione-S-transferase, and P450 monooxygenases, were increased with exposure time. The second-instar larvae of C. sinica exposed to sublethal concentrations of tolfenpyrad exhibited an oxidative stress response that increased the levels of malondialdehyde and reactive oxygen species (ROS). Within 48-120 h after treatment, the contents of mitochondrial respiratory chain complex I and adenosine triphosphate in the second-instar larvae were decreased. This resulted in an imbalance between the production and clearance of ROS and caused cellular damage.

Transcriptome analysis in the thiamethoxam resistance of seven-spot ladybird beetle, Coccinella septempunctata (Coleoptera: Coccinellidae)

The seven-spot ladybird beetle, Coccinella septempunctata Linnaeus (Coleoptera: Coccinellidae) has been used as the main biological control agent against all kinds of aphids in farmland and greenhouse. In this study, a thiamethoxam-resistant strain (ThR) and a susceptible strain (SS) of seven-spot ladybird beetle were established, and differentially expressed genes (DEGs) associated with thiamethoxam resistance were recorded through de novo Illumina HiSeq 4000 sequencing. A total of 53.5 Gb of clean data were obtained and finally assembled into 21,217 unigenes from ThR and SS transcriptomes. 1798 DEGs were identified between the ThR libraries and the SS libraries, including 560 up-regulated genes and 1238 down-regulated genes. Some cytochrome p450 monooxygenases (CYP450s), UDP-glycosyltransferases (UGTs), esterases (ESTs) and ATP-binding cassette (ABC) transporters were observed to be up-regulated and the nicotinic acetylcholine receptors (nAChRs) α subunit gene down-regulated in the ThR strain compared to the SS strain. This study provides genetic information for further studies on thiamethoxam resistance mechanisms in the seven-spot ladybird beetle.

Comparative ecotoxicity of insecticides with different modes of action to Osmia excavata (Hymenoptera: Megachilidae)

Osmia excavata is an important pollinator in commercial fruit orchards. Little information has been published about ecotoxicity to O. excavata, especially the larvae. To clarify the risk of commonly used insecticides with different modes of action to the larvae of O. excavata, six insecticides (clothianidin, acetamiprid, sulfoxaflor, lambda-cyhalothrin, chlorfenapyr and abamectin) were selected for evaluation of their acute lethal toxicity and sublethal effects. Clothianidin and abamectin were the two most toxic insecticides to the larvae of O. excavata with LD₅₀ values of 0.007 (0.006-0.008) and 0.0004 (0.0003-0.0006) μg active ingredient (a.i.) bee^-1, respectively. And their ecological risks were high according to the hazard quotient values (HQ > 2500). Sulfoxaflor was identified as the only safe insecticide for O. excavata (HQ < 50) under field conditions. Sublethal toxicity tests showed that larval weight was significantly decreased by ingesting food treated with clothianidin, lambda-cyhalothrin and abamectin (less than the maximum field registered concentrations on fruit trees) due to interference with consumption per larva and reduction of the efficiency of conversion of ingested food. Additionally, above three insecticides significantly prolonged larval developmental duration before cocooning and decreased eclosion rate. Overall, there results suggested that clothianidin and abamectin should not be applied, especially during the flowering phase, the application frequency of lambda-cyhalothrin should be minimized for the purpose of conserving O. excavata. Our results provided important evidences for selecting appropriate insecticides for use in fruit orchards.

The influence of tolfenpyrad on fitness, development, and reproduction in parents and offspring of Coccinella septempunctata

Coccinella septempunctata (ladybird) is one of the foremost natural predators that feed on aphids. Thus, C. septempunctata serves as an effective biological control agent in integrated pest management (IPM) programs. To supplement the activity of biological control agents, IPM programs often incorporate chemical pesticides to bolster crop protection. To evaluate the effects of a potent insecticide, tolfenpyrad, on C. septempunctata, we tested the sublethal effects of tolfenpyrad on all developmental stages of the life cycle of C. septempunctata and its effects on the next generation. For sublethal testing of the parent generation, the LR₅₀ of tolfenpyrad for C. septempunctata was determined to range from 1.04 to 8.43 g a.i. /hm² within a set exposure period, while the hazard quotient (HQ) values were above our threshold value of 2 during the entire observation period. These data indicated a potential toxicity risk from tolfenpyrad exposure. The no observed effect application rates (NOERs) of tolfenpyrad on parents (F₀) were determined for survival (0.485 g a.i. /hm²), developmental time of pupation (0.242 g a.i. /hm²), and fecundity (0.485 g a.i. /hm²). Application of sublethal doses to unexposed progeny (F₁) of exposed parents, prolonged the L1 (1st instar of larvae) and L2 (2nd instar of larvae) stage, while the total longevity, intrinsic rate of increase (r), finite rate of increase (γ), net reproductive rate (R₀), and mean generation time (T) were significantly reduced. These results demonstrated the negative influence of sublethal concentrations of tolfenpyrad on C. septempunctata and its persistent effects on subsequent generations.

Lethal and Sublethal Effects of Chlorpyrifos on Biological Traits and Feeding of the Aphidophagous Predator Harmonia axyridis

Except of pest control, insecticides have shown adverse effects on natural enemies as well. Thus, risk assessment of pesticides for biological control agents is critical for effective use in integrated pest management (IPM) schemes. In the present study, the lethal and sublethal effects of chlorpyrifos, a commonly used insecticide that may negatively affect biological control agents, were evaluated on a non-target predator, the Asian ladybeetle Harmonia axyridis. Previous studies have reported on lethal concentrations, but the effects of sublethal concentrations remain unclear. Lethal and sublethal concentrations of chlorpyrifos were applied to third instar larvae of H. axyridis, and different growth and developmental parameters were measured. Treatment with LC10 (4.62 mg a.i. L-1) significantly shortened the developmental period of third instar larvae, whereas it significantly prolonged those of fourth instar larvae and pupa. Treatment with LC30 (9.59 mg a.i. L-1) significantly increased the larval and pupal developmental period compared with that of the control, whereas feeding potential, female fecundity, and adult longevity significantly decreased after LC10 and LC30 treatment. The pre-oviposition period significantly increased compared with that of the control. Population growth parameters, the finite (λ) and intrinsic rate of increase (r) and the net reproductive rate (R0), decreased following exposure to sublethal concentrations of chlorpyrifos. According to the results, the use of chlorpyrifos in IPM schemes requires further research because even sublethal concentrations of this insecticide were harmful to H. axyridis population growth.

Acute lethal and sublethal effects of four insecticides on the lacewing (Chrysoperla sinica Tjeder)

The lacewing, Chrysoperla sinica, is an important predatory insect, which plays an important role in the integrated pest management of agroforestry pests. However, the extensive use of insecticides negatively affects C. sinica. The acute toxicity, risk level, and, sublethal effects on growth and production, predation ability, protective enzyme activity and genotoxicity of four insecticides: indoxacarb, emamectin benzoate, imidacloprid and lambda-cyhalothrin to C. sinica were studied. The results showed that all four insecticides had lethal toxicity to larvae of C. sinica. Among them, emamectin benzoate had the highest toxicity with LC₅₀ value of 7.41 mg/L. The insecticides also had different effects on the growth and reproduction of C. sinica, of which lambda-cyhalothrin had the greatest impacts. Even at a very low LC₁ concentration (3.37 mg/L), it had strong impacts on the growth, reproduction and predatory ability of C. sinica. The four insecticides also caused a decrease in the predatory ability of the lacewing, of which lambda-cyhalothrin had the greatest effect. During the larval stage, the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were significantly decreased by the four insecticides. At the pupal and adult stages, the effects of the four insecticides on the activities of protective enzymes were different, and the activities of SOD, CAT and POD decreased or increased. Indoxacarb and lambda-cyhalothrin exposure induced DNA damage in the haemocytes of C. sinica and produced obvious genotoxicity. These results provide important scientific basis for the rational use of these insecticides and the protection and utilization of lacewing.

Responses of Harmonia axyridis (Coleoptera: Coccinellidae) to sulfoxaflor exposure

Harmonia axyridis is an important predator of several pest species and is part of many Integrated Pest Management (IPM) programs. To assess the risks of pesticide application to H. axyridis, we studied the effects of sulfoxaflor on H. axyridis larvae. At 72 h after treatment, the acute toxicity LR₅₀ was 311.9476 g a. i. ha^-1 by the residual contact method. This result indicated low-contact toxicity against second-instar H. axyridis larvae. The LR₅₀ of the F1 generation decreased from 69.96 to 36.41 g a. i. ha^-1 in a long-term toxicity test. The daily hazard quotient (HQ) for H. axyridis larvae lowered the safety threshold value in the first 5 d. However, the HQ values were greater than 2 during days 6-18 after sulfoxaflor treatments. We determined the No Observed Effect Application Rates of sulfoxaflor on the survival (<11.25 g a. i. ha^-1), duration of larval and pupal stages (45 g a. i. ha^-1), adult stage (90 g a. i. ha^-1), total pre-oviposition period, adult pre-oviposition period (45 g a. i. ha^-1), and reproduction (11.25 g a. i. ha^-1). Pupation, adult emergence, and eggs counts of H. axyridis were reduced after sulfoxaflor treatments. The predation ability and population demography parameters were significantly impaired by higher application rates. At 90 g a. i. ha^-1 or less, sulfoxaflor was slightly harmful to H. axyridis but a rate of 180 g a. i. ha^-1 was moderately harmful. These results demonstrated that sulfoxaflor is harmful to H. axyridis when applied at high application rates.

Comparative ecotoxicity of neonicotinoid insecticides to three species of Trichogramma parasitoid wasps (Hymenoptera: Trichogrammatidae)

Compatibility of neonicotinoid insecticides with the natural enemies has been concerned for decades. This study aims to evaluate and compare the acute and sublethal toxicity effects of neonicotinoid insecticides on three species of Trichogramma parasitoid wasps (i.e. Trichogramma dendrolimi, T. ostriniae and T. confusum) with broad distribution and great relevance to integrated pest management (IPM) strategies. A residual contact bioassay demonstrated that nitenpyram had the greatest intrinsic toxicity to T. dendrolimi and T. ostriniae with LC₅₀ values of 0.060 (0.056-0.065) and 0.066 (0.050-0.087) mg a.i. L^-1, respectively. But for T. confusum, the most toxic neonicotinoid insecticide is dinotefuran with a LC₅₀ value of 0.065 (0.055-0.078) mg a.i. L^-1. Furthermore, based on the risk quotient estimation, acetamiprid was considered to be the only safe neonicotinoid insecticide (Class 1, RQ＜50). A dipped egg contact bioassay showed that neonicotinoid insecticides induced significant toxic effects on the parasitism of three Trichogramma spp. at low-lethal concentrations. Additionally, emergence probability of the unexposed offspring was also significantly reduced by neonicotinoids. According to the estimated EC₅₀ values, acetamiprid possessed the least toxicity to the parasitism and emergence of T. dendrolimi and T. ostriniae, and for T. confusum, the least toxic neonicotinoid insecticide was thiacloprid. Overall, among the test neonicotinoid insecticides, acetamiprid and thiacloprid may exhibit the less ecotoxicity to the test Trichogramma species.

Sublethal Effects of Four Insecticides on the Seven-Spotted Lady Beetle (Coleoptera: Coccinellidae)

To further develop integrated pest management (IPM) strategies against two sucking insect pests, Aleurocanthus spiniferus (Quaintanca) (Hemiptera: Aleyrodidae) and Toxoptera aurantii Boyer (Hemiptera: Aphididae), in Chinese tea plantations, it is important to evaluate the effects of insecticides on biological control agents, such as the seven-spot lady beetle, Coccinella septempunctata L. (Coleoptera: Coccinellidae). Therefore, we tested the toxicity and sublethal effects of spirotetramat, clothianidin, lambda-cyhalothrin, and bifenthrin on C. septempunctata. The side effects of the active ingredients of the insecticides were evaluated with residual contact tests on the larvae of C. septempunctata in the laboratory. Spirotetramat and clothianidin exhibited lower lethality to C. septempunctata as shown by the higher LC50 values and had higher selectivity for A. spiniferus and T. aurantii based on the selective toxicity ratios being superior to other tested insecticides. Spirotetramat also did not affect survival, longevity, fecundity, and egg hatching of C. septempunctata. Clothianidin and bifenthrin prolonged the duration of larval development stages of C. septempunctata obviously. Clothianidin at >2.5 mg/liter, lambda-cyhalothrin at >0.03 mg/liter, and bifenthrin at >0.125 mg/liter significantly reduced the survival and pupation rates of C. septempunctata larvae. Furthermore, spirotetramat at 3.125 mg/liter was harmless (IOBC class 1) to larvae of this coccinellid species. Based on the results, spirotetramat was innocuous to C. septempunctata larvae compared with clothianidin, lambda-cyhalothrin, and bifenthrin. Therefore, spirotetramat might be incorporated into IPM programs in combination with C. septempunctata for control of A. spiniferus and T. aurantii in the tea plantations.

Compatibility of chlorantraniliprole with the generalist predator Coccinella septempunctata L. (Coleoptera: Coccinellidae) based toxicity, life-cycle development and population parameters in laboratory microcosms

Coccinella septempunctata is a common insect predator that provides biological control of many destructive arthropod pests. An assessment of the toxicity of pesticides to predators is a necessary component of Integrated Pest Management (IPM) strategies. In order to evaluate the risks of field insecticide application, we studied the influence of chlorantraniliprole on C. septempunctata larvae using different exposure doses. Chlorantraniliprole exhibited low contact toxicity against 2nd instar larvae of C. septempunctata with the LR₅₀ was 482.7063 g a.i. ha^-1 by after a 72-h exposure. In a long-term test, the LR₅₀ of chlorantraniliprole for C. septempunctata decreased from 88.97 to 58.22 g a.i. ha^-1, while the hazard quotient (HQ) values were below the threshold value of 2 during the entire observation period. This indicated a low toxicity risk from insecticide exposure. The total effect (E) suggested that chlorantraniliprole could be classified as harmless/slightly harmful to C. septempunctata below/at 200% of the MRFR (the manufacturer maximum recommended field rate) of 120 g a.i. ha^-1. We also determined no observed effect application rates (NOERs) of chlorantraniliprole on survival (7.5 g a.i. ha^-1), developmental time (15 g a.i. ha^-1) and fecundity (30 g a.i. ha^-1). Chlorantraniliprole significantly reduced the pupation rate, adult emergence, egg hatchability, and predation success. Population parameters, including R₀, r, λ, and T were significantly affected when C. septempunctata were treated with chlorantraniliprole at higher label rates. These results demonstrated that the use of chlorantraniliprole may reduce C. septempunctata population levels and the level of biological control provided by this species.