Sublethal and transgenerational effects of thiamethoxam on the demographic fitness and predation performance of the seven-spot ladybeetle Coccinella septempunctata L. (Coleoptera: Coccinellidae)

Sublethal and transgenerational effects of lufenuron on biological characteristics and expression of reproductive related genes in the fall armyworm, Spodoptera frugiperda

The fall armyworm, Spodoptera frugiperda, is a notorious polyphagous pest that causes serious economic losses in crucial crops and has invaded Africa and Asia. Lufenuron is widely used for controlling S. frugiperda in China, owing to its high toxicity against this key pest, and less pollution and little impact on natural enemies. In the present study, the sublethal and transgenerational effects of lufenuron on S. frugiperda were investigated to provide in-depth information for the rational use of lufenuron. Results showed that the development time and pupae weight were not significantly affected following exposure of females to LC10 and LC25 and male S. frugiperda to the LC10 of lufenuron. However, LC25 exposure significantly reduced pupal and total development time and pupae weight of male S. frugiperda. The longevity of S. frugiperda adults was prolonged by lufenuron and the fecundity of S. frugiperda treated with LC10 of lufenuron was significantly increased by 40% compared to the control. In addition, our study demonstrated that the LC25 of lufenuron had transgenerational effects on the progeny generation. The development time of female S. frugiperda whose parents were exposed to LC25 of lufenuron was significantly decreased compared to the control. And then, the expression profiles of Vg, VgR, JHEH, JHE, JHAMT, JHBP, CYP307A1, CYP306A1, CYP302A1 and CYP314A1 genes involved in insect reproduction and development were analyzed using Quantitative Real-Time PCR (RT-qPCR). Results showed that Vg, VgR, JHE, JHAMT, and CYP306A1 were significantly upregulated at the LC10 of lufenuron, which revealed that these upregulated genes might be linked with increased fecundity of S. frugiperda. Taken together, these findings highlighted the importance of sublethal and transgenerational effects under laboratory conditions and these effects may change the population dynamics in the field. Therefore, our study provided valuable information for promoting the rational use of lufenuron for controlling S. frugiperda.

Chronic Paternal/Maternal Exposure to Environmental Concentrations of Imidacloprid and Thiamethoxam Causes Intergenerational Toxicity in Zebrafish Offspring

Imidacloprid (IMI) and thiamethoxam (THM) are ubiquitous in aquatic ecosystems. Their negative effects on parental fish are investigated while intergenerational effects at environmentally relevant concentrations remain unclear. In this study, F0 zebrafish exposed to IMI and THM (0, 50, and 500 ng L-1) for 144 days post-fertilization (dpf) was allowed to spawn with two modes (internal mating and cross-mating), resulting in four types of F1 generations to investigate the intergenerational effects. IMI and THM affected F0 zebrafish fecundity, gonadal development, sex hormone and VTG levels, with accumulations found in F0 muscles and ovaries. In F1 generation, paternal or maternal exposure to IMI and THM also influenced sex hormones levels and elevated the heart rate and spontaneous movement rate. LncRNA-mRNA network analysis revealed that cell cycle and oocyte meiosis-related pathways in IMI groups and steroid biosynthesis related pathways in THM groups were significantly enriched in F1 offspring. Similar transcriptional alterations of dmrt1, insl3, cdc20, ccnb1, dnd1, ddx4, cox4i1l, and cox5b2 were observed in gonads of F0 and F1 generations. The findings indicated that prolonged paternal or maternal exposure to IMI and THM could severely cause intergenerational toxicity, resulting in developmental toxicity and endocrine-disrupting effects in zebrafish offspring.

Toxicity and Lethal Effect of Greenhouse Insecticides on Coccinella septempunctata (Coleoptera: Coccinellidae) as Biological Control Agent of Myzus persicae (Hemiptera: Aphididae)

Deltamethrin and imidacloprid are commonly used insecticides for controlling sub-sucking insects in greenhouses. However, their application may cause sublethal effects on the aphid coccinellid predator Coccinella septempunctata (Coleoptera: Coccinellidae). Here, we study (i) the toxicity and the effect of two sublethal doses (LD₁₀ and LD₃₀) of deltamethrin and imidacloprid on C. septempunctata in a laboratory microcosm and (ii) the residual toxicity of the two insecticides in a greenhouse. The results showed that both insecticides reduced fecundity, longevity, the intrinsic rate of increase, the finite rate of increase and the net reproductive rate. However, the developmental time of the fourth instar larvae was prolonged by both insecticides at LD₁₀ and LD₃₀. Deltamethrin residues were toxic 21 DAT (days after treatment) to C. septempunctata fourth instar larvae. In contrast, imidacloprid began in the slightly harmful category (75%) 1 DAT and declined to the harmless category (18.33%) 21 DAT. These results indicate that deltamethrin and imidacloprid have potential risks to C. septempunctata. This study provides information to guide the development of integrated pest management (IPM) strategies in greenhouses.

Sublethal effects of acetamiprid and afidopyropen on Harmonia axyridis: insights from transcriptomics analysis

Evaluating the sublethal effects of insecticide is crucial for protecting and utilizing natural enemies. In this study, we determined the sublethal effects of acetamiprid and afidopyropen on Harmonia axyridis (Pallas) and explored the potential molecular mechanisms underlying these effects through transcriptomics analysis. The results showed that sublethal concentrations of acetamiprid significantly reduced the adult fecundity and longevity of F₀H. axyridis and decreased the survival time and survival rate of the F₁ generation. Sublethal concentrations of afidopyropen prolonged the developmental time of 4th instar larvae in the F₀ generation. Additionally, acetamiprid and afidopyropen treatments significantly decreased the predation of H. axyridis. Furthermore, transcriptome sequencing analysis revealed that several P450 and UGT genes expressed differently when H. axyridis were exposed to sublethal concentrations of acetamiprid and afidopyropen, suggesting that the differential expression of detoxifying genes might be involved in the response and detoxification metabolism of acetamiprid and afidopyropen in H. axyridis. Our findings demonstrate that sublethal concentrations of acetamiprid adversely influences the development and predation of H. axyridis, while afidopyropen has limited effects on H. axyridis. These results are helpful for protecting and utilizing natural enemies and guiding the scientific use of pesticides in the field.

Hormetic effects of neonicotinoid insecticides on Rhizoglyphus robini (Acari: Acaridae)

The stimulation of biological processes by sublethal doses of insecticides or other stressors is known as hormesis. Here, we have evaluated whether exposure to field-relevant or low concentrations of neonicotinoids induce changes in the reproductive capacity of the bulb mite Rhizoglyphus robini (Acari: Acaridae). Among the tested neonicotinoids imidacloprid, thiamethoxam, and dinotefuran, the highest hormetic effect on the reproduction of R. robini occurred 24 h after the 48 h exposure period to imidacloprid at concentrations of 70 and 140 mg a.i./L. Despite the stimulating effects of imidacloprid on mite reproduction, no significant differences were observed in the offspring (F₁) for biological aspects including egg hatch rate, embryonic period and sex ratio, while an increase was found in the duration of development time from egg to adult. Evaluation of the detoxification enzyme activities of treated adults showed that the highest activity of carboxyl/cholinesterases, cytochrome P450s, and glutathione S-transferases was obtained when exposed to 70, 140 and 70 mg a.i./L imidacloprid, immediately after the exposure period, respectively. Also, an increase in the activity of the antioxidant enzyme catalase was observed compared to that of the control. After imidacloprid pretreatment (140 mg a.i./L), the tolerance of adult mites to diazinon was increased about two-fold. This study shows that exposure to imidacloprid can induce hormetic effects on R. robini and could severely complicate its control due to a higher reproduction, enhanced detoxification enzyme activities, and increased tolerance against other pesticides.

Life-table parameters, functional response, flight ability, and cross-generational effects of matrine demonstrate its safety to Hippodamia variegata (Coleoptera: Coccinellidae)

In Xinjiang's cotton growing area of China, previous studies have shown that matrine is a selective botanical insecticide, with high toxicity to Aphis gossypii Glover (Hemiptera: Aphididae) and low toxicity to its dominant natural enemy, Hippodamia variegata Goeze (Coleoptera: Coccinellidae). However, lethal effects alone are not sufficient evidence to justify introducing matrine into local IPM strategies. In this context, we systematically evaluated the safety of matrine to H. variegata by investigating the effects of contact and stomach toxicity of matrine on the lady beetle's life-table parameters, predatory ability, flight ability of parental adults, and cross-generational effects on life-table parameters of the predator's offspring. We found that matrine at 2,000 mg/l did not have any significant negative effects to adult fecundity, longevity, or the predatory capacity of parental adults of H. variegata. Moreover, it is the same for cross-generational effects of matrine on H. variegate. The contact toxicity of matrine significantly reduced the flight time of H. variegata males, but did not significantly affect flight time and average velocity. Our results support the view that matrine is safe to H. variegata and can be recommended for use in the local IPM strategy for control of A. gossipii.

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.

Sublethal and transgenerational effects of synthetic insecticides on the biological parameters and functional response of Coccinella septempunctata (Coleoptera: Coccinellidae) under laboratory conditions

Synthetic insecticides have been an inevitable part of plant protection throughout the world. Sublethal effects of these chemicals on beneficial insect species are one of the contemporary issues these days. Using the age-stage, two-sex life table model, this study evaluated the sublethal and transgenerational effects of six synthetic insecticides (imidacloprid, thiamethoxam, lambda-cyhalothrin, cypermethrin, chlorpyrifos and profenofos) commonly applied to winter vegetables, on the fitness and predation of the seven-spotted ladybeetle, Coccinella septempunctata, which is an efficient predator of aphids worldwide. According to results, all insecticides at their sublethal doses (LC₃₀) significantly suppressed the emergence of adults, adult weight, fertility and fecundity of the parental generation compared to control treatment. The larval stage was prolonged and oviposition, fecundity and total longevity of the adult beetles were decreased in unexposed progeny whose parents were exposed to sublethal doses of all insecticides. Moreover, the biological parameters of adults, including the intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R ₀) were significantly reduced when exposed to sublethal doses of insecticides. The predation rate of the F₁ generation adults was also decreased after exposure to the sublethal doses of insecticides. However, chlorpyrifos, profenofos, lambda-cyhalothrin and cypermethrin exhibited more deleterious effects on the fitness and population parameters of beetles than imidacloprid and thiamethoxam.

Decreased cuticular penetration minimizes the impact of the pyrethroid insecticide λ-cyhalothrin on the insect predator Eocanthecona furcellata

The use of broad-spectrum pesticides may reduce the biological control efficacy of predatory arthropods. Hence, the risks of pesticides to predators need to be evaluated. Here, we assessed the effects of a broad spectrum pyrethroid λ-cyhalothrin on a polyphagous predatory insect Eocanthecona furcellata via contact exposure route. The recommended application rate of λ-cyhalothrin was lower than the LR₅₀ and HQ _(in-field) was equal to 0.57, indicating the risk of λ-cyhalothrin to E. furcellata was low. Dried λ-cyhalothrin residue had no effect on the mortality, body weight, protein content of cuticle, or activities of major detoxification enzymes in E. furcellata. Residual of λ-cyhalothrin was only detected in the cuticle and legs of E. furcellata with a decreasing trend as time went by and no λ-cyhalothrin was detected inside the body. Additionally, a comparative transcriptome analysis was conducted to study global changes in gene expression in E. furcellata at different time points following exposure to λ-cyhalothrin-contaminated environment. A total of 57,839 unigenes with an average length of 1044 bp and an N50 of 1820 bp were obtained. In total, 118 and 109 differentially expressed genes (DEGs) at 12 h, and 60 h were identified between two groups. The DEGs were largely enriched in functional categories related to the structural constituent of cuticle. Accordingly, multiple cuticle protein-coding genes were up-regulated at 12 h after pesticide exposure. The present study stressed the importance of evaluating the compatibility between a specific pesticide (λ-cyhalothrin) and E. furcellata via simulating the releasing predators after insecticide application. The data could help optimize the pesticide use, optimizing the ecological services of E. furcellata as a BCA, and expanding its use into more areas of agriculture.

Toxicity and risk assessment of nine pesticides on nontarget natural predator Harmonia axyridis (Coleoptera: Coccinellidae)

BACKGROUND

Harmonia axyridis (Coleoptera: Coccinellidae) is a beneficial predatory arthropod in the agricultural ecosystem. For the success and development of integrated pest management strategies, it is essential to assess the toxicity risks of commonly used pesticides to nontarget arthropods.

RESULTS

The glass tube residue method was used to determine the risk of nine pesticides to H. axyridis after second-instar exposure. To assess the potential risk of the selected pesticides, the pre-adult LR₅₀ values were calculated by the hazard quotient (HQ) method. The LR₅₀ (application rate causing 50% mortality) values of imidacloprid, dinotefuran, thiamethoxam, acetamiprid, bifenthrin, and dimethoate were 0.44, 0.82, 0.10, 0.05, 0.04, and 0.21 g a.i. ha^-1 , respectively, showing unacceptable risk to H. axyridis after exposure to in and off field. However, emamectin benzoate and two fungicides, tebuconazole and myclobutanil, posed a low risk to H. axyridis and their HQ values were less than the trigger value of 5.

CONCLUSIONS

The four neonicotinoid insecticides (imidacloprid, dinotefuran, thiamethoxam, and acetamiprid), pyrethroid bifenthrin, and organophosphorus dimethoate showed a high risk to H. axyridis. Emamectin benzoate, tebuconazole, and myclobutanil showed a low risk to H. axyridis under both exposure scenarios. The results provide critical scientific evidence to guide future regulation of pesticide management practices and protection of nontarget arthropods like H. axyridis. © 2022 Society of Chemical Industry.

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.

Hormetic and transgenerational effects in spotted-wing Drosophila (Diptera: Drosophilidae) in response to three commonly-used insecticides

Although insecticide formulations and spray rates are optimized to achieve lethal exposure, there are many factors in agricultural settings that can reduce the effective exposure of insect pests. These include weather patterns, timing of application, chemical degradation/volatilization, plant structural complexity, and resistant populations. While sub-lethal exposure to insecticides can still have negative impacts on pest populations, they can also lead to stimulatory, or hormetic, responses that can increase the fitness of surviving insects. Sub-lethal concentrations may also produce increased tolerance in the offspring of surviving adults through transgenerational effects. Sub-lethal effects are pertinent for the invasive fruit pest, spotted-wing Drosophila, Drosophila suzukii (Matsumura), because its small size, diurnal movement patterns, and utilization of hosts with complex plant structures, such as caneberries and blueberries, make effective insecticide applications tenuous. In this study, we measured spotted-wing Drosophila survivorship, reproductive performance, and offspring tolerance in flies exposed to sub-lethal concentrations of three commonly-used insecticides (zeta-cypermethrin, spinetoram, and pyrethrin). We found some evidence for hormesis, with survival effects being sex- and concentration-dependent for all insecticides. Males were far more susceptible to insecticides than females, which in some cases exhibited higher eclosion success and reproductive rates when exposed to sub-lethal doses. We did not observe significant transgenerational effects at sub-lethal concentrations, despite trends of increased offspring viability for zeta-cypermethrin and spinetoram. More research, however, is needed to fully understand the role that sub-lethal effects may play in pest population dynamics, insecticide efficacy, and the development of genetic resistance.

Detrimental Impact of λ-Cyhalothrin on the Biocontrol Efficacy of Eocanthecona furcellata by Affecting Global Transcriptome and Predatory Behavior

Whether and how insecticide exposure will affect the biological control efficacy of predatory arthropods is critical in insecticide toxicology research but largely unexplored. In the current study, reduced biocontrol efficacy was observed in a predatory stink bug─Eocanthecona furcellata─after insecticide application in the field. Thus, we constructed a comparative transcriptome analysis and identified a total of 4364 upregulated and 1043 down regulated differentially expressed genes following the sublethal exposure of λ-cyhalothrin. The reduced juvenile hormone (JH) titer and increased trehalose content were observed. The predation capacity and theoretical maximum predation of predators were decreased by 31.08 and 48.90% in response to λ-cyhalothrin, respectively. Furthermore, JH supplementation after λ-cyhalothrin treatment could significantly stimulate trehalase and detoxification enzyme activities, as well as restore the predatory ability of E. furcellata. Our results help to understand the toxicological mechanism of predatory stink bug species in responding to insecticides, benefit predators' ecological services, and optimize the insecticide selection.

Biotoxicity Evaluation of a Cationic Star Polymer on a Predatory Ladybird and Cooperative Pest Control by Polymer-Delivered Pesticides and Ladybird

Although employing nanocarriers for gene/drug delivery shows great potential in agricultural fields, the biotoxicity of nanocarriers is a major concern for large-scale applications. Herein, we synthesized a cationic star polymer (SPc) as a pesticide nanocarrier/adjuvant to evaluate its safety against a widely used predatory ladybird (Harmonia axyridis). The application of SPc at extremely high concentrations nearly did not influence the hatching of ladybird eggs but it led to the death of ladybird larvae at lethal concentration 50 (LC₅₀) values of 43.96 and 19.85 mg/mL through the soaking and feeding methods, respectively. The oral feeding of SPc downregulated many membrane protein genes and lysosome genes significantly, and the cell membrane and nucleus in gut tissues were remarkably damaged by SPc application, revealing that the lethal mechanism might be SPc-mediated membrane damage. Furthermore, the oral feeding of SPc increased the relative abundance of Serratia bacteria in ladybird guts to result in bacterial infection. Coapplication of ladybird and SPc-loaded thiamethoxam/matrine achieved desired control efficacies of more than 80% against green peach aphids, revealing that the coapplication could overcome the slow-acting property of ladybirds. To our knowledge, this is the first attempt to investigate the polymer-mediated lethal mechanism toward natural enemies and explore the possibility of coapplying SPc-loaded pesticides and natural enemies for pest management.

Transgenerational Effects of a Neonicotinoid and a Novel Sulfoximine Insecticide on the Harlequin Ladybird

Simple Summary

The coccinellid Harmonia axyridis is an important natural enemy of various agricultural pests, including aphids. Agrochemicals can negatively affect the performance of arthropod natural enemies and, thus, the ecological services they provide. In this context, we assessed the lethal and sublethal effects of two neuroactive compounds with different chemical structures: the long-established neonicotinoid insecticide, imidacloprid, and the novel, sulfoximine insecticide, sulfoxaflor, both of which act on nicotinic acetylcholine receptors against adult and developmental stages of H. axyridis. Estimated LC₂₀ and LC₅₀ doses of imidacloprid for a target pest species, Aphis gossypii, resulted in significantly greater mortality in contact bioassays against adult H. axyridis compared with equivalent LC₂₀ and LC₅₀ doses of sulfoxaflor. Both concentrations of imidacloprid and sulfoxaflor significantly reduced the proportion of ovipositing females of parental generation. LC₂₀ and LC₅₀ dose of imidacloprid and LC₅₀ dose of sulfoxaflor significantly reduced both the fecundity and fertility of parental generation. In progeny of parents exposed to both insecticides at LC₅₀ concentrations the juvenile survival rate was significantly reduced, and both concentrations of imidacloprid and sulfoxaflor, except LC₂₀ dose of sulfoxaflor, significantly prolonged the larval development time. These experimental results disclose the negative influence of sulfoxaflor and imidacloprid at low concentrations on the harlequin ladybird and its subsequent generation. Hence, actions should be taken to optimize imidacloprid and sulfoxaflor applications for the control of aphid pests, aiming at preserving the biocontrol services provided by this important predator.

Abstract

The harlequin ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae), is a generalist predator and an effective biocontrol agent of various insect pests that has been exploited for the control of aphid pests in the greenhouse and field. However, insecticides are widely used to control aphid pests worldwide and the potential non-target effects of sulfoxaflor and imidacloprid for controlling aphid pests towards this biocontrol agent are little known. Although both sulfoxaflor and imidacloprid act on nicotinic acetylcholine receptors of insects, sulfoxaflor has a novel chemical structure compared with neonicotinoids. We assessed the lethal, sublethal and transgenerational effects of sulfoxaflor and imidacloprid on H. axyridis simultaneously exposed via ingestion of contaminated prey and via residual contact on the host plant at LC₂₀ and LC₅₀ doses estimated for the cotton aphid. Imidacloprid significantly reduced the survival of H. axyridis adults compared to sulfoxaflor at the same lethal concentration against cotton aphid. Both concentrations of imidacloprid and sulfoxaflor reduced the proportion of ovipositing females, and both concentrations of imidacloprid and sulfoxaflor, except LC₂₀ dose of sulfoxaflor, reduced the fecundity and fertility of the parental generation. In the progeny of imidacloprid- and sulfoxaflor-exposed parents, both tested LC₅₀ concentrations significantly decreased the juvenile survival rate, and both concentrations of imidacloprid and sulfoxaflor, except LC₂₀ dose of sulfoxaflor, prolonged the development time. Our findings provide evidence of the negative influence of imidacloprid and sulfoxaflor at low lethal concentrations on the harlequin ladybird and on the progeny of exposed individuals, i.e., transgenerational effects. Hence, these findings stress the importance of optimizing the applications of imidacloprid and sulfoxaflor for the control of aphid pests, aiming at preserving the biocontrol services provided by H. axyridis throughout the integrated pest management approach.

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.

Ecotoxicity of neonicotinoids and diamides on population growth performance of Zygogramma bicolorata (Coleoptera: Chrysomelidae)

Relative ecotoxicity of approved neonicotinoids (i.e. imidacloprid, clothianidin, acetamiprid, thiacloprid, thiamethoxam and dinotefuran) and diamides (i.e. chlorantraniliprole, cyantraniliprole and flubendiamide) was examined on population growth parameters of Zygogramma bicolorata Pallister on parthenium under laboratory conditions at 27 ± 1 °C, 65 ± 5% relative humidity and 10 L : 14D photoperiod. The dose of all tested insecticides in the bioassay procedure was within a minimum range of their recommended field rate. In acute toxicity trial, imidacloprid caused highest rate of mortality in treated adults of Z. bicolorata, however, it was lowest in flubendiamide treatment followed by cyantraniliprole and chlorantraniliprole. Further, based on toxicity coefficient (E) value in acute toxicity trial, all were classified as harmful (H) and diamides were classified as moderately harmful (MH) as per IOBC classification. Moreover, chronic toxicity trials were carried out through life table response experiments (LTREs) in the F₁ progeny of acute toxicity experienced group. Prolonged development with the highest mortality was evident in as compared to diamides. Furthermore, population growth parameters i.e. potential fecundity (Pf), natality rate (m_x), intrinsic rate of increase (r_m), net reproductive rate (R₀) and finite rate of increase (λ) was greatly reduced in Z. bicolorata treated with neonicotinoids as compared with diamides. However, mean generation time (T_c), corrected generation time (τ) and the doubling time (DT) was prolonged in neonicotinoids followed by diamides. Furthermore, proportion of females was greatly reduced (0.43-0.48 females) in neonicotinoids as comparison to diamides (0.53-0.55 females) and control (0.67 females). On the basis of ecotoxicity trials, the tested neonicotinoids were highly toxic to Z. bicolorata than diamides. Therefore, diamide insecticides could be used with Z. bicolorata, however, for validation experimentation need to be done under natural field conditions.

Sublethal effects of a juvenile hormone analog, Pyriproxyfen on demographic parameters of non-target predator, Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae)

Insect predators, in general, play an important role in regulating pest populations in agricultural systems, but may be negatively affected by pesticides used in pest management. Convergent lady beetle, Hippodamia convergens Guerin-Meneville (Coleoptera: Coccinellidae) is known as an important biological control agent of soft-bodied insect pests. The development of Integrated Pest Management (IPM) program against insect pests requires an assessment of the side effect of insecticides on biological control agents. In the present work, we assessed the sublethal effects of an insect growth regulator, Pyriproxyfen (juvenile hormone mimic) on a common aphidophagous beetle, H. convergens by computing its demographic parameters through age-stage, two-sex life table theory. Present results showed that sublethal (LC₁₀ and LC₃₀) concentrations of tested insecticide prolonged the pre-adult developmental duration while adult longevity, fecundity and fertility were reduced following treatment compared with control. However, total pre-ovipositional period (TPOP) was declined with the increasing trend of insecticide concentration. In additions, population growth parameters such as intrinsic rate of increase r, finite rate of increase λ and net reproductive rate R₀ were dramatically reduced in H. convergens population when they treated with sublethal concentrations pyriproxyfen. Therefore, the results obtained through this study reflected that pyriproxyfen impairs the population growth parameters and could reduce the biological services provided by H. convergens. Thus, more attention should be paid to the use of this insecticide in IPM program.

Assessment of Lethal, Sublethal, and Transgenerational Effects of Beauveria Bassiana on the Demography of Aedes Albopictus (Culicidae: Diptera)

Dengue fever is one of the most rapidly spreading arthropod-borne diseases. Diurnal vectorial properties of Aedes albopictus contribute to the dispersion of the dengue viruses. Frequent and injudicious use of synthetic insecticides led to the evolution of resistant phenotypes in Ae. albopictus which necessitates the search for an alternative of current control strategies. Developing a long-lasting and environmentally safe tactic based on knowledge of ecology and population dynamics of Ae. albopictus is critical. Therefore, with a view towards biological control and ecology, the effect of entomopathogenic fungi (EPF) Beauveria bassiana on filial and first filial generations of Ae. albopictus were studied. Investigations showed 87.5% adulticidal activity leading to altered fecundity and adult longevity in a filial generation. The lethal (LC₅₀) and sublethal (LC₂₀) concentrations of B. bassiana were applied to filial generation (F₀) to study demographic parameters in the first filial generation (F₁). Results showed reduced net reproductive rates (R_o) intrinsic rate of increase (r), and mean generation time (T) compared to uninfected controls. Prolonged larval and pupal duration were observed followed by reduced longevity of male and female adults. Fecundity in the first filial generation was significantly changed with the lethal and sublethal concentrations of B. bassiana. Thus, it is concluded that B. bassiana has the potential to play a vital role in integrated mosquito management strategies.

Exploring the multilevel hazards of thiamethoxam using Drosophila melanogaster

Thiamethoxam (THIA) is a widely used pesticide. However, its effects on the growth and development of insects remain unclear. Herein, the lethal concentration 50 (LC50) of THIA (3.13 μg/mL for adults, 20.25 μg/mL for third-instar larvae) were identified. THIA (1/3 LC50) prolonged the time required for growth and development, and decreased the fecundity, the rates of pupation and eclosion, and lifespan of Drosophila. The uniform architecture of the compound eyes was disturbed. It also triggered DNA damage, and reduced the viability of fat body cells and hemocytes. Moreover, RNA-sequencing showed that differentially expressed genes in response to THIA were mainly related to stratum corneum development, immune function. Genes involved in stratum corneum proteins (Lcp65Ag3, Cpr65Ax1), hemocyte proliferation (RyR), and immune responses (IM4) were significantly induced. Genes associated with lipid metabolism (sxe2), lifespan (Atg7 and NalZ), pupa development (IIp8, Blimp-1), female fertility (Ddc), male mating behavior (ple), neural retina development (Nnad), was significantly downregulated. These findings provide a basis for further research to fully assess the hazards of exposure to neonicotinoid pesticides.

Sublethal effects of anthranilic diamide insecticides on the demographic fitness and consumption rates of the Coccinella septempunctata (Coleoptera: Coccinellidae) fed on Aphis craccivora

As for developing effective integrated pest management (IPM), it is necessary to understand the sublethal effects of common insecticides on the non-target beneficial arthropods. In this lab-scale study, the sublethal effects of two anthranilic diamide insecticides chlorantraniliprole and cyantraniliprole on the populations of 7-spot ladybird Coccinella septempunctata (Coleoptera: Coccinellidae) were determined and compared using an age-stage, TWO-SEX life table and CONSUME-MSChart computer program. Cyantraniliprole at low-lethal concentrations of 1 and 10 mg L^-1 significantly prolonged the larval stages and reduced the total adult longevity, compared with the control. Additionally, the net reproductive rate (R₀), intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) were significantly reduced in the group treated with 10 mg L^-1 of cyantraniliprole. Similarly, the net predation (C₀), the finite predation rate (ω), and stable predation rate (ψ) were significantly reduced by cyantraniliprole at 1 and 10 mg L^-1. In contrast, no significant difference in the demographic parameters above was determined for chlorantraniliprole at 1 mg L^-1. Therefore, C. septempunctata population may develop faster and possess greater predation potential against aphids under the exposure of chlorantraniliprole, compared to cyantraniliprole. Chlorantraniliprole may be a preference to cyantraniliprole as a combined alternative with ladybeetle predators in IPM framework.

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.

Lethal and sub-lethal effects of imidacloprid on the aphidophagous coccinellid hippodamia variegata

Hippodamia variegata is one of the most abundant ladybird species in Greece, preying on several aphid species and other arthropods, of which many are pests of cultivated plants. Imidacloprid, a neonicotinoid insecticide, is commonly used for controlling sucking insects; at the same time, however, it can cause various sub-lethal effects on non-target organisms. The development of IPM programs against pests requires an evaluation of the side effects of insecticides on natural enemies. We evaluated the sub-lethal effects of imidacloprid on H. variegata. Our results demonstrate that imidacloprid at a LC₁₀ (3.92 mg (a.i.) L^-1 and LC₃₀ (8.69 mg (a.i.) L^-1) decreased adult longevity and survival rate. In addition, demographic parameters, such as the intrinsic rate of increase (r), finite rate of increase (λ) and net reproductive rate (R₀), were reduced when exposed to sub-lethal concentrations of imidacloprid. These results demonstrate a negative influence of imidacloprid at sub-lethal concentrations on H. variegata which could reduce biological control services provided by this predator.