Lethal effect of imidacloprid on the coccinellid predator Serangium japonicum and sublethal effects on predator voracity and on functional response to the whitefly Bemisia tabaci

Molecular mechanisms for selective action of afidopyropen to Myzus persicae and Coccinella septempunctata

BACKGROUND

Afidopyropen is a novel insecticide with high selectivity between sucking insects such as the peach aphids Myzus persicae and natural enemies like the seven-spotted lady beetle Coccinella septempunctata. However, the mechanisms of selective action for afidopyropen remain unknown.

RESULTS

The LC50 values of afidopyropen to the 1st-4th instar larvae and adult C. septempunctata were 372- to more than 7267-fold higher than that to adult M. persicae. Though the activity of cytochrome P450s in M. persicae was 6.1- to 7.5-fold higher than that in C. septempunctata, the latter has much higher activities of carboxylesterase (CarEs) and glutathione S-transferases (GSTs), and the crude enzyme of C. septempunctata and M. persicae showed similar metabolism efficiency to afidopyropen. Molecular docking results demonstrated that afdopyropen showed higher binding affinity to the vanilloid-type transient receptor potential (TRPV) channel of M. persicae (-9.1 kcal/mol) than to that of C. septempunctata (-8.2 kcal/mol). And the EC50 value of afdopyropen to the TRPV channel of C. septempunctata (41 360 nM) was 19 885-fold higher than that in M. persicae (2.08 nM).

CONCLUSIONS

Our results demonstrated that the significantly different sensitivity of M. persicae and C. septempunctata TRPV channel to afidopyropen play a key role in the high selectivity of afidopyropen. These findings provide new insights into the selective mechanisms of afidopyropen against insect pests and natural enemies as well as the theory support for coordinated application of chemical control and biological control. © 2024 Society of Chemical Industry.

Gut bacterium Burkholderia cepacia (BsNLG8) and immune gene Defensin A contribute to the resistance against Nicotine-induced stress in Nilaparvata lugens (Stål)

Nicotine, a naturally occurring alkaloid found in tobacco, is a potent neurotoxin extensively used to control Nilaparvata lugens (Stål), a destructive insect pest of rice crops. The insect gut harbors a wide array of resident microorganisms that profoundly influence several biological processes, including host immunity. Maintaining an optimal gut microbiota and immune homeostasis requires a complex network of reciprocal regulatory interactions. However, the underlying molecular mechanisms driving these symbiotic exchanges, particularly between specific gut microbe and immunity, remain largely unknown in insects. Our previous investigations identified and isolated a nicotine-degrading Burkholderia cepacia strain (BsNLG8) with antifungal properties. Building on those findings, we found that nicotine intake significantly increased the abundance of a symbiotic bacteria BsNLG8, induced a stronger bacteriostatic effect in hemolymph, and enhanced the nicotine tolerance of N. lugens. Additionally, nicotine-induced antimicrobial peptides (AMPs) exhibited significant antibacterial effects against Staphylococcus aureus. We adopted RNA-seq to explore the underlying immunological mechanisms in nicotine-stressed N. lugens. Bioinformatic analyses identified numerous differentially expressed immune genes, including recognition/immune activation (GRPs and Toll) and AMPs (i.e., Defensin, Lugensin, lysozyme). Temporal expression profiling (12, 24, and 48 hours) of immune genes revealed pattern recognition proteins and immune effectors as primary responders to nicotine-induced stress. Defensin A, a broad-spectrum immunomodulatory cationic peptide, exhibited significantly high expression. RNA interference-mediated silencing of Defensin A reduced the survival, enhanced nicotine sensitivity of N. lugens to nicotine, and decreased the abundance of BsNLG8. The reintroduction of BsNLG8 improved the expression of immune genes, aiding nicotine resistance of N. lugens. Our findings indicate a potential reciprocal immunomodulatory interaction between Defensin A and BsNLG8 under nicotine stress. Moreover, this study offers novel and valuable insights for future research into enhancing nicotine-based pest management programs and developing alternative biocontrol methods involving the implication of insect symbionts.

Sublethal effects of chlorantraniliprole on immunity in Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae): Promote encapsulation by upregulating a heat shock protein 70 family gene SfHSP68.1

As an agricultural pest, the fall armyworm (FAW), Spodoptera frugiperda, poses a severe threat to agriculture in China. Chlorantraniliprole has been widely used to control this pest. In our previous studies, we discovered that LD10, LD20, and LD30 chlorantraniliprole promoted encapsulation in the 4th instar larvae of the FAW, with LD30 chlorantraniliprole having the most significant effect. To further investigate the molecular mechanism underlying the sublethal effects of chlorantraniliprole on encapsulation in the FAW, this study conducted the effects of encapsulation in 4th instar larvae of the FAW exposed to LD30 chlorantraniliprole. Then, we analyzed the transcriptome of the FAW hemolymph treated with LD30 chlorantraniliprole and identified genes related to encapsulation using RNAi. Our results showed that the encapsulation in the FAW was enhanced at 6, 12, 18, 24, and 48 h after exposure to LD30 chlorantraniliprole. Additionally, LD30 chlorantraniliprole significantly affected the expression of certain immune-related genes, with the heat shock protein 70 family gene SfHSP68.1 showing the most significant upregulation. Subsequent interference with SfHSP68.1 resulted in a significant inhibition of encapsulation in FAW. These findings suggested that LD30 chlorantraniliprole can promote encapsulation in the FAW by upregulating SfHSP68.1 expression. This study provides valuable insights into the sublethal effects of chlorantraniliprole on encapsulation in the FAW and the interaction between encapsulation and heat shock proteins (HSPs).

Distribution and accumulation of Cadmium in different trophic levels affecting Serangium japonicum, the predatory beetle of whitefly Bemisia tabaci, biologically, physiologically and genetically: An experimental study

Cadmium (Cd) is a heavy metal that is of great concern in agroecosystems due to its toxicity to plants, herbivores, carnivores, and human beings. The current study evaluated the allocation and bioaccumulation of Cd from soil to cotton plants, cotton plants to herbivore pests, and herbivorous pests to a natural enemy predator. When soil was spiked with 100 mg/kg Cd, results demonstrated that cotton roots accumulated more Cd than the stems and leaves. The bioaccumulation of Cd was less in 4th instar larvae, pupa, and adults of Serangium japonicum than in Bemisia tabaci adults. The bioaccumulation in S. japonicum elongated the immature development period and reduced adult longevity, oviposition days, fertility, and total pre-oviposition duration. The net reproduction of S. japonicum was also reduced, as was female mature weight and feeding potential; as a result, Cd exposure could reduce the future population size compared to uncontaminated populations. There was decreased activity of the antioxidant enzymes (SOD, CAT, and POD) and energy-conserving lipids (glycogen, triglyceride, and total cholesterol) in Cd-contaminated S. japonicum compared to controls. The detoxifying enzyme activity of GST and P450 increased while AChE activity did not change. The qRT-PCR research showed that SOD1, CAT, POD, glycogen, and triglyceride gene expression was higher than in controls, whereas detoxification gene expression did not change. Our results indicate that Cd exposure has a physiological trade-off between its adverse effects on life history traits and elevated detoxification and antioxidation of S. japonicum, which could result from gene expression alteration. Further studies are needed to assess whether Cd exposure causes irreversible DNA damage in S. japonicum.

The comparison of species diversity and abundance of insect natural enemies in the domesticated species of cotton using the yellow pan trap method

India is the world's largest cotton producer and the only country that grows all four cultivated cotton species. There have been very few studies on the diversity and abundance of natural enemies of cotton insect pests in these cultivated cotton species. Therefore, the current study (2016-2018) was conducted to assess the diversity and abundance of natural enemies that cultivated cotton species harbour. Phule Dhanwantari, Suraj, Suvin, RCH-2, and DCH-32 were the five genotypes used in the study, each with a distinct genetic background. Using the adiv 2.0.1 and vegan R packages, we identified significant differences in natural enemies in terms of species diversity, richness, evenness, and abundance. Analysis of Similarity (ANOSIM) and Non-metric Multidimensional Scaling (NMDS) indicated substantial differences in the natural enemy community structure among the examined genotypes. A total of 17,279 natural enemies were collected and identified across genotypes from seven predatory families and five parasitoid families. The percentage share of these natural enemy families across genotypes and years, in descending order, is Coccinellidae (28.23%) < Tachinidae (19.23%) < Braconidae (12.68%) < Chrysopidae (11.65%) < Chalcididae (9.41%) < Aphelinidae (6.33%) < Pentatomidae (3.29%) < Ichneumonidae (2.37%) < Syrphidae (2.33%) < Vespidae (1.81%) < Asilidae (1.79%) < Geocoridae (0.89%). Coccinellidae, Tachinidae, Braconidae, Chrysopidae, Chalcididae, and Aphelinidae are the six major families that account for more than 85% of all recorded natural enemies. These six families have a higher percentage share in Phule Dhanwantary (90%) compared to the other genotypes. The conservation and better utilization of these natural enemies are crucial for the ecological and safe management of insect pests in the cotton ecosystem.

Sublethal effects of imidacloprid on the fitness of two species of wheat aphids, Schizaphis graminum (R.) and Rhopalosiphum padi (L.)

Imidacloprid is a neonicotinoid insecticide that efficiently controls piercing-sucking mouthparts pests. However, the impact of low lethal concentration of imidacloprid on key demographic parameters of wheat aphids, Schizaphis graminum (R.) and Rhopalosiphum padi (L.) has been scarcely studied. In this study, we used the age stage, two-sex life table approach to investigate the sublethal effects of imidacloprid on the biological traits of S. graminum and R. padi. Bioassays showed that imidacloprid possesses high toxicity to adult S. graminum and R. padi, with LC50 of 3.59 and 13.78 mg L-1 following 24 h exposure. A low lethal concentration of imidacloprid (LC25) significantly decreased adult longevity and total longevity of progeny generation aphids (F1) of S. graminum. Nevertheless, imidacloprid (LC25) had no significant effects on the fecundity and longevity of directly exposed parental parental S. graminum and R. padi (F0). Our results showed that the low lethal concentration of imidacloprid affected the demographic parameters that ultimately impact on the population of S. graminum. This study provides detailed information about the overall effects of imidacloprid on S. graminum and R. padi that might help to manage these two key pests.

Functional response of an egg parasitoid, Trichogramma chilonis Ishii to sublethal imidacloprid exposure

BACKGROUND

The effectiveness of a biological control agent depends on how well it can control pests and how compatible it is with pesticides. Therefore, we reported the multigenerational effect of a commonly used insecticide, imidacloprid, on the functional response of a widely acclaimed egg parasitoid, Trichogramma chilonis Ishii, to different densities of the host Corcyra cephalonica Stainton eggs. The study investigated the outcomes of the median lethal concentration (LC50 ) and sublethal concentrations (LC5 , LC30 ), along with control treatments for five continuous generations (F1 to F5 ).

RESULTS

The results showed that the F5 generation of LC30 , both of the F1 and F5 generations of LC50 , and the control all had a Type II functional response. A Type I functional response was exhibited for the F1 generation of LC30 and both generations of LC5 . The attack rate on host eggs treated with LC5 and LC30 did not change (decrease) with the shift in the type of functional response as compared to the control. A significant increase in the searching efficiency (a) was observed in the later generation (F5 ) under the exposure of LC5 and LC30 imidacloprid concentrations. A lower handling time (Th ) in both generations of the LC5 followed by LC30 treated individuals was observed when compared with the control and LC50 treatments. The per capita parasitization efficiency (1/Th ) and the rate of parasitization per handling time (a/Th ) were also considerably higher in both the generations of LC5 and LC30 than in the control and LC50 , thereby implying positive effects of imidacloprid on the parasitization potential of T. chilonis.

CONCLUSION

Altogether, these multigenerational outcomes on the functional response of T. chilonis could be leveraged to control the intractable lepidopteran pests under the mild exposure of imidacloprid in integrated pest management (IPM) programs as well as in the mass rearing of the parasitoid, T. chilonis. © 2023 Society of Chemical Industry.

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 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.

Effects of Tebufenozide on Eggs, Larvae and Adults of Chrysoperla carnea (Neuroptera: Chrysopidae)

Quantifying compatibility among control agents is essential for development of integrated pest management (IPM). Chrysoperla carnea (Siemens) and insect growth regulator insecticides are widely used in IPM of Lepidoptera. C. carnea is a generalist predator naturally present in the Mediterranean agroecosystems and bred in insectariums for commercial purposes. Here, we evaluated lethal and sublethal effects of tebufenozide on C. carnea under laboratory conditions. The treatment of eggs with tebufenozide 24 or 48 h after they were laid did not affect the hatching rate or survival of the neonate larvae. Toxic effects of tebufenozide on topically treated larvae was low; development times of surviving larvae and pupae decreased significantly compared with controls. In choice bioassays, a high percentage of third-instar larvae chose prey (Spodoptera littoralis) treated with tebufenozide in preference to untreated prey. Moreover, second-instar larvae of C. carnea that had previously consumed tebufenozide-treated prey (0.75 mL/L) had significantly reduced larval development time compared with controls, while longevity of surviving adults, fecundity and egg viability were unaffected. Ingestion of tebufenozide by adults of C. carnea at the recommended field dose had no significant effect on female fecundity, egg viability or adult longevity. Tebufenozide exhibited low toxicity towards the developmental stages of C. carnea and is therefore a candidate for inclusion in IPM strategies.

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.

Acute and chronic toxicity of imidacloprid in the pollinator fly, Eristalis tenax L., assessed using a novel oral bioassay

Imidacloprid is a neonicotinoid neurotoxin that remains widely used worldwide and persists in the environment, resulting in chronic exposure to non-target insects. To accurately map dose-dependent effects of such exposure across taxa, toxicological assays need to assess relevant modes of exposure across indicator species. However, due to the difficulty of these experiments, contact bioassays are most frequently used to quantify dose. Here, we developed a novel naturalistic feeding bioassay to precisely measure imidacloprid ingestion and its toxicity for acute and chronic exposure in a dipteran, Eristalis tenax L., an important member of an under-represented pollinator group. Flies which ingested imidacloprid dosages lower than 12.1 ng/mg all showed consistent intake volumes and learned improved feeding efficiency over successive feeding sessions. In contrast, at doses of 12.1 ng/mg and higher flies showed a rapid onset of severe locomotive impairment which prevented them from completing the feeding task. Neither probability of survival nor severe locomotive impairment were significantly higher than the control group until doses of 1.43 ng/mg or higher were reached. We were unable to measure a median lethal dose for acute exposure (72 h) due to flies possessing a relatively high tolerance for imidacloprid. However, with chronic exposure (18 days), mortality went up and an LD50 of 0.41 ng/mg was estimated. Severe locomotive impairment (immobilisation) tended to occur earlier and at lower dosages than lethality, with ED50s of 7.82 ng/mg and 0.17 ng/mg for acute and chronic exposure, respectively. We conclude that adult Eristalis possess a much higher tolerance to this toxin than the honeybees that they mimic. The similarity of the LD50 to other dipterans such as the fruitfly and the housefly suggests that there may be a phylogenetic component to pesticide tolerance that merits further investigation. The absence of obvious adverse effects at sublethal dosages also underscores a need to develop better tools for quantifying animal behaviour to evaluate the impact of insecticides on foraging efficiency in economically important species.

Response of Doru luteipes (Dermaptera: Forficulidae) to insecticides used in maize crop as a function of its life stage and exposure route

The present study aimed to evaluate insecticide toxicity to Doru luteipes (Scudder), a major predator of maize pests. Lethal and sublethal effects were assessed on nymphs and adults exposed to the insecticides through contact (maize leaves) and ingestion (prey eggs) routes. Tested insecticides included a biopesticide (Spodoptera frugiperda multiple nucleopolyhedrovirus, SfMNPV), modern (flubendiamide and metaflumizone), and older neurotoxins (imidacloprid + β-cyfluthrin). The imidacloprid/β-cyfluthrin mix was highly toxic (100% mortality) to the predator, regardless of the exposure route and predator stage. Metaflumizone caused mortality higher than 95% and 45% of nymphs and adults. Flubendiamide and SfMNPV were the least toxic insecticides, not differing from the untreated control in any of the assessed endpoints. Adult tibial length did not differ among treatments. Metaflumizone impaired egg consumption by nymphs and walking distance of adult D. luteipes. Overall, the insecticides caused a more pronounced effect on D. luteipes nymphs than on adults and were more toxic by the contact route. From these findings, flubendiamide and SfMNPV are safer for D. luteipes and should head insecticide choice in integrated pest management programs in maize.

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.

Sub-Lethal Effects of Bifenthrin and Imidacloprid on Megacephala carolina carolina L. (Coleoptera: Carabidae) in Turfgrass

The tiger beetle, Megacephala carolina carolina L. (Coleoptera: Carabidae), is a common predator in turfgrass and ornamental landscapes in Georgia, USA. Among insecticides used in turfgrass to control foliar and root-feeding insect pests, bifenthrin and imidacloprid are routinely used. It was unclear whether sub-lethal doses of bifenthrin and imidacloprid could cause nontarget effects on larvae and M. carolina carolina adults. Thus, the objective was to determine the sub-lethal effects of bifenthrin and imidacloprid on larvae and M. carolina carolina adults. The results show that M. carolina carolina larvae actively hunt for passing prey by waiting at the hole of the tunnel during the day and nighttime. This larval behavior was affected by sub-lethal doses (up to 25% of full label rate) of bifenthrin but not of imidacloprid. The walking behavior of adult M. carolina carolina was also altered when exposed to sub-lethal doses of bifenthrin as they traveled further distances at greater velocities than the nontreated control. The results imply that turfgrass managers should avoid treating lawns where tiger beetles have actively colonized.

Detection of ryanodine receptor G4911E and I4754M mutation sites and analysis of binding modes of diamide insecticides with RyR on Galeruca daurica (Coleoptera: Chrysomelidae)

In recent years, the leaf beetle Galeruca daurica has broken out in the northern grasslands of Inner Mongolia, its management still mainly depends on chemical control using traditional insecticides or with novel action. The study was aim to identify mutation locus associated with resistance to diamide insecticides in field population of G. daurica, to provide a reference for rational selection of insecticides and to avoid the rapid resistance development to diamide insecticides. We cloned the full length of the ryanodine receptor gene of G. daurica (GdRyR), constructed 3D model and transmembrane regions by homologous modeling based on deduced amino acid sequence. Two potential mutation loci (Gly4911Glu and Ile4754Met) and allelic mutation frequencies were detected in individuals of G. daurica. In addition, their binding patterns to two diamide insecticides (chlorantraniliprole, cyantraniliprole) were analyzed separately using a molecular docking method. The full-length cDNA sequence of GdRyR (GenBank accession number: OP828593) was obtained by splicing and assembling, which is 15,399 bp in length and encodes 5,133 amino acids. The amino acid similarity of GdRyR with that of other Coleopteran insects were 86.70%-91.33%, which possessed the typical structural characteristics. An individual resistance allelic mutation frequency test on fifty field leaf beetles has identified 12% and 32% heterozygous individuals at two potential mutation loci Gly4911Glu and Ile4754Met, respectively. The affinity of the I4754M mutant model of GdRyR for chlorantraniliprole and cyantraniliprole was not significantly different from that of the wild type, and all had non-covalent interactions such as hydrogen bonding, hydrophobic interactions and π-cation interactions. However, the G4911E mutant model showed reduced affinity and reduced mode of action with two diamide insecticides, thus affecting the binding stability of the ryanodine receptor to the diamide insecticides. In conclusion, the G4911E mutation in GdRyR may be a potential mechanism for the development of resistance to diamide insecticides on G. daurica and should be a key concern for resistance risk assessment and reasonable applications of diamide insecticides for control in future. Moreover, this study could provide a reference for ryanodine receptor structure-based insecticides design.

Dynamic light scattering and zeta-potential as a tool for understanding the mechanism of pesticides binding toward individual components of transition metal nanoparticles and graphene oxide hybrids

Pesticides present in their commercial formulations are studied for their preferable binding toward carbon-based graphene oxide (GO) or transition metal nanoparticles (Fe, Co, Ni, and Cu), present as hybrids. This simple study also reveals the mechanism of interaction of few selected different classes of pesticides, namely, λ-cyhalothrin, imidacloprid, and metsulfuron-methyl toward these hybrids. Individually, to study this comparative binding when hybrids are not used, the understanding of preferred binding toward any of these selected compounds could be challenging, costly, and time-consuming. Dynamic light scattering (DLS) is used to study the changes observed for hydrodynamic radius and zeta potential for the stability of the resulting products. This simple method can also be extended to identify the binding mechanism for other diverse set of combinations. These studies are supported by binding of GO with nanoparticles in batch adsorption and the best fit using Langmuir and Freundlich isotherms is presented. Moreover, pesticide adsorption toward GO-nanoparticle composites is also evidenced.

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.

Lethal and sublethal effects of insecticides used in the management of Plutella xylostella (Lepidoptera: Plutellidae) on the predator Cycloneda sanguinea L. (Coleoptera: Coccinellidae)

BACKGROUND

The application of synthetic insecticides is the main strategy used to reduce the damage caused by the diamondback moth Plutella xylostella in commercial Brassica crops. However, incorrect insecticide use can cause biological and ecological disturbances in agroecosystems. Cycloneda sanguinea is a generalist voracious predator and is distributed widely in cultivated and noncultivated ecosystems. This study investigated the efficiency of four insecticides for the control of P. xylostella and the lethal and sublethal effects of these insecticides on C. sanguinea.

RESULTS

Spinosad (92% mortality) and chlorfenapyr (76% mortality) were highly toxic to P. xylostela. However, chlorantraniliprole (10% mortality) and methomyl (no mortality) were ineffective against this pest. Chlorantraniliprole was the only insecticide that was highly toxic to C. sanguinea by contact (90% mortality), however, it was nontoxic following the ingestion of chlorantraniliprole-contaminated aphids. Interestingly, ingestion of prey contaminated with methomyl and chlorfenapyr was highly toxic (100% mortality) to C. sanguinea. Spinosad was nontoxic to C. sanguinea via exposure to contaminated surfaces and following ingestion of contaminated prey. However, direct contact of the insects with both methomyl and spinosad significantly affected C. sanguinea flight activity (vertical flight and free-fall flight), whereas chlorfenapyr impacted vertical flight only.

CONCLUSION

These findings showed that chlorantraniliprole was not only ineffective for the control of P. xylostela, but was also highly toxic to C. sanguinea. The results indicated that spinosad was efficient against P. xylostela and was of low toxicity to C. sanguinea; however, the deleterious effects of this insecticide on flight behavior could result in reduced predatory efficiency. © 2022 Society of Chemical Industry.

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.

Behavioral, Histological, and Physiological Evaluation of the Effect of Imidacloprid on the Spider Misumenops maculissparsus

The aim of the present study was to evaluate the effects of the neonicotinoid insecticide imidacloprid (commercial formulation) on juveniles of the spider Misumenops maculissparsus (Keyserling, 1891). We first analyzed whether spiders recognized the presence of the insecticide on surfaces and in drinking water (in the form of droplets). Next, we investigated if the insecticide generated histologic, physiologic, and/or biochemical alterations. We observed that spiders do not detect the insecticide on a surface (e.g., paper) or in the form of droplets. After the imidacloprid ingestion by droplet intake, most spiders exhibited a paralysis that reverted after 48 h. Consequently, we observed histopathologic damage (i.e., pigment accumulation, necrosis, and cuticle detachment), and an increased catalase (CAT) activity and total-protein concentration in the individuals treated. The activities of glutathione-S-transferase, glutathione peroxidase, glutathione reductase, and superoxide dismutase, however, did not undergo significant variations. The results obtained emphasize the need to consider different classes of biomarkers, such as CAT and other proteins, to identify and evaluate the histologic, biologic, and biochemical effects of imidacloprid, one of the most widely used insecticides. Environ Toxicol Chem 2022;41:2152-2161. © 2022 SETAC.

Impacts of Winter Annual Cover Crops and Neonicotinoid Seed Treatments on Arthropod Diversity in Mississippi Soybean

Winter annual cover crops can be planted before soybean in Mississippi for many agronomic reasons. Incorporating winter annual cover crops into soybean production changes the seasonal hosts within fields. Some studies suggest that reducing tillage and using diverse species of cover crops can increase arthropod diversity and predator activity. Neonicotinoid seed treatments are often implemented to combat early season insect pests in soybean that follow cover crops, but negative effects on the environment such as reductions in biodiversity are often attributed to these compounds. We conducted an experiment to measure the effects on the diversity of the soybean epigeal and foliar communities when incorporating cover crops as well as insecticidal seed treatments into Mississippi soybean growing systems. Our results showed that legume cover crops had significant impacts on the epigeal community diversity of soybean planted behind them. These cover crops, especially hairy vetch, supported a more diverse foliar community before termination. To prevent increases in herbivorous arthropods, neonicotinoid seed treatments can be used without affecting epigeal predators such as beetles, ants, and spiders. The neonicotinoid seed treatments affected arthropod diversity, but the reductions were mainly caused by decreases in herbivorous pest insects that fed on treated soybean plants.

Side effects of insecticides applied to cotton on adult Trichogramma pretiosum by three exposure routes

BACKGROUND

Trichogramma pretiosum Riley (Hymenoptera: Trichogrammatidae) is released in extensive areas cultivated with cotton worldwide, but the use of synthetic insecticides threatens the establishment of augmented populations. Thus, an assessment of insecticides' effects on T. pretiosum is required to establish their compatibility with mass releases of the parasitoid. We studied in the laboratory the impact of insecticides administered through different exposure routes (direct-spraying, ingestion and residue contact) on T. pretiosum. Based on their toxicity, the insecticides were rated into four categories (harmless, slightly harmful, moderately harmful and harmful) as per the International Organization for Biological Control.

RESULTS

The survival, parasitism ability and emergence of the treated adults and offspring (F₁ and F₂ ), in addition to the persistence of the toxic effects in semi-field conditions, were assessed. Teflubenzuron did not reduce female survival and caused a lesser impact on T. pretiosum on both direct-spraying and ingestion bioassays. In the residue contact bioassay, teflubenzuron and flupyradifurone were rated as harmless and slightly harmful, respectively. The other active substances (chlorfenapyr, thiodicarb and methomyl) were harmful to the parasitoid by all exposure routes and were persistent (with toxicity duration surpassing 30 days).

CONCLUSION

From these findings, teflubenzuron is the insecticide most compatible with T. pretiosum releases and should be preferred over the other active substances. Further studies with the harmful insecticides (thiodicarb, chlorfenapyr and methomyl) are required to determine their toxicity under field conditions and confirm their incompatibility with T. pretiosum releases.

Floral Resources Enhance Fecundity, but Not Flight Activity, in a Specialized Aphid Predator, Hippodamia convergens (Coleoptera: Coccinellidae)

Adult aphid predators disperse across the landscape seasonally in search of prey aggregations that are patchily distributed and temporally variable. However, flight is energetically costly and consumes resources that could be invested in reproduction. Hippodamia convergens is an important aphid predator in North American cereal crops and other agricultural systems. Consumption of floral resources can enhance adult survival during periods of low prey availability and may improve reproductive success. We tested how an omnivorous adult diet containing floral resources (diluted honey and pulverized bee pollen) interacts with body size to influence reproduction and flight behavior compared to a prey-only diet. Two sizes of beetles were produced by controlling larval access to food—3 h daily access produced small beetles; ad libitum access produced large beetles with faster development. Reproductive performance was tracked for 18 days, and female flight activity was assayed via 3 h bouts of tethered flight. Diet composition and body size interacted to influence preoviposition period, with large females in prey-only treatments delaying oviposition the longest. The omnivorous adult diet improved 18-day fecundity relative to a prey-only diet, but egg fertility was unaffected. Adult size affected oviposition pattern, with small beetles laying smaller, but more numerous, clutches. Females flew up to 7 km in 6 h, but neither body size nor adult diet influenced flight distance, suggesting that all diet treatments generated energy reserves sufficient to power flights of short duration. However, pre-reproductive females flew &gt; 60% further than they did post-reproduction, likely due to the energetic costs of oviposition. Thus, access to pollen and nectar increased reproductive success and altered oviposition patterns in H. convergens, indicating the importance of floral resources in the agricultural landscape to conservation of this predator and its biological control services.

Toxicity, Sublethal and Low Dose Effects of Imidacloprid and Deltamethrin on the Aphidophagous Predator Ceratomegilla undecimnotata (Coleoptera: Coccinellidae)

Simple Summary

Chemical insecticides are used to control agricultural pests all over the world. However, extensive use of chemical insecticides can be harmful to human health and negatively impact the environment and biological control agents. We studied the toxicity and sublethal effects of imidacloprid and deltamethrin on the aphidophagous coccinellid predator Ceratomegilla undecimnotata (Coleoptera: Coccinellidae). We evaluated one low (LD₃₀) and one sublethal dose (LD₁₀) for both insecticides. Lethal and sublethal effects of both insecticides negatively affected survival, development, reproduction, and longevity, and reduced the intrinsic (r) and finite (λ) rate of increase and the net reproduction rate (R₀) of treated populations compared to the control. Our findings indicate that the use of imidacloprid and deltamethrin in combination with C. undecimnotata in the context of IPM should be taken with caution due to the toxic effects of the chemicals in the biocontrol agent under laboratory conditions.

Abstract

Ceratomegilla undecimnotata (Coleoptera: Coccinellidae) is a common aphidophagous coccinellid predator used in biological control against aphid pests. Knowing toxicity, lethal, and sublethal effects of insecticides on natural enemies is essential in order to incorporate them into Integrated Pest Management (IPM). In the present study, the lethal and sublethal effects of imidacloprid and deltamethrin were evaluated on the fourth instar larvae of C. undecimnotata and subsequently on the full life cycle. Our results strongly suggest that sublethal and low doses of imidacloprid and deltamethrin at LD₁₀ and LD₃₀ affected fourth instar larvae duration time, adult preoviposition period, total preoviposition period, and fecundity. Moreover, the intrinsic (r) and finite (λ) rate of increase and the net reproduction rate (R₀) significantly decreased in populations treated with imidacloprid compared to the control population. The data clearly suggest that imidacloprid and deltamethrin have a negative influence on population growth parameters of C. undecimnotata at sublethal and low doses and, therefore, these insecticides should be used with caution within the context of IPM.

Exposure Route Affects the Toxicity Class of Thiamethoxam for the Predatory Bug, Orius albidipennis (Hemiptera: Anthocoridae) by Changing Its Fitness

In many cases, pesticides' side effects on natural enemies have closely related to their exposure route. We assessed long-term lethal and sublethal effects of thiamethoxam (TMX) on the predatory bug, Orius albidipennis (Reuter), fed on Aphis gossypii Glover (Hemiptera: Aphididae), through three exposure routes. First-instar nymphs were treated with the maximum field recommended concentration (MFRC), ½ MFRC, and ¼ MFRC of TMX for 24 h. Based on the results, the soil-application treatment (bottom-up effect: plant-aphid-predator) led to the lowest survival reduction. In contrast, leaf-dip (residual contact) and aphid-dip (oral exposure route) treatments decreased the survival severely. While the soil-application treatment had no significant effect on adult longevity and egg production, all tested concentrations of TMX in the leaf-dip and aphid-dip treatments negatively affected both traits. The egg hatchability was not affected by the insecticide in all exposure routes. Among all treatments, ¼ MFRC of TMX in the residual contact and oral treatments shortened the egg incubation period compared to control, but others failed to affect it. Finally, based on the criteria provided by the International Organization for Biological and Integrated Control (IOBC) regarding toxicity classification, systemic (soil) application of TMX was harmless for this predator. However, it was moderately harmful and harmful (depending on concentration) to the predator through the residual contact and oral exposures, even at ¼ MFRC. Given our results, the soil-application of TMX is compatible with O. albidipennis, and it can improve conservation approaches of the predator in the integrated management of A. gossypii.

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.

Imidacloprid-mediated stress on non-Bt and Bt cotton, aphid and ladybug interaction: Approaches based on insect behaviour, fluorescence, dark respiration and plant electrophysiology

Plants and insects are parts of a complex system that involves interactions among many trophic levels, and it is important to understand the nature of such interactions. In the complex of interactions involving aphids and transgenic cotton expressing Bacillus thuringiensis, both the spraying of neonicotinoids and the occurrence of predatory coccinellids are common. However, there are gaps regarding the knowledge about possible impacts of neonicotinoids on physiological variables of the host plant and behavioural traits of the aphid (Aphis gossypii) and predator (Cycloneda sanguinea). Therefore, this study aimed to highlight the photosynthetic and electrical responses of the plant to the stress caused by the aphid attack combined with the stress generated by the use of imidacloprid in Bt and non-Bt cotton (Gossypium hirsutum L.) cultivars and to evaluate how this stress can influence the behavioural ecology of the predator and prey. Chlorophyll a fluorescence tests, dark respiration and electrophysiology on non-Bt and Bt cotton were carried out, the behaviour of the prey and predator was also evaluated with a video capture system. Our research is a study model that generates insights about possible impacts when using Imidacloprid without the occurrence of the pest on the plant, because the exposure of non-Bt and Bt cotton plants and the predator to imidacloprid unnecessarily, may result in stress on the physiology of the cotton plants and on the behaviour of the predator.

Detrimental sublethal effects hamper the effective use of natural and chemical pesticides in combination with a key natural enemy of Bemisia tabaci on tomato

BACKGROUND

Bemisia tabaci (Hemiptera: Aleyrodidae) represents one of the greatest threats to agricultural crops. Chemical control is the primary tool used in integrated pest management (IPM) programs. However, release of the predator Nesidiocoris tenuis (Hemiptera: Miridae) on tomato plants is a highly recommended control tactic. The objective of this study was to evaluate the efficacy of a commercial borax plus citrus oil (BCO) product against B. tabaci in the presence and absence of N. tenuis. The synthetic insecticide lambda-cyhalothrin was used as a positive control. We also evaluated the sublethal effects of BCO on the behavior and predation rate of N. tenuis.

RESULTS

Our results demonstrated that BCO, alone and at its maximum recommended field rate for B. tabaci, was not effective in controlling the pest under laboratory conditions. Application of BCO simultaneous with N. tenuis release did not reduce the increase in the B. tabaci population. Effective control of B. tabaci was achieved using only N. tenuis. However, synthetic lambda-cyhalothrin pyrethroid, used here as a control, caused high pest mortality and led to on-site extinction of N. tenuis, which did not occur for insects exposed to BCO. Lambda-cyhalothrin and BCO significantly affected the foraging behavior of N. tenuis, reducing the predation rate, especially following exposure to lambda-cyhalothrin.

CONCLUSION

The insecticide lambda-cyhalothrin achieved satisfactory results in suppressing B. tabaci, but was harmful to N. tenuis. Additionally, lambda-cyhalothrin and BCO affected predator behavior. © 2020 Society of Chemical Industry.

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.

Can contamination by major systemic insecticides affect the voracity of the harlequin ladybird?

Systemic neurotoxic insecticides are widely used to control aphid pests worldwide and their potential non-target effects on aphid predators are often unknown. Behavioral responses linked to biological control services are crucial when assessing the compatibility of chemicals with biocontrol organisms. This is particularly relevant for insecticides at low and sublethal concentrations. We studied the acute toxicity and the sublethal effect on the voracity of the generalist predator Harmonia axyridis (Coleoptera: Coccinellidae) caused by the exposure to three systemic insecticides routinely used against aphids. The tested insecticide concentrations were the Lethal Concentration 50% (LC₅₀), 20% (LC₂₀) and 1% (LC₁) estimated for the target pest Aphis gossypii (Hemiptera: Aphididae) in a companion study. The survival and the voracity differed among the tested chemicals and concentrations, but only thiamethoxam at LC₅₀ caused a significant predator mortality, and individuals that survived showed a reduced predation rate. The predators showed a density independent functional response after the exposure to most of the insecticide-concentration combinations, while an inverse density dependence of the prey consumption rate was observed for coccinellids exposed to sulfoxaflor and thiamethoxam at their lowest tested concentration. The estimated parameters, i.e., the attack rate and the prey handling time, were affected at higher concentrations by both imidacloprid and sulfoxaflor. These findings stress the importance of carefully evaluating side effects of insecticides at very low concentrations on beneficial arthropods in the risk assessment schemes for sustainable pest control programmes.

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.

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.

Disentangling the ecotoxicological selectivity of clove essential oil against aphids and non-target ladybeetles

The plant-based biopesticides have been proposed as insect pest control tools that seem to be safer for the environment and human health when compared to synthetic conventional molecules. However, such assumptions are generally made without considering the absence of detrimental effects on sublethally-exposed non-target organisms or showing the physiological basis of the selective action of such botanical products. Thus, by using in silico-based and in vivo toxicological approaches, the present investigation aimed to disentangle the ecotoxicological selectivity of clove, Syzygium aromaticum, essential oil against the aphid Rhopalosiphum maidis and the non-target ladybeetle, Coleomegilla maculata. We also investigated whether the sublethal exposure to clove essential oil would affect the locomotory and predatory abilities of C. maculata. We found that the clove essential oil concentration estimated to kill 95% (LC₉₅: 0.17 μL/cm²) of the aphids was lethal to <18% of C. maculata. Indeed, our in silico results reinforced such differential susceptibility, as it predicted that eugenol and β-caryophyllene (i.e., the clove essential oil major components) bound to three potential molecular targets (i.e., transient receptor potential (TRP) channels, octopamine, and gamma-aminobutyric acid (GABA) receptors) of the aphids but only to the octopamine receptors of the ladybeetles. Additionally, the ladybeetles that were exposure to the clove essential oil exhibited unaffected abilities to locomote and to prey upon R. maidis aphids when compared to unexposed ladybeetles. Thus, by displaying lower toxicity against the ladybeetles, the clove essential oil represents a safer alternative tool to be integrated into programs aiming to manage aphid infestations.

Target and non-target impact of systemic insecticides on a polyphagous aphid pest and its parasitoid

Systemic insecticides are used to control agricultural pests globally and their non-target impact at non-lethal doses on beneficial arthropods has been recognized. We assessed the baseline toxicity of imidacloprid, thiamethoxam and sulfoxaflor-based insecticides on the polyphagous aphid pest, Aphis gossypii (Hemiptera: Aphididae), and their non-target effects on its main parasitoid, Aphidius colemani (Hymenoptera: Braconidae), evaluated by residual contact exposure to the median lethal (LC₅₀), the low lethal (LC₂₀) and the sublethal (LC₁) concentrations of the three tested insecticides, earlier estimated for the target pest. The results showed that the LC₅₀s for the aphid were 6.4 × 10^-3, 5 × 10^-3, 2.9 × 10^-2 times lower compared to the label concentrations of imidacloprid, thiamethoxam and sulfoxaflor, respectively. LC₅₀ of thiamethoxam caused the highest mortality rate on the parasitoid followed by sulfoxaflor, while imidacloprid had the lowest impact. No significant sublethal effects on reprodution were observed for A. colemani survived to the insecticide exposure. Our findings highlight the importance of case-specific evaluation to optimize pesticide applications in Integrated Pest Management packages taking into account the ecological services provided by biological control agents.

Impact of Imidacloprid Soil Drenching on Survival, Longevity, and Reproduction of the Zoophytophagous Predator Podisus maculiventris (Hemiptera: Pentatomidae: Asopinae)

Systemic insecticides when applied as seed treatments or soil drenches are often more toxicologically selective for natural enemies than target pests. This may not be the case, however, for omnivorous predators, which are at risk of extended exposure to systemically applied pesticides through ingestion while feeding on treated plants for nutrients or water. Such exposure may kill or have sublethal consequences for these natural enemies, compromising their role as biocontrol agents of agricultural pest species. The spined soldier bug, Podisus maculiventris (Say) (Hemiptera: Pentatomidae: Asopinae), is an important zoophytophagous biocontrol agent (i.e., able to substitute zoophagy by phytophagy for survival) that may be exposed to systemic insecticides in many agricultural systems. We, therefore, examined effects on P. maculiventris following exposure to cabbage plants subject to soil-drench treatments with imidacloprid, a systemic neonicotinoid insecticide. Predator survival, development, body weight, and reproduction were recorded. Imidacloprid significantly affected nymph survival and adult emergence, but not duration of the nymphal period or adult body weight. At one-twentieth the recommended field rate for whitefly and aphid management, imidacloprid treatments reduced longevity, fecundity, and fertility of female predators. These findings demonstrate that soil treatments with systemic insecticide can negatively impact zoophytophagous natural enemies.

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.

De Novo Transcriptome Sequencing of Serangium japonicum (Coleoptera: Coccinellidae) and Application of Two Assembled Unigenes

The ladybird beetle Serangium japonicum is an important predator of whiteflies. Investigations of the molecular mechanisms of this predatory beetle have been hindered by the scarcity of gene sequence data. To obtain gene sequences for the ladybird beetle and determine differences in gene expression between the summer and winter seasons, paired-end sequencing was performed. Real-time PCR was used to validate differences in Krueppel homolog 1 gene (Kr-h1) mRNA expression in summer vs. winter samples. To determined the diversity of the population, annotated cytochrome c oxidase subunit I gene (COX1) gene fragments were amplified from several ladybird beetle populations. The analysis yielded 191,246 assembled unigenes, 127,016 of which (66.4%) were annotated. These functional annotations of gene sequences are currently available from the National Center for Biotechnology Information (NCBI), and will provide a basis for studying the molecular mechanisms underlying the biological characteristics of S. japonicum We found a change in expression of ribosome-associated genes across seasons, and postulate that this change is because of seasonal variation in temperature and photoperiod. The differential expression of Kr-h1 suggests that S. japonicum can successfully overwinter because the adults enter diapause. To explain the effects of season on Kr-h1 gene expression, we hypothesize a model in which that a short photoperiod affects the density of Ca²⁺, the subsequent activity of methyl farnesoate epoxidase and the synthesis of JH, and in turn Kr-h1 gene expression. COX1 annotation was concordant with the morphological ID. The same COX1 sequence was found in the samples from several provinces in China. Therefore, the COX1 sequence is worth further study to distinguish beetle species and populations.

Histopathological and cytotoxic changes induced by spinosad on midgut cells of the non-target predator Podisus nigrispinus Dallas (Heteroptera: Pentatomidae)

Broad-spectrum insecticides used in pest control are a risk for non-target insects. Their compatibility to the insecticide spinosad, used in agriculture and forestry as a biological control tool, needs to be evaluated. Podisus nigrispinus Dallas (Heteroptera: Pentatomidae) is a predatory bug used in the pest management of agricultural and forest systems where spinosad is also frequently applied. The aim of this study was to evaluate the toxicity, histopathology and cytotoxicity in midgut cells of P. nigrispinus exposed to spinosad. The toxicity test was performed to determine the lethal concentrations of spinosad after exposure by ingestion. The histopathology and cytotoxicity caused by spinosad were analyzed in the three midgut regions (anterior, middle and posterior) of P. nigrispinus during different exposure periods. Spinosad, at low concentrations, was toxic to P. nigrispinus [LC₅₀ = 3.15 (3.02-3.26) μg.L^-1]. Cell degeneration features such as cytoplasm vacuolization, chromatin condensation and release of cell fragments to the midgut lumen were observed in this organ. Cell death via apoptosis was found in the three midgut regions of this predator after exposure to the insecticide. Spinosad is toxic to P. nigrispinus, and causes histological and cytological damage followed by cell death in the midgut, suggesting a dangerous effect on a beneficial non-target insect.

Essential oil from Negramina (Siparuna guianensis) plants controls aphids without impairing survival and predatory abilities of non-target ladybeetles

Plant essential oils are regarded as interesting alternative tools to be integrated into the management of pest insects. However, as they generally consist of mixtures of numerous molecules, the physiological basis for their action is unresolved. Here, we evaluated the effects of essential oil of the Neotropical plant Siparuna guianensis Aubl., commonly known as Negramina, against an important pest insect: the green peach aphid Myzus persicae (Sulzer), and also in two non-target natural enemies: the ladybeetle predators Coleomegilla maculata (DeGeer) and Eriopis connexa (Germar). In addition, we conducted a computational docking analysis for predicting the physical interactions between the two Negramina essential oil major constituents: β-myrcene and 2-undocanone, and the transient receptor potential (TRP) channels as potential binding receptors in the aphid and ladybeetles. As the most important results, Negramina essential oil caused mortality in M. persicae aphids with an LC₉₅ = 1.08 mg/cm², and also significantly repelled the aphids at concentrations as low as 0.14 mg/cm². Our computational docking analysis reinforced such selectivity actions as the Negramina essential oil major compounds (i.e., β-myrcene and 2-undocanone) bound to the TRP channels of M. persicae but not to ladybeetle-related TRP channels. Interestingly, the exposure to the Negramina essential oil did not affect the predatory abilities of C. maculata but increased the abilities of E. connexa to prey upon M. persicae. Collectively, our findings provided a physiological basis for the insecticidal and selectivity potential of Negramina essential oil, reinforcing its potential as a tool to be used in integrated pest control programs.

Predation on Diamondback Moth Larvae and Aphid by Resistant and Susceptible Lady Beetle, Eriopis connexa

A successful pest control requires both chemical and biological agents for most commercially grown crops. However, insecticide resistance is increasing worldwide. Cabbage, a widely grown Brassicaceae, hosts the most resistant insect pest to insecticides, the diamondback moth (DBM), Plutella xylostella L. However, insecticide-resistant populations Eriopis connexa (Germar), a lady beetle often found controlling aphids and other soft-bodied pest species sharing brassica fields with DBM. Thus, as a model for integration of insecticide and biological control methods, we evaluated predation by pyrethroid-resistant and pyrethroid-susceptible lady beetles on DBM larvae offered alone and in the presence of a preferred prey, the aphid Lipaphis pseudobrassicae (Davis). During 24-h exposure, resistant and susceptible E. connexa consumed an average of 9.8 and 6.0 second-instar instar DBM larvae, respectively. Resistant beetles showed no significant preferences for prey consumption between untreated and deltamethrin-treated leaf surfaces, at field-recommended rate. As a function of DBM availability, resistant beetles exhibited similar predation on treated and untreated arena and higher predation than susceptible beetles in a treated arena. In greenhouse cages, resistant and susceptible beetles exhibited similar survival after 10 days on cabbage treated with deltamethrin and promoted the reduction of DBM to 5.0% and 5.6%, respectively. Both populations fed on a mixed diet of aphids and DBM larvae even under high availability of the preferred aphid prey. Resistant E. connexa survives deltamethrin exposure and do not alter their predatory behavior in response to this insecticide-treated environment.

Prey contaminated with neonicotinoids induces feeding deterrent behavior of a common farmland spider

Neonicotinoids are thought to have negligible repellent or anti-feeding effects. Based on our preliminary observations, we hypothesized that the contamination of spider prey with commonly used neonicotinoids has repellent or feeding deterrent effects on spiders. We tested this hypothesis by providing prey treated or not with field-realistic concentrations of neonicotinoids to the spiders and determining the number of (a) killed only and (b) killed and eaten prey. We exposed adult freshly molted and starved Pardosa agrestis, a common agrobiont lycosid species, to flies treated with neonicotinoids (acetamiprid, imidacloprid, thiacloprid and thiamethoxam) at field-realistic concentrations or with distilled water as a control. There were no effects of the exposure of the prey to neonicotinoids on the number of flies captured. However, the spiders consumed less of the prey treated with neonicotinoids compared to the ratio of control prey consumed, which resulted in increased overkilling (i.e., killing without feeding). In female P. agrestis, the overkilling increased from only 2.6% of control flies to 25–45% of neonicotinoid-treated flies. As the spiders avoided consuming the already captured neonicotinoid-treated prey, the sublethal effects of neonicotinoids extend beyond the simple attractivity/deterrence of the prey itself. The present study demonstrated that prey overkilling serves as a physiological response of spiders to the contact with the prey contaminated with agrochemicals. We speculate that primary contact with neonicotinoids during prey capture may play a role in this unexpected behavior.

Impact of insect growth regulators on biology and behavior of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae)

This study investigated the effects of four insect growth regulators (IGRs) on biology and behavior of Chrysoperla carnea. IGRs were sprayed on eggs, larvae (~24-h old), and pupae at recommended doses along with their relatively low and high dose. Eggs, larval, and pupal survival were assessed along with effects on fecundity and fertility of C. carnea adults emerged when pupae were treated. IOBC (International Organization for Biological and Integrated Control) proposed toxicity scale was used to categorize the IGRs. Concerning the eggs lufenuron, pyriproxyfen, and diflubenzuron were categorized as slightly harmful (class 2), whereas buprofezin was categorized as moderately harmful (class 3). Lufenuron and diflubenzuron were classified as slightly harmful (class 2) to C. carnea larvae, while pyriproxyfen and buprofezin were categorized as harmless (class 1). Buprofezin did not affect the locomotion behavior of the larvae as time proportion spent in the treated and untreated zone was equal, while all others were affected significantly. Regarding the pupae, pyriproxyfen and buprofezin were found slightly harmful (class 2) and moderately harmful (class 3), respectively, and considerably reduced fecundity and fertility of the C. carnea adults. Lufenuron and diflubenzuron did not affect significantly when pupae were treated. Based on combined effect, the IGRs lufenuron and diflubenzuron did nott influence the significantly on population parameters comparatively. This could be helpful for the use of IGRs in integration with C. carnea towards their conservation in agroecosystem.

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.

Contact application of neonicotinoids suppresses the predation rate in different densities of prey and induces paralysis of common farmland spiders

Neonicotinoids are very effective in controlling crop pests but have adverse effects on predators and pollinators. Spiders are less sensitive to neonicotinoids compared to insects because of the different structure of their acetylcholine receptors, the binding targets of neonicotinoids. We tested whether short-term exposure to neonicotinoids affected the predation rate in different densities of prey of spiders and led to their paralysis or eventual death. To examine these effects, we topically exposed dominant epigeic, epiphytic and sheet-weaving farmland spiders to four widely used neonicotinoids (imidacloprid, thiamethoxam, acetamiprid and thiacloprid). We applied the neonicotinoids at concentrations recommended by the manufacturers for spray application under field conditions. Short-term exposure to the formulations of all four tested neonicotinoids had adverse effects on the predation rate of spiders, with imidacloprid (Confidor) associated with the most severe effects on the predation rate and exhibiting partial acute lethality after one hour (15–32%). Acetamiprid also displayed strong sublethal effects, particularly when applied dorsally to Philodromus cespitum. Day-long exposure to dorsally applied acetamiprid or thiacloprid led to paralysis or death of multiple Linyphiidae spp., with the effects particularly prominent in males. To conclude, we provided multiple lines of evidence that short-term exposure to neonicotinoids, which were applied at recommended field concentrations, caused severe health effects or death in multiple families of spiders. Even acetamiprid caused strong effects, despite being subject to less strict regulations in the European Union, compared with those for imidacloprid because of claims of its negligible off-target toxicity.

Effects of clothianidin-treated seed on the arthropod community in a mid-Atlantic no-till corn agroecosystem

BACKGROUND

Nearly all corn seed in the US is coated with neonicotinoid insecticides to protect against soil and foliar arthropod pests. Exposure in the soil and the systemic activity in the plant can pose non-target risks. We assessed the community-level effects of clothianidin-treated seed on the diversity and abundance of arthropod communities in a no-till corn agroecosystem over a single growing season.

RESULTS

Epigeal and foliage-dwelling communities were disturbed by the clothianidin seed treatment, with significant negative and positive changes in taxa abundances. Clothianidin reduced the abundance of minute pirate bugs by 66.2%, lady beetles by 44.7%, ants by 43.4%, ground beetle adults and larvae by 31.7%, and rove beetles by 44.1% during the early corn growth stages. Herbivores, particularly thrips, were more negatively affected by clothianidin than other trophic groups. In contrast, some groups, such as collembolans and leafhoppers, exhibited significantly higher abundances in the seed treated plots.

CONCLUSION

Clothianidin primarily influenced arthropod communities during the 4 weeks following planting, with disruptions to major natural enemy taxa, but communities showed trends toward recovery at the later corn stages. While the insecticide suppressed multiple herbivores, none were economically damaging to corn; thus, the pest suppression benefits of clothianidin observed in this study did not justify the non-target impacts. © 2018 Society of Chemical Industry.