Chronic Effects of an Insect Growth Regulator (teflubenzuron) on the Life Cycle and Population Growth Rate of Folsomia candida.

Current standard toxicity tests on nontarget soil invertebrates mainly focus on the endpoints survival and reproduction. Such results are likely insufficient to predict effects at higher organizational levels, for example, the population level. We assessed the effects of exposure to the pesticide teflubenzuron on the collembolan Folsomia candida, by performing a full life-cycle experiment exposing single individuals via contaminated food (uncontaminated control and 0.2, 0.32, 0.48, 0.72, 1.08, and 1.6 mg/kg dry yeast). Several life-history traits were considered by following the growth and development of newly hatched individuals over a period of 65 days. We assessed survival, body length, time to first oviposition, cumulative egg production, and hatchability of eggs. A two-stage model was applied to calculate the population growth rate (λ) combined with elasticity analysis to reveal the relative sensitivity of λ to the effects of teflubenzuron on each life-history parameter. Body length was the least sensitive life-history parameter (median effective concentration = 1.10 mg teflubenzuron/kg dry yeast) followed by time to first oviposition (0.96 mg/kg), survival (median lethal concentration = 0.87 mg/kg), cumulative egg production (0.32 mg/kg), and egg hatchability (0.27 mg/kg). Population growth decreased with increasing concentrations of teflubenzuron (λ = 1.162/day in control to 1.005/day in 0.72 mg/kg dry yeast, with populations going extinct at 1.08 and 1.6 mg/kg dry yeast). Elasticity analysis showed that changes in juvenile survival had a greater impact on the population growth rate compared with the other life-history traits. Our study provides a comprehensive overview of individual-level effects of long-term exposure to teflubenzuron and integrates these effects to assess the potential risk to collembolan populations. Environ Toxicol Chem 2024;43:1173-1183. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Toxicological effects of trace amounts of pyriproxyfen on the midgut of non-target insect silkworm.

Pyriproxyfen is an insect growth regulator that is widely used in public health and pest control in agriculture. Our previous studies have shown that trace amounts of pyriproxyfen in the environment can cause serious toxic effects in the non-target insect silkworm, including failing to pupate, metamorphose and spin cocoons. However, it is unknown why pyriproxyfen not only has no lethal effects on fifth instar larvae but also tend to increase their body weight. The midgut is the main digestive organs of the silkworm, our results showed that the residual of pyriproxyfen in the silkworm at 24 h after 1 × 10-4 mg/L pyriproxyfen treatment caused severe damage to the midgut microvilli, goblet cells, and nuclei of the silkworm, but body weight and digestibility of the larval were both increased. In addition, pyriproxyfen significantly (p < 0.05) increased the activities of digestive enzymes (α-amylase, trehalase, trypsin and lipase) in the midgut of silkworm. However, it caused down-regulation of ecdysone synthesis-related genes at the end of the fifth instar silkworm, decreased ecdysone titer, and prolonged larval instar. At the same time, pyriproxyfen also activated transcription of detoxification enzymes-related genes such as the cytochrome P450 enzyme genes Cyp9a22 and Cyp15C1, the carboxylesterase genes CarE-8 and CarE-11, and the glutathione S-transferase gene GSTo2. This study elucidated a novel toxicological effect of pyriproxyfen to insects, which not only expands the understanding of the effects of juvenile hormone pesticides on lepidopteran insects but also provides a reference for exploring the ecological security of non-target organisms.

Modulation of ecdysteroid and juvenile hormone signaling pathways by bisphenol analogues and polystyrene beads in the brackish water flea Diaphanosoma celebensis.

Owing to its high production and world-wide usage, plastic pollution is an increasing concern in marine environments. Plastic is decomposed into nano- and micro-sized debris, which negative affect reproduction and development in aquatic organisms. Bisphenol A (BPA), an additive of plastic, is released into the water column upon plastic degradation, and is known as a representative endocrine-disrupting chemical. However, the reproductive effects of plastics and bisphenols at the molecular level have not yet been explored in small marine crustaceans. In this study, we investigated the effects of polystyrene (PS) beads (0.05, 0.5, and 6 - µm) and bisphenol analogues (BPs; BPA, BPS, and BPF) on reproduction and development of small marine crustaceans. Effects on transcriptional changes in ecdysteroid and juvenile hormone (JH) signaling pathway-related genes were examined in the brackish water flea Diaphanosoma celebensis exposed to PS beads and BPs for 48 h. As results, BPs and PS beads delayed emergence time of first offspring, and increased fecundity in a concentration-dependent manner. BPs differentially modulated the expression of ecdysteroid and JH signaling pathway-related genes, indicating that BP analogs can disrupt endocrine systems via mechanisms different from those of BPA. PS beads was also changed the gene expression of both pathway, depending on their size and concentration. Our findings suggest that BP analogues and PS beads disrupt the endocrine system by modulating the hormonal pathways, affecting reproduction negatively. This study provides a better understanding of the molecular mode of action of BPs and PS beads in the reproduction of small crustaceans.

Toxicity and biochemical impact of methoxyfenozide/spinetoram mixture on susceptible and methoxyfenozide-selected strains of Spodoptera littoralis (Lepidoptera: Noctuidae).

Methoxyfenozide (M) is one of the selective insecticides used in integrated pest management (IPM) programs for lepidopteran pests. However, recent studies reported a development of M-resistance, which prompted us to look for alternatives. Here, we investigate the potency of a mixture of M with spinetoram (Sp) on M-resistant insects. In the laboratory, a selection pressure with M has carried out on Spodoptera littoralis (Lepidoptera: Noctuidae) strains. A dipping technique was used to evaluate the toxicity of a sublethal concentration of M and Sp. on S. littoralis larvae, and the same concentrations were used to assess the toxic impact of their combination on susceptible (SUS) and M-selected (MS) strains. The toxicity of M/Sp mixtures was computed using a combination index equation, and a potentiation effect was observed in the two tested strains. Synergism tests revealed that piperonyl butoxide had considerable synergistic effects on M toxicity in the MS strain. The results revealed that the M/Sp mixture's negative effect on both monooxygenases and esterases is most likely the cause of its potentiation effect on the SUS and MS strains. It was concluded that M/Sp mixtures are effective against M-resistant S. littoralis strains, so these can be used in IPM programs.

Insecticide resistance in Australian Spodoptera frugiperda (J.E. Smith) and development of testing procedures for resistance surveillance.

Spodoptera frugiperda (J.E. Smith) is a highly invasive noctuid pest first reported in northern Australia during early 2020. To document current status of resistance in S. frugiperda in Australia, insecticide toxicity was tested in field populations collected during the first year of establishment, between March 2020 and March 2021. Dose-response was measured by larval bioassay in 11 populations of S. frugiperda and a susceptible laboratory strain of Helicoverpa armigera. Emamectin benzoate was the most efficacious insecticide (LC50 0.023µg/ml) followed by chlorantraniliprole (LC50 0.055µg/ml), spinetoram (LC50 0.098µg/ml), spinosad (LC50 0.526µg/ml), and methoxyfenozide (1.413µg/ml). Indoxacarb was the least toxic selective insecticide on S. frugiperda (LC50 3.789µg/ml). Emamectin benzoate, chlorantraniliprole and methoxyfenozide were 2- to 7-fold less toxic on S. frugiperda compared with H. armigera while spinosyns were equally toxic on both species. Indoxacarb was 28-fold less toxic on S. frugiperda compared with H. armigera. There was decreased sensitivity to Group 1 insecticides and synthetic pyrethroids in S. frugiperda compared with H. armigera: toxicity was reduced up to 11-fold for methomyl, 56 to 199-fold for cyhalothrin, and 44 to 132-fold for alpha cypermethrin. Synergism bioassays with metabolic inhibitors suggest involvement of mixed function oxidase in pyrethroid resistance. Recommended diagnostic doses for emamectin benzoate, chlorantraniliprole, spinetoram, spinosad, methoxyfenozide and indoxacarb are 0.19, 1.0, 0.75, 6, 12 and 48µg/µl, respectively.

Juvenile hormone synthesis and signaling disruption triggering male offspring induction and population decline in cladocerans (water flea): Review and adverse outcome pathway development.

Juvenile hormone (JH) are a family of multifunctional hormones regulating larval development, molting, metamorphosis, reproduction, and phenotypic plasticity in arthropods. Based on its importance in arthropod life histories, many insect growth regulators (IGRs) mimicking JH have been designed to control harmful insects in agriculture and aquaculture. These JH analogs (JHAs) may also pose hazards to nontarget species by causing unexpected endocrine-disrupting (ED) effects such as molting and metamorphosis defects, larval lethality, and disruption of the sexual identity. This critical review summarizes the current knowledge of the JH-mediated effects in the freshwater cladoceran crustaceans such as Daphnia species on JHA-triggered endocrine disruptive outputs to establish a systematic understanding of JHA effects. Based on the current knowledge, adverse outcome pathways (AOPs) addressing the JHA-mediated ED effects in cladoceran leading to male offspring production and subsequent population decline were developed. The weight of evidence (WoE) of AOPs was assessed according to established guidelines. The review and AOP development aim to present the current scientific understanding of the JH pathway and provide a robust reference for the development of tiered testing strategies and new risk assessment approaches for JHAs in future ecotoxicological research and regulatory processes.

Juvenile hormone and transcriptional changes in honey bee worker larvae when exposed to sublethal concentrations of thiamethoxam.

Thiamethoxam, an insecticide with high usage and large amounts of environmental residues, has been reported to affect the pupation and survival of honey bee larvae at sublethal concentrations. The molecular mechanisms are not fully understood. In this study, we measured the response of juvenile hormone (JH) to environmental concentrations of thiamethoxam using liquid chromatography-tandem mass spectrometry (LC-MS/MS), monitored the dynamic changes in the transcription of genes encoding major JH metabolic enzymes (CYP15A1, FAMET, JHAMT and JHE) using RT-qPCR, and analysed the transcriptome changes in worker larvae under thiamethoxam stress using RNA-seq. Thiamethoxam significantly increased the levels of JH3 in honey bee larvae, but no significant changes in the transcript levels of the four major metabolic enzymes were observed. Thiamethoxam exposure resulted in 140 differentially expressed genes (DEGs). P450 CYP6AS5 was upregulated, and some ion-related, odourant-related and gustatory receptors for sugar taste genes were altered significantly. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that amino acid metabolism and protein digestion and absorption were influenced by thiamethoxam. These changes may do harm to honey bee caste differentiation, foraging behaviour related to sensory perception and nutrient levels of bee colonies. These results represent the first assessment of the effects of thiamethoxam on JH in honey bee larvae and provides a new perspective and molecular basis for the study of JH regulation and thiamethoxam toxicity to honey bees.

Efficacy of biorational insecticides against Bemisia tabaci (Genn.) and their selectivity for its parasitoid Encarsia formosa Gahan on Bt cotton.

The toxicity of seven biorational insecticides [five insect growth regulators (Buprofezin, Fenoxycarb, Pyriproxyfen, Methoxyfenozide, and Tebufenozide) and two oil-extracts of neem and bitter gourd seeds] against Bemisia tabaci and their selectivity for its parasitoid, Encarsia formosa were evaluated in laboratory and field conditions for 2 years (2018-2019) in Pakistan. Toxicity results demonstrate that Pyriproxyfen, Buprofezin, and Fenoxycarb proved to be effective (80-91% mortality and 66.3-84.2% population-reduction) against B. tabaci followed by Methoxyfenozide, Tebufenozide (50-75% mortality and 47.8-52.4% population-reduction), and then oil-extracts of neem and bitter gourd (25-50% mortality and 36.5-39.8% population-reduction) in the laboratory [72 h post-application exposure interval (PAEI)] and field trails (168 h PAEI), respectively. All tested biorationals, except Methoxyfenozide [(slightly-harmful/Class-II), i.e., causing mortality of parasitoids between a range of 25-50%] and Tebufenozide [(moderately-harmful/Class-III), i.e., causing mortality of parasitoids between the ranges of 51-75%], proved harmless/Class-I biorationals at PAEI of 7-days in the field (parasitism-reduction < 25%) and 3-days in the lab (effect < 30%). In laboratory bioassays, exposure of parasitized-pseudopupae and adult-parasitoids to neem and bitter gourd oils demonstrated that these compounds proved harmless/Class-I biorationals (< 30% mortality). Alternatively, Pyriproxyfen, Buprofezin, Fenoxycarb, Methoxyfenozide, and Tebufenozide were slightly-harmful biorationals (30-79% mortality) against the respective stages of E. formosa. We conclude that most of the tested biorationals proved harmless or slightly harmful to E. formosa, except tebufenozide after PAEI of 7-days (168 h) in the field and, therefore, may be used strategically in Integrated Pest Management (IPM) of B. tabaci.

Evaluation and comparison of the effects of three insect growth regulators on honey bee queen oviposition and egg eclosion.

Honey bees (Apis mellifera) are highly valued pollinators that help to ensure national food security in the United States, but reports of heavy annual losses to managed colonies have caused concerns and prompted investigations into the causes of colony losses. One factor that can negatively affect honey bee health and survival is agrochemical exposure. Investigations into the sublethal effects of agrochemicals on important metrics of colony health such as reproduction and queen fecundity has been limited by the availability of targeted methods to study honey bee queens. This work investigates the effects of three insect growth regulators (IGR), a class of agrochemicals known to target pathways involved in insect reproduction, on honey bee queen oviposition, egg hatching, and worker hypopharyngeal development in order to quantify their effects on the fecundity of mated queens. The reported results demonstrate that none of the IGRs affected oviposition, but all three affected egg eclosion. Worker bees consuming methoxyfenozide had significantly larger hypopharyngeal glands at two weeks of age than bees not fed this compound. The results suggest that although IGRs may not exhibit direct toxic effects on adult honey bees, they can affect larval eclosion from eggs and the physiology of workers, which may contribute to colony population declines over time.

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.

Mosquitocidal Chips Containing the Insect Growth Regulator Pyriproxyfen for Control of Aedes aegypti (Diptera: Culicidae).

Aedes aegypti were exposed to water treated with mosquitocidal chips containing the insecticide pyriproxyfen in a polymer formulation. Chips were tested under different conditions; different water volumes, in containers made of different material, and in water with different levels of organic matter. Treated chips caused 100% mortality of Ae. aegypti during their pupal stage independent of size or type of container, and the mount of organic matter contained in the water to which the mosquito larvae were exposed. When mosquitocidal chips were used in >25% of the oviposition containers within their cages, there was a significant control of the mosquito populations. Mosquitocidal chips worked in different environments, caused significant mosquito population decreases, and were effective in controlling Ae. aegypti.

Exposure to sublethal concentrations of methoxyfenozide disrupts honey bee colony activity and thermoregulation.

Methoxyfenozide is an insect growth regulator (IGR) commonly used in agriculture to simultaneously control pests and preserve beneficial insect populations; however, its impact on honey bees in not fully understood. We conducted field and laboratory experiments to investigate bee health in response to field-relevant concentrations of this pesticide. Significant effects were observed in honey bee colony flight activity and thermoregulation after being exposed over 9 weeks to supplemental protein patty containing methoxyfenozide. Compared to bee colonies in the control group, colonies fed pollen patty with 200 ppb methoxyfenozide (as measured by residue analysis) had: 1) a significantly reduced rate of weight loss due to forager departure in the morning; and 2) higher temperature variability during the winter. Colonies in the 100 ppb (as measured by residue analysis) treatment group had values between the 200 ppb group and control for both response variables. The dusk break point, which is the time associated with the end of forager return, differed among all treatment groups but may have been confounded with direction the hives were facing. Bee colony metrics of adult bee mass and brood surface area, and measurements of bee head weight, newly-emerged bee weight, and hypopharyngeal gland size were not significantly affected by methoxyfenozide exposure, suggesting that there may be significant effects on honey bee colony behavior and health in the field that are difficult to detect using standard methods for assessing bee colonies and individuals. The second experiment was continued into the following spring, using the same treatment groups as in the fall. Fewer differences were observed among groups in the spring than the fall, possibly because of abundant spring forage and consequent reduced treatment patty consumption. Residue analyses showed that: 1) observed methoxyfenozide concentrations in treatment patty were about 18-60% lower than the calculated concentrations; 2) no residues were observed in wax in any treatment; and 3) methoxyfenozide was detected in bee bread only in the 200 ppb treatment group, at about 1-2.5% of the observed patty concentration.

Effects of insect growth-regulator insecticides on the immature stages of Harmonia axyridis (Coleoptera: Coccinellidae).

Harmonia axyridis is an important biological control predator in greenhouses and agricultural fields, and it plays a significant role in the integrated pest management (IPM) of several arthropod pests. We studied the effects of eight insect growth-regulator insecticides (IGRs) on immature stages of H. axyridis by residual toxicity (eggs and pupae) and contact toxicity (larvae) to evaluate the risk of using these IGRs in IPM systems. Diflubenzuron, hexaflumuron and lufenuron caused more than 80% mortality to H. axyridis eggs, larvae and pupae, respectively. Pyriproxyfen was also highly harmful to larvae and pupae of H. axyridis. In contrast, methoxyfenozide and buprofezin caused little mortality and were classified as slightly harmful to immature stages based on a reduction coefficient. In addition to mortality and developmental time, the fecundity, fertility and deformed eggs of offspring were affected, when the predators were exposed to IGRs. Benzoylphenylurea insecticides significantly reduced H. axyridis female fecundity and fertility and increased the number of deformed eggs. The adverse effects are closely connected with the developmental stages of the predators and types and methods of insecticides exposed. All IGRs affected, to some extent, the life-table parameters of H. axyridis when the insecticides applied on immature stages at the highest field rates. Tebufenozide, diflubenzuron, hexaflumuron and lufenuron significantly reduced the Ro, T, r and λ of beetles exposed to the insecticides. The results indicate that IGRs could disturb the population growth and biocontrol activities of H. axyridis when applied at the highest field label rates. Additional studies should be conducted to assess the effects of IGRs on H. axyridis under field conditions before incorporating them in IPM strategies.

The Effects of the Insect Growth Regulators Methoxyfenozide and Pyriproxyfen and the Acaricide Bifenazate on Honey Bee (Hymenoptera: Apidae) Forager Survival.

The honey bee (Apis mellifera L. (Hymenoptera: Apidae)) contributes an essential role in the U.S. economy by pollinating major agricultural crops including almond, which depends entirely on honey bee pollination for successful nut set. Almond orchards are often treated with pesticides to control a variety of pests and pathogens, particularly during bloom. While the effects to honey bee health of some insecticides, particularly neonicotinoids, have received attention recently, the impact of other types of insecticides on honey bee health is less clear. In this study, we examined the effects to honey bee forager survival of three non-neonicotinoid pesticides widely used during the 2014 California almond bloom. We collected foragers from a local apiary and exposed them to three pesticides at the label dose, or at doses ranging from 0.5 to 3 times the label dose rate. The selected pesticides included the insect growth regulators methoxyfenozide and pyriproxyfen, and the acaricide bifenazate. We simulated field exposure of honey bees to these pesticides during aerial application in almond orchards by using a wind tunnel and atomizer set up with a wind speed of 2.9 m/s. Experimental groups consisting of 30-40 foragers each were exposed to either untreated controls or pesticide-laden treatments and were monitored every 24 hr over a 10-d period. Our results revealed a significant negative effect of all pesticides tested on forager survival. Therefore, we suggest increased caution in the application of these pesticides in almond orchards or any agricultural crop during bloom to avoid colony health problems.

Oral and dermal diflubenzuron exposure causes a hypothalamic-pituitary-thyroid (HPT) axis disturbance in the Mongolian racerunner (Eremias argus).

Diflubenzuron (DFB) is a potential endocrine-disrupting chemical. However, its thyroid endocrine effect on reptiles has not been reported. In this study, immature lizards (Eremias argus) were exposed to 20 mg kg-1 DFB once a week for 42 days through oral or dermal routes. Their body weight, plasma thyroid hormone levels, thyroid gland histology and the transcription of hypothalamic-pituitary-thyroid (HPT) axis-related genes in different tissues were assessed to explore the effects of DFB on the HPT axis of lizards. The body weight decreased significantly only after the dermal exposure to DFB. Triiodothyronine (T3) to thyroxine (T4) ratio in the male plasma also significantly increased after the dermal exposure. After oral exposure, the activity of thyroid gland was positively related to the thyroid hormone levels. Furthermore, the alterations in thyroid hormone levels affected the HPT axis-related gene expression, which was tissue dependent and sexually selected. The thyroid hormone receptor genes (trα and trß) in the brain and thyroid were more sensitive to oral exposure. However, only the dermal treatment affected the trα, trß and type 2 deiodinase (dio2) genes in the male liver. These results suggest that DFB exposure caused sex-specific changes in the thyroid function of lizards, and the dermal treatment may be an important route for the risk assessment of reptiles.

Cyromazine resistance in a field strain of house flies, Musca domestica L.: Resistance risk assessment and bio-chemical mechanism.

Developing resistance management strategies for eco-friendly insecticides is essential for the management of insect pests without harming the environment. Cyromazine is a biorational insecticide with very low mammalian toxicity. Resistance to cyromazine has recently been reported in house flies from Punjab, Pakistan. In order to propose a resistance management strategy for cyromazine, experiments were planned to study risk for resistance development, possibility of cross-resistance and bio-chemical mechanisms. A field strain of house flies with 8.78 fold resistance ratio (RR) to cyromazine was re-selected under laboratory conditions. After seven rounds of selection (G1-G7), the RR values rapidly increased from 8.8 to 211 fold. However, these values declined to 81fold when the cyromazine selected (CYR-SEL) strain was reared without selection pressure, suggesting an unstable nature of resistance. The CYR-SEL strain showed lack of cross-resistance to pyriproxyfen, diflubenzuron, and methoxyfenozide. Synergism bioassays using enzyme inhibitors: piperonyl butoxide (PBO) and S,S,S-tributylphosphorotrithioate (DEF), and metabolic enzyme analyses revealed increased activity of carboxylesterase (CarE) and mixed-function oxidase (MFO) in the CYR-SEL strain compared to the laboratory susceptible (Lab-susceptible) strain, suggesting the metabolic resistance mechanism responsible for cyromazine resistance in the CYR-SEL strain. In conclusion, risk of rapid development of cyromazine resistance under consistent selection pressure discourages the sole reliance on cyromazine for controlling house flies in the field. The unstable nature of cyromazine resistance provides window for restoring cyromazine susceptibility by uplifting selection pressure in the field. Moreover, lack of cross-resistance between cyromazine and pyriproxyfen, diflubenzuron, or methoxyfenozide in the CYR-SEL strain suggest that cyromazine could be rotated with these insecticides whenever resistance crisis occur in the field.

Susceptibility of Ceraeochrysa cubana larvae and adults to six insect growth-regulator insecticides.

The impacts of six insect growth-regulators were assessed on the predator Ceraeochrysa cubana (Hagen) larvae and adults. Our results showed that diflubenzuron, lufenuron and pyriproxyfen caused 100% larva mortality, whereas buprofezin, methoxyfenozide and tebufenozide were similar to control treatment. In comparison to the control, buprofezin prolonged the duration of larval stage, while methoxyfenozide and tebufenozide reduced the predator larva development time. Buprofezin, methoxyfenozide and tebufenozide did not affect the C. cubana duration and survival of pupal stage, fecundity and fertility. However, methoxyfenozide and tebufenozide reduced predator female and male longevities. Based on a reduction coefficient, diflubenzuron, lufenuron and pyriproxyfen were highly harmful to first instar larvae, while buprofezin, methoxyfenozide and tebufenozide were considered slightly harmful to the predator. Estimating the life table parameters, our results showed that buprofezin, methoxyfenozide and tebufenozide reduced the C. cubana Ro, r and λ. In comparison to the control, buprofezin prolonged the T and methoxyfenozide and tebufenozide shortened the predator T. In adults, our results showed that the insecticides did not cause significant mortality, but diflubenzuron, lufenuron and pyriproxyfen reduced the C. cubana fecundity and longevity. Diflubenzuron and lufenuron also reduced the C. cubana fertility. Based on a reduction coefficient, diflubenzuron and lufenuron were highly harmful to C. cubana adults, while pyriproxyfen was slightly harmful and buprofezin, methoxyfenozide and tebufenozide were considered harmless to the predator. Therefore, insect growth-regulators affect the C. cubana biological or populational parameters, and they can harm the integrated pest management programs that aim the predator conservation and/or augmentation in agroecosystems.

Impact of insect growth regulators on the predator Ceraeochrysa cincta (Schneider) (Neuroptera: Chrysopidae).

The generalist predator Ceraeochrysa cincta (Schneider) (Neuroptera: Chrysopidae) is an important biological control agent of several arthropod pests in different agroecosystems. This study assessed the lethal and sublethal effects of six insect growth regulators sprayed on first-instar larvae of C. cincta. Lufenuron and diflubenzuron were highly harmful to first-instar larvae of C. cincta, causing 100 % of mortality before they reached the second instar. Buprofezin caused ~25 % mortality of the larvae and considerably reduced the fecundity and longevity of the insects, but substantially increased the proportion of females in the surviving population of C. cincta. Methoxyfenozide and tebufenozide did not affect the duration and survival of the immature stages, but methoxyfenozide significantly reduced the fecundity and longevity of the insects. Pyriproxyfen reduced the survival of the larval stage by 19.5 %, but did not affect the development, survival and reproduction of the surviving individuals. Based on reduction coefficient, the insecticides diflubenzuron and lufenuron were considered harmful to C. cincta, whereas buprofezin and methoxyfenozide were slightly harmful and tebufenozide and pyriproxyfen were harmless. The estimation of life-table parameters indicated that buprofezin and methoxyfenozide significantly reduced the R o , r and λ of C. cincta, whereas pyriproxyfen and tebufenozide caused no adverse effect on population parameters, indicating that these insecticides could be suitable for use in pest management programs towards the conservation and population increase of the predator in agroecosystems. However, more studies should be conducted to evaluate the compatibility of these insecticides with the predator C. cincta under semi-field and field conditions.

In vitro and in vivo evaluations of the P-glycoprotein-mediated efflux of dibenzoylhydrazines.

P-glycoprotein (P-gp) is a member of the ATP-binding cassette transporter family. It actively transports a wide variety of compounds out of cells to protect humans from xenobiotics. Thus, determining whether chemicals are substrates and/or inhibitors of P-gp is important in risk assessments of pharmacokinetic interactions among chemicals because P-gp-mediated transport processes play a significant role in their absorption and disposition. We previously reported that dibenzoylhydrazines (DBHs) such as tebufenozide and methoxyfenozide (agrochemicals) stimulated P-gp ATPase activity. However, it currently remains unclear whether these derivatives are transport substrates of P-gp and inhibit transport of other chemicals by P-gp. In the present study, in order to evaluate the interactions of DBHs with other chemicals in humans, we determined whether DBHs are P-gp transport substrates using both the in vitro bidirectional transport assay and the in vivo study of rats. In the in vivo study, we investigated the influence of P-gp inhibitors on the brain to plasma ratio of methoxyfenozide in rats. We also examined the inhibitory effects of DBHs on quinidine (a P-gp substrate) transport by P-gp in order to ascertain whether these derivatives are inhibitors of P-gp. Based on the results, DBHs were concluded to be weak P-gp transport substrates and moderate P-gp inhibitors. However, the risk of DBHs caused by interaction with other chemicals including drugs was considered to be low by considering the DBHs' potential as the substrates and inhibitors of P-gp as well as their plasma concentrations as long as DBHs are properly used.

Effects of an insect growth regulator and a solvent on honeybee (Apis mellifera L.) brood development and queen viability.

Honeybee toxicology is complex because effects on individual bees are modulated by social interactions between colony members. In the present study, we applied high doses of the insect growth regulator fenoxycarb to honeybee colonies to elucidate a possible interplay of individually- and colony-mediated effects regarding honey bee toxicology. Additionally, possible effects of the solvent dimethyl sulfoxide (DMSO) were assessed. We conducted studies on egg hatching and brood development to assess brood care by nurse bees as well as queen viability. Egg hatching was determined by the eclosion rate of larvae from eggs originating from colonies (i) treated with sugar syrup only, (ii) treated with sugar syrup containing DMSO and (iii) treated with sugar syrup containing fenoxycarb (dissolved in DMSO). To evaluate brood development, combs with freshly laid eggs were reciprocally transferred between colonies, and development of brood was examined in the recipient hive. Brood reared inside DMSO- and fenoxycarb-treated colonies as well as brood from DMSO- and from fenoxycarb-exposed queens showed higher mortality than brood not exposed to the chemicals. No differences were found in egg hatching among the treatments, but there was a higher variability of eclosion rates after queens were exposed to fenoxycarb. We also observed queen loss and absconding of whole colonies. Based on our results we infer that fenoxycarb has queen- as well as nurse bee-mediated effects on brood quality and development which can lead to the queen's death. There also is an effect of DMSO on the nurse bees' performance that could disturb the colony's equilibrium, at least for a delimited timespan.