Residue dynamics and dietary risk assessment of new formulation of novaluron and lambda cyhalothrin on tomato.

Presence of residues on food commodities is major bottleneck of insecticide use under good agricultural practices (GAPs). The use of less persistent with two different mode of action insecticide is novel approach of getting maximum insect control without developing insecticide resistance. Novaluron, an insect growth disruptor and lambda cyhalothrin, a nerve poison has been used widely for the management of lepidopteran pests. Dissipation and consumer risk analysis studies were carried out on a new combination product of novaluron and lambda cyhalothrin are used for control insects of tomato at recommended standard dose of 71 + 14 g/ha and double dose of 142 + 28 g/ha of active ingredients. Extraction and cleanup of sample residues was done using QuEChERS technique and analyzed in GC-ECD. The residues of novaluron were dissipated within 10 to 15 days, and the residues of lambda cyhalothrin were at 7 to 10 days, both at the standard and double the standard dose, following a first order reaction kinetics. Analysis of risk and hazard quotient revealed that the test insecticides do not pose any dietary risk to consumer as TMDI < MPI and HQ < 1.

Identification and functional characterisation of N-acetylglucosamine kinase from Helicoverpa armigera divulge its potential role in growth and development via UDP-GlcNAc salvage pathway.

N-acetylglucosamine kinase (NAGK), a major enzyme of sugar-kinase/Hsp70/actin superfamily, catalyses the conversion of N-acetylglucosamine to N-acetylglucosamine-6-phosphate, the first step leading to the salvage synthesis of uridine diphosphate N-acetylglucosamine. Here, we present the first report on identification, cloning, recombinant expression and functional characterisation of NAGK from Helicoverpa armigera (HaNAGK). The purified soluble HaNAGK exhibited a molecular mass of ∼39 kDa with monomeric conformation. It catalysed the sequential transformation of GlcNAc into UDP-GlcNAc, indicating its role as the initiator of UDP-GlcNAc salvage pathway. HaNAGK exhibited ubiquitous expressions across all the developmental stages and major tissues of H. armigera. The gene was significantly upregulated (80 %; p < 0.01) by the moulting hormone 20-hydroxyecdysone and significantly downregulated (89 %; p < 0.001) by the chitin synthesis inhibitor novaluron, indicating its involvement in ecdysis and chitin metabolism. Furthermore, RNAi of HaNAGK caused poor weight gain, deformed insect bodies, aberrant metamorphosis and pronounced wing abnormalities in >55 % of surviving adults, while recording 7.79 ± 1.52 % and 24.25 ± 7.21 % mortality during larval and pupal stages, respectively. Altogether, the present findings suggest that HaNAGK plays a crucial role in the growth and development of H. armigera and thus, could be considered as a compelling gene of interest while formulating novel pest management strategies.

Effects of three chitin synthesis inhibitors on egg masses, nymphs and adults of Halyomorpha halys (Hemiptera: Pentatomidae).

BACKGROUND: Halyomorpha halys, (brown marmorated stink bug, BMSB), is a high-concern invasive species causing severe damage to orchards in many countries outside its native Asian range. Management methods other than frequent sprays of broad-spectrum insecticides are needed to restore integrated pest management (IPM) practices in orchards. Chitin synthesis inhibitors are usually regarded as desirable options in IPM programs because of lower toxicity to beneficial insects and non-target organisms compared to neurotoxic insecticides. In this study, the activity of three chitin synthesis inhibitors (namely buprofezin, novaluron and triflumuron) was investigated on BMSB egg masses, third instars and adults by means of laboratory bioassays. RESULTS: Novaluron and to a lesser extent triflumuron were detrimental to BMSB nymphs exposed to residues on potted peach plants. Novaluron caused high mortality among early instars that emerged from sprayed egg masses. No significant differences were found between buprofezin and water control on eggs or third instars. When sprayed on BMSB adults, none of the chitin synthesis inhibitors affected survival, fecundity, or egg hatching. CONCLUSION: Given the activity on nymphs, but the lack of effects on adults, novaluron and triflumuron might be considered for field applications only as a tool in a wider management strategy along with other methods aimed at preventing the invasion of crops by BMSB adults. © 2023 Society of Chemical Industry.

Persistence and dissipation kinetics of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC insecticides in tomato crop under semi-arid region.

In recent decades, fate studies of pesticides have been a topic of interest worldwide due to human health concerns tomato, contain abundant nutritional phytochemicals and lycopene which is known for antioxidant. Tomato is susceptible to many pest, so to overcome from these pests many insecticides are used, leaving residual effects on the crop. So to find out the persistence, the present study was carried out to investigate the residual levels and dissipation behaviour of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC in tomato crop during Rabi session of 2017-18 in randomized block design. The first spray of insecticide was done at fruit formation stage and second spray at 10-day interval at recommended dose @43.31 g a.i. ha-1 and double of recommended dose @86.62 g a.i. ha-1. The residue of novaluron determined by HPLC (high-performance liquid chromatography) on 0 day (two hours after spraying) was 0.154 ppm at lower dose and 0.234 ppm at higher dose. The residue of lambda-cyhalothrin determined by GC ECD (gas chromatography electron capture detector) at 0 day (two hours after spraying) was 0.451 ppm at lower dose and 0.849 ppm at higher dose. The deposition of novaluron 9.45% + lambda-cyhalothrin 1.9% ZC was gradually decreased with increasing days after spraying (DAS). The mean initial deposition of the pesticide novaluron and lambda-cyhalothrin was recorded as 0.154 mg/kg, 0.451 mg/kg, respectively, at the recommended dose @43.31 g a.i. ha-1 while at double of recommended dose @86.62 g a.i. ha-1 novaluron and lambda-cyhalothrin, the mean initial deposition of 0.234 mg/kg and 0.849 mg/kg was recorded, respectively. The residue of the novaluron and lambda-cyhalothrin was at BDL (below determination level) (0.01 and 0.05 ppm) on 5th and 7th day, respectively, at lower dose (x), whereas at higher dose (2x) it was below determination level on 7th and 10th day, respectively. In soil samples, the residue levels were at below the determination level (0.01 mg/kg) for novaluron and (0.05 mg/kg) for lambda-cyhalothrin at both doses. The half-life DT50 of novaluron and lambda-cyhalothrin in the tomato fruit was found to be 2 days at recommended dose (X) @43.31 g a.i. ha-1 for both the pesticide and at double of the recommended dose @86.62 g a.i. ha-1 it was 3 and 2 days, respectively.

Susceptibility status of major malaria vectors to novaluron, an insect growth regulator South-Eastern Tanzania.

Introduction: application of Insect Growth Regulator (IGR) such as pyriproxyfen has shown a promising result in controlling malaria transmitting mosquitoes through autodissemination technique. Novaluron that inhibits the chitin development at mosquito larval stage present a promising candidate IGR for rotation with pyriproxyfen to prevent a chance of resistance development. This study assessed the susceptibility of immature stages of Anopheles arabiensis, Anopheles gambiae and Anopheles funestus to novaluron. Methods: susceptibility bioassays using technical grade novaluron (98% active ingredient) were performed inside the semi-field system using first instar larvae of Anopheles species. For each tested species, a total of 1500 larvae were used in the bioassay. Concentration range of 0.01 mg/l to 2 mg/l of novaluron were tested to establish Lethal Concentration (LC) sufficient to kills 50%, 90% and 99% of the exposed larvae by using log-dose response analysis. Results: of the tested mosquitoes, Anopheles gambiae were highly susceptible to novaluron followed by An. Arabiensis and then An. funestus. Lethal concentrations, LC50, LC90 and LC99 (95%CI) in mg/l for An. gambiae were 0.018, 0.332 and 2.001 respectively. For An. arabiensis were 0.026, 0.546 and 2.013; and for An. funestus were 0.032, 1.00 and 5.580. High larval mortality was recorded at high concentration (2mg/L), with 80% mortality within 3 days post exposure. Conclusion: the study demonstrates the efficacy of novaluron in controlling Anopheles mosquito species at immature stages via larval mortality. These findings warrant further testing of novaluron for autodissemination by different vector species for its inclusion in rotation to prevent development of resistance.

A Novel Enantioseparation Method and Enantioselective Dissipation of Novaluron in Tomatoes Using Ultrahigh-Performance Liquid Chromatography Tandem Mass Spectrometry via a Box-Behnken Design.

Enantioseparation parameters of novaluron were optimized on a Chiralpak IG-3 column by ultrahigh-performance liquid chromatography tandem mass spectrometry via response surface methodology. The absolute configuration and elution order were identified as R-(+)-novaluron and S-(-)-novaluron by polarimetry and X-ray diffraction. A modified QuEChERS method was developed for enantioselective determination of novaluron in eight food and environmental samples. Under optimal conditions, the mean recoveries of the novaluron enantiomers in the eight matrices were 74.4-108.1% with intraday relative standard deviations (RSDs) of 0.3-9.7% and interday RSDs of 0.1-4.1%. Enantioselective dissipation was observed in tomatoes. The dissipation of S-(-)-novaluron was faster than that of R-(+)-novaluron with a half-life of 7.1 and 7.9 days, and the enantiomer fraction value changed from 0.49 to 0.53 in 21 days. An effective method for monitoring novaluron enantiomer residues in food and the environment was established for the first time and had been successfully applied to real samples. This study is of great significance for strengthening the risk assessment and supervision level of chiral pesticides.

Review of the existing maximum residue levels for novaluron according to Article 12 of Regulation (EC) No 396/2005.

According to Article 12 of Regulation (EC) No 396/2005, EFSA has reviewed the maximum residue levels (MRLs) currently established at European level for the pesticide active substance. Although this active substance is not authorised within the European Union, MRLs were established by the Codex Alimentarius Commission (codex maximum residue limits; CXLs) and import tolerances were reported by Member States and the UK (including the supporting residues data). Considering that no toxicological reference values are currently established in Europe for novaluron because the peer review for the approval was terminated before an EFSA conclusion was issued, the toxicological profile of novaluron was also assessed, in order to be able to perform the consumer risk assessment in the framework of the art 12 MRL review. Based on the assessment of the available data, toxicological reference values were derived, and a consumer risk assessment was carried out for the existing CXLs and import tolerances. All CXLs and import tolerances were found to be supported by inadequate data and a possible chronic risk to consumers was identified. Hence, further consideration by risk managers is needed.

Insect growth regulators elicit transovarial effects on Teleonemia scrupulosa (Hemiptera: Tingidae).

BACKGROUND: Lantana lace bug, Teleonemia scrupulosa Stål (Hemiptera: Tingidae), is an important insect pest of lantana (Lantana camara L.). The adults and nymphs feed on the leaves, gradually deteriorating the quality of leaf tissue, as the affected leaves appear brown and desiccated. Infestations of T. scrupulosa reduce the market value of container plants in nurseries and the aesthetic value of ornamental landscapes. Because T. scrupulosa typically is managed using neonicotinoids and concerns related to the nontargeted effects of neonicotinoids on pollinators are mounting, practitioners are seeking alternative options to manage T. scrupulosa infestations. Insect growth regulators (IGRs) elicit transovarial activity, where adults exposed to IGRs produce nonviable eggs, but this effect has not been documented for T. scrupulosa. RESULTS: A significantly lower number of T. scrupulosa nymphs was produced when adults were sprayed topically with novaluron and pyriproxyfen than nontreated adults. The number of T. scrupulosa nymphs produced was not significantly different when adults were exposed to a lower dose (0.125×) and a maximum dose (1.0×) of novaluron. CONCLUSION: Novaluron and pyriproxyfen elicited transovarial effects on T. scrupulosa when adults were exposed to these IGRs. Evidence of transovarial effects was demonstrated when T. scrupulosa adults were exposed to lower doses (≤0.125×) than the maximum label dose, as densities of nymphs were similar between the lower doses and the maximum label dose of novaluron.

Novaluron Has Detrimental Effects on Sperm Functions.

Although novaluron is an insect growth regulator with a low mammalian acute toxicity and a low risk to the environment and nontarget organisms, toxic effects of novaluron have been reported. However, no studies have yet evaluated the effect of novaluron on reproduction. Therefore, we examined the effects of novaluron on sperm functions. The spermatozoa of ICR mice were incubated with various concentrations of novaluron to induce capacitation. Then, sperm motion parameters and capacitation status were evaluated using CASA program and H33258/chlortetracycline staining. In addition, PKA activity and tyrosine phosphorylation were evaluated by Western blotting. After exposure, various sperm motion parameters were significantly decreased in a dose-dependent manner. The acrosome reaction was also significantly decreased in the high concentration groups. Sperm viability was significantly reduced at the highest concentration. In addition, PKA activity and tyrosine phosphorylation were also significantly altered. Thus, novaluron affects sperm viability, sperm motility, and motion kinematics during capacitation. Furthermore, it may promote the reduction in acrosome reactions. The physiological suppression of sperm function may depend on abnormal tyrosine phosphorylation via the alteration of PKA activity. Therefore, we suggest that it is necessary to consider reproductive toxicity when using novaluron as a pesticide.

Dissipation kinetics and consumer risk assessment of novaluron + lambda-cyhalothrin co-formulation in cabbage.

Cabbage, one of the most popular vegetables in the world is infested by several insect-pests and diseases. Novaluron, a chitin synthesis inhibitor and lambda-cyhalothrin, a synthetic pyrethroid group insecticide are used to manage insect-pests on cabbage. The dissipation kinetics and risk assessment of combination formulation (novaluron 9.45% + lambda-cyhalothrin 1.9%) with different modes of action has not yet been investigated in cabbage. Multi-location supervised field trials were therefore, conducted in different agro-climatic regions of India for safety evaluation of the combination product. The co-formulation at the recommended (novaluron 750 g a.i. ha-1 + lambda-cyhalothrin 750 g a.i. ha-1) and double the recommended (novaluron 1500 g a.i. ha-1 + lambda-cyhalothrin 1500 g a.i. ha-1) dose was sprayed on the cabbage crop. The samples were extracted and cleaned up using a modified QuEChERS method, and the residues analyzed by GC-ECD and GC-MS. The half-life (t1/2) varied between 1.77 and 2.51 and 2.00-3.38 days for novaluron and 1.36-2.24 and 1.69-3.82 days for lambda-cyhalothrin in cabbage at respective doses. The Food Safety and Standards Authority of India (FSSAI) has set the MRL of 0.7 mg kg-1 for novaluron at PHI of 5 days, and no MRL is set for lambda-cyhalothrin in cabbage. On the basis of OECD MRL calculator, the MRLs of 0.6 and 1.5 mg kg-1 for novaluron and lambda-cyhalothrin, respectively were calculated at the respective doses at PHI of 3 days. Hazard quotient (HQ) <1, theoretical maximum daily intake (TMDI) < acceptable daily intake (ADI) and < maximum permissible intake (MPI), percent acute hazard index (% aHI) <1, and percent chronic hazard index (% cHI) <1 for both novaluron and lambda-cyhalothrin suggested that the combination formulation is safe and will not pose any dietary risk to the consumers. The study will be helpful to conduct risk assessment of other pesticides/combination pesticides on food crops on which their MRLs have not yet been fixed.

Effects of novaluron ingestion and topical application on German cockroach (Blattella germanica) development and reproduction.

BACKGROUND: Insect growth regulators disrupt insect development and reproduction. Chitin synthesis inhibitors (CSIs) allow the insect to grow normally, but because chitin is an essential component of the cuticle, formation of a new cuticle and ecdysis are prevented and the insect dies. CSIs can also kill embryos by disrupting their normal development. We evaluated the potential utility of novaluron in bait formulations against the German cockroach (Blattella germanica L.). RESULTS: The minimum novaluron intake that interfered with molting and reproduction was assessed by exposing nymphs and adult females to novaluron. Results showed that 1 day of feeding on 0.1% novaluron was sufficient to disrupt molting in nymphs and prevent adult females from developing viable oothecae. The long-term effects on gravid females were investigated by feeding females 0.1% novaluron for different 5-day intervals during successive stages of gestation. Results demonstrated that gravid females fed novaluron during any period of gestation were able to produce viable eggs. To determine if ingestion of novaluron affected mating success and fertility of adult males, males were fed novaluron and then allowed to mate with untreated virgin females. Males that fed on novaluron successfully mated, and the females produced viable oothecae. Finally, direct comparisons revealed that novaluron is equally effective by ingestion and topical application. CONCLUSIONS: Novaluron caused mortality in nymphs and interfered with ootheca production in adult females, but only before they formed an ootheca. It successfully reduced German cockroach populations in cages and has potential to be incorporated in cockroach baits.

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.

Novaluron prevents oogenesis and oviposition by inducing ultrastructural changes in ovarian tissue of young adult Lygus lineolaris.

BACKGROUND: The tarnished plant bug, Lygus lineolaris (Palisot de Beauvois), has emerged as a major pest of cotton, Gossypium hirsutum L, in the mid-southern USA. In the early 1990s L. lineolaris populations developed resistance to several classes of conventional insecticides, increasing the need for insecticides with alternative modes of action such as insect growth regulators (IGRs) for integrated pest management (IPM). The benzoylphenyl urea (BPU) class of IGRs acts by disrupting the growth and development of immature stages of insects, but little is known about its impact on adult stages. RESULTS: The effect of novaluron (Diamond™ 0.83EC), a BPU with known chitin synthesis inhibitor activity, was investigated on adult females of L. lineolaris. Treatment of 1-day-old adults with 600 ppm of novaluron in the diet prevented oviposition, while treatment of older females had no impact on oviposition. Oral novaluron exposure of adults of all ages reduced the viability of eggs laid. Novaluron treatment caused ultrastructural changes in the ovaries of 1-day-old adults (48 h post exposure), distorting the follicular epithelial cell architecture of developing oocytes. Additionally, novaluron treatment decreased the chitin content in ovarian tissue. CONCLUSION: Our results suggest that chitin or chitin-like components in the developing ovaries of adult L. lineolaris are a target of IGRs such as novaluron, but its activity is specific to a critical time during development. This enhances our understanding of the effects of BPUs on adult insects and could lead to incorporation of IGRs in IPM for controlling adult insect pest populations in the field. © 2020 Society of Chemical Industry.

Field-based evaluation of novaluron EC10 insect growth regulator, a chitin synthesis inhibitor against dengue vector breeding in leaf axils of pineapple plantations in Gampaha District, Sri Lanka.

BACKGROUND: Insect growth regulators (IGRs) are considered a novel group of insecticides to control mosquitoes. Novaluron is an IGR with benzoylphenyl urea insecticide, which inhibits chitin synthesis in insects and can reduce insect population density; it is also known to have a high margin of safety for mammals. METHODS: The effective minimum concentration of novaluron formulation EC10 was tested. Six pineapple plantations [control (n = 3) and test (n = 3)] were selected from Meerigama Medical Officer of Health area in Gampaha District, Sri Lanka. Fifteen plots (10 × 10 m) were demarcated in each site with a 200 m distance apart. Leaf axils of 450 pineapple plants (30 plants × 15 plots) were screened for immature stages of Aedes mosquitoes weekly for 12 weeks. The required concentration (20 ppm) of novaluron was sprayed onto the selected pineapple plants (n = 1350) individually in 3 selected test sites for 5-10 s. The reduction in the vector population was interpreted as the percentage of reduction in immature stages of Aedes mosquitoes. RESULTS: The 100% mortality of the Ae. aegypti larvae within 24 h was observed at 20 ppm (0.05 ml of novaluron 100 g/l in 250 ml of water) as the minimum dose. Variation in the number of Aedes larvae present in the control and intervention sites was found to be significantly different throughout the entire observational period (χ2 = 128.29, df = 11, P < 0.001). The total elimination of Aedes larvae continued for up to 2 weeks and a 50% reduction was observed until the 8th week. CONCLUSIONS: The present study emphasizes that novaluron (10% EC) can be used as an effective larvicide at the treatment dose of 20 ppm. The residual effect of the IGR lasted for 12 weeks with a functional efficacy of 8 weeks. The 100% reduction of larval breeding was observed up to the 2nd week after application and the percentage reduction of immature stages remained > 50% until the 8th week. The lowest reduction (34.2%) was observed at 12 weeks after the initial treatment. Therefore, re-treatment may be recommended based on the reduction in the efficacy of the IGR.

Ingestion of Novaluron Elicits Transovarial Activity in Stephanitis pyrioides (Hemiptera: Tingidae).

Azaleas (Rhododendron L. spp.) are widely grown ornamental plants in eastern and western regions of the USA. The azalea lace bug, Stephanitis pyrioides (Scott) (Hemiptera: Tingidae), is an important insect pest of azaleas. Adults and nymphs of S. pyrioides consume chlorophyll in azalea foliage, and severely affected plants appear bleached. Neonicotinoid insecticides are effective and widely used for S. pyrioides control; however, nursery growers and landscape professionals are concerned about nontarget effects on beneficial insects and demand neonicotinoid-free plants. There is clearly a need to develop reduced-risk control strategies for S. pyrioides. The insect growth regulator (IGR) novaluron elicits transovarial activity when adult S. pyrioides are exposed to it. However, it is not certain whether transovarial effects can be observed when S. pyrioides adults that colonize the abaxial leaf surface ingest novaluron residues deposited on the adaxial leaf surface. Experiments were conducted to assess transovarial activity upon exposure to various application rates of novaluron alone and novaluron with various adjuvants. The numbers of nymphs were significantly lower when the full rate of novaluron was applied on the adaxial surface of leaves compared to the number of nymphs on non-treated leaves. The densities of nymphs were not significantly different between the half and full rates of novaluron treatment. When novaluron with various adjuvants was applied to the adaxial surface of the leaves, the densities of nymphs were significantly lower under the novaluron treatments compared to the non-treated leaves, regardless of the type of adjuvant added. There was no significant difference between treatment with novaluron alone and the treatments of novaluron with adjuvants. These data show that transovarial activity was elicited in adults of S. pyrioides when novaluron was applied on the adaxial leaf surface.

Development-Disrupting Chitin Synthesis Inhibitor, Novaluron, Reprogramming the Chitin Degradation Mechanism of Red Palm Weevils.

Disruption in chitin regulation by using chitin synthesis inhibitor (novaluron) was investigated to gain insights into the biological activity of chitinase in red palm weevils, an invasive pest of date palms in the Middle East. Impact of novaluron against ninth instar red palm weevil larvae was examined by dose-mortality response bioassays, nutritional indices, and expression patterns of chitinase genes characterized in this study. Laboratory bioassays revealed dose-dependent mortality response of ninth-instar red palm weevil larvae with LD50 of 14.77 ppm of novaluron. Dietary growth analysis performed using different doses of novaluron (30, 25, 20, 15, 10, and 5 ppm) exhibited very high reduction in their indexes such as Efficacy of Conversion of Digested Food (82.38%) and Efficacy of Conversion of Ingested Food (74.27%), compared with control treatment. Transcriptomic analysis of red palm weevil larvae characterized numerous genes involved in chitin degradation including chitinase, chitinase-3-like protein 2, chitinase domain-containing protein 1, Endochitinase-like, chitinase 3, and chitin binding peritrophin-a domain. However, quantitative expression patterns of these genes in response to novaluron-fed larvae revealed tissue-specific time-dependent expression patterns. We recorded overexpression of all genes from mid-gut tissues. Growth retarding, chitin remodeling and larvicidal potential suggest novaluron as a promising alternate for Rhynchophorus ferrugineus management.

Influence of Insect Growth Regulators on Stephanitis pyrioides (Hemiptera: Tingidae) Eggs and Nymphs.

The azalea lace bug, Stephanitis pyrioides (Scott) (Hemiptera: Tingidae), is an important insect pest of azaleas (Rhododendron L. spp.) in the USA. Stephanitis pyrioides feeds on azalea foliage and causes extensive chlorosis, which reduces the aesthetic value and marketability of these plants. Because the use of neonicotinoid insecticides has been dramatically reduced or discontinued, growers and landscape managers are seeking alternative tools or strategies to control this insect. Although insect growth regulators (IGRs) are known for their activity against immature insect stages, their activity against egg hatching has not been addressed thoroughly, specifically against S. pyrioides. Thus, a series of experiments was conducted to understand the ovicidal activity of IGRs using novaluron, azadirachtin, pyriproxyfen, and buprofezin against S. pyrioides. The number of newly emerged young instars was significantly lower when leaves implanted with eggs were sprayed on both sides with novaluron, azadirachtin, and buprofezin compared to nontreated and pyriproxyfen treatments. When IGRs plus adjuvant were applied to the adaxial surface of the leaves, the densities of the newly emerged nymphs were significantly lower under the novaluron treatment compared to the nontreated leaves. However, there was no significant difference in the number of nymphs that emerged in the absence of adjuvant. Furthermore, close monitoring revealed reduced levels of egg hatching in the presence of adjuvant with novaluron compared to its absence. The data show that the survival of S. pyrioides first instars was not affected by exposure to dried IGR residues.

Negative impact of Novaluron on the nontarget insect Bombyx mori (Lepidoptera: Bombycidae).

Due to increased use of agrochemicals and growing concerns about ecotoxicology, the development of new insecticides, moving away from those with neurotoxic and broad spectrum effects towards insecticides that are safer for the environment and nontarget beneficial species, has been a research priority. Novaluron stands out among these newer insecticides, is an insect growth regulator that is used for the control of insect pests in crops grown close to mulberry plantations. Mulberry serves as food for the silkworm Bombyx mori, which is a nontarget insect of great economic importance to silk production. We investigated the lethal and sublethal effects of Novaluron on the development of B. mori. Larvae were segregated into experimental groups: the control groups (CGs) and the treatment groups (TGs), which were treated with the Novaluron concentration of 0.15 mL/L. Following exposure, we analyzed: larval mortality, changes in the insect life cicle and cytotoxic effects on the midgut cells. This is the first report about the Novaluron's effects on B.mori. We detected rupture in the integument, complete cessation of feeding, late development, incomplete ecdysis and production of defective cocoons. After 240 h of exposure, there was 100% mortality in TG larvae exposed in the 3rd instar and 20% mortality from larvae exposed in the 5th instar. Cytotoxic effects was observed, such as dilation of cells, emission of cytoplasmic protrusions, extreme rarefaction of the cytoplasm and nuclei, dilation of the endoplasmic reticulum in addition to changes in mitochondria, the presence of large digestive vacuoles and intercellular spaces and the presence of active caspase. Novaluron exposure impairs the midgut and may affect the physiological functions of this organ. Novaluron additionally compromises several phases of insect development, indicating the importance of toxicology studies that utilize different life stages of nontarget species to evaluate the safe use of insecticides.

Transovarial effects of insect growth regulators on Stephanitis pyrioides (Hemiptera: Tingidae).

BACKGROUND: Azalea lace bug, Stephanitis pyrioides (Scott) (Hemiptera: Tingidae) is a serious insect pest of azaleas (Rhododendron L. spp.) in the USA. S. pyrioides feeding causes chlorosis, which affects the aesthetic value and marketability of azalea plants. Management of S. pyrioides primarily involves neonicotinoid insecticides and their use has been drastically reduced or discontinued. Insect growth regulators (IGRs) are known to elicit transovarial activity as IGR-exposed adults produce non-viable eggs, which is not documented for S. pyrioides. Thus, transovarial activity of novaluron, azadirachtin, pyriproxyfen and buprofezin has been explored against S. pyrioides. RESULTS: A low number of S. pyrioides young instars was produced when adults were exposed to topical novaluron compared with non-treated adults. When adults contacted dried residues of novaluron and buprofezin, production of young instars was reduced relative to non-treated controls. When insects exposed to 1.0× and < 1.0× doses of novaluron were compared, the number of young instars produced was similar. CONCLUSION: Transovarial activity was elicited in S. pyrioides when adults were exposed to IGRs, especially novaluron. When adults were exposed to < 1.0× (up to 0.25×) and 1.0× doses of novaluron, the transovarial effect was similar. © 2019 Society of Chemical Industry.

Dissipation and safety evaluation of novaluron, pyriproxyfen, thiacloprid and tolfenpyrad residues in the citrus-field ecosystem.

The dissipations and residues of four pesticides in citrus, under field conditions, were measured using solid-phase extraction and LC-MS/MS. In the method validation, satisfactory results were obtained with fortified recoveries ranging from 80.6 to 113% and relative standard deviations ≤9.0%. In the dissipation test, the half-lives for the pesticides in citrus, according to first-order kinetics, ranged from 13.3 to 28.9 days. Based on the terminal residue test, two evaluation models (hazard quotient, HQ; risk quotient, RQ) were applied on citrus fruits for dietary exposure risk assessment. The results showed that HQs ranged from 0.0031 to 0.78%, and RQs from 7.3 to 57%, which are both acceptable for human consumption. Therefore, 14-day was proposed as a pre-harvest interval for the target compounds in citrus fruits. This work also contributes to residue data and, therefore, scientifically validated maximum residue limits in citrus, which are lacking in China currently.