Effects Of Insect Growth Regulators Research Articles

Effects of the Insect Growth Regulators Azadirachtin, Pyriproxyfen, and Tebufenozide on the Fatty Acid Metabolome of Bactrocera Dorsalis Larvae.

Insects' lipids, including fatty acids, as the second largest constituents in insects, play a variety of fundamental and vital functions. However, there is a lack of reports on the effects of insect growth regulators on fatty acid profiles and metabolic mechanisms. Therefore, in this study, a comparative study of three growth regulators, azadirachtin, pyriproxyfen, and tebufenozide, on fatty acids was carried out using a targeted metabolomics approach to fill this gap. The results showed that when exposed to azadirachtin, pyriproxyfen, and tebufenozide, there were 14, 17, and 11 differentially regulated fatty acids, respectively. The pathway of biosynthesis of unsaturated fatty acids was the common shared pathway, while fatty acid biosynthesis and linoleic acid metabolism were the specific pathways affected by the 3 insect growth regulators. Therefore, the results could be helpful to deepen the effects of azadirachtin and insect growth regulators on terrestrial insects.

Effects of Insect Growth Regulators on Mortality, Survival, and Feeding of Euprosterna elaeasa (Lepidoptera: Limacodidae) Larvae

The potential of insecticides that affect the growth and insect development to control Euprosterna elaeasa was evaluated. Fenoxycarb, methoxyfenozide, pyriproxyfen, and tebufenozide were assessed against E. elaeasa larvae for toxicity, survivorship, and feeding inhibition in the laboratory, and mortality in semifield conditions. Concentration–mortality bioassays demonstrated that insect growth regulators (IGRs) have a lethal effect on this insect, with pyriproxyfen (LC50 = 0.141 g L−1) being the most effective, followed by fenoxycarb (LC50 = 0.199 g L−1), methoxyfenozide (LC50 = 0.233 g L−1), and tebufenozide (LC50 = 0.259 g L−1). The survival rate was 99.8% in the control group, compared to 44.6%, 42.9%, 42.2%, and 39.5% in insects treated with pyriproxyfen, fenoxycarb, methoxyfenozide, and tebufenozide, respectively. IGRs caused feeding inhibition in E. elaeasa larvae 3 h after exposure. Furthermore, mortality in semifield conditions was similar to the results found in the laboratory. Our findings suggest that fenoxycarb, methoxyfenozide, pyriproxyfen, and tebufenozide are effective against E. elaeasa and, therefore, we confirm the potential of these IGRs for the control of this pest.

Effect of insect growth regulators and the fungi Beauveria bassiana (Bals.) alone and in combination on the larvae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in different cereals

Effect of insect growth regulators and the fungi Beauveria bassiana (Bals.) alone and in combination on the larvae of Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in different cereals

Suppressive effects of insect growth regulators on development, reproduction and nutritional indices of the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera: Noctuidae)

ABSTRACT The insect growth regulators (IGRs) chlorfluazuron, flufenoxuron and pyriproxyfen were evaluated, using the leaf-dip technique, on the various developmental and reproductive aspects of Spodoptera littoralis in the parental generation (P), first filial generation (F1) and second filial generation (F2). Additionally, the effect of these IGRs on nutritional indices was also evaluated. The effect on development and reproduction was IGR and generation dependent, with a profound negative impact in the case of the P generation treated with chlorfluazuron. In all treatments, fecundity and fertility increased progressively from the P generation to the F2 generation, and thereby both approached those of the controls. The change in nutritional indices was found to be a function in the candidate IGR and age of the same instar larvae, with a drastic change in late last larval instar (3-day-old 6th larval instar), particularly in the case of treatment with chlorfluazuron. Furthermore, toxicity and morphological deformities induced by the IGRs were reported. The overall results suggest that the IGRs under investigation, particularly chlorfluazuron, interfere with the development process and have the potential for S. littoralis control.

Effectiveness of insect growth regulators for management of legume pod borer, Maruca vitrata F. in yard long bean

Effectiveness of insect growth regulators for management of legume pod borer, Maruca vitrata F. in yard long bean

Influence of abiotic factors on the efficacy of insect growth regulators against Trogoderma granarium (Everts)(Coleoptera: Dermestidae): Presentation

Present study was designed to investigate the effects of different combinations of three temperatures (20, 25 and 30?) and three relative humidity levels (55, 65 and 75%) on the efficacy of three synthetic IGRs i.e., pyriproxyfen, lufenuron and buprofezin at concentrations of 1, 5 and 10ppm on fecundity and adult emergence inhibition of T. granarium under controlled laboratory conditions. This study was conducted at Grain Research Training and Storage management Cell, Department of Entomology, University of Agriculture, Faisalabad, Pakistan. All the treatments were replicated three times using Completely Randomized Design. Larvae of T. granarium were exposed to IGRs at different levels of temperature and relative humidity. F1 adult emergence results showed that at temperature 20°C, the highest percent reduction in adult emergence (84.38, 70.65 and 79.94%) was recorded after exposure to lufenuron, buprofezin and pyriproxyfen treated diet, respectively. At 75% relative humidity, lufenuron, buprofezin and pyriproxyfen caused 77.53, 80.00 and 80.32% reduction in adult emergence, respectively. Adults were exposed to IGRs at different temperature and relative humidity to evaluate the oviposition inhibition. The results revealed that at temperature 20°C, maximum percent reduction in fecundity (87.95, 80.45 and 70.55%) was recorded after exposure to buprofezin, pyriproxyfen and lufenuron treated diet, respectively. At 75% relative humidity buprofezin, pyriproxyfen and lufenuron caused 86.73, 83.72 and 69.11% reduction in fecundity, respectively. It is concluded that temperature and relative humidity play an important role in the effectiveness of insect growth regulators.

Insecticidal toxicity of thirteen commercial plant essential oils against Spodoptera exigua (Lepidoptera: Noctuidae)

We evaluated the chemical composition of thirteen commercially available plant essential oils and their insecticidal activity against the beet armyworm, Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae). Gas chromatography-mass spectrometry was used to characterize the chemical components of the essential oils. A total of 113 compounds were identified, with terpenes (>80%) and aromatic compounds as primary constituents. The toxicity of each pure essential oil was tested separately on third instar larvae and adult beet armyworms by topical application of 0.5 μl oil/ insect. All plant essential oils were found to be harmful to S. exigua, with third instar larvae showing significantly more susceptibility than adults. Essential oils of Cinnamomum zeylanicum and Juniperus virginiana showed the highest toxicity (mortality above 90%) to larvae, while C. zeylanicum and Pogostemon cablin oils were the most harmful compounds (95% mortality) to adults. Cymbopogon winterianus oil caused delayed mortality (similar to the effects of insect growth regulators) as well as malformations in pupae. C. winterianus, Ocimum basilicum and Rosmarinus officinalis oils significantly reduced fecundity, whereas no significant effects were observed on fertility.

Genotoxic Effect of Insect Growth Regulators on Different Stages of Peach Fruit Fly,Bactrocera zonata(Saunders) (Diptera: Tephritidae)

The present study aimed to evaluate the genotoxic effect of insect growth regulators (IGRs) pyriproxyfen and novaluron on the fully grown larvae and 1-day-old pupae of Bactrocera zonata. The genotoxic investigations occurred on the whole body cells of adults that emerged from the fully grown larvae in sand treated with lethal concentrations (LC50 = 0.96, 11.4ppm of pyriproxyfen and novaluron, respectively) and those emerged from the 1-day-old pupae in sand treated with lethal concentrations (LC50 = 4.5, 6200 ppm of pyriproxyfen and novaluron, respectively). Comet assay is the technique used in this study. The comet assay (SCGE - single-cell gel electrophoresis) is often used in measurements of the level of DNA strand breaks in individual eukaryotic cells as a rapid, sensitive and inexpensive method. However, the IGR is considered to have little human toxicity because humans do not make chitin and do not make or use the hormones that insects use in moulting, but it was noticed that IGR-treated insects resulted a significant increase in DNA damage values expressed as tail length (TL), tail moment (TM) and DNA tail%in the body cells compared to the control insects. These results mean that workers should be careful when using IGRs in the field due to the conservation of genes and pathways affecting key biological processes between flies and humans.

Short-term biochemical ill effects of insect growth regulator (IGR) pesticides in Cyphoderus javanus Borner (Collembola: Insecta) as potential biomarkers of soil pollution.

The insect growth regulator (IGR) chemicals are considered as safe alternatives to synthetic organic pesticides, but only scant information are available on their possible impact on non-target and ecologically important soil insect fauna of croplands. Previous studies by the authors showed that recommended agricultural doses of IGRs buprofezin (Applaud 25SC at 250 g a.i. ha(-1)), flubendiamide (Takumi 20WG at 50 g a.i. ha(-1)) and novaluron (Rimon 10EC at 100 g a.i. ha(-1)) produced less mortality of adults of a non-target soil insect Cyphoderus javanus Borner (Collembola) but decreased major life history parameters namely moulting, fecundity and egg hatching success. This detritivorous microarthropod is very sensitive to soil characteristics and is ecologically relevant to the tropical soils. Present microcosm study showed strong biochemical impact of the above doses of IGRs on tissue nutrient levels and digestive enzyme activities in C. javanus within 7 days of exposure to treated sandy loam soil. The levels of tissue proteins, carbohydrates, lipids and free amino acids declined significantly and persistently in the specimens reared in IGR-treated soils than in the specimens of untreated soil. Similarly, α-amylase, cellulase and protease activities declined significantly in the specimens of IGR-treated soil. These nutritional scarcities would reduce metabolism, growth and reproduction in the affected insects. Therefore, the observed biochemical responses, especially the levels of tissue proteins, carbohydrates and α-amylase activity in C. javanus are early warning indices and potential biomarkers of soil pollution in croplands.

Purification and characterization of a phenoloxidase in the hemocytes of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae): effects of insect growth regulators and endogenous inhibitors

A phenoloxidase was extracted and purified from hemocytes of Ephestia kuehniella by using ammonium sulfate, Sepharyl G-100 and DEAE-Cellulose fast flow chromatographies. At the final stage of purification, a protein was purified by molecular mass of 78.5 kDa, specific activity of 1.17 U/mg protein, recovery of 20.48% and purification fold of 16.71. The purified PO showed the highest activity at pH 4–5 and temperatures of 35–40 °C. Na+, K+, Mn+, Zn2+ and Mg2+ decreased activity of the purified PO but Ca2+ and Cu2+ increased the enzymatic activity. EDTA (General chelating agent), DTC (Copper chelating agent) and EGTA (Calcium chelating agent) significantly decreased PO activity but TTHA (Magnesium chelating agent) showed no statistically significant effects. Kinetic parameters of the purified enzyme showed the highest Vmax when L-DOPA was used as substrate but no significant differences were observed in case of Km for used L-DOPA, pyrocatechol and hydroquinone. In vitro inhibition of the purified PO by using two insect growth regulators, Hexaflumuron and Pyriproxyfen, revealed IC50 of 96.41 and 38.59 µg/ml for these compounds, respectively. Kinetic studies using different concentrations of L-DOPA and IC50 concentrations of the two IGRs revealed the increase of Km value versus control and competitive inhibition. Finally, column chromatography of hemolymph revealed peak III showing endogenous inhibitors of phenoloxidase by molecular weight of 27.3 that showed competitive inhibition on the PO.

Effect of insect growth regulators combined with nucleopolyhedrovirus on certain biological and histological aspects of Spodopera littoralis

Five insect growth regulators (IGR's) were tested for increasing the susceptibility of the cotton leaf worm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) to its homologous nucleopolyhedrovirus (SpliMNPV). S. littoralis MNPV was tested alone or in combination with IGR's at LC10 level against the 2nd instar larvae of the pest. An increased viral infection rate was detected in the mixture treatment in the case of using Chlorfluazuron, Flufenoxuron, Triflumuron, Hexaflumuron or Teflubenzuron at 10%. The LC50 value of the virus alone treatment 1x107 PIB's was reduced to 4.3x106, 9.9x104, 4.9x104, 3.1x105 and 1.69x106 PIB's, with the tested five IGR's, respectively. It was observed that Flufenoxuron and Triflumuron mixtures slightly prolongated larval duration compared either untreated control or IGR's alone treatments. The highest rate of decrease in the pupation percentage (47%) was recorded in case of Triflumuron mixed with SpliMNPV followed by Flufenoxuron and Chlrofluazuron mixes. On the other hand there is no significance difference in pupal weight for all treatments. Changes Adult longevity was increased for all treatments compared to untreated control. Addition Flufenxuron (LC10) to SpliMNPV (LC50) showed histopathological effects to mid gut e.g. loss of the compact appearance of the muscularis layer, vaculation and exfoliation of the columnar cells.

Effects of insect growth regulators on the mosquito-parasitic nematode Romanomermis iyengari

Pyriproxyfen, a juvenile hormone analogue, diflubenzuron, a chitin synthesis inhibitor, and azadirachtin, an ecdysone agonist, are three insect growth regulators (IGRs) considered as selective and effective insecticides for mosquitoes. Romanomermis iyengari (Welch) is a mosquito-parasitic mermithid that can provide biological control against many medically important mosquito species. The compatibility of these two control tactics was tested by evaluating the sublethal effects of exposure to IGR on nematode developmental stages (preparasitic, parasitic, and preparasitic + parasitic) using Culex pipiens larvae as the host. Sublethal concentrations of IGRs were 90 % emergence inhibition of host mosquito. Preparasitic exposure to pyriproxyfen, azadirachtin, and diflurbenzuron had no effect on infectivity, parasite load, sex ratio, or male size but reduced nematode female length and increased male sex ratio at one parasite/larva. When IGRs treatments were made against the parasitic and preparasitic + parasitic stages, pyriproxyfen and azadirachtin reduced R. iyengari infectivity, parasite load, and male nematode length, whereas pyriproxyfen exposure increased male sex ratio and reduced the female R. iyengari length. Thus, IGRs have significant negative impacts on different stages of mosquito mermithid that can destabilize the balance of host-parasite population interaction. Therefore, IGRs should be used with caution in mosquito habitats where these parasites have established.

Morphological effects of some insect growth regulators on Musca domestica, (Diptera, Muscidae).

The current work was carried out to evaluate the morphological effects of insect growth regulators e.g. : applaud (buprofezin), consult (hexaflumuron) and match (lufenuron) as chitin synthesis inhibitors (CSIs), mimic (tebufenozide) as ecdysone agonist (EA) and admiral (pyripyroxyfen) as juvenile hormone analogue (JHA) against the housefly, M. domestica. Various morphological aberrations were induced in larvae, pupae and adults of M. domestica. The highest percentage of larval deformities caused by mimic, (can not molt or shrinked). Consult gave the highest percentage of malformation in the resulting pupae (C. shaped, elongated, distorted, two constricted, tapering anterior and broad posterior , cylindrical adult uncompleted). Admiral and mimic induced high percentage of abnormalities in the adult flies (small size body and curved legs, crumbled wings and curved abdomen). Larval-pupal intermediates and pupal-adult intermediates were induced as a result of these treatments.

Susceptibilidade do besouro rola-bosta africano a reguladores de crescimento de insetos

Verificou-se a ação dos reguladores de crescimento de insetos (IGR), diflubenzuron e methoprene, sobre o besouro rola-bosta africano, Digitonthophagus gazella (Fabricius), um inimigo natural da mosca-dos-chifres, Haematobia irritans irritans (Linnaeus). Casais de besouros foram colocados em baldes contendo terra úmida e alimentados com fezes bovinas contendo 1, 0,5 ou 0,2ppm de diflubenzuron e 0,2ppm de methoprene. Os insetos e sua prole foram recuperados com o auxílio de armadilhas pitfall. Diflubenzuron e methoprene não afetaram a sobrevivência dos adultos inicialmente expostos, mas interferiram na produção de descendentes. Diflubenzuron, nas concentrações de 1 e 0,5ppm, também afetou a duração do ciclo de vida dos besouros. Nenhum dos IGRs alterou a razão sexual dos descendentes obtidos. As concentrações testadas de diflubenzuron mostraram-se moderadamente nocivas ao besouro enquanto methoprene a 0,2ppm mostrou ser pouco nocivo, segundo os critérios da International Organization for Biological Control.

Modelling long‐term effects of IGRs on honey bee colonies

Systems have been developed to monitor the direct effects of insect growth regulator (IGR) pesticide exposure on honey bee development, but there has been little work on the longer-term impact of exposure on the colony. A honey bee population model provided the opportunity to investigate the effects of short-term mortality of brood and of sublethal changes in behaviour of the surviving adults on honey bee populations. The model showed that brood mortality alone has limited effect on colony size. There were two mechanisms that could have greater influence on productivity. Precocious foraging in affected adult bees, and hence early loss of brood-rearing (nurse) capabilities, had a much larger effect than expected. Increasing mortality rates by 30% to simulate sublethal effects on lifespan, rather than reduced brood-rearing capability, gave a significantly smaller effect. In order to simulate an effect with the 'shortened lifespan' mechanism as large as that with the 'premature ageing' mechanism, the mortality rate of affected adults had to be increased by 500%. A significant finding from the model is that application of IGRs in spring and early summer could have substantial effects on colony size and viability. Sublethal effects such as precocious foraging can have worse effects than massive brood mortality, as it severely reduces the ability to rear the next generation of nurse bees.

Multigeneration effects of insect growth regulators on the springtail Folsomia candida

Multigeneration tests are very useful for the assessment of long term toxicity of pollutants such as endocrine disruptor compounds. In this study, multigeneration reproduction tests adapted from the ISO standard 11267 were conducted with the Collembola Folsomia candida. Springtails were exposed to artificial soil contaminated with four insect growth regulators (methoprene, fenoxycarb, teflubenzuron, and precocene II) according to two different experimental set-ups. In the first set-up, the parental generation (F 0) of Collembola was exposed to a pollutant for 28 days. Juveniles from the F 1 generation were transferred to uncontaminated soil for another 28-day period to generate the F 2 generation. In the second set-up, the F 0 generation was exposed to a pollutant for 10 days before being transferred to uncontaminated soil to reproduce. After 18–28 days, juveniles from the F 1 were transferred to clean soil to generate the F 2 generation. An effect on the number of hatched juveniles of the F 2 generation was observed for methoprene after exposure of the F 0 for 28 days and hatching of F 1 in contaminated soil. For methoprene and teflubenzuron, significant effects were even observed on the F 2 generation with the second experimental set-up, when only the F 0 generation was exposed for 10 days. This shows that the impact of these substances is transgenerational, which can have important consequences for the population of these or other organisms. No effect on the F 2 generation was observed with fenoxycarb and precocene II with the 10-day exposure experiment. Our results show that the developed experimental procedures are appropriate to assess the long term effects of endocrine disrupting compounds on the reproduction of the non-target species F. candida. Another important finding is that two substances with the same predicted mode of action (i.e., the two juvenile hormone analogues fenoxycarb and methoprene) do not necessarily affect the same endpoints in F. candida.

Long-Term Effects of Insect Growth Regulators On Cabbage Armyworm, Mamestra brassicae, in Sugar Beet

Long-Term Effects of Insect Growth Regulators On Cabbage Armyworm, <I>Mamestra brassicae</I>, in Sugar Beet

Effects of insect growth regulators on the nontarget soil arthropod Folsomia candida (Collembola)

The aim of this study was to assess the effect of several insect growth regulators (IGRs) on the nontarget soil arthropod Folsomia candida (Collembola). The survival and reproduction rates of F. candida were evaluated after 28 days of exposure to six IGRs (methoprene, fenoxycarb, precocene II, tebufenozide, hexaflumuron and teflubenzuron) and to one herbicide (diuron) in artificial soil. The differences in the sensitivity of F. candida to these different substances are high. The chitin synthesis inhibitors teflubenzuron and hexaflumuron were the most toxic compounds with an EC50 of 0.05 mg/kg (dry weight) for teflubenzuron and an EC50 of 0.6 mg/kg for hexaflumuron. Teflubenzuron is toxic for F. candida at concentrations that are probably close to environmental levels of this insecticide. Inhibition of reproduction is strongly related to adult survival for the juvenile hormone agonist methoprene and for the antijuvenile hormone precocene II, with an EC50 of 173 mg/kg and a LC50 of 178 mg/kg for methoprene and an EC50 of 15 mg/kg and a LC50 of 26 mg/kg for precocene II. Fenoxycarb, another juvenile hormone analog, showed a dose–response curve for mortality different from that of methoprene; at concentrations such as 3052 mg/kg no effect on adult survival was observed. However, the EC50 value of 113 mg/kg is of the same order of magnitude as that obtained for methoprene. A test with compressed soil contaminated with fenoxycarb was conducted to observe parameters such as numbers of eggs laid and juveniles hatched. No differences were observed between these two endpoints for fenoxycarb. An EC50 of 109 mg/kg was obtained for the ecdysone agonist tebufenozide. The herbicide diuron showed a relatively high toxicity for F. candida with an EC50 of 20 mg/kg. Our results show that some of the tested IGRs can have effects on Collembola at environmentally relevant concentrations (toxicity/exposure ratios < 5 for teflubenzuron, hexaflumuron, and diuron).

Effects of insect growth regulators on the hairy rose beetle, Tropinota squalida (Col., Scarabeidae)

Abstract: Saponin extract from alfalfa roots, azadirachtin from the neem seed oil, synthetic ecdysteroid agonist RH‐2485, and the juvenoid hydroprene disturb the development and reproduction of Tropinota squalida. Feeding beetles on diets containing 750 p.p.m. saponins, 7.5 p.p.m. RH‐2485, and 1.13 p.p.m. azadirachtin reduces their progeny from 51 second instar larvae per female to 24, 15, and 15 larvae, respectively. When the larvae of untreated adults are fed for 1 week on dung with 75 p.p.m. saponins, 50 p.p.m. RH‐2485, and 0.45 p.p.m. azadirachtin, the rate of adult emergence drops from 80% (controls) to 20, 0 and 13%, respectively. No adults emerge when the treatment is continued through the second and third larval instars. Two topical treatments of larvae with 0.2 μg hydroprene decrease the rate of adult emergence from 90 to 11%, and treatments with 2 μg prevent adult development in all insects. The observed effects warrant testing of azadirachtin, RH‐2485, and hydroprene in the field. Several types of their application for the control of T. squalida are suggested.

Effect of Insect Growth Regulators on Citrus Mealybug [Planococcus citri (Homoptera: Pseudococcidae)] Egg Production

Greenhouse trials were conducted in 2000-2001 to evaluate the indirect effects of insect growth regulators, whether stimulatory or inhibitory, on the egg production of female citrus mealybug [Planococcus citri (Risso)]. Green coleus [Solenostemon scutellarioides (L.) Codd] were infested with 10 late third instar female citrus mealybugs. The insect growth regulators kinoprene, pyriproxyfen, azadirachtin, buprofezin, and novaluron were applied to infested plants at both the high and low manufacturer recommended rates. Beginning two days after treatments were applied, plants were monitored daily to determine when female mealybugs began to oviposit. Individual mealybugs were removed from plants, placed into glass vials containing 70% isopropyl alcohol when female mealybugs started to oviposit, and dissected to determine the number of eggs. Overall, there were no consistent patterns to suggest that the insect growth regulators and different rates tested had any effect on the egg production of citrus mealybug females. Although, in one instance, the insect growth regulators kinoprene and pyriproxyfen actually lowered citrus mealybug egg production. In addition, the insect growth regulator buprofezin numerically increased female citrus mealybug egg production.