Ovicidal activity of three insect growth regulators against Aedes and Culex mosquitoes (original) (raw)
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Journal of entomology and zoology studies, 2016
Current researches for mosquito control have focused on insect specific insecticides without environmental concerns. The present study was conducted to evaluate the Ovicidal activity of an ecdysone agonist (methoxyfenozide) on Culex pipiens L. (Culicidae: Diptera) under laboratory conditions using standard WHO protocol. Lethal concentrations (LC50= 24.54 μg/L and LC90= 70.79 μg/L) previously determined were tested against freshly laid eggs. The egg viability was examined and the deferred effects of treatment were also investigated on the development duration and the sex ratio. Data obtained show that egg hatching inhibition was dose dependent, with a reduction of 13.44% and 46.99% with LC50 and LC90, respectively. In treated groups, the total development duration was significantly longer as compared to controls. The adult sex ratio was significantly skewed in favor of males emerged from treated eggs with LC50 and LC90 of methoxyfenozide. Moreover, changes in the egg shell morphology...
Journal of the Egyptian Society of Parasitology, 2010
The biological effects of two insect growth regulators (IGRs), pyriproxyfen and diflubenzuron against larvae of the mosquito Aedes aegypti (L.) have been evaluated. Mosquitoes were collected from Jeddah governorate, west of the Kingdom of Saudi Arabia and maintained in the laboratory. According to IC50 values obtained (concentrations which inhibit the emergence of 50% of adults), diflubenzuron (0.00036 ppm) proved to be more effective by 11.4 fold of pyriproxyfen (0.0041 ppm). In addition to the delayed lethal action, larval treatment with the two IGRs, pyriproxyfen and diflubenzuron led to pronounced reduction in the reproductive potential of mosquito adults that emerged from these treatments. Pyriproxyfen caused a 33.2% decrease in egg production compared to 25.5% for diflubenzuron. The reduction in egg hatchability was by 40.6 and 36.2% for pyriproxyfen and diflubenzuron, respectively, with up to 4 fold higher reduction rates than in the control tests. These results shed light on...
Complications with Controlling Insect Eggs
Insecticides Resistance, 2016
Eggs are difficult to kill because of the unique structure of the eggshell, comprised of multiple layers that have evolved to allow the embryo to breathe while simultaneously limiting water loss. The eggshell has been shown to be an excellent barrier to insecticides, fungal pathogens, and some fumigants. The insect eggshell contains only a few areas that could allow penetration of insecticides, the aeropyles and micropyles, which seem to be either so few in number or small in size that they do not allow a sufficient amount of insecticide through the eggshell. Resistance is also a contributing factor to control failures of insect eggs. Resistance in eggs has been documented in several insect species and a few studies have shown that some insect eggs produce elevated numbers of enzymes to break down insecticides. This chapter focuses on the structure and respiration of the insect eggshell as a barrier to insecticides and also covers various management strategies against insect eggs. Lastly, we discuss the few documentations of resistance in insect eggs thus far.
Susceptibility and alterations by diflubenzuron in larvae of Aedes aegypti
Archives of Insect Biochemistry and Physiology, 2019
Benzoylphenyl ureas inhibit chitin synthesis and interfere with the molting process in arthropods. In this study, the effect of diflubenzuron on third-instar larvae of Aedes aegypti was evaluated. The susceptibility to the product was determined, and the alterations generated were shown through light and electron microscopy. LC 50 and LC 90 were 0.23 and 0.47 ppm, respectively. The main alterations observed were the incapacity to complete the molt, a reduction of mobility, the fragmentation of the old cuticle, a division of the body segments that was not evident, and the deformation of the caudal structures. Images of the ultrastructure are included, where breaking zones in the cuticle were observed, separation of the cuticle, the epidermis and the muscles, and these latter with a disorganized arrangement. In low concentrations, from 0.15 ppm, diflubenzuron causes alterations in the behavior and morphology of Ae. aegypti.
Journal of Medical Entomology, 2014
Dengue and dengue hemorrhagic fever are mosquito-borne viral diseases that coincide with the distribution of Aedes aegypti (L.), the primary vector in the tropical and semitropical world. With no available vaccine, controlling the dengue vector is essential to prevent epidemics. The effects of the insect growth regulator pyriproxyfen on Ae. aegypti adults that survived a treatment with a sublethal dose were investigated in the laboratory, including effects on their reproductive potential. Pyriproxyfen was released from a fumigant formulation at a dose causing 20 or 40% emergence inhibition (%EI). Females were dissected before and after blood feeding and the basal follicle number was counted. There were no differences between the control and treated group on the basal follicle number for both doses used. Fertility and fecundity were reduced at a concentration of EI 40 but no at EI 20. There was no ovicidal effect of pyriproxyfen by immersion of eggs in treated water neither when the females laid their eggs on a pyriproxyfen-treated surface. This work shows that sublethal doses of pyriproxyfen can have effects on fertility and fecundity of Ae. aegypti females, which together with its larvicidal activity could contribute to an overall decrease in a given population.
PloS one, 2015
The Asian tiger mosquito, Aedes albopictus, is a highly invasive mosquito species that transmits chikungunya and dengue. This species overwinters as diapausing eggs in temperate climates. Early diapause termination may be a beneficial strategy for winter mosquito control; however, a mechanism to terminate the diapause process using chemicals is not known. We tested the hypothesis that a hormonal imbalance caused by the administration of juvenile hormone analog would terminate egg diapause in A. albopictus. We tested the insect growth regulator pyriproxyfen on all developmental stages to identify a susceptible stage for diapause termination. We found that pyriproxyfen treatment of mosquito eggs terminated embryonic diapause. The highest rates of diapause termination were recorded in newly deposited (78.9%) and fully embryonated (74.7%) eggs at 0.1 and 1 ppm, respectively. Hatching was completed earlier in newly deposited eggs (25-30 days) compared to fully embryonated eggs (71-80 day...
Journal of Economic Entomology, 2003
Susceptibility of the lepidopteran parasitoid Hyposoter didymator (Thunberg) to seven modern insecticides, azadirachtin, dißubenzuron, halofenozide, methoxyfenozide, pyriproxyfen, tebufenozide, and spinosad, was tested in the laboratory. Pupae were exposed to different doses of each compound by direct topical application. At the Þeld recommended doses, methoxyfenozide and tebufenozide had no effect on H. didymator. Halofenozide had a low effect on both adult emergence and adult survival but the progeny size and parasitism capacity were not affected. Dißubenzuron was moderately toxic to the parasitoid, while azadirachtin, pyriproxyfen and spinosad were very toxic, affecting all its life parameters. In the pyriproxyfen and spinosad treatments, no progeny was obtained. As a second approach of this study, we determined the rate of penetration through the pupal cocoon and absorption in the parasitoid body as pharmacokinetic parameters important for toxicity. Most of the radioactivity was retained in the silken cocoon, indicating a low accumulation in the parasitoid body. Among all compounds tested, dißubenzuron exhibited the highest absorption in the parasitoid body, followed by pyriproxyfen. For halofenozide, methoxyfenozide and tebufenozide, low absorption (Ͻ2%) was found. In addition, we tested for the presence of molting hormone receptors in Hyposoter tissues using a monoclonal antibody 9B9. Our data suggest that the use of dißubenzuron azadirachtin, pyriproxyfen, halofenozide, and spinosad in combination with H. didymator in integrated pest management (IPM) programs should be carefully evaluated. Methoxyfenozide and tebufenozide could be considered safe for this parasitoid.
Experimental and Applied Acarology, 2019
Two pyrethroids, deltamethrin (D) and alphacypermethrin (AC), have been used as commercial products for tick control worldwide. However, the effects of sublethal doses of these compounds on various tick species and their developmental stages have not been fully explored yet, although such knowledge could contribute to a more effective application of both pyrethroids and simultaneous reduction of their costs and undesirable side effects, including the harmful impact on other organisms and environmental contamination. This study investigates the effect of sublethal concentrations of D and AC applied to engorged females on the fecundity, development of eggs and larvae, and the number of offspring in the Ixodes ricinus (L.) tick, which is the most important vector of tick-borne diseases of humans in Europe. After detachment from rabbit's skin, fully engorged I. ricinus females were treated with 20 μl of pyrethroid solutions at five concentrations from 0.01562 to 0.25% and kept at 28 °C and 75% relative humidity. The impact of the pyrethroids on maturation and development of eggs as well as development of larvae was assessed based on parameters of the preoviposition and oviposition periods and the course of embryogenesis and egg hatch. The investigations have shown that both tested acaricides reduce the reproductive rate in I. ricinus females by inhibition of egg development and disturb embryonic development and larval hatch. Females did not lay eggs at concentrations higher than 0.0625% AC and 0.125% D. The lower concentrations of both pyrethroids disturbed or inhibited the embryogenesis and egg hatch in I. ricinus.
Alexandria Science Exchange Journal: An International Quarterly Journal of Science Agricultural Environments, 2010
This study was carried out to evaluate the biological effects of two IGRs (Match ® and Baycidal ®) on Culex pipiens mosquitoes when fed the adults on sugar solution mixed with 0.1, 0.5 and 1 ppm of each compound. Some delayed effects of these treatments were also determined. The results indicated that the use of each of the tested IGRs caused a reduction in the blood-feeding activity of mosquito female when compared with the controls. The reductions were 18.2, 22.7 and 31.8% by using Match and 25, 27.3 and 36.3% by using Baycidal ® , respectively, at the tested concentrations. The reduction in biting activity of mosquito females may lead to a decrease in the number of fully engorged females and accordingly affect their reproductive capacity of mosquitoes. The use of Match ® and Baycidal ® at the tested concentrations caused a marked prolongation in the time needed for blood meal digestion by C. pipiens females. The prolongation percentages were 44.4, 48,8 and 55.5% by using Match and 51.1, 55.5 and 62.2% by using Baycidal ® , respectively. Also, treatments caused a reduction in the reproductive capacity. The maximum decreasing in egg production was 30.3% at concentration of 1 ppm of Match ®. The result showed that the treatment by Baycidal ® at 0.1, 0.5 and 1ppm led to a remarkable reduction in the egg production by 61.9, 66.1 and 69.2%, respectively and also the hatchability was reduced in the treated females. Subsequent study was carried out to investigate the delayed effect of IGRs Match ® and Baycidal ® on the hatched larvae. The result showed that the larval development was gradually inhibited by 17.8, 49.8 and 92.7% by using Match ® at 0.1, 0.5 and 1 ppm, respectively. On the other hand the larval development was completely inhibited after the treatment of adults fed by 0.5 and 1 ppm Baycidal ®. The larvae developed till the 2 nd instar but completely failed in molting to the 3 rd instar. Subsequent study was conduced on the effect of Match ® and Baycidal ® on the longevity of the survived mosquito adults that, the records showed that no significant differences in the mean of adult longevity between treatments and control.
Journal of Tropical Medicine, 2011
The inhibitory function of Dimilin (Diflubenzuron), mostly a chitin synthesis regulator, on the ecdysis of mosquitoes (Anopheles gambiae s.l., Culex quinquefasciatus) and housefly was evaluated in the field and in laboratory. Three formulations of Diflubenzuron were evaluated in this study: Dimilin, Wettable powder (25%), Dimilin granules (2%), and Dimilin tablets (2%). The laboratory and field evaluation used different rates of concentrations of these formulations. Generally, at higher dosages larvae developments, eggs hatchability and pupation were impossible. The development of mosquitoes was significantly higher in control while highly depressed in different dosages of treatment in both laboratory and field experiments. In houseflies, the adult population decreased sharply after treatment of their breeding sites while pupae mortality was noticed to be high in laboratorytreated samples. Dimilin could be opted as one of the choice of the larval control chemicals to be incorporated in the integrated vector control programmes in urban and rural areas.