| Nanotechnology is an emerging field of interdisciplinary research.It opens up a wide array of chances in various fields like insecticides,pharmaceuticals,electronics and agriculture.The potential uses and benefits of nanotechnology are enormous.These include management of insect pests through preparing the formulations of nanomaterials-based insecticides,pesticides and insect repelling chemicals.Traditional strategies like integrated pest management used in agriculture are insufficient,and application of chemical pesticides have adverse effects on animals and human beings apart from the decline in soil fertility.Therefore,nanotechnology would provide green and efficient alternatives for the management of insect pests in agriculture without harming the nature.This technique is focused on the new strategies used for the management of insect pests and potential of nanomaterials based on biological synthesis in insect pest control as modern approaches of nanotechnologyArthropods are dangerous vectors of often deadly agents of diseases and parasites to humans and animals;in addition it causes severe damage and transmits a number of virus diseases to plants.Among them,mosquitoes(Diptera:Culicidae)represent a key threat for millions of people worldwide,since they act as vectors for important pathogens,including malaria,dengue,yellow fever,Japanese encephalitis,West Nile,and parasites,such as filariasis.Therefore,the trend was to control this dangerous pest using unconventional methods based on nanotechnology.Consequently,the green synthesis of silver nanoparticles of Cassia fistula fruit pulp as an innovative and operative tool against vector mosquitoes was presented.Silver nanoparticles were characterized by a series of techniques including FT-IR,TEM and confirmed by SEM,UV-Vis spectrophotometry and XRD.Silver nanoparticles were highly effective against the larvae(I-IV instar)and pupae of Aedes albopictus and Culex pipiens pallens after 24,48 and 72 hours of treatment.Ae.albopictus had LC50 values ranging from 8.3 mg/L(I instar)to 17.3 mg/L(pupae)and LC50 ranging from 1.1 mg/L(I instar)to 19.0 mg/L(pupae)against Cx.pipiens pallens.The systemic effect of AgNPs was further assessed in the fourth instar larvae of Ae.Albopictus andCx.pipiens pallens by measuring the levels of total proteins and activity of two important marker enzymes:Acetylcholinesterase and a-and ?-carboxylesterase.Overall,the findings of the study suggest that the use of Cassia fistula-fruit pulp extract mediated synthesis of silver nanoparticles can be used for controlling vector mosquitoes.Similarly,in order to protect the people from diseases,the anti-mosquito population is necessary that uses safe and new bio-pesticides such as Bacteria-mediated synthesis of AgNPs.Thus,we used two kinds of bacteria to synthesize silver nanoparticles to examine the toxic effect on the larvae and pupae of Cx.pipiens pallens and also used as antimicrobial activity.The larvicidal and pupicidal assays revealed that the lethal concentration LC50 values of Bacillus amyloliquefaciens-AgNPs were 0.72 mg/L(?),0.73 mg/L(?),0.69 mg/L(?),1.16 mg/L(IV)and 4.18 mg/L(Pupae),while LC50 values of Bacillus subtilis-AgNPs were 0.60 mg/L(I),0.62 mg/L(II),0.21 mg/L(III),0.28 mg/L(IV)and 3.46 mg/L(Pupae)after 72h of exposure.Antibacterial activity test of AgNPs reveals better results against rice pathogenic bacteria than bacteria alone.Thus,bacteria-mediated silver nanoparticles have a rapid effect on vector mosquito and microbial pathogen suggesting savings of energy and resources.Hence,bacteria-AgNPs may be used in the future as an effective weapon to control vector mosquito and harmful bacteria.On the other hand,we have studied new and safe methods to control brown planthopper.It causes huge losses of rice yield by sucking sap often causing "hopper burn" and transmits many viral diseases to the rice plants.The new methods are based on the optimal use of organic ligands for the synthesis of silver nanoparticles.The synthesized silver nanoparticles were characterized using UV-visible spectroscopy,FTIR,SEM,EDX,TEM,XRD,zeta potential and DLS.UV-visible spectrum of synthesized H4L-NPs and TBAPy-NPs showed maximum peak at 420 and 430 nm,respectively.SEM analysis exposed that the particles were spherical,hexagonal and irregular in shape and size ranging from 15.9 to 51.6 nm(H4L-NPs)and from 15.9 to 91.3 nm(TBAPy-NPs),and EDX spectrum also confirmed the presence of Ag metal.Moreover,DLS showed the average size of 7.62 and 7.06 nm and the zeta values were measured(-3.06 and-0.45 mV)which served as evidence for the stability of silver nanoparticles for H4L-NPs and TBAPy-NPs,respectively.The insecticidal assays detected that H4L was more tolerant against Brown plant hoppers(N.lugens)where the lethal concentration LC50 value was 1038.4 mg/L,while the toxicity levels increased in TBAPy and LC50 value was 672.5 mg/L after 7 days of exposure to high concentrations 1000 mg/L.On the other hand,the TBAPy-NP was highly toxic with low concentrations of 8 mg/L and LC50 value was 1.13 mg/L,168 h after contact with brown plant hoppers.Whereas,the H4L-NP at the same concentration was less toxic and LC50 value was 1.44 mg/L,168 h post-treatment.These results suggest that the synthesized AgNPs using two ligands solution could be an economical,environmentally safer nano-pesticides,which could be used for protection the rice plants from the infest by insects and provided possibility insecticidal effect on Nilaparvata lugens.In summary,new types of formulation were developed to control the insect pests and plant pathogens.One of the most promising aspects is the use of micro and nanotechnology to promote a more efficient assembly of the active compound in a matrix in order to protect core materials from adverse reactions due to factors like air or light.An outcry is exhibited against the use of pesticides due to their hazardous effects on human as well as environment.In view of its simplicity,low cost involvement,higher reducing potential,zero contamination and reduced or less environmental impact,the plant extract,bacteria and organic ligands based green chemistry process has recently been emerged as one of the active areas of current nano-biotechnological research.The AgNPs formed in this way demonstrated significant insecticidal activity against both mosquitoes and crop pests.The obvious increase in resistance to widely applied insecticides indicates that insecticide resistance management strategies are urgently needed to discover new methods to control insects such as nano-pesticides. |
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