Green synthesis of gold nanoparticles using Gracilaria crassa leaf extract and their ecotoxicological potential: Issues to be considered.

The use of vegetal species for gold nanoparticles (AuNPs) biosynthesis can constitute an alternative to replacing the extensive use of several hazardous chemicals commonly used during NPs synthesis and, therefore, can reduce biological impacts induced by the release of these products into the natural environment. However, the "green nanoparticles" and/or "eco-friendly nanoparticles" label does not ensure that biosynthesized NPs are harmless to non-target organisms. Thus, we aimed to synthesize AuNPs from seaweed Gracilaria crassa aqueous extract through an eco-friendly, fast, one-pot synthetic route. The formation of spherical, stable, polycrystalline NPs with a diameter of 32.0 nm ± 4.0 nm (mean ±SEM) was demonstrated by UV-vis spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy, energy-dispersive X-ray and X-ray diffraction measurement, and Fourier-transform infrared spectroscopy analysis. In addition, different phytocomponents were identified in the biosynthesized AuNPs, using Gas Chromatography-Mass Spectrometry (GC-MS). However, both G. crassa aqueous extract and the biosynthesized AuNPs showed high ecotoxicity in Anopheles stephensi larvae exposed to different concentrations. Therefore, our study supports the potential of seaweed G. crassa as a raw material source for AuNPs biosynthesis while also shedding light on its ecotoxicological potential, which necessitates consideration of its risk to aquatic biota.

Comparative efficacy of two mycotoxins against Spodoptera litura Fab. And their non-target activity against Eudrilus eugeniae Kinb.

Entomopathogenic fungi are feasible and effective against the agricultural pest. In the current research we investigated the bioactive comparison of two widely accepted entmopathogens (Beauveria bassiana (Bals.) Vuill. and Metarhizium anisopliae, (basionym)) against the Spodoptera litura (Fab.) through the assessment of larval tolerance and regulation of antioxidants and non-target impact on the earth worm, E. eugeniae, along with commercial pesticides. The entomopathogenic fungus exposure resulted in the modification of the levels of detoxification enzymes as well as significant increases in catalase and superoxide dismutase activity after exposure to the entomopathogenic fungus. Bioassay results showed that B. bassiana and M. anisopliae displayed larval mortality against third and fourth instars. Correspondingly, sub-lethal concentrations of B. bassiana showed development impairment as compared to M. anisopliae. Gut-histology revealed that mycotoxins dosage (4 × 105) showed significant changes in the midgut tissues as compared to control larvae. The non-target screening through artificial soil assay on the earth worm E. eugeniae, with mycotoxins B. bassiana (5 × 108 conidia/ml/kg) and M. anisopliae (5 × 108 conidia/ml/kg) showed less toxicity as compared to Monocrotophos (10 ppm/kg). Current results suggest that the fungal mycotoxins of M. anisopliae and B. bassiana significantly reduce the development of lepidopteran pests, while having only lesser impact on beneficial earthworms.

Chemicals isolated from Justicia adhatoda Linn reduce fitness of the mosquito, Aedes aegypti L.

Extracts from Justicia adhatoda L. (Acanthaceae) strongly reduced the fitness of the mosquito, Aedes aegypti Linn. The methanolic extracts inhibited several enzymes responsible for protecting insects from oxidative and other damage, including glutathione-S-transferase, superoxide dismutase, cytochrome P450, and α- and ß-esterases. They increased repellency (maximum repellency at 100 ppm) in host-seeking adult females using the "arm-in cage assay." Histopathological examination showed the extracts led to serious midgut cell damage. Justicia adhatoda extracts led to reduced fecundity and oviposition of gravid females compared to controls. The extracts led to substantially reduced A. aegypti survival. We infer that the extracts have potential to reduce pathogen transmission by suppressing population growth of A. aegypti, and possibly other mosquito species.

Impact of Terminalia chebula Retz. against Aedes aegypti L. and non-target aquatic predatory insects.

Aedes aegypti Linn is one of the most important mosquito species. The vectors are responsible for causing deadly diseases like dengue and dengue hemorrhagic fever. Several chemical pesticides used to control these dengue vectors caused severe toxic significances on human health and other non-target beneficial insects. Therefore the current investigation has been made to access the bio-efficacy of the crude seed extracts of T. chebula against the dengue vector Ae. aegypti. The GC-MS analysis of crude seed extracts of T. chebula identified nine chemical compounds with major peak area in the 1,2,3-Benzenetriol (61.96%), followed by Tridecanoic acid (09.55%). Ae. aegypti larvae showed dose dependent mortality rate was observed between the treatments. Prominent protection rate at greater concentrations of 100ppm and moderate protection at 75 and 50ppm was observed in the repellent assay. Lethal concentration (LC50 and LC90) of fourth instar larvae of Ae. aegypti was observed in 138 and 220ppm concentration respectively. Similarly, the seed extracts showed 100% adulticidal activity at the concentration of 400ppm at 30min of exposure time. Phytochemicals present in the seed extracts of T. chebula significantly affects the major portions of the midgut tissues of Ae. aegypti at the concentration of 100ppm. The toxicological evaluation of seed extracts also proved non-toxic towards the A. bouvieri and Tx. splendens aquatic predatory insects. Hence, the present result suggest that bio-rational plant derived T. chebula could be incorporated in the dengue vector control and have no adverse effects on non-target beneficial insects.

Comparative analysis of mosquito (Diptera: Culicidae: Aedes aegypti Liston) responses to the insecticide Temephos and plant derived essential oil derived from Piper betle L.

Resistance to treatments with Temephos or plant derived oil, Pb-CVO, between a field collected Wild Strain (WS) and a susceptible Laboratory Strain (LS) of Ae. aegypti were measured. The Temephos (0.1mg/L) showed the greatest percentage of mosquito mortality compared to Pb-CVO (1.5mg/L) in LS Ae. aegypti. However, WS Ae. aegypti was not significantly affected by Temephos (0.1mg/L) treatment compare to the Pb-CVO (1.5mg/L). However, both strains (LS and WS) when treated with Pb-CVO (1.5mg/L) displayed steady larval mortality rate across all instars. The LC50 of Temephos was 0.027mg in LS, but increased in WS to 0.081mg/L. The LC50 of Pb-CVO treatment was observed at concentrations of 0.72 and 0.64mg/L for LS and WS strains respectively. The enzyme level of α- and ß-carboxylesterase was reduced significantly in both mosquito strains treated with Pb-CVO. Whereas, there was a prominent deviation in the enzyme ratio observed between LS and WS treated with Temephos. The GST and CYP450 levels were upregulated in the LS, but decreased in WS, after treatment with Temephos. However, treatment with Pb-CVO caused both enzyme levels to increase significantly in both the strains. Visual observations of the midgut revealed cytotoxicity from sub-lethal concentrations of Temephos (0.04mg/L) and Pb-CVO (1.0mg/L) in both strains of Ae. aegypti compared to the control. The damage caused by Temephos was slightly less in WS compared to LS mosquito strains.

Target and non-target toxicity of botanical insecticide derived from Couroupita guianensis L. flower against generalist herbivore, Spodoptera litura Fab. and an earthworm, Eisenia foetida Savigny.

Botanical insecticides may provide alternatives to synthetic insecticides for controlling Spodoptera litura (F.) and they are target specific, biodegradable, and harmless to mammals. Eight natural chemical compounds with larvicidal activity were identified from fraction F6 of C. guianensis flower extract. Probit analysis of 95% confidence level exposed an LC50 of 223ppm against S. litura third instar larvae. The growth and development of S. litura was affected in sub-lethal concentrations of fraction F6 (50, 100, 150 and 200ppm) compared to controls. Similarly nutritional indices values decreased significantly compared to controls. Fraction F6 also damaged the gut epithelial layer and brush border membrane (BBM). This study also resolved the effects of toxicity to non-target earthworm treated with fraction F6 and chemical pesticides (monotrophos and cypermethrin) and the results showed that fraction F6 had no harmful effect on E. fetida. Further, fraction F6 was eluted and sub fractions F6c (50ppm) showed high mortality against S. litura third instar larvae. Octacosane from fraction F6c was established and confirmed using IR spectrum and HPLC. The time of retention of fraction F6c was confirmed with the octacosane standard. Fraction F6 of C. guianensis extract caused dose-dependent mortality towards S. litura. Octacosane in fraction F6c was establish to be the prominent chemical compound associated with causing mortality but other compounds present in the fraction F6 were shown to be associated with changes in development of S. litura at low dosages. S. litura at low dosage. Therefore, these findings suggest that octacosane may be one of the major insecticidal compounds affecting S. litura survival.

Potential mode of action of a novel plumbagin as a mosquito repellent against the malarial vector Anopheles stephensi, (Culicidae: Diptera).

Plumbagin was isolated and characterized from the roots of Plumbago zeylanica using chromatography: TLC, Column chromatogram, HPLC, FTIR and 1H NMR. The isolated pure compounds were assayed for potency as inhibitors of: acetylcholine esterase (AchE), glutathione S-transferases (GST), superoxide dismutase (SOD), cytochrome P450 and α, ß-esterase, and for repellency with Anopheles stephensi at four different concentrations (25, 50, 75 and 100ppm). The enzyme assay against the pure compound reveals that the level of esterase and SOD was decreased significantly in contrast the level of GST and cytochrome P450 was increased significantly. Our results suggests that novel Plumbagin has significantly alters the level of enzyme comparable to the control. Evaluations resulted in Plumbagin producing maximum repellency scores against An. stephensi mosquitoes in dose dependent manner with highest repellence was observed in the 100ppm. Histological examination showed that the midgut, hindgut and muscles are the most affected tissues. These tissues affected with major changes including separation and collapse of epithelial layer and cellular vacuolization. The results support the utility of plant compound Plumbagin for vector control as an alternative to synthetic insecticides, however, more vigorous field trials are needed to determine viability under natural conditions.

Physiological and biochemical alterations in Vigna rdiate L. triggered by sesame derived elicitors as defense mechanism against Rhizoctonia and Macrophomina infestation.

Improving agricultural products by the stimulation of plant growth and defense mechanisms by priming with plant extracts is needed to attain sustainability in agriculture. This study focused to consider the possible improvement in Vigna radiata L. seed germination rate, plant growth, and protection against the natural stress by increasing the defense mechanisms through the incorporation of Sesamum indicum phytochemical compounds with pre-sowing seed treatment technologies. The gas chromatography coupled with mass spectroscopy (GC-MS) analysis revealed that the methanol extract of S. indicum leaf extract contained eight major bioactive compounds, namely, 2-ethylacridine (8.24%), tert-butyl (5-isopropyl-2-methylphenoxy) dimethylsilane (13.25%), tris(tert-butyldimethylsilyloxy) arsane (10.66%), 1,1,1,3,5,5,5-heptamethyltrisiloxane (18.50%), acetamide, N-[4-(trimethylsilyl) phenyl (19.97%), 3,3-diisopropoxy-1,1,1,5,5,5-hexamethyltrisiloxane (6.78%), silicic acid, diethyl bis(trimethylsilyl) ester (17.71%) and cylotrisiloxane, hexamethyl-(4.89%). The V. radiata seeds were treated with sesame leaf extract seeds at concentrations 0, 10, 25, 50, and 100 mg/L. Sesame leaf extract at 50 and 100 mg/L concentrations was effective in increasing the germination percentage and the fresh and dry weights of roots and shoots. The increased peroxidase activity was noticed after treatment with S. indicum extract. In addition, disease percentage (< 60%) of both fungal pathogens (Rhizoctonia and Macrophomina) was significantly reduced in V. radiata plants treated with 100 mg/L of sesame leaf extract. These results revealed that physiochemical components present in S. indicum mature leaf extract significantly enhanced growth and defense mechanism in green gram plants.

Systematic induced resistance in Solanum lycopersicum (L.) against vascular wilt pathogen (Fusarium oxysporum f. sp. lycopersici) by Citrullus colocynthis and Trichoderma viride.

The antifungal effects of Citrullus colocynthis extract (Hexane, chloroform, methanol, and water) were tested in vitro on Fusarium oxysporum f. sp. lycopersici (Sacc.) W. C. Snyder & H. N. Hans (FOL), the causal agent of Fusarium wilt. Of these, methanol and water extract at 10% showed the highest inhibition of mycelial growth of FOL by 12.32 and 23.61 mm respectively. The antifungal compounds were identified through Fourier transform infrared (FT-IR) spectroscopy and gas chromatography-mass spectroscopy (GC-MS). The methanol extract was compatible with the biocontrol agent Trichoderma viride. The antagonistic fungi were mass-cultured under laboratory conditions using sorghum seeds. Both T. viride and C. colocynthis methanol extract was also tested alone and together against FOL under both in vitro and in vivo conditions. The combination of T. viride and C. colocynthis showed the highest percentage of antifungal activity (82.92%) against FOL under in vitro conditions. This study revealed that induced systemic resistance (ISR) in enhancing the disease resistance in tomato plants against Fusarium wilt disease. The combined treatment of T. viride and C. colocynthis significantly reduced the disease incidence and index by 21.92 and 27.02% in greenhouse conditions, respectively. Further, the induction of defense enzymes, such as peroxidase (PO), polyphenol oxidase (PPO), ß-1,3-glucanase, and chitinase were studied. The accumulation of defense enzyme was greater in plants treated with a combination of T. viride and C. colocynthis compared to the control. Reduction of wilt disease in tomato plants due to the involvement of defense-related enzymes is presumed through this experiment.

Biological activity of selected Lamiaceae and Zingiberaceae plant essential oils against the dengue vector Aedes aegypti L. (Diptera: Culicidae).

The larvicidal activity of hydrodistillate extracts from Mentha piperita L. Ocimum basilicum L. Curcuma longa L. and Zingiber officinale L. were investigated against the dengue vector Aedes aegypti L. (Diptera: Culicidae).The results indicated that the mortality rates at 80, 100, 200 and 400 ppm of M. piperita, Z. officinale, C. longa and O. basilicum concentrations were highest amongst all concentrations of the crude extracts tested against all the larval instars and pupae of A. aegypti. Result of log probit analysis (at 95% confidence level) revealed that lethal concentration LC50 and LC90 values were 47.54 and 86.54 ppm for M. piperita, 40.5 and 85.53 ppm for Z. officinale, 115.6 and 193.3 ppm for C. longa and 148.5 and 325.7 ppm for O. basilicum, respectively. All of the tested oils proved to have strong larvicidal activity (doses from 5 to 350 ppm) against A. aegypti fourth instars, with the most potent oil being M. piperita extract, followed by Z. officinale, C. longa and O. basilicum. In general, early instars were more susceptible than the late instars and pupae. The results achieved suggest that, in addition to their medicinal activities, Lamiaceae and Zingiberaceae plant extracts may also serve as a natural larvicidal agent.

Larvicidal and repellent activity of N-methyl-1-adamantylamine and oleic acid a major derivative of bael tree ethanol leaf extracts against dengue mosquito vector and their biosafety on natural predator.

Aegle marmelos (L.) Correa belongs to the family Rutaceae is generally known as "bael fruit tree" occuring across the south Asian countries. The current investigation screened the main derivatives from crude ethanolic extracts of the Bael tree leaf and evaluated activity effects on the larvae and adults of Aedes aegypti (L.) Dengue vector mosquito and a non-target aquatic predator. The GC-MS results showed that the peak area was found to be profound in N-methyl-1-adamantaneacetamide (N-M 1a) followed by oleic acid (OA) with 63.08 and 11.43% respectively. The larvicidal activity against the fourth instar larvae and the crude Ex-Am showed prominent mortality rate (93.60%) at the maximum dosage of 100 ppm. The mortality rate of N-M 1a and OA was occurred at 10 ppm (97.73%) and 12 ppm (95.4%). The repellent activity was found to be prominent at crude Ex-Am (50 ppm) as compared to the pure compounds (N-m 1a and OA) with maximum protection time up to 210 min. The non-target screening of Ex-Am, N-M 1a, and OA on mosquito predator Tx. splendens showed that they are scarcely toxic even at the maximum dosage of 1000 ppm (34.13%), 100 ppm (27.3%), and 120 ppm (31.3%) respectively. Thus, the present investigation clearly proved that the crude Ex-Am and their major derivatives Nm 1-a and OA showed their acute larval toxicity as well as potential mosquito repellent against the dengue mosquito and eco-safety against the mosquito predator.

RNA Interference Suppression of v-ATPase B and Juvenile Hormone Binding Protein Genes Through Topically Applied dsRNA on Tomato Leaves: Developing Biopesticides to Control the South American Pinworm, Tuta absoluta (Lepidoptera: Gelechiidae).

The South American pinworm Tuta absoluta (Meyrick) (Family: Gelechiidae) is one of the most devastating lepidopteran pests in the developing countries of South America, Africa, and Asia. This pest is classified as the most serious threat for tomato production worldwide. In the present study, we analyzed RNAi-mediated control through exogenously applied dsRNA delivery on tomato. The dsRNA treatments were made to target the juvenile hormone binding protein and the v-ATPase B. Both mRNA targets were cloned, validated by sequencing, and used to produce each dsRNA. After treatments the relative transcript expression was analyzed using qRTPCR to assess to efficacy of RNAi. A leaf-dip assay was used to provide late 2nd instar larvae three feeding access periods: 24, 48, and 72 h, to evaluate the effect of gene silencing of each target. Larvae were fed tomato leaves coated with five different RNAi concentrations (10, 20, 30, 40, and 50 micrograms/centimeter-squared), that suppressed two genes (juvenile hormone protein, JHBP, and vacuolar-type adenosine triphosphatase enzyme, v-ATPase). Treatments with dsRNA showed a significant increase in mortality at 24, 48, and 72 h after ingestion (P < 0.01, α = 0.05), along with reduced leaf damage, and increased feeding deterrence. The results suggest that these two RNAi products may provide a suitable treatment for control of this and other lepidopteran pests.

Biological activity of chitosan inducing resistance efficiency of rice (Oryza sativa L.) after treatment with fungal based chitosan.

Reduced pathogen resistance and management of the left-over rice stubble are among the most important challenges faced in rice cultivation. A novel and eco-friendly strategy to synthesise 'Fungal Chitosan' (FC) from Aspergillus niger using rice straw could serve as a sustainable treatment approach to improve both disease resistance and yields, while also effectively managing the rice stubble waste. The FC treatment promoted germination as well as growth parameters in rice varieties, TN1 (high yielding-susceptible) and PTB33 (low yielding-resistant) better than a commercial chitosan (PC). Treatments of exogenously applied FC to plants produced direct toxicity to Xoo, and reduced the BLB disease index by 39.9% in TN1. The capability of FC to trigger a cascade of defense pathways was evident from the measurable changes in the kinetics of defense enzymes, peroxidase (POD) and polyphenol oxidase (PPO). FC treatment increased levels of POD in TN1 by 59.4%, which was 35.3% greater than that of untreated PTB33. Therefore, the study demonstrated the effectiveness of FC treatments for use in agriculture as a potential biostimulant as well as protective agent against bacterial leaf blight, BLB, of rice (Oryza sativa) that could be produced from stubble waste and improve rice stubble management strategies.

Toxicity and behavioral effect of 3beta,24,25-trihydroxycycloartane and beddomei lactone on the rice leaffolder Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae).

Treatment of Dysoxylum pure triterpenes 3beta,24,25-trihydroxycycloartane and beddomei lactone to the rice leaffolder (RLF), Cnaphalocrocis medinalis (Guenée) (Lepidoptera: Pyralidae), resulted in prolonged larval duration and reduced larval weight. In leaf cut choice assay and topical application experiments, beddomei lactone and 3beta,24,25-trihydroxycycloartaneto showed strong antifeedant and growth inhibitor activity against fourth instar larvae of C. medinalis. Also average leaf consumption was decreased (89%) by the treatment of the two terpinoids when compared with controls. Number of eggs laid by the female (fecundity) was decreased and oviposition deterrence index was increased due to the treatment. This result further shows that the pure triterpenes of Dysoxylum act as both an antifeedant and chronic toxin to the rice leaffolder larvae.

Toxicity and physiological effects of neem pesticides applied to rice on the Nilaparvata lugens Stål, the brown planthopper.

The effects of two different neem products (Parker Oil and Neema) on mortality, food consumption and survival of the brown planthopper, Nilaparvata lugens Stål (BPH) (Homoptera: Delphacidae) were investigated. The LC(50) (3.45 ml/L for nymph and 4.42 ml/L for adult in Parker Oil treatment; 4.18 ml/L for nymph and 5.63 ml/L for adult in Neema treatment) and LC(90) (8.72 ml/L for nymph and 11.1 ml/L for adult in Parker Oil treatment; 9.84 ml/L for nymph and 13.07 ml/L for adult in Neema treatment) were identified by probit analysis. The LC(90) (equal to recommended dose) was applied in the rice field. The effective concentration of both Parker Oil and Neema took more than 48 h to kill 80% of the N. lugens. Fourth instar nymph and adult female N. lugens were caged on rice plants and exposed to a series (both LC(50) and LC(90)) of neem concentrations. Nymph and adult female N. lugens that were chronically exposed to neem pesticides showed immediate mortality after application in laboratory experiment. The quantity of food ingested and assimilated by N. lugens on neem-treated rice plants was significantly less than on control rice plants. The results clearly indicate the neem-based pesticide (Parker Oil and Neema), containing low lethal concentration, can be used effectively to inhibit the growth and survival of N. lugens.

Target and non-target botanical pesticides effect of Trichodesma indicum (Linn) R. Br. and their chemical derivatives against the dengue vector, Aedes aegypti L.

The effects of crude ethanol derived leaf extract Trichodesma indicum (Linn) (Ex-Ti) and their chief derivatives were accessed on the survival and development of the dengue mosquito Ae. aegypti also their non-toxic activity against mosquito predator. T. indicum is recognized to be the vital weed plant and a promising herb in the traditional ayurvedic medicine. In this study, the GC-MS chromatogram of Ex-Ti showed higher peak area percentage for cis-10-Heptadecenoic acid (21.83%) followed by cycloheptadecanone (14.32%). The Ex-Ti displayed predominant mortality in larvae with 96.45 and 93.31% at the prominent dosage (200 ppm) against III and IV instar. Correspondingly, sub-lethal dosage against the enzymatic profile of III and IV instar showed downregulation of α,ß-carboxylesterase and SOD protein profiles at the maximum concentration of 100 ppm. However, enzyme level of GST as well as CYP450 increased significantly dependent on sub-lethal concentration. Likewise, fecundity and hatchability of egg rate of dengue mosquito decreased to the sub-lethal concentration of Ex-Ti. Repellent assay illustrates that Ex-Ti concentration had greater protection time up to 210 min at 100 ppm. Also, activity of Ex-Ti on adult mosquito displayed 100% mortality at the maximum dosage of 600, 500 and 400 ppm within the period of 50, 60 and 70 min, respectively. Photomicrography screening showed that lethal dosage of Ex-Ti (100 ppm) produced severe morphological changes with dysregulation in their body parts as matched to the control. Effects of Ex-Ti on the Toxorhynchites splendens IV instar larvae showed less mortality (43.47%) even at the maximum dosage of 1500 ppm as matched to the chemical pesticide Temephos. Overall, the present research adds a toxicological valuation on the Ex-Ti and their active constituents as a larvicidal, repellent and adulticidal agents against the global burdening dengue mosquito.

The toxicity and physiological effect of goniothalamin, a styryl-pyrone, on the generalist herbivore, Spodoptera exigua Hübner.

Efficacy of Goniothalamin a styryl-pyrone isolated from Goniothalamus wightii Hook.f. and Thoms, against beet armyworm, Spodoptera exigua (Hübner), populations was determined under laboratory condition. The experiments were carried out with concentrations of 5, 10, 15 and 30 ppm in an artificial diet and compared with control insects. Laboratory bioassay showed that the goniothalamin had a strong effect on food utilization, moulting and gut histology. The food consumption and conversion of ingested and digested food to body matter decreased with increasing pyrone concentration. The antifeedant activity was also observed in larvae of S. exigua. The treated third instar larvae exhibited mortality in a dose dependent manner. At 5, 10, 15 and 30 ppm/insect, the pyrone gave 23%, 45% 63% and 100% mortality respectively. The larvae of S. exigua gained significantly less weight until pupation in the 10 and 15 ppm pyrone concentrations. Duration of larval period was also affected after treatment with pyrone. The metamorphosis was delayed with additional moulting (7th instar) after treatment with 10 and 15 ppm of goniothalamin, the percentage of larvae successfully moulted into progressive instars was significantly decreased with an increase in pyrone concentrations. The effects of goniothalamin on midgut ultrastructure of third instar larvae of S. exigua were investigated by using light microscopy. Cross sections of the midgut showed that the epithelial cells were destroyed. Significant damage of the midgut epithelium was observed along with lysis.

Effect of azadirachtin on acetylcholinesterase (AChE) activity and histology of the brown planthopper Nilaparvata lugens (Stål).

The effect of azadirachtin (AZA), a tetranortriterpene from neem, on the mortality, acetylcholinesterase (AChE) activity, and the development of the ovaries of female brown planthopper (BPH), Nilaparvata lugens (Stål) was tested in laboratory experiments. The lethal concentrations were determined and applied topically to the adult female BPH (LC(50)=0.47 ppm and LC(90)=0.96 ppm). The treated insects exhibited toxic symptoms with a dose-dependent mortality. The LC(50) concentrations were tested against AChE activity of the BPH. The results indicate that AZA significantly inhibits the activity of AChE only at the high dose (P<.0001) compared with control. Adult females that were exposed to AZA showed a significant reduction in weight (23%, 40%, and 64% for 0.1, 0.25, and 0.5 ppm, respectively). Fecundity was also significantly reduced in AZA treatments compared to the control. Histological study of ovary sections revealed abnormalities in follicular epithelial cells due to AZA treatment.

Botanical essential oils and uses as mosquitocides and repellents against dengue.

Plants naturally produce bioactive compounds along with many secondary metabolites which serve as defensive chemical against herbivorers including insect pests. One group of these phytochemicals are the 'Essential Oils' (EO's), which possess an extensive range of biological activity especially insecticidal and insect repellents. This review provides a comprehensive viewpoint on potential modes of action of biosafety plant derived Essential Oils (EO's) along with their principal chemical derivatives against larvae and adult mosquito vectors of dengue virus. The development and use of Essential Oils (EO's) effectively applied in small rural communities provides an enormous potential for low cost effective management of insect vectors of human pathogens which cause disease.

Toxicological effects of chemical constituents from Piper against the environmental burden Aedes aegypti Liston and their impact on non-target toxicity evaluation against biomonitoring aquatic insects.

Dengue is the most rapidly spreading mosquito-borne viral disease in the world. The mosquito, Aedes aegypti, also spreads Yellow fever, Chikungunya, and Zika virus. As the primary vector for dengue, Ae. aegypti now occurs in over 20 countries and is a serious concern with reports of increasing insecticide resistance. Developing new treatments to manage mosquitoes are needed. Formulation of crude volatile oil from Piper betle leaves (Pb-CVO) was evaluated as a potential treatment which showed larvicidal, ovipositional, and repellency effects. Gut-histology and enzyme profiles were analyzed post treatment under in-vitro conditions. The Pb-CVO from leaves of field collected plants was obtained by steam distillation and separated through rotary evaporation. The Pb-CVO were evaluated for chemical constituents through GC-MS analyses revealed 20 vital compounds. The peak area was establish to be superior in Eudesm-7(11)-en-4-ol (14.95%). Pb-CVO were determined and tested as four different concentrations (0.25, 0.5, 1.0, and 1.5 mg/L) of Pb-CVO towards Ae. aegypti. The larvicidal effects exhibited dose dependent mortality being greatest at 1.5 mg Pb-CVO/10 g leaves. The LC50 occurred at 0.63 mg Pb-CVO/L. Larva of Ae. aegypti exposed to Pb-CVO showed significantly reduced digestive enzyme actions of α- and ß-carboxylesterases. In contrast, GST and CYP450 enzyme levels increased significantly as concentration increased. Correspondingly, oviposition deterrence index and egg hatch of Ae. aegypti exposed to sub-lethal doses of Pb-CVO demonstrated a strong effect suitable for population suppression. Repellency at 0.6 mg Pb-CVO applied as oil had a protection time of 15-210 min. Mid-gut histological of Ae. aegypti larvae showed severe damage when treated with 0.6 mg of Pb-CVO treatment compared to the control. Non-toxic effects against aquatic beneficial insects, such as Anisops bouvieri and Toxorhynchites splendens, were observed at the highest concentrations, exposed for 3 h. These results suggest that the Pb-CVO may contain effective constituents suitable for development of new vector control agents against Ae. aegypti.