Search

Insects have innate immunity comprising cellular and humoral defense reactions. Nodulation is a predominant cellular immune response to bacterial infections and the prophenoloxidase (PPO)-activating system acts in nodulation with a melanization reaction that darkens the nodules and produces reactive oxygen species that probably kill the bacteria. Although several eicosanoid actions have been reported in insect immune functions, these actions are relatively understudied among dipterans. We addressed this gap by exploring nodulation reactions to bacterial infections in the 3rd instar of the flesh fly Thomsonea argyrostoma. The Gram-positive bacterium, Micrococcus luteus, was injected either alone or coupled with eicosanoids biosynthesis inhibitors (EBIs). Nodulation exhibits a maximum at 24 h post injection. At zero time of control larvae, a constitutive level of phenoloxidase (PO) was found in plasma. Intrahemocoelic injection of M. luteus induces biosynthesis of PPO in hemocytes, and also its release into and activation in plasma via M. luteus challenge. EBIs suppress nodulation and PPO content of both hemocytes and plasma, but not PO content of plasma. The results imply the mediation of eicosanoids in PPO biosynthesis in hemocytes and its release, but not its activation in plasma. The injection of biogenic monoamines Octopamine (OA) and 5-hydroxytryptamine (5-HT) elevates nodulation and PPO biosynthesis and its activation in plasma. [ABSTRACT FROM AUTHOR]

Pollutants in an environment can have long-term implications for the species living there, resulting in local adaptations with implications for their genetic structure. Heavy metal pollutants infiltrate soils and groundwater, bioaccumulate in food webs, and negatively impact biota. In this study, we investigated the degree to which the genetic structure and variability of the slender green-winged grasshopper (Aiolopus thalassinus (Fabricius) (Orthoptera: Acrididae)) were impacted by heavy metal pollution and distance. We used the random amplified polymorphic DNA-polymerase chain reaction (RAPD-PCR) method to examine the genetic variability of populations in 3 heavy metal-polluted and 3 unpolluted locations across varying geographical distances in Egypt. The heavy metal concentrations of cadmium, copper, lead, and zinc were measured from the grasshopper tissue and soils. Sixty-nine unique and polymorphic bands were produced by 4 primers. Cluster and principal component analyses separated the populations inside and outside Cairo into 2 main branches, which were further divided into smaller branches corresponding to their geographical regions. We found no differences in the Shannon genetic diversity index between populations or with increasing heavy metal concentrations in either the soil or the grasshopper tissue. Our results showed a greater genetic variation among populations than between populations within the same location, indicating populations within locations were less differentiated than those between locations. The moderate correlation between genetic similarity and spatial distance suggests geographical isolation influenced grasshopper population differentiation. Based on the RAPD analysis, environmental pollutants and geographical distances impact the A. thalassinus population structure, potentially restricting gene flow between sites even at small spatial scales. [ABSTRACT FROM AUTHOR]

The presence of harmful heavy metals (HMs) in the aquatic environment can damage the environment and threaten human health. Traditional remediation techniques can have secondary impacts. Thus, more sustainable approaches must be developed. Microalgae have biological properties (such as high photosynthetic efficiency and growth), which are of great advantage in the HMs removal. In this study, the effect of various concentrations (2×, 4×, and 6×) of copper (Cu), cobalt (Co), and zinc (Zn) on microalgae (C. sorokiniana GEEL-01, P. kessleri GEEL-02, D. asymmetricus GEEL-05) was investigated. The microalgal growth kinetics, HMs removal, total nitrogen (TN), total phosphor (TP), and fatty acids (FAs) compositions were analyzed. The highest growth of 1.474 OD680nm and 1.348 OD680nm was obtained at 2× and 4×, respectively, for P. kessleri GEEL-02. P. kessleri GEEL-02 showed high removal efficiency of Cu, Co, and Zn (38.92–55.44%), (36.27–68.38%), and (32.94–51.71%), respectively. Fatty acids (FAs) analysis showed that saturated FAs in C. sorokiniana GEEL-01 and P. kessleri GEEL-02 increased at 2× and 4× concentrations while decreasing at 6×. For P. kessleri GEEL-02, the properties of biodiesel including the degree of unsaturation (UD) and cetane value (CN) increased at 2×, 4×, and 6× as compared to the control. Thus, this study demonstrated that the three microalgae (particularly P. kessleri GEEL-02) are more suitable for nutrient and HMs removal coupled with biomass/biodiesel production. [ABSTRACT FROM AUTHOR]

The main aim of this study is to improve productivity, physical and chemical properties of the fruits and fruit quality of Eureka Lemon trees while lowering production costs by investigating the use of different NPK alternative sources (slow release, and bio) to reduce the use of chemical NPK fertilizers. Ten treatments of NPK fertilizers were applied. The results indicate that the highest values of yield (111.0 and 114.0 kg/tree) were found with 100% chemical NPK (control) for both first and second seasons, respectively. The lemon fruit weight ranged from 131.3 to 152.4 and 131.4 to 153.5 g for first and second seasons, respectively, for all treatments under study. The highest values of fruit length and fruit diameter were found with 100% chemical NPK (control) for both two seasons. The highest values of juice quality parameters (TSS, juice acidity, TSS/acid ratio and vitamin C concentration) responded favorably to higher chemical NPK treatment rates. The highest values of TSS, juice acidity, TSS/Acid ratio, and vitamin C concentration were 9.45%, 6.25%, 1.524 and 4.27 mg/100 g, respectively, were found with 100% chemical NPK (control) for both two seasons. Meanwhile, the lowest value of total sugar was found with 100% chemical NPK (control) for both two seasons. [ABSTRACT FROM AUTHOR]

Juvenoids are juvenile hormone (JH) mimetics, with specific structural features and defined molecular size that disrupt the target insect development. Juvenoid activity (= JH-type activity) of various isoprenoid-based derivatives as insecticidal candidates of the insect growth disruptors (IGDs) type were rated against the house fly, Musca domestica L. The epoxidized decenyl and nonenyl phenyl ether derivatives have more active compounds than those of both parent alkoxidized or olefinic structures. The highest juvenoid potency was shown by 3,4-methylenedioxyphenyl ethers of 8,9-epoxy-5,9-dimethy1-3,8-decadiene. Qualitative structure-activity relationships are offered to relate the chemical structure criteria to observed juvenoid-related activity. Differences in activity among the reported isoprenoid-based derivatives were qualitatively rationalized. This study advances understanding of the structural qualifications and activity determinants of isoprenoid juvenoids, which is important for the development of new filth flies eco-friendly insecticides. [ABSTRACT FROM AUTHOR]

In order to find effective, biorational, and eco-friendly pest control tools, Cupressus sempervirens var. horizontalis essential oil (EO) was produced using hydrodistillation, before being analyzed with gas chromatography, specifically, using flame ionization detection. The monoterpene components α-pinene (46.3%), δ-3-carene (22.7%), and α-cedrol, a sesquiterpene hydrocarbon, (5.8%), were the main fractions. An oil-in-water nanoemulsion was obtained following a green protocol. The EO, its nanoemulsion, and its terpenes each exhibited both insecticidal and insect repellent activities against the rice weevil, Sitophilus oryzae. In a contact bioassay, the nanoemulsion induced a 100% adult mortality rate in a concentration of 10.0 µL/cm2 after 4 days of treatment, whereas 40 µL/cm2 of EO and α-cedrol was required to kill 100% of weevils. Using fumigation, nanoemulsion and EO at 10 µL/L air caused a 100% adult mortality rate after 4 days of treatment. The LC50 values of botanicals ranged between 5.8 and 53.4 µL/cm2 for contact, and between 4.1 and 19.6 µL/L for fumigation. The phytochemicals strongly repelled the weevil at concentrations between 0.11 and 0.88 µL/cm2, as well as considerably inhibiting AChE bioactivity. They were found to be safe for earthworms (Eisenia fetida) at 200 mg/kg, which also caused no significant alteration in wheat grain viability. This study provides evidence for the potential of using the EO of C. sempervirens and its nanoemulsion as natural, eco-friendly grain protectants against S. oryzae. [ABSTRACT FROM AUTHOR]

In order to search for bio-rational and eco-friendly pest control agents to protect crops from insect infestation, while avoiding the toxic hazards of chemical pesticides, essential oils (EOs) were hydrodistilled from Juniperus procera and Thymus vulgaris and analyzed using gas chromatography–flame ionization detection (GC–FID), and gas chromatography–mass spectrometry (GC–MS). Eugenol (71.3%), β-caryophyllene (11.8%), and α-pinene (6.1%) were isolated as the major components of J. procera EO, whereas thymol (58.1%), p-cymen (10.3%), and carvacrol (8.3%) were the main terpenes in T. vulgaris EO. The EOs and terpenes exhibited considerable bioactivity against the khapra beetle using the contact and fumigation bioassays, where T. vulgaris EO was superior in bioactivity. Among the terpenes tested, carvacrol and eugenol were superior. Regarding contact toxicity using impregnated filter paper and after 24 h of exposure, the LC50 values ranged between 21.4 and 77.0 µL/cm2 against larvae and between 16.1 and 69.6 µL/cm2 against adults. After 48 h, these values decreased remarkably. Upon fumigation and after 48 h of exposure, the LC50 values ranged between 23.0 and 65.3 µL/L against larvae, and from 14.2 to 56.4 µL/L against adults. The botanicals effectively inhibited the acetylcholinesterase activity of the larvae; however, they were safe for the earthworm E. fetida and did not alter the viability of wheat grains. There is a potential for using these botanicals to control T. granarium. However, further investigations are needed to confirm the safety of these phytochemicals before use as grain protectants on a commercial scale. [ABSTRACT FROM AUTHOR]

Essential oil (EO) of Origanum vulgare L. was hydrodistilled and analysed using gas chromatography–flame ionization detection and gas chromatography–mass spectrometry. The monoterpenes, carvacrol (61.2%), γ-terpinene (9.6%), thymol (8.3%), and p-cymene (5.7%) were identified. Oil-in-water nanoemulsion was prepared and characterized from the EO through a green procedure. Botanicals had a remarkable mosquitocidal and effectively inhibited acetylcholinesterase activity of Aedes aegypti. The nanoemulsion at 40 µg/ml caused 100% adult and larval mortality after 12 h. At 80 µg/ml, percentage mortality caused by EO products ranged between 55.11-100% for larvae, and 63.0 -100%. for adults After 24 h exposure, LC50's ranged between 13.2 and 75.7 µg/ml against larvae, and between 10.1 and 36.0 µg/ml against adults. The lethal time (LT50) decreased with nanoemulsion, EO and carvacrol. Test products were safe towards the non-target aquatic species, Gambusia affinis and Diplonychus indicus. Results recommend test botanicals as natural alternatives to control Ae. aegypti. [ABSTRACT FROM AUTHOR]

The essential oil (EO) was hydrodistilled from of Deverra tortuosa aerial parts. Fifty-six components amounting 99.3% were identified in EO through using gas chromatography–flame ionization detection (GC–FID) and (GC–MS). Phenylpropanoids, dillapiole (41.6%), elemicin (7.3%) and myristicin (5.1%), and the monoterpene, sabinene (4.2%) were identified as the major terpenes. An oil-in-water nanoemulsion (particle size 70.3 nm) was developed from EO adopting a low-energy method. The EO products showed insecticidal and biochemical effects against the cowpea weevil Callosobruchus maculatus. Based on a 48-h exposure period, the oil nanoemulsion exhibited a superior contact bioactivity (LC50 = 10.3 µg/cm2), followed by EO (LC50 = 23.1 µg/cm2), dillapiole (LC50 = 27.8 µg/cm2), and myristicin (LC50 = 37.1 µg/cm2). Upon fumigation, nanoemulsion and EO were superior as fumigants (LC50 after 48 h were 6.9 and 14.3 µl/l, respectively). Test materials showed a residual bioactivity against C. maculatus, where EO, dillapiole, and myristicin showed the strongest grain protecting activity. EO products significantly inhibited acetylcholinesterase (AChE) activity of C. maculatus adults. Test products were safe toward the non-target earthworms and did not alter the viability of cowpea seeds. There are evidences for the potential of using EO of D. tortuosa and its nanoemulsion and phenylpropanoids as natural grain protectants against C. maculatus. [ABSTRACT FROM AUTHOR]

BACKGROUND The house mosquito, Culex pipiens L. is a harmful species, widespread in urban areas, and considered the primary enzootic vector of West Nile arbovirus. Widespread insecticide resistance in mosquito populations and the environmental risks and toxicity hazards of chemical pesticides make insecticides an inadequate mosquito control strategy. Seeking ecofriendly tools for mosquito control tools has become necessary. RESULTS: Essential oil (EO) was hydrodistilled from the fruits of Brazilian pepper, Schinus terebinthifolius Raddi and analyzed using gas chromatography–flame ionization detection and gas chromatography–mass spectrometry. An oil‐in‐water nanoemulsion (particle size 41.3 nm) was developed and characterized from EO using a green low‐energy approach. EO, its nanoemulsion and monoterpenes showed mosquitocidal, repellent and acetylcholinesterase inhibitory activities against Cx. pipiens. A nanoemulsion concentration of 30 μl L–1 caused 100% larval mortality after 24 h of exposure, whereas EO, d‐limonene and α‐phellandrene at 60 μl L–1 caused 100%, 92.4% and 88.2% larval mortality, respectively. The concentration that killed 50% of organisms (LC50) for larvae after 24 h ranged between 6.8 and 40.6 μl L–1. Upon fumigation, 15.0 μl L–1 of nanoemulsion killed 94.5% of adults after 24 h of exposure. LC50 values against adults ranged between 5.3 and 31.2 μl L–1. EO products exhibited repellence activity at concentrations between 0.5 and 4.0 μl cm–2. Test materials effectively inhibited the acetylcholinesterase activity of mosquito and were safe toward the non‐target organisms Gambusia affinis and Eisenia fetida. CONCLUSION: There is a potential for using S. terebinthifolius EO, its nanoemulsion and monoterpenes as ecofriendly natural mosquitocides. [ABSTRACT FROM AUTHOR]

The essential oil (EO) of Cupressus sempervirens was obtained by hydrodistillation and analysed using gas chromatography–flame ionization detection (GC–FID) and gas chromatography–mass spectrometry (GC–MS). Two monoterpenes, α-pinene (49.1%) and δ-3-carene (21.4%), and one sesquiterpene hydrocarbon, α-cedrol (5.1%), were isolated as the EO major terpenes. An oil-in-water nanoemulsion (particle size 71.2 nm) was produced from the EO through a low-energy method. The EO, its nanoemulsion and its main constituents showed mosquitocidal and biochemical effects against Culex quinquefasciatus Say, the common vector of lymphatic filariasis parasites. All treatments showed dose-dependent bioactivity, and adults were more susceptible to the EO products than the larvae. The nanoemulsion showed superior activity, followed by the crude EO and α-cedrol. At 40 μg/ml, the nanoemulsion caused 100% larval mortality, while the EO and α-cedrol required twice this concentration to achieve the same larval mortality. The LC50 values were 8.4, 16.1, 15.1, 30.7 and 53.4 μg/ml at 24 h after exposure for the nanoemulsion, crude oil, α-cedrol, δ-3-carene and α-pinene, respectively. For adults, 20.0 μl/l nanoemulsion caused 100% mortality, while twice this concentration of the EO was required to achieve the same effect. The LC50's against adults ranged between 6.2 and 40.4 μl/l. EO products prominently repelled mosquitoes at concentrations between 0.75 and 6.0 μl/cm2. The EO products caused remarkable inhibition of Cx. quinquefasciatus acetylcholinesterase activity but were safer towards the non-target aquatic species Gambusia affinis. These results recommend the use of C. sempervirens EO, its nanoemulsion and main terpenes as natural tools to control Cx. quinquefasciatus. [ABSTRACT FROM AUTHOR]

To seek new mosquito control agents while avoiding the environmental impacts and toxicity hazards of conventional pesticides, the essential oil of Dysphania ambrosioides was obtained by hydrodistillation and analysed using GC–FID and GC–MS. The compounds 1-methyl-4-(1-methylethyl)-2,3-dioxabicyclo[2.2.2]oct-5-ene (cis-ascaridole), 1-methyl-4-(1-methylethyl) benzene (р-cymene), and 1-isopropyl-4-methyl-1,3-cyclohexadiene (p-mentha-1,3-diene also known as α-terpinene) were identified as the major components. The EO and the major fractions showed remarkable mosquitocidal activity against third instar larvae and adults of Culex quinquefasciatus Say. The oil and fractions were assayed at 3.125, 6.25, 12.5, 25, and 50 μl/l. Mortality was time- and dose-dependent. At 24 h post-exposure at an assayed concentration of 50 μl/l, the larval and adult mortalities ranged between 80.11–100% and 91.22–100%, respectively. Strong larvicidal and adulticidal activities were recorded in the cases of the crude oil and cis-ascaridole. The LC50 values after 24 h of treatment ranged between 6.2–20.1 μl/l and 5.1–13.9 μl/l against larvae and adults, respectively. The corrected percentage mortalities increased over time with the tested plant oil and the major fractions relative to the control. The time required to achieve 50% mortality (LT50) decreased remarkably with all treatments. The tested EO and major fractions effectively inhibited larval acetylcholinesterase activity with IC50 values ranging from 8.44 to 64.80 mM compared with 2.08 × 10−3 mM for the reference standard, methomy. The results indicate the potential of developing natural mosquitocides against C. quinquefasciatus based on the tested EO and its major fractions. [ABSTRACT FROM AUTHOR]

The development of visible‐light photocatalysts with desirable material characteristics and efficient performance is an existing challenge for photocatalysis community. Herein, we report on the synthesis of silver nanoparticles (AgNPs) modified porous silicon (PSi) nanopowder and its effective use in the photo‐reduction of hexavalent chromium Cr(VI) to trivalent Cr(III) under direct visible light irradiation in the presence of citric acid. The PSi was prepared via simple stain etching of Si microparticles in HF/HNO3 aqueous solution, followed by the deposition of AgNPs onto PSi by the immersion plating technique. The developed photocatalyst composed of PSi with <20 nm mesoporous structure, decorated with crystalline 15‐50 nm AgNPs. Photocatalytic experiments using unmodified Si microparticles, either PSi or sonicated one, indicated inactive catalytic behavior toward the photo‐reduction of Cr(VI). Remarkable photo‐reduction efficiency (97.4%) was achieved after 180 minutes irradiation using the AgNPs/PSi sample. The efficient photo‐reduction capability of AgNPs/PSi photocatalyst is attributed to the enhanced separation between photo‐generated electrons and holes (e−‐h+) enabling better utilization of light, as revealed from the photoluminescence measurement. Additionally, the presence of citric acid in solution promoted greatly the photo‐reduction reaction as it acted as a hole scavenger, suppressing further the rate of e−‐h+ recombination through rapid consumption of photo‐generated holes. Excellent reusability of the current photocatalyst was evidenced by performing cyclic five runs with minimal reactivity loss. Results of synthesis, characterization, photocatalytic activity and reaction mechanism are thoroughly addressed and discussed. [ABSTRACT FROM AUTHOR]

In order to find new, less toxic and eco-friendly pest control agents, natural products are considered to be alternative options of potentially active compounds. In this context, the aim of the present study was the isolation and structural elucidation of the β-carboline and quinazoline alkaloids of Peganum harmala L. seeds. Silver nanoparticles (AgNPs) were prepared using alkaloids through a green synthesis procedure. Harmala alkaloids and their AgNPs showed considerable insecticidal and growth inhibitory activities against khapra beetle, Trogoderma granarium (Everts) (Coleoptera: Dermestidae). On a toxicity bioassay using treated filter papers, the total harmala alkaloids (THAs) were the most toxic followed by harmaline, harmine and harmalol, where LC50' s ranged between (30.6-61.7 μg/ cm2) and (24.4-46.1 μg/cm2) 24 h post-treatment against larvae and adults, respectively. The two quinazolines, vasicine and vasicinone, showed moderate to weak activities. At 48 h post-exposure, efficacy of all alkaloids was increased. When tested as AgNPs (size 22.5-66.2 nm diameter), toxicity of alkaloids, especially the β-carbolines, was strongly increased, where LC50 values ranged between (4.7-11.4 μg/ cm2) and (4.1-10.2 μg/cm2) 48 h post-treatment against larvae and adults, respectively. Feeding the 2nd instar larvae AgNPs-treated grains at sublethal concentrations led to significant drawbacks on the normal growth and development of the insect. These effects appeared as a high percentage of malformed larvae and pupae, a prolonged life span and a significant reduction in adult emergence. Results suggest the potential of using harmala alkaloids and their AgNPs as a natural approach for controlling T. granarium. [ABSTRACT FROM AUTHOR]