Chemical composition and bio-efficacy of agro-waste plant extracts and their potential as bioinsecticides against Culex pipiens mosquitoes

Mosquitoes are considered one of the most lethal creatures on the planet and are responsible for millions of fatalities annually through the transmission of several diseases to humans. Green trash is commonly employed in agricultural fertilizer manufacturing and microbial bioprocesses for energy production. However, there is limited information available on the conversion of green waste into biocides. This study investigates the viability of utilizing green waste as a new biopesticide against Culex pipiens mosquito larvae. The current study found that plant extracts from Punica granatum (98.4 % mortality), Citrus sinensis (92 % mortality), Brassica oleracea (88 % mortality), Oryza sativa (81.6 % mortality), and Colocasia esculenta (53.6 % mortality) were very good at killing Cx. pipiens larvae 24 h post-treatment. The LC50 values were 314.43, 370.72, 465.59, 666.67, and 1798.03 ppm for P. granatum, C. sinensis, B. oleracea, O. sativa, and C. esculenta, respectively. All plant extracts, particularly P. granatum extract (14.93 and 41.87 U/g), showed a significant reduction in acid and alkaline phosphate activity. Additionally, pomegranate extract showed a significant decrease (90 %) in field larval density, with a stability of up to five days post-treatment. GC-MS results showed more chemical classes, such as terpenes, esters, fatty acids, alkanes, and phenolic compounds. HPLC analysis revealed that the analyzed extracts had a high concentration of phenolic and flavonoid components. Moreover, there are many variations among these plants in the amount of each compound. The docking interaction showed a simulation of the atomic-level interaction between a protein and a small molecule through the binding site of target proteins, explaining the most critical elements influencing the enzyme's activity or inhibitions. The study's findings showed that the various phytochemicals found in agro-waste plants had high larvicidal activity and provide a safe and efficient substitute to conventional pesticides for pest management, as well as a potential future in biotechnology.

Larvicidal potential of Trachyspermum ammi essential oil and Delphinium speciosum extract against malaria, dengue, and filariasis mosquito vectors

Mosquito-borne diseases, such as malaria, dengue, and Zika, pose major public health challenges globally, affecting millions of people. The growing resistance of mosquito populations to synthetic insecticides underscores the critical need for effective and environmentally friendly larvicides. Although chemical pesticides can initially be effective, they often lead to negative environmental consequences and health hazards for non-target species, including humans. This study aimed to evaluate the larvicidal effects of Trachyspermum ammi essential oil and Delphinium speciosum extract on the larvae of three major mosquito species: Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Mosquito larvae of Ae. aegypti, An. stephensi, and Cx. quinquefasciatus were reared under controlled laboratory conditions. The larvicidal activity of T. ammi essential oil and D. speciosum extract was evaluated through standard bioassays, using various concentrations of essential oils (10, 20, 40, 80, and 160 ppm) and extracts (160, 320, 640, 1280, and 2560 ppm) to determine the lethal concentration (LC50) values after 24 h of exposure. Fresh plant materials were collected, with the essential oil extracted via hydro-distillation, and the extract prepared using methanol solvent extraction. The chemical composition of T. ammi essential oil was examined using gas chromatography-mass spectrometry (GC-MS). Additionally, the preliminary analysis of the chemical compounds in D. speciosum extract was carried out using thin layer chromatography (TLC) and nuclear magnetic resonance spectroscopy (NMR) techniques. The results indicated that the essential oil of T. ammi exhibited more effective larvicidal activity compared to the D. speciosum extract. Specifically, the essential oil demonstrated LC50 values of 18 ppm for Cx. quinquefasciatus and 19 ppm for Ae. aegypti. In contrast, the D. speciosum extract showed the strongest larvicidal effect against An. stephensi, with an LC50 of 517 ppm. Concentrations of 40 ppm of the essential oil and 1280 ppm of the extract resulted in 100% mortality across all three species. Both the essential oil of T. ammi and the D. speciosum extract exhibited concentration-dependent larvicidal activity, and these results were statistically significant (p < 0.001) compared to the no-treatment group. GC-MS analysis revealed thymol (88.95%), o-cymen-5-ol (4.11%), and γ-terpinene (2.10%) as the major constituents of the T. ammi essential oil. Additionally, TLC verified the presence of alkaloids in both chloroform and methanolic extracts. Proton NMR identified a diterpene structure for these alkaloids. These findings suggest that T. ammi essential oil is a promising candidate for natural mosquito control strategies. Given its efficacy, further research is warranted to explore its potential in integrated vector management programs.

Biopesticides: a Green Approach Towards Agricultural Pests

Biopesticides are biological products or organisms which are potential candidates for eco-friendly pest management and crop protection over the chemical pesticides. The so-called biopesticides include viruses, bacteria, fungi, predators, parasites, and pheromones exhibiting a variety of modes of actions. They are less toxic, rapidly degradable, and more targeted to specific pests. However, it is noted that the formulation of biopesticides plays a crucial link between production and application, and the former dictates economy, longer shelf life, ease of application, and enhanced field efficacy. Moreover, there is an urgent need for organic farmers to gain more proficiency in using biopesticides. Even though biopesticides have more advantages, the main challenge is the marketing of biopesticides. Advances in biopesticide research and development significantly reduce the environmental damage caused by the residues of synthetic insecticides and support sustainable agriculture. Numerous products have been developed since the introduction of biopesticides, some of which have taken the lead in the agro-market after being registered and released. The types of biopesticides; their mode of action; formulation strategies; recent advancements of biopesticides focusing mainly on improvement of its action spectra, to thereby replace chemical pesticides; and finally, the future aspects of biopesticides have been discussed in this review.

Acaricidal Efficacy of Thirty-Five Egyptian Plants Against the Camel Tick, Hyalomma Dromedarii

PURPOSE

Alternative and affordable tick control strategies are crucial to control and prevent tick bites and tick-borne diseases.

METHODS

In this study, we evaluated the acaricidal efficacy of 35 aqueous plant extracts (17%) against the camel tick, Hyalomma dromedarii.

RESULTS

The phytochemical profile indicated the presence of various secondary substances. Plants were classified into three groups according to their mortality percentage 15 days post-treatment with 17%. This highly effective group (91%-95%) comprised Ocimum basilicum, Mespilus germanica, and Viola alpine followed by Carum carvi, Cucurbita pepo (peel), and Peganum harmala. A moderately effective group (80%-90%) included Acacia nilotica, Apium graveolens, Capsicum annuum, Ceratonia siliqua, Cucurbita pepo (seeds), Equisetum arvense, Eruca sativa, Ginkgo biloba, Plantago psyllium, Phyllanthus emblica, Punica granatum, and Ziziphus spinachristi. The 20 remaining plants were assigned to the less effective group (< 80%). Viscum album (58.3%), which was the least effective reference plant. The high potency of six plant extracts as acaricides may be attributed to the high content of active principles, e.g., phenols, flavonoids, and tannins.

CONCLUSION

All of these highly effective plants are recommended for use as an acaricide, in case of facing acaricidal resistance or limited options for tick control.

Synthesis of eco-friendly layered double hydroxide and nanoemulsion for jasmine and peppermint oils and their larvicidal activities against Culex pipiens Linnaeus

Mosquito-borne diseases represent a growing health challenge over time. Numerous potential phytochemicals are target-specific, biodegradable, and eco-friendly. The larvicidal activity of essential oils, a jasmine blend consisting of Jasmine oil and Azores jasmine (AJ) (Jasminum sambac and Jasminum azoricum) and peppermint (PP) Mentha arvensis and their nanoformulations against 2nd and 4th instar larvae of Culex pipiens, was evaluated after subjecting to different concentrations (62.5, 125, 250, 500, 1000, and 2000 ppm). Two forms of phase-different nanodelivery systems of layered double hydroxide LDH and oil/water nanoemulsions were formulated. The synthesized nanoemulsions showed particle sizes of 199 and 333 nm for AJ-NE and PP-NE, with a polydispersity index of 0.249 and 0.198, respectively. Chemical and physiochemical analysis of TEM, SEM, XRD, zeta potential, drug loading capacity, and drug release measurements were done to confirm the synthesis and loading efficiencies of essential oils' active ingredients. At high concentrations of AJ and PP nanoemulsions (2000 ppm), O/W nanoemulsions showed higher larval mortality than both LDH conjugates and crude oils. The mortality rate reached 100% for 2nd and 4th instar larvae. The relative toxicities revealed that PP nanoemulsion (MA-NE) was the most effective larvicide, followed by AJ nanoemulsion (AJ-NE). There was a significant increase in defensive enzymes, phenoloxidase, and α and β-esterase enzymes in the treated groups. After treatment of L4 with AJ, AJ-NE, PP, and PP-NE, the levels of phenoloxidase were 545.67, 731.00, 700.00, and 799.67 u/mg, respectively, compared with control 669.67 u/mg. The activity levels of α-esterase were 9.71, 10.32, 8.91, and 10.55 mg α-naphthol/min/mg protein, respectively. It could be concluded that the AJ-NE and PP-NE nanoformulations have promising larvicidal activity and could act as safe and effective alternatives to chemical insecticides.

Insecticidal activity, Chemical Constituents of Trachyspermum ammi, Withania coagulans and Murraya koenigii ethanloic extracts against Bemisia tabaci

Abstract Whitefly is one of the most widespread agricultural pests in the world. Essential oils might be used to control this insect in an environmentally responsible way. The fumigant, repellent, and anti-oviposition activity of ethanol-extracted essential oils of Trachyspermum ammi, Withania coagulans, and Murraya koenigii against Bemisia tabaci was investigated in this study. In the experiment, three essential oil concentrations (2.5 mg/mL, 5 mg/mL, and 10 mg/mL) were used. Trachyspermum ammi had the highest percentage of whitefly death in laboratory experiments due to its fumigant toxicity; the same tendency was found in contact toxicity and repellent effect. Mortality percent rises as the concentration of essential oil increases with bioassay time. As the concentration of essential oil grows with bioassay time, so does the mortality rate. The most adult whiteflies escaped from the treated plants' greenhouse due to the highest essential oil concentration. The greatest repellency was found with Trachyspermum ammi essential oil at 10 mg/mL. The essential oil had the greatest anti-oviposition efficacy against whiteflies. Trachyspermum ammi possessed the most potent anti-oviposition deterrent, followed by Withania coagulans in second place. Murraya koenigii finished third with moderate anti-oviposition, which affects the number of eggs produced in comparison to the control. As a consequence, these three oils might be used as an effective and environmentally acceptable bio-insecticide to control B. tabaci.

In Vivo Bioassay of the Repellent Activity of Caraway Essential Oil against Green Peach Aphid

An in vivo dual choice bioassay with white cabbage as a host plant was used to determine the repellent effect of three different accessions of caraway (Carum carvi L.) essential oils (EOs) against the green peach aphid Myzus persicae (Sulzer). The dominant components of the EO were D-Carvone (47.3-74.4%) and D-limonene (25.2-51.9%), which accounted for 99.2-99.5% of the EOs determined by GC/MS. The EO with the highest D-limonene content (51.9%) showed the highest repellence (Repellency Index (RI) = +41%), which was stable up to 330 min. The incorporation of several surfactants with different hydrophilic-lipophilic balance values (from 12.4 to 16.7) with caraway EO caused a general inhibition of the repellent effect during the testing period (RI from +41% to -19%). Overall, the findings indicate that caraway EO could be used as a green peach aphid repellent, but more work is needed to formulate the EO into a ready-to-use product.

Novel acaricidal and growth-regulating activity of Aloe vera and Rheum rhabarbarum extracts and their oil/water nanoemulsions against the camel tick, Hyalomma dromedarii

Hyalomma dromedarii is an important tick species infesting livestock. This work evaluated the novel adulticidal, insect growth-regulating, and enzymatic efficacy of ethanol plant extracts of Aloe vera and Rheum rhabarbarum and their nanoemulsions against males and engorged females of the camel tick, H. dromedarii. The physicochemical properties of nanoemulsions were evaluated. The High-Performance Liquid Chromatography (HPLC) analyses indicated that the extracts contained polyphenols and flavonoids, which could enhance their acaricidal effect. Dynamic light scattering (DLS) of the nanoemulsions of A. vera and R. rhabarbarum were 196.7 and 291 nm, whereas their zeta potentials were - 29.1 and - 53.1 mV, respectively. Transmission electron microscope (TEM) indicated that nanoemulsions showed a regular spherical shape (less than 100 nm). Fifteen days post-treatment (PT) with 25%, the mortality% of A. vera and R. rhabarbarum were 88.5 and 96.2%, respectively. Five days PT, the median lethal concentration values of A. vera, R. rhabarbarum, and their nanoemulsions were 7.8, 7.1, 2.8, and 1.02%, respectively, and their toxicity indices were 91.02, 100, 36.4, and 100%, respectively. Their median lethal time values PT with 3.5% were 6.09, 5.09, 1.75, and 1.34 days, respectively. Nanoemulsions enhanced the efficacy of the crude extract 1-7 folds, 5 days PT, and accelerated their speed of killing ticks 2-4 times. The total protein and carbohydrates, Acetylcholinesterase, Alpha esterase, and Amylase were affected PT. The reproductive potential of engorged females was adversely impacted. In conclusion, the novel A. vera and R. rhabarbarum extracts were promising acaricides, and their nanoformulations enhanced their efficacies.

Evolution of the Genetic Structure of the Didymella tanaceti Population During Development of Succinate Dehydrogenase Inhibitor Resistance

Emergence of pathogens with decreased sensitivity to succinate dehydrogenase inhibitor fungicides is a global agronomical issue. Analysis of Didymella tanaceti isolates (n = 173), which cause tan spot of pyrethrum (Tanacetum cinerariifolium), collected prior to (2004 to 2005) and after (2009, 2010, 2012, and 2014) the commercial implementation of boscalid in Tasmanian pyrethrum fields identified that insensitivity developed over time and has become widespread. To evaluate temporal change, isolates were characterized for frequency of mutations in the succinate dehydrogenase (Sdh) B, C, and D subunits associated with boscalid resistance, mating type, and SSR genotype. All isolates from 2004 and 2005 exhibited wild-type (WT) Sdh alleles. Seven known Sdh substitutions were identified in isolates collected from 2009 to 2014. In 2009, 60.7% had Sdh substitutions associated with boscalid resistance in D. tanaceti. The frequency of WT isolates decreased over time, with no WT isolates identified in 2014. The frequency of the SdhB-H277Y genotype increased from 10.7 to 77.8% between 2009 and 2014. Genotypic evidence suggested that a shift in the population structure occurred between 2005 and 2009, with decreases in gene diversity (uh; 0.51 to 0.34), genotypic evenness (E5; 0.96 to 0.67), genotypic diversity (G; 9.3 to 6.8), and allele frequencies. No evidence was obtained to support the rapid spread of Sdh genotypes by clonal expansion of the population. Thus, insensitivity to boscalid has developed and become widespread within a diverse population within 4 years of usage. These results suggest that D. tanaceti can disperse insensitivity through repeated frequent mutation, sexual recombination, or a combination of both.

Phytochemical Screening and Evaluation of Pesticidal Efficacy in the Oleoresins of Globba sessiliflora Sims and In Silico Study

Globba sessiliflora Sims is an aromatic rhizomatous herb of family Zingiberaceae which is endemic to Peninsular India. This study first reports the phytochemical profile and pesticidal potential of oleoresins obtained from the aerial and rhizome parts of Globba sessiliflora Sims. The oleoresins were prepared by the cold percolation method and were analyzed by a gas chromatography-mass spectrometry (GC-MS) method. Both the oleoresins varied greatly in composition, the major compounds identified in aerial part oleoresin (GSAO) were methyl linoleate, methyl palmitate, and phytol, while the major compounds present in rhizome part oleoresin (GSRO) were γ-sitosterol, 8 (17),12-labdadiene-15, 16-dial, methyl linoleate, and methyl palmitate. In order to evaluate the biological activities, the oleoresins were tested under laboratory conditions for nematicidal action and inhibition of egg hatching potential against root knot nematode, where GSRO was more effective. Insecticidal activity was performed against mustard aphid, Lipaphis erysimi and castor hairy caterpillar, Selepa celtis. In case of mustard aphid, GSRO (LC₅₀ = 154.8 ppm) was more effective than GSAO (LC₅₀ = 263.0 ppm), while GSAO (LC₅₀ = 346.7.0 ppm) was more effective against castor hairy caterpillar than GSRO (LC₅₀ = 398.1 ppm). The herbicidal activity was performed in the receptor species Raphanus raphanistrum subsp. sativus, and the oleoresins showed different intensities for seed germination inhibition and coleoptile and radical length inhibition. Molecular docking studies were conducted to screen the in vitro activities and through molecular docking, it was found that the major oleoresins components were able to interact with the binding pocket of HPPD and AChE with γ-sitosterol showing the best binding affinity.

Effect of daidzein on growth, development and biochemical physiology of insect pest, Spodoptera litura (Fabricius)

Anti- insecticidal potential of daidzein was studied by feeding second instar larvae of Spodoptera litura (Fabricius) on artificial diet incorporated with different concentrations (5 ppm, 25 ppm, 125 ppm, 625 ppm) of diadzein. Results revealed high larval mortality, prolongation of pupal and total developmental period of the larvae treated with diadzein. Anti-nutritional/post ingestive toxicity of diadzein was also revealed by the decrease in the nutritional indices such as relative growth rate (RGR), relative consumption rate (RCR), efficiency of conversion of digested food (ECD), efficiency of conversion of ingested food (ECI) and approximate digestibility (AD). The suppression of immune function due to decline in the total hemocytes count was also observed in treated S. litura larvae. Profiles of detoxifying enzymes viz. superoxide dismutases (SOD), catalase (CAT), ascorbate peroxidases (APOX) and glutathione S-transferase (GST) were also significantly increased with diadzein treatment. The hydrogen peroxide content (H₂O₂), lipid peroxide content (LP) and protein carbonyl content were also significantly enhanced in the treated larvae thus, indicating oxidative stress in the insect. Our findings suggest that daidzein can be used as the alternative to conventional pesticides for controlling S. litura population.

Biochemical and insecticidal effects of plant essential oils on insecticide resistant and susceptible populations of Musca domestica L. point to a potential cross-resistance risk

Essential oils (EOs) can provide important alternatives to chemical insecticides in the control of pests. In this study, 12 EOs of native plant species from Iran were evaluated for their adulticidal activity against the house fly. In addition, we examined the insecticidal activity of Zataria multiflora and Rosmarinus officinalis EOs on adult female house flies from pyrethroid and organophosphate resistant and susceptible populations, using both fumigant and topical bioassays. The involvement of detoxification enzymes in susceptibility was investigated with synergism experiments in vivo, while the inhibitory effects of R. officinalis and Zataria multiflora EOs on the activities of cytochrome P450-dependent monooxygenases (P450s), carboxylesterases (CarEs) and glutathione S-transferases (GSTs) were determined by enzymatic inhibition assays in vitro. The EOs of Z. multiflora, Mentha pulegium, R. officinalis and Thymus vulgaris were the most effective against adults in contact topical assays, while oils extracted from Eucalyptus cinerea, Z. multiflora, Citrus sinensis, R. officinalis, Pinus eldarica and Lavandula angustifolia where the most effective in fumigant assays. Rosmarinus officinalis and Z. multiflora EOs were selected for further investigation and showed higher toxicity against a susceptible population, compared to two insecticide-resistant populations. Correlation analysis suggested cross-resistance between these EOs and pyrethroids in the resistant populations. The toxicity of both EOs on the resistant populations was synergized by three detoxification enzyme inhibitors. Further, in vitro inhibition studies showed that R. officinalis and Z. multiflora EOs more effectively inhibited the activities of the detoxification enzymes from flies of the susceptible population compared to those of the pyrethroid resistant populations. Synergistic and enzymatic assays further revealed that increased activities of P450s, GSTs, and CarEs are possibly involved in the cross-resistance between EOs and pyrethroids. Investigating the molecular mechanisms of P450s, GSTs, and CarEs in the resistance to EOs should be subject to further studies.

Mg-LDH Nanoclays Intercalated Fennel and Green Tea Active Ingredient: Field and Laboratory Evaluation of Insecticidal Activities against Culex pipiens and Their Non-Target Organisms

(1) Background: Mosquito control with essential oils is a growing demand. This work evaluated the novel larvicidal and adulticidal activity of fennel and green tea oils and their Layered double hydroxides (LDHs) nanohybrid against Culex pipiens (Cx. pipiens) in both laboratory and field conditions and evaluated their effect against non-target organisms; (2) Methods: Two types of nanoclays, MgAl-LDH and NiAl-LDH were synthesized and characterized using PXRD, TEM and SEM, whereas their elemental analysis was accomplished by SEM-EDX; (3) Results: Mg and Ni LDHs were synthesized by the co-precipitation method. The adsorption and desorption of active ingredients were conducted using LC MS/MS, with reference to the SEM-EXD analysis. The desorption process of MgAl-LDH intercalated green tea oil was conducted using ethanol, and reveled significant peaks related to polyphenols and flavonoids like Vanillin, Catechin, Daidzein, Ellagic acid, Naringenin, Myricetin and Syringic acid with concentrations of 0.76, 0.73, 0.67, 0.59, 0.52, 0.44 and 0.42 μg/g, respectively. The larvicidal LC50 values of fennel oil, Mg-LDH-F, and Ni-LDH-F were 843.88, 451.95, 550.12 ppm, respectively, whereas the corresponding values of green tea were 938.93, 530.46, and 769.94 ppm. The larval reduction percentage of fennel oil and Mg-LDH-F reached 90.1 and 96.2%, 24 h PT and their persistence reached five and seven days PT, respectively. The reduction percentage of green tea oil and Mg-LDH-GT reached 88.00 and 92.01%, 24 h PT and their persistence reached five and six days PT, respectively. Against adults, Mg-LDH-GT and Ni-LDH-GT were less effective than green tea oil as their LC95 values were 5.45, 25.90, and 35.39%, respectively. The reduction in adult density PT with fennel oil, Mg-LDH-F, green tea oil, and Mg-LDH-GT reached 83.1, 100, 77.0, and 99.0%, respectively, 24 h PT and were effective for three days. Mg-LDH-GT and Mg-LDH-F increased the predation Cybister tripunctatus (71% and 69%), respectively; (4) Conclusions: For the first time, Mg-LDH-GT and Mg-LDH-F was the best system loaded with relatively good desorption release to its active ingredients and significantly affected Cx. pipiens larvae and adults in both laboratory and field circumstances, and it could be included in mosquito control.

Nanostructured Lipid Carriers (NLC) for Biologically Active Green Tea and Fennel Natural Oils Delivery: Larvicidal and Adulticidal Activities against Culex pipiens

(1) Background: The control of mosquitoes with essential oils is a growing demand. (2) Methods: This study evaluated the novel larvicidal and adulticidal activity of fennel and green tea oils and their nanostructured lipid carriers (NLC) against Culex pipiens (C. pipiens) in the laboratory, field conditions and evaluated their effect against non-target organisms. SLN type II nanoformulations were synthesized and characterized using dynamic light scattering (DLS), zeta potential and transmission electron microscope. (3) Results: The synthesized NLCs showed spherical shaped, homogenous, narrow, and monomodal particle size distribution. The mortality percent (MO%) post-treatment (PT) with 2000 ppm for 24 h with fennel oil and NLC fennel (NLC-F) reached 85% (LC50 = 643.81 ppm) and 100% (LC50 = 251.71), whereas MO% for green tea oil and NLC green tea (NLC-GT) were 80% (LC50 = 746.52 ppm) and 100% (LC50 = 278.63 ppm), respectively. Field trial data showed that the larval reduction percent of fennel oil and NLC-F reached 89.8% and 97.4%, 24 h PT and the reduction percent of green tea oil and NLC-GT reached 89% and 93%, 24 h PT with persistence reached 8 and 7 days, for NLC-F and NLC-GT, respectively. The adulticidal effects showed that NLC-F and NLC-GT (100% mortality) were more effective than fennel and green tea oils (90.0% and 83.33%), with 24 h PT, respectively. Moreover, their reduction of adult density after spraying with LC95 X2 for 15 min, with fennel oil, NLC-F, and green tea oil, NLC-GT were 83.6%, 100%, 79.1%, and 100%, respectively, with persistence (>50%) lasting for three days. The predation rate of the mosquitofish, Gambusia affinis, and the bug, Sphaerodema urinator, was not affected in both oil and its NLC, while the predation rate of the beetle, Cybister tripunctatus increased (66% and 68.3%) by green tea oil and NLC-GT, respectively. (4) Conclusions: NLCs nanoformulation encapsulated essential oils was prepared successfully with unique properties of size, morphology, and stability. In vitro larvicidal and adulticidal effects against C. pipiens supported with field evaluations have been performed using essential oils and their nanoformulations. The biological evaluation of nanoformulations manifested potential results toward both larvicidal and adulticidal compared to the essential oils themselves, especially NLC encapsulated fennel oil which had promising larvicidal and adulticidal activity.

Larvicidal and adulticidal effects of some Egyptian oils against Culex pipiens

Mosquitoes and mosquito-borne diseases represent an increasing global challenge. Plant extract and/or oils could serve as alternatives to synthetic insecticides. The larvicidal effects of 32 oils (1000 ppm) were screened against the early 4th larvae of Culex pipiens and the best oils were evaluated against adults and analyzed by gas chromatography-mass spectrometry (GC mass) and HPLC. All oils had larvicidal activity (60.0-100%, 48 h Post-treatment, and their Lethal time 50 (LT50) values ranged from 9.67 (Thymus vulgaris) to 37.64 h (Sesamum indicum). Oils were classified as a highly effective group (95-100% mortalities), including Allium sativum, Anethum graveolens, Camellia sinensis, Foeniculum vulgare, Nigella sativa, Salvia officinalis, T. vulgaris, and Viola odorata. The moderately effective group (81-92% mortalities) included Boswellia serrata, Cuminum cyminum, Curcuma aromatic, Allium sativum, Melaleuca alternifolia, Piper nigrum, and Simmondsia chinensis. The least effective ones were C. sativus and S. indicum. Viola odorata, Anethum graveolens, T. vulgaris, and N. sativa provide 100% adult mortalities PT with 10, 25, 20, and 25%. The mortality percentages of the adults subjected to 10% of oils (H group) were 48.89%, 88.39%, 63.94%, 51.54%, 92.96%, 44.44%, 72.22%, and 100% for A. sativum, An. graveolens, C. sinensis, F. vulgare, N. sativa, S. officinalis, T. vulgaris, and V. odorata, respectively. Camellia sinensis and F. vulgare were the most potent larvicides whereas V. odorata, T. vulgaris, An. graveolens and N. sativa were the best adulticides and they could be used for integrated mosquito control.

Evaluation of Bio-Pesticides against the South American Tomato Leaf Miner, Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) in India

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is one of the most economically important pests of tomato worldwide. Despite its global importance, the management of this oligophagous pest has still been a challenging task, due to its high capability to develop resistance against synthetic insecticides. Given the limited studies on the effectiveness of different bio-pesticides in India, the objective of this research was to determine the pathogenicity of different commercial formulations of Beauveria bassiana, Bacillus thuringiensis, and neem (Azadirachtin), against T. absoluta, under laboratory and field conditions. For the Bacillus thuringiensis formulations, Green Larvicide® and Delfin® recorded an LC50 of 4.10 × 10⁹ CFU/mL and 8.06 × 106 spores/mg, respectively, while for the B. bassiana formulations, Green Beauveria® and BB Power® were 4.473 × 107 spores/mL and 1.367 × 107 CFU/g, respectively. Furthermore, the results showed high susceptibility to both the commercial neem formulations with Ecotin®, recording an LC50 of 91.866 ppm, and Econeem Plus® recording 212.676 ppm. The results from the field conditions at different locations of Andhra Pradesh, India, showed significant differences (p < 0.001) for leaf and fruit infestation among the interaction effect of treatments and locations. Bio-pesticides, especially neem and B. thuringiensis formulations, reduced T. absoluta infestation similarly to the chemical treatment, without affecting the yield. Therefore, bio-pesticides can be considered as safe alternatives to synthetic pesticides, for the management of T. absoluta.

Chrysopogon zizanioides-a review on its pharmacognosy, chemical composition and pharmacological activities

Vetiver is a traditional plant with versatile applications in medicine, aroma, commerce, environmental-protection, and agriculture. This review was designed to compile all the latest information on phytochemistry, pharmacology, and traditional uses of C. zizanioides. All the information related to this plant was gathered from several authentic sites, using keywords like Chrysopogon zizanioides, Vetiveria zizanioides, Khus, and Khas-Khas. The included resources were journaled articles, book chapters, books, Ayurvedic Pharmacopoeias, and Ayurvedic Formulary of India, from science direct, PubMed, research gate etc. All the necessary, relevant, authentic, and updated information were tried to inculcate in the manuscript. The literature was collected via online sites like Pub med, Scopus, and Science direct as well. During compilation, it observed that many traditional utilities of vetiver got their authentication when tested using different disease-based pharmacological models taking various extracts of roots, leaves, and root oil as test samples. However, systematic studies for isolation of active constituents and establishing their mechanism of action are still required to be validated. On the other hand, the development of novel and robust techniques needed for oil extraction can further enhance the exploration of biological utilities faster. Moreover, the cultivators and harvesters must address carefully to prevent the linked drawback of soil erosion.

Repellent Effects of Selected Organic Leaf Extracts of Tithonia diversifolia (Hemsl.) A. Gray and Vernonia lasiopus (O. Hoffman) against Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Introduction

Sitophilus zeamais infestation is among the major setbacks to sustainable maize farming and availability. It causes an estimated annual loss of 5-10% and 20-30% of the total maize grains loss in the temperate and tropical zones, respectively. Although synthetic pesticides are quick and effective in managing crop pests, their overuse and misuse is discouraged due to their detrimental effects on human and environment. Natural pesticidal products that are extracted from plants are particularly gaining importance as an alternative to synthetic pesticides. They are available, easily biodegraded and have low toxicity to nontarget organisms. Most botanical pesticides act on insects by repelling them away from the crops in the field or in the stores. Therefore, this study aimed to determine repellency potential of organic leaf extracts of Tithonia diversifolia and Vernonia lasiopus on S. zeamais. Materials and methods. The phytochemical profile of T. diversifolia and V. lasiopus was determined using GC-MS. Laboratory-based experiments were carried out using area preference method to assess the efficacy of the extracts against weevils for a test period of 5 h. Six groups of experiments were set up with ten S. zeamais in each test: positive control (Actellic), negative control (solvent only), and four different experimental extract concentrations (25, 50, 75, and 100%).

Results

The results indicated that T. diversifolia and V. lasiopus leaf extracts possess potent repellency effect on weevils. All the extracts simply discouraged S. zeamais from the treated areas recording significantly good levels of repellent activities between 26 and 96%. Furthermore, the GC-MS analysis manifested the presence of bioactive compound in the extracts which are associated with the repellency effects.

Conclusion

The study scientifically confirms the traditional use of the T. diversifolia and V. lasiopus and provides important platform for further study on the extracts as bioresource of botanical repellent.

Target Activity of Isaria tenuipes (Hypocreales: Clavicipitaceae) Fungal Strains against Dengue Vector Aedes aegypti (Linn.) and Its Non-Target Activity Against Aquatic Predators

The present investigation aimed to determine the fungal toxicity of Isaria tenuipes (My-It) against the dengue mosquito vector Aedes aegypti L. and its non-target impact against the aquatic predator Toxorhynchitessplendens. Lethal concentrations (LC50 and LC90) of My-It were observed in 2.27 and 2.93 log ppm dosages, respectively. The sub-lethal dosage (My-It-1 × 104 conidia/mL) displayed a significant oviposition deterrence index and also blocked the fecundity rate of dengue mosquitos in a dose-dependent manner. The level of major detoxifying enzymes, such as carboxylesterase (α-and β-) and SOD, significantly declined in both third and fourth instar larvae at the maximum dosage of My-It 1 × 105 conidia/mL. However, the level of glutathione S-transferase (GST) and cytochrome P-450 (CYP450) declined steadily when the sub-lethal dosage was increased and attained maximum reduction in the enzyme level at the dosage of My-It (1 × 105 conidia/mL). Correspondingly, the gut-histology and photomicrography results made evident that My-It (1 × 105 conidia/mL) heavily damaged the internal gut cells and external physiology of the dengue larvae compared to the control. Moreover, the non-target toxicity against the beneficial predator revealed that My-It at the maximum dosage (1 × 1020 conidia/mL) was found to be less toxic with <45% larval toxicity against Tx.splendens. Thus, the present toxicological research on Isaria tenuipes showed that it is target-specific and a potential agent for managing medically threatening arthropods.

Biological activity and safety profile of monoterpenes against Plutella xylostella L. (Lepidoptera: Plutellidae)

Plutella xylostella L. is a cosmopolitan pest of wild and cultivated crucifer vegetables worldwide. It has developed resistance to almost all commercial chemicals, making them one of the most problematic field pests in China. The natural plant extracts and essential oils (EOs) could be a safe alternative for agricultural pests. The development and production of EOs decrease the negative effects of synthetic chemicals. In the present study, the fumigation activity of 8 pure monoterpenes against P. xylostella was evaluated. Results from fumigation tests revealed that 8 tested compounds exhibited various degrees of toxicity against adults of the diamondback moth. Cuminaldehyde was the most toxic compound based on the 12-h LC₅₀ (0.17 mg/L) and 24-h LC₅₀ (0.12 mg/L) values, respectively. Also for larvae and eggs, cuminaldehyde was the most toxic compound. The 12-h LC₅₀ value for cuminaldehyde to 1st, 2nd, and 3rd instar larvae was 0.10 mg/L, 0.12 mg/L, and 0.55 mg/L, respectively. The 24-h LC₅₀ value for the different instar larvae was 0.07 mg/L, 0.09 mg/L, and 0.35 mg/L, respectively. The 24-h LC₅₀ value for eggs (endpoint hatching rate) was 1.95 mg/L for cuminaldehyde, followed by carvacrol and eugenol (2.05 mg/L and 2.31 mg/L, respectively). Cuminaldehyde was very friendly to the larvae and adults of Harmonia axyridis and did not cause any mortality. Our results indicated that cuminaldehyde had potential insecticidal activity against P. xylostella and could be utilized in the novel biological pesticide development.

Repellent and acaricidal activity of essential oils and their components against Rhipicephalus ticks in cattle

Ticks, particularly the Rhipicephalus which are the most prevalent and invasive affect 80 % of the cattle population worldwide. Through transmission of pathogens, tick worry and physical damage to the hides, ticks cause economic loss of billions of dollars each year with 1 billion US dollars loss per annum reported only in Latin-America. These losses can be minimized only by successful management of Rhipicephalus ticks. Various strategies like chemical control, vaccination and biological control are aimed at control of Rhipicephalus ticks. There are some serious limitations associated with them like tick resistance, drug toxicity, antigenic variations etc. In contrast to these issues related with chemical tick control, the botanicals particularly the essential oils obtained from aromatic plants of medicinal importance are eco-friendly and non-toxic to most host. In recent years, essential oils-based control of cattle ticks has gained considerable attraction of scientists all over the world as depicted from this review. A comprehensive effort has been made to critically analyze the role of essential oils in controlling Rhipicephalus ticks with particular emphasis on the mode of action of bioactive compounds both as repellents and acaricides. Furthermore, we have pointed out the most important challenges which need to be addressed for development and commercialization of an essential oil based anti-tick product.

Essential Oils as Potential Alternative Biocontrol Products against Plant Pathogens and Weeds: A Review

Naturally produced by aromatic plants, essential oils (EO) contain a wide range of volatile molecules, including mostly secondary metabolites, which possess several biological activities. Essential oils properties such as antioxidant, antimicrobial and anti-inflammatory activities are known for a long time and hence widely used in traditional medicines, cosmetics and food industries. However, despite their effects against many phytopathogenic fungi, oomycetes and bacteria as well as weeds, their use in agriculture remains surprisingly scarce. The purpose of the present review is to gather and discuss up-to-date biological activities of EO against weeds, plant pathogenic fungi, oomycetes and bacteria, reported in the scientific literature. Innovative methods, potentially valuable to improve the efficiency and reliability of EO, have been investigated. In particular, their use towards a more sustainable agriculture has been discussed, aiming at encouraging the use of alternative products to substitute synthetic pesticides to control weeds and plant diseases, without significantly affecting crop yields. An overview of the market and the recent advances on the regulation of these products as well as future challenges to promote their development and wider use in disease management programs is described. Because of several recent reviews on EO insecticidal properties, this topic is not covered in the present review.

Efficacy and repellency of some essential oils and their blends against larval and adult house flies, Musca domestica L. (Diptera: Muscidae)

House flies are global pests and notoriously difficult to control. Essential oils of vetiver, cinnamon, and lavender and their blends were tested for toxic and repellent effects against larval and adult flies. All of the oils had moderate toxicity for eggs. Mortality of 2^nd instar larvae was 57-78% in dipping assays, 38-100% in contact assays, and 94-100% in treated media. Lavender was less effective (38% mortality) than the others (91-100%) in contact bioassays. Oil blends were not more effective against larvae than individual oils. Vetiver and cinnamon oils were strongly repellent (84 and 78%, respectively) for larvae in treated media. None of the oils were repellent for adult house flies in olfactometer assays, but testing of additional products demonstrated significant repellency for neem oil, p-menthane-3,8-diol (PMD), and vanillin. Contact/fumigant toxicity of vetiver, cinnamon, and lavender oils was 100%, significantly higher than mortality from sunflower oil (67%). Blends of oils were not more effective against adults than the individual oils, but blends diluted with sunflower oil were as effective as the individual oils. Essentials oils of vetiver and cinnamon may have potential for fly management in situations where conventional insecticides cannot be used.

Multiple mutations across the succinate dehydrogenase gene complex are associated with boscalid resistance in Didymella tanaceti in pyrethrum

Failures in control of tan spot of pyrethrum, caused by Didymella tanaceti, has been associated with decreased sensitivity within the pathogen population to the succinate dehydrogenase inhibitor (SDHI) fungicide boscalid. Sequencing the SdhB, SdhC, and SdhD subunits of isolates with resistant and sensitive phenotypes identified 15 mutations, resulting in three amino acid substitutions in the SdhB (H277Y/R, I279V), six in the SdhC (S73P, G79R, H134R, H134Q, S135R and combined H134Q/S135R), and two in the SdhD (D112E, H122R). In vitro testing of their boscalid response and estimation of resistance factors (RF) identified isolates with wild-type (WT) Sdh genotypes were sensitive to boscalid. Isolates with SdhB-I279V, SdhC-H134Q and SdhD-D112E exhibited moderate resistance phenotypes (10 ≥ RF < 100) and isolates with SdhC-H134R exhibited very high resistance phenotypes (RF ≥ 1000). All other substitutions were associated with high resistance phenotypes (100 ≥ RF < 1000). High-resolution melt assays were designed and used to estimate the frequencies of substitutions in four field populations (n = 774) collected in August (pre-boscalid application) and November (post-boscalid application) 2012. The SdhB-H277Y, SdhC-H134R and SdhB-H277R genotypes were most frequently observed across populations at 56.7, 19.0, and 10.3%, respectively. In August 92.9% of D. tanaceti contained a substitution associated with decreased sensitivity. Following boscalid application, this increased to 98.9%, with no WT isolates detected in three fields. Overlaying previously obtained microsatellite and mating-type data revealed that all ten recurrent substitutions were associated with multiple genotypes. Thus, boscalid insensitivity in D. tanaceti appears widespread and not associated with clonal spread of a limited pool of individuals.

The insecticidal activity of Satureja hortensis essential oil and its active ingredient -carvacrol against Acrobasis advenella (Zinck.) (Lepidoptera, Pyralidae)

Nowadays, Acrobasis advenella is considered a pest of the highest economic significance in black chokeberry plantations, negatively affecting the quantity and quality of fruits. The aim of this study was to investigate the effect of Satureja hortensis essential oil and its main constituent, carvacrol, on the life cycle and physiology of A. advenella. The metabolic activity of both preparations was evaluated against insect α- and β- glucosidase, catalase, peroxidase and polyphenol oxidase. The results showed S. hortensis essential oil and carvacrol, are characterized by insecticidal activity against A. advenella larvae. It found an increase in catalase activity in A. advenella homogenates under the influence of carvacrol and an induction of polyphenol oxidase by S. hortensis EO with no changes in POX activity. Also, it was shown that the activity of α- and β-glucosidase significantly increased in larvae fed on inflorescences treated with the essential oil and carvacrol. These preparations particularly strongly affected β-glucosidase activity in the insect homogenates. S. hortensis essential oil reduced emergence the longevity of moths. The obtained results suggest that S. hortensis essential oil and carvacrol can be useful in protecting organic crops of black chokeberry but essential oils may be more effective biopesticides than their active ingredients separately.

Repellent action and contact toxicity mechanisms of the essential oil extracted from Chinese chive against Plutella xylostella larvae

Botanical pesticides play increasingly important roles in the control of agricultural pests. In this study, the insecticidal effects, specifically the repellent action and contact toxicity, of the essential oil extracted from Chinese chive (EOC) against Plutella xylostella larvae were confirmed. The mechanisms of repellent's action were studied using electroantennograms (EAGs), and the effects on glutathione S-transferase (GST), carboxylesterase (CarE), and acetyl cholinesterase were investigated after EOC treatments. The EOC affected the EAG results and inhibited the activities of GST and CarE in treated P. xylostella larvae, which could explain its insecticidal effects. And, four pyrazines showed greater repellent activities than that of the EOC, which was confirmed as the main active compounds of EOC.

Evidence for Sexual Recombination in Didymella tanaceti Populations, and Their Evolution Over Spring Production in Australian Pyrethrum Fields

Tan spot, caused by Didymella tanaceti, is one of the most important foliar diseases affecting pyrethrum in Tasmania, Australia. Population dynamics, including mating-type ratios and genetic diversity of D. tanaceti, was characterized within four geographically separated fields in both late winter and spring 2012. A set of 10 microsatellite markers was developed and used to genotype 774 D. tanaceti isolates. Isolates were genotypically diverse, with 123 multilocus genotypes (MLG) identified across the four fields. Fifty-eight MLG contained single isolates and P_sex analysis estimated that, within many of the recurrent MLG, there were multiple clonal lineages derived from recombination. Isolates of both mating types were at a 1:1 ratio following clone correction in each field at each sampling period, which was suggestive of sexual recombination. No evidence of genetic divergence of isolates of each mating type was identified, indicating admixture within the population. Linkage equilibrium in two of the four field populations sampled in late winter could not be discounted following clone correction. Evaluation of temporal changes in gene and genotypic diversity identified that they were both similar for the two sampling periods despite an increased D. tanaceti isolation frequency in spring. Genetic differentiation was similar in populations sampled between the two sampling periods within fields or between fields. These results indicated that sexual reproduction may have contributed to tan spot epidemics within Australian pyrethrum fields and has contributed to a genetically diverse D. tanaceti population.

Biomarkers as predictive tools to test the in vivo anti-sarcoptic mange activity of propolis in naturally infested rabbits

The present study was designed to investigate the use of specific biomarkers, such as albumin, serum total protein, aspartate amino transferase (AST), globulin, alanine amino transferase (ALT), serum cortisol and alkaline phosphatase (ALP), as predictive tools for sarcoptic mange in rabbits. A total of 40 naturally infested rabbits were equally divided into four groups.Thirty infested rabbits were administered with three different treatments (propolis,ivermectin, and propolis with ivermectin) and were compared to10 infested un-treated rabbits. The impact of treatment was assessed via microscopic examination of skin scrapings, clinical signs, and blood measurements relating to the liver. The present study demonstrated that topical application of 10% propolis ointment resulted in complete recovery from clinical signs and complete absence of mites based on microscopic examination after 10-15 days of treatment. Moreover, AST, ALP, ALT, and cortisol were determined to be acceptable biomarkers to track the response of diseased rabbits to the therapeutic use of propolis.

Structural characterization of Bacillus licheniformis Dahb1 exopolysaccharide-antimicrobial potential and larvicidal activity on malaria and Zika virus mosquito vectors

Microbial polysaccharides produced by marine species play a key role in food and cosmetic industry, as they are nontoxic and biodegradable polymers. This investigation reports the isolation of exopolysaccharide from Bacillus licheniformis Dahb1 and its biomedical applications. Bacillus licheniformis Dahb1 exopolysaccharide (Bl-EPS) was extracted using the ethanol precipitation method and structurally characterized. FTIR and ¹H-NMR pointed out the presence of various functional groups and primary aromatic compounds, respectively. Bl-EPS exhibited strong antioxidant potential confirmed via DPPH radical, reducing power and superoxide anion scavenging assays. Microscopic analysis revealed that the antibiofilm activity of Bl-EPS (75 μg/ml) was higher against Gram-negative (Pseudomonas aeruginosa and Proteus vulgaris) bacteria over Gram-positive species (Bacillus subtilis and Bacillus pumilus). Bl-EPS led to biofilm inhibition against Candida albicans when tested at 75 μg/ml. The hemolytic assay showed low cytotoxicity of Bl-EPS at 5 mg/ml. Besides, Bl-EPS achieved LC₅₀ values < 80 μg/ml against larvae of mosquito vectors Anopheles stephensi and Aedes aegypti. Overall, our findings pointed out the multipurpose bioactivity of Bl-EPS, which deserves further consideration for pharmaceutical, environmental and entomological applications.

Commercially Available Natural Benzyl Esters and Their Synthetic Analogs Exhibit Different Toxicities against Insect Pests

Benzyl methyl ester, also known as methyl benzoate (MB), is a volatile organic compound that exists naturally as a floral fragrance in many plants. Our behavioral bioassays show that MB and some of its naturally occurring and synthetic analogs kill insects at different life stages. Compared to commercial pesticides containing pyriproxyfen and acetamiprid, MB and some analogs are 1.3 to 3.4 times more toxic to gypsy moth larvae and brown marmorated stinkbug nymphs. The arthropod repellent DEET is also a benzyl ester, and shares the same chemical skeleton with MB. They differ by the diethylamide ester and a methyl group on the benzene ring in DEET. However, unlike MB, DEET does not kill insects; instead, it deters or repels them. Exactly how DEET causes the repellent effect in target organisms is still a mystery. Due to the MB's structural similarity to DEET, exploring the structure - activity relationship (SAR) of the MB analogs will provide useful information for the discovery of the mode and mechanistic actions of DEET as an insect repellent. In addition, the SAR will allow researchers to modify the chemical structure of the MB molecule, leading to the development of more efficient, safe, and environmentally - friendly green pesticides.

The desert wormwood (Artemisia herba-alba) - From Arabian folk medicine to a source of green and effective nanoinsecticides against mosquito vectors

The development of eco-friendly and effective insecticides is crucial for public health worldwide. Herein, we focused on the desert wormwood (Artemisia herba-alba), a plant widely used in Arabian traditional medicine, as a source of green nanoinsecticides against mosquito vectors, as well as growth inhibitors to be employed against microbial pathogens. Ag nanoparticles (AgNPs) fabricated with the A. herba-alba extract were tested on Indian and Saudi Arabian strains of Anopheles, Aedes and Culex mosquitoes. The chemical profile of the A. herba-alba extract was determined by LC-DAD-MS and ¹H NMR studies. Then, AgNPs were studied using UV-vis spectroscopy, XRD, FTIR spectroscopy, TEM, and EDX analyses. Artemisia herba-alba-synthesized AgNPs showed high larvicidal toxicity against mosquitoes from both Indian and Saudi Arabian strains. LC₅₀ of AgNPs against Indian strains was 9.76 μg/ml for An. stephensi, 10.70 μg/ml for Ae. aegypti and 11.43 μg/ml for Cx. quinquefasciatus, whereas against Saudi Arabian strains it was 33.58 μg/ml for Ae. aegypti and 38.06 μg/ml for Cx. pipiens. In adulticidal experiments, A. herba-alba extract showed LC₅₀ ranging from 293.02 to 450 μg/ml, while AgNP LC₅₀ ranged from 8.22 to 27.39 μg/ml. Further, low doses of the AgNPs inhibited the growth of selected microbial pathogens. Overall, A. herba-alba can be further considered as a source of phytochemicals, with special reference to saponins, for effective and prompt fabrication of AgNPs with relevant insecticidal and bactericidal activity against species of high public health importance.

Toxicity and growth inhibition potential of vetiver, cinnamon, and lavender essential oils and their blends against larvae of the sheep blowfly, Lucilia sericata

BACKGROUND

Myiasis induced by the sheep blowfly, Lucilia sericata, represents a public health problem widely distributed throughout the world. L. sericata larval stages feed on both humans and animals. L. sericata adults and larvae can play a role in spreading agents of mycobacterial infections.

OBJECTIVES

It is critical to establish new and safe alternative methods of controlling L. sericata.

METHODS

The insecticidal effectiveness and growth inhibition potential of three commercially available essential oils (EOs), vetiver (Chrysopogon zizanioides), cinnamon (Cinnamomum zeylanicum), and lavender (Lavandula angustifolia), as well as their blends, were tested against the second (L2) and third (L3) larval stages of L. sericata. Sunflower (Helianthus annuus) oil was used as a carrier and tested on L2 and L3 larvae. To the best of our knowledge, all applied essential oils, except lavender, and oil blends were tested against L. sericata for the first time.

RESULTS

All applied oils did not repel L2 from the treated liver but adversely affected their development. Contact treatments on L. sericata L3 indicated that vetiver and cinnamon oils significantly affected treated larvae. Total mortality rates were 93.33 and 95.56%, respectively. Furthermore, oil blends tested through contact assays killed larvae when used at higher concentrations; adult emergence was eliminated post-treatment with doses >30% for oil blend 1 and >10% for oil blend 2.

CONCLUSION

Overall, cinnamon and vetiver oils (5%) were selected as reliable and cheap biopesticides for controlling larvae of L. sericata. The tested oils are inexpensive and represent new promising botanical insecticides in the fight against blowflies causing myiasis.

Ovicidal and larvicidal activity and possible mode of action of phenylpropanoids and ketone identified in Syzygium aromaticum bud against Bradysia procera

Bradysia procera is a serious insect pest of Panax ginseng plants. This study was conducted to determine the toxicity and mechanism of action of three phenylpropanoids, three terpenoids, and a ketone from Syzygium aromaticum bud methanol extract and hydrodistillate against third-instar larvae and eggs of B. procera. In a filter-paper mortality bioassay, methyl salicylate (LC₅₀, 5.26μg/cm²) was the most toxic compound, followed by 2-nonanone, eugenol, and eugenyl acetate (8.77-15.40μg/cm²). These compounds were significantly less toxic than either thiamethoxam, clothianidin, or cypermethrin. Egg hatching was inhibited by 97, 85, and 40% at 11.7μg/cm² of methyl salicylate, 2-nonanone, and eugenol, respectively. The egg-hatching inhibition of these insecticides was between 90 and 94% at 0.09μg/cm². These constituents were consistently more toxic in closed versus open containers, indicating that toxicity was achieved mainly through the action of vapor. The mechanism of larvicidal action of methyl salicylate, eugenol, and eugenyl acetate might be primarily due to interference with the octopaminergic system. 2-Heptyl acetate and 2-nonanone might act on both acetylcholinesterase and the octopaminergic receptor. 2-Heptanone might act primarily on acetylcholinesterase. Further studies will warrant possible applications of S. aromaticum bud-derived products as potential larvicides and ovicides for the control of B. procera.

Neurotoxic Effects of Linalool and β-Pinene on Tribolium castaneum Herbst

Effective, ethical pest control requires the use of chemicals that are highly specific, safe, and ecofriendly. Linalool and β-pinene occur naturally as major constituents of the essential oils of many plant species distributed throughout the world, and thus meet these requirements. These monoterpenes were tested as repellents against Tribolium castaneum, using the area preference method, after four hours of exposure and the effect transcriptional of genes associated with neurotransmission. Changes in gene expression of acetylcholinesterase (Ace1), GABA-gated anion channel splice variant 3a6a (Rdl), GABA-gated ion channel (Grd), glutamate-gated chloride channel (Glucl), and histamine-gated chloride channel 2 (Hiscl2) were assessed and the interaction with proteins important for the insect using in silico methods was also studied. For linalool and β-pinene, the repellent concentration 50 (RC₅₀) values were 0.11 µL/cm² and 0.03 µL/cm², respectively. Both compounds induced overexpression of Hiscl2 gen in adult insects, and β-pinene also promoted the overexpression of Grd and the Ace1 gene. However, β-pinene and linalool had little potential to dock on computer-generated models for GABA-gated ion channel LCCH3, nicotinic acetylcholine receptor subunits alpha1 and alpha2, and putative octopamine/tyramine receptor proteins from T. castaneum as their respective binding affinities were marginal, and therefore the repellent action probably involved mechanisms other than direct interaction with these targets. Results indicated that β-pinene was more potent than linalool in inducing insect repellency, and also had a greater capacity to generate changes in the expression of genes involved in neuronal transmission.

Azadirachtin induced larval avoidance and antifeeding by disruption of food intake and digestive enzymes in Drosophila melanogaster (Diptera: Drosophilidae)

Botanical insecticides are a promising alternative to reduce the harmful effects of synthetic chemicals. Among the botanical biopesticides, azadirachtin obtained from the Indian neem tree Azadirachta indica A. Juss. (Meliaceae) is probably the biorational insecticide with greatest agriculture use nowadays due to its broad insecticide activity. The current study, evaluated the lethal and sublethal effects of azadirachtin on larval avoidance, food intake and digestive enzymes of Drosophila melanogaster larvae as biological model. Azadirachtin was applied topically at two doses LD₂₅ (0.28μg) and LD₅₀ (0.67μg) on early third instars larvae. Results evaluated 24h after treatment showed that larvae exhibited significant repellence to azadirachtin and prefer keeping in untreated arenas rather than moving to treated one. In addition, azadirachtin avoidance was more marked in larvae previously treated with this compound as compared with naïf larvae (controls). Moreover, azadirachtin treatment decreased significantly the amount of larval food intake. Finally, azadirachtin reduced significantly the activity of larval α-amylase, chitinase and protease and increased the activity of lipase. This finding showed that azadirachtin induced behavioral and physiological disruption affecting the ability of the insect to digest food. This rapid installation of avoidance and long term antifeedancy might reinforce the action of azadirachtin and provide a new behavioral strategy for integrated pest management programs.

Mating-Type Gene Structure and Spatial Distribution of Didymella tanaceti in Pyrethrum Fields

Tan spot of pyrethrum (Tanacetum cinerariifolium) is caused by the ascomycete Didymella tanaceti. To assess the evolutionary role of ascospores in the assumed asexual species, the structure and arrangement of mating-type (MAT) genes were examined. A single MAT1-1 or MAT1-2 idiomorph was identified in all isolates examined, indicating that the species is heterothallic. The idiomorphs were flanked upstream and downstream by regions encoding pyridoxamine phosphate oxidase-like and DNA lyase-like proteins, respectively. A multiplex MAT-specific polymerase chain reaction assay was developed and used to genotype 325 isolates collected within two transects in each of four fields in Tasmania, Australia. The ratio of isolates of each mating-type in each transect was consistent with a 1:1 ratio. The spatial distribution of the isolates of the two mating-types within each transect was random for all except one transect for MAT1-1 isolates, indicating that clonal patterns of each mating-type were absent. However, evidence of a reduced selection pressure on MAT1-1 isolates was observed, with a second haplotype of the MAT1-1-1 gene identified in 4.4% of MAT1-1 isolates. In vitro crosses between isolates with opposite mating-types failed to produce ascospores. Although the sexual morph could not be induced, the occurrence of both mating-types in equal frequencies suggested that a cryptic sexual mode of reproduction may occur within field populations.

Chemical Compositions of Ligusticum chuanxiong Oil and Lemongrass Oil and Their Joint Action against Aphis citricola Van Der Goot (Hemiptera: Aphididae)

In order to develop novel botanical insecticides, the joint action of Ligusticum chuanxiong oil (LCO) and lemongrass oil (LO) against Aphis citricola van der Goot was determined systematically indoors and outdoors. The chemical profiles of LCO and LO as determined by gas chromatography-mass spectrometry (GC-MS) analysis revealed that the main compounds from LCO were (Z)-ligustilide (44.58%) and senkyunolide A (26.92%), and that of LO were geranial (42.16%) and neral (32.58%), respectively. The mixture of LCO and LO showed significant synergy against A. citricola, with a common-toxicity coefficient (CTC) value of 221.46 at the optimal ratio of LCO to LO (4:1, w:w). Based on the results of solvents and emulsifiers screening, L. chuanxiong oil·Lemongrass oil 20% emulsifiable concentrate (20% LCO·LO EC) was developed, and its stability was confirmed with tests of cold and thermal storage. Field trials indicated that the insecticidal activity of the diluted 20% LCO·LO EC (1000 fold dilution) was comparable to conventional pesticide (20% imidacloprid EC) on A. citricola seven days after application. Thus, the mixture of LCO and LO has the potential to be further developed as a botanical pesticide.

EVALUATION OF SUBLETHAL EFFECTS OF Ipomoea cairica LINN. EXTRACT ON LIFE HISTORY TRAITS OF DENGUE VECTORS

Plant derived insecticides have considerable potential for mosquito control because these products are safer than conventional insecticides. This study aimed to investigate sublethal activities of Ipomoea carica or railway creeper crude acethonilic extract against life history trait of dengue vectors, Aedes albopictus and Aedes aegypti. The late third instar larvae of Ae. albopictus and Ae. aegypti were exposed to a sublethal dose at LC50 and larvae that survived were further cultured. Overall, Ipomea cairica crude extracts affected the whole life history of both Aedes species. The study demonstrated significantly lower egg production (fecundity) and eggs hatchability (fertility) in Ae. albopictus. The sublethal dose of crude extracts reduced significantly the width of larval head capsule and the wing length of both sexes in both Aedes species. The significance of sublethal effects of I. cairica against Aedes mosquitoes was an additional hallmark to demonstrate further activity of this plant despite its direct toxicity to the larvae. The reduced reproductive capacity as well as morphological and physiological anomalies are some of the effects that make I. cairica a potential candidate to be used as a new plant-based insecticide to control dengue vectors.

Erratum to: the acaricidal efficacy of peracetic acid and deltamethrin against the fowl tick, Argas persicus, infesting laying hens

The fowl tick, Argas persicus (Oken), is of veterinary importance as a parasite of poultry and wild birds. The antitick efficacy, in vitro and in vivo, of peracetic acid (PAA) and deltamethrin (DMT) was tested separately against A. persicus through the dipping technique. PAA (0.5%) was highly efficient against soft tick larvae (A. persicus), resulting in 100 % mortality after 2 min. The lethal concentrations LC₅₀ and LC₉₅ were 0.310 and 0.503 %, respectively. The lethal time values LT₅₀ and LT₉₅ were 5.34 and 40.00 min, respectively, after treatment with PAA (0.25%). Two minutes after exposure to DMT, LC₅₀ and LC₉₅ values were 0.0033 and 0.0052% (33.204 and 51.527 mg/L), respectively. The LT₅₀ and LT₉₅ values were 27.03 and 305.46 min, respectively, after treatment with 0.0025% DMT (25 mg/L). After dipping in PAA (0.5%), the chickens did not show respiratory signs or inflammation on the eyes and/or skin. By contrast, temporary coughing, sneezing, and ocular inflammations without dermatitis were observed in chickens dipped in DMT (0.005 % or 50 mg /L). Seven days posttreatment (PT), the reduction in the percentages of A. persicus infesting laying hens were 99.15 and 63.42% after dipping in PAA and DMT, respectively. However, complete elimination of the number of ticks occurred after 28 days PT with DMT. PAA inhibits molting effectively (28%) when compared with that of DMT (52%). Results indicated that PAA is a more potent and promising acaricide against A. persicus (in vitro and in vivo) than DMT.