Repellent Screening of Selected Plant Essential Oils Against Dengue Fever Mosquitoes Using Behavior Bioassays

Green synthesis of Eucalyptus globulus zinc nanoparticles and its use in antimicrobial insect repellent paint formulation in bulk industrial production

Mitigating climate change can be achieved by opting for sustainable, plant-based materials instead of relying on hazardous chemicals that come with various side effects. Various natural plant extracts find widespread application in synthesizing insect-repellent coatings, particularly in industries such as paint manufacturing. The increasing demand for these coatings has led us to find out the effects of different plant extracts for the efficient preparation of paints with more advanced impacts and low cost. For this purpose, zinc nanoparticles of Eucalyptus globulus L. and its extracts were used in this study due to their remarkable biocidal and antimicrobial activities. The extract was prepared by the process of oven-drying and heating followed by their filtration. Then, they were subjected to different phytochemical tests that were performed in which plant material did not contain flavonoids and glycol. The comparison of the size of nanoparticles was visible during the weighing which was found to be 4.451 mg. Advanced characterization techniques like FTIR, UV visible spectroscopy, and particle size analysis were adopted for the analysis of nanoparticles of plant extract. The FTIR analysis of the plant material was reported to lie in the range of 1000-1800 cm-1. On the other hand, the results of UV visible spectroscopy of nanoparticles of plant extract showed absorption peaks around 300 nm. The produced material was integrated into paint formulations to impart insect-repellent and antibacterial characteristics. Painted panels exhibited notable antibacterial efficacy, presenting an inhibition zone of 0.7 cm for Escherichia coli and 0.3 cm for Staphylococcus aureus when utilizing biocide. Plant nanoparticles yielded inhibition zones of 1 and 1.2, while aqueous extract resulted in zones of 0.2 and 0.5, respectively. A thorough evaluation of the paint's color attributes, including ΔL, Δa, Δb, and ΔE, indicated noteworthy differences. The CMC ΔE values from the trials exceeded 1, indicating a substantial change in shade. The batches of paints containing E. globulus extracts and nanoparticles were found to be lighter in color specifically green and yellow colors. Their antimicrobial and insect repellant activity was tested using the mosquitos of Aedes aegypti with an age of 4-5 weeks, revealing that formulations with plant extracts exhibited a 61 % effective period, greater than the 7 % observed in non-biocidal formulations. The paint responded best towards these mosquitoes in terms of repellency and the ultimate target of this study was achieved.

Sustainable Pest Management Using Novel Nanoemulsions of Honeysuckle and Patchouli Essential Oils against the West Nile Virus Vector, Culex pipiens, under Laboratory and Field Conditions

Essential oils are natural plant products that are very interesting, as they are important sources of biologically active compounds. They comprise eco-friendly alternatives to mosquito vector management, particularly essential oil nanoemulsion. Therefore, the aim of this study is to evaluate the effectiveness of 16 selected essential oils (1500 ppm) in controlling mosquitoes by investigating their larvicidal effects against the larvae and adults of the West Nile virus vector Culex pipiens L. (Diptera: Culicidae); the best oils were turned into nanoemulsions and evaluated under laboratory and field conditions. The results show that honeysuckle (Lonicera caprifolium) and patchouli (Pogostemon cablin) essential oils were more effective in killing larvae than the other oils (100% mortality) at 24 h post-treatment. The nanoemulsions of honeysuckle (LC50 = 88.30 ppm) and patchouli (LC50 = 93.05 ppm) showed significantly higher larvicidal activity compared with bulk honeysuckle (LC50 = 247.72 ppm) and patchouli (LC50 = 276.29 ppm) oils. L. caprifolium and P. cablin (100% mortality), followed by Narcissus tazetta (97.78%), Rosmarinus officinalis (95.56%), and Lavandula angustifolia (95.55%), were highly effective oils in killing female mosquitoes, and their relative efficacy at LT50 was 5.5, 5.3, 5.8, 4.1, and 3.2 times greater, respectively, than Aloe vera. The results of the field study show that the honeysuckle and patchouli oils and their nanoemulsions reduced densities to 89.4, 86.5, 98.6, and 97.0% at 24 h post-treatment, respectively, with persistence for eight days post-treatment in pools. Nano-honeysuckle (100% mortality) was more effective than honeysuckle oils (98.0%). Our results show that honeysuckle and patchouli oils exhibited promising larvicidal and adulticidal activity of C. pipiens.