Carvacrol is a monoterpenoid phenol found in many essential oils that has antibacterial, antifungal and antiparasitic activities. Drug loaded-invasome systems are used to deliver drugs utilizing nanoparticles to improve bioavailability, efficacy, and drug release duration. As a result, the present study developed carvacrol-loaded invasomes and evaluated their acaricidal effect against Rhipicephalus annulatus (cattle tick) and Rhipicephalus sanguineus (dog tick). Carvacrol loaded-invasome (CLI) was prepared and characterized using UV/Vis spectrophotometer, zeta potential measurements, Scanning Transmission Electron Microscopy (STEM), Fourier Transform Infrared (FT-IR) Spectroscopy, and Differential Scanning Calorimetry Analysis. CLI (5%) induced significant mortality (100%) in R. annulatus adult ticks with LC₅₀ of 2.60%, whereas the LC₅₀ of pure carvacrol was 4.30%. Carvacrol and CLI were shown to have a significant larvicidal action on both tick species, with LC₅₀s of 0.24 and 0.21% against R. annulatus and 0.27 and 0.23% against R. sanguineus, respectively. Carvacrol and CLI (5%) induced significant repellent activities for 24 h against R. annulatus and R. sanguineus, as evidenced by the rod method and the petri-dish selective area choice method, respectively. High-performance liquid chromatography (HPLC) demonstrated that the CLI form had 3.86 times the permeability of pure carvacrol. Moreover, carvacrol and CLI inhibited acetylcholinesterase activity and decreased glutathione and malonedealdehyde levels in the treated ticks. In conclusion, invasomes significantly improved adulticidal and repellency activities of carvacrol against both tick species.

Tick infestation is a serious problem in many countries since it has an impact on the health of animals used for food production and pets, and frequently affects humans. Therefore, the present study aimed to investigate the acaricidal effects of nanoemulsions of essential oils of Melaleuca alternifolia (tea tree, TT) and Citrus limon (lemon oil, CL) against the different stages (adult, eggs, and larvae) of deltamethrin-resistant Rhipicephalus annulatus ticks. Three forms of these oils were tested: pure oils, nanoemulsions, and a binary combination. Tea tree and lemon oil nanoemulsions were prepared, and their properties were assessed using a zeta droplet size measurement and a UV-Vis spectrophotometer. The results showed that TT and CL exhibited higher adulticidal effects in their pure forms than in their nanoemulsion forms, as demonstrated by the lower concentrations required to achieve LC₅₀ (2.05 and 1.26%, vs. 12.8 and 11.4%, respectively) and LC₉₀ (4.01% and 2.62%, vs. 20.8 and 19.9%, respectively). Significant larvicidal activity was induced by the TTCL combination, and LC₅₀ was reached at a lower concentration (0.79%) than that required for the pure and nanoemulsion forms. The use of pure CL oil was found to have the most effective ovicidal effects. In conclusion, pure TT and CL have potent acaricidal effects against phenotypically resistant R. annulatus isolates. It is interesting that the activity levels of TT and CL EOs’ binary and nanoemulsion forms were lower than those of their individual pure forms.

The aim of the present study was to evaluate in vitro and in vivo the acaricidal activity of two forms of geranium (Pelargonium graveolens) (PG). These two forms were the P. graveolens essential oil nanoemulsion (PGN), and the PG in combination with the sesame oil (SO), PGSO). These forms were first evaluated in vitro for their adulticidal, ovicidal, and larvicidal activities against the different stages of acaricide-resistant Rhipicephalus annulatus (Say). Geranium nanoemulsion was prepared and then characterized by UV–Vis spectrophotometer, and zeta droplet size measurement. The results revealed that LC₅₀ of the PG against the adult ticks was attained at concentration of 7.53% while it was decreased to 1.91% and 5.60% for PGSO and PGN, respectively. Also, the LC₅₀ of PGN and PGSO were reached at concentrations of 1.688 and 0.944%, respectively against the larvae while the LC₅₀ of the PG was reached at concentration of 3.435% for. The combination of PGN with PG exhibited non-significant ovicidal effect meanwhile PGSO showed significant ovicidal effect even at the low concentration (2.5%). The PGSO and PGN formulations were applied in a field trial to control the ticks of the naturally infested cattle. PGSO and PGN significantly reduced the tick burden to 74.83% and 87.97%, respectively at 3 weeks post-application with performance better than the deltamethrin (29.88%). In conclusion, the two PG forms can be used as suitable alternatives to control R. annulatus tick and they need further modifications for effective field application.

Tribolium castaneum is a damaging pest of stored grains, causing significant losses and secreting lethal quinones, which render the grains unfit for human consumption. Chemical insecticides are the most commonly used approach for control; however, they create insecticide resistance and affect the health of humans, animals, and the environment. As a result, it is critical to find an environmentally friendly pest-management strategy. In this study, two naturally occurring chemicals, benzyl alcohol (BA) and benzoyl benzoate (BB), were investigated for insecticidal activity against T. castaneum using different assays (impregnated-paper, contact toxicity, fumigant, and repellency assays). The results showed that BA had a significant insecticidal effect, with the LC₅₀ achieved at a lower concentration in the direct-contact toxicity test (1.77%) than in the impregnated-paper assay (2.63%). BB showed significant effects in the direct-contact toxicity test, with an LC₅₀ of 3.114%, and a lower toxicity in the impregnated-paper assay, with an LC₅₀ of 11.75%. Furthermore, BA exhibited significant fumigant toxicity against T. castaneum, with an LC₅₀ of 6.72 µL/L, whereas BB exhibited modest fumigant toxicity, with an LC₅₀ of 464 µL/L. Additionally, at different concentrations (0.18, 0.09, 0.045, and 0.0225 µL/cm²), BA and BB both showed a notable and potent repelling effect. BA and BB significantly inhibited acetylcholinesterase, reduced glutathione (GSH), and increased malondialdehyde (MDA) in treated T. castaneum. This is the first report of BA insecticidal activity against the red flour beetle. Also, the outcomes of various assays demonstrated that the application of BA induces a potent bio-insecticidal effect. BA may be a promising eco-friendly alternative to control T. castaneum due to its safety and authorization by the EFSA (European Food Safety Authority).