Larvicidal and repellent effects of essential oils on the brown dog tick (Rhipicephalus sanguineus Sensu lato) with description of new larval repellent activity test method.

The aim of this research was to investigate the larvicidal and repellent effects of essential oils (EOs) obtained from two Lamiaceae plant species, Origanum minutiflorum O. Schwarz & P.H. Davis and Dorystoechas hastata Boiss. & Heldr. ex Bentham, both endemic to Turkey, on Rhipicephalus sanguineus s.l. Latreille (Acari: Ixodidae). The study also introduces a new test method that can be used to assess the repellent effects against ticks. Both plant EOs exhibited the highest larvicidal activity against brown dog tick larvae after 24 h and LC50 and LC90 values were determined as 0.101% and 0.125% for O. minutiflorum essential oil and 0.937% and 2.1% for D. hastata essential oil, respectively. In this study, we have described a detailed protocol for a novel larval repellent activity test (LRAT) for essential oils and extracts, using simple equipment. The advantages and limitations of LRAT, when compared to other tests commonly used to determine repellent effect against ticks, are also included in this study. The LRAT was developed with modifications of the larval immersion test (LIT) and proves to be a highly efficient and easily observable method. It can be used to test any active substance that may be toxic to humans and animals. According to the LRAT, at the end of 3 h, O. minutiflorum essential oil showed a high repellent effect, varying between 84.14% and 100% at 1% concentration. This result was not statistically different from the DEET, the positive control. When comparing the larvicidal and repellent activities, O. minutiflorum essential oil was found to be more effective than D. hastata essential oil.

Exploring the Larvicidal and Repellent Potential of Taurus Cedar (Cedrus libani) Tar against the Brown Dog Tick (Rhipicephalus sanguineus sensu lato).

This study investigated the potential acaricidal and repellent effects of tar obtained from the Lebanon cedar (Cedrus libani A. Rich.) against the brown dog tick species Rhipicephalus sanguineus sensu lato Latreille (Acari: Ixodidae). The goal was to find an alternative, safe, and effective way to eliminate ticks. Tar is traditionally extracted from cedar trees in the Antalya region of Türkiye. The composition of the tar is primarily characterized by a diverse mixture of terpenes, with ß-himachalene (29.16%), α-atlantone (28.7%), ar-turmerone (8.82%), longifolene-(V4) (6.66%), α-himachalene (5.28%), and ß-turmerone (5.12%) emerging as the predominant constituents. The toxic effects of tar on tick larvae were studied through larval immersion tests (LIT), and its repellent activity was evaluated using a new larval repellent activity test (LRAT). The results revealed significant acaricidal effects, with mortality rates of 77.7% and 82.2% for the Konyaalti and Kepez strains of the brown dog tick, respectively, in response to a 1% concentration of tar. LC50 and LC90 values were determined as 0.47% and 1.52% for the Kepez strain and 0.58% and 1.63% for the Konyaalti strain, respectively. When comparing the repellent effect of tar to the widely used synthetic repellent DEET, repellency rates of up to 100% were observed. As a result, this study establishes, for the first time, the larvicidal and repellent effects of C. libani tar on ticks.

Use of micro and macroalgae extracts for the control of vector mosquitoes.

Mosquitoes are one of the most dangerous vectors of human diseases such as malaria, dengue, chikungunya, and Zika virus. Controlling these vectors is a challenging responsibility for public health authorities worldwide. In recent years, the use of products derived from living organisms has emerged as a promising approach for mosquito control. Among these living organisms, algae are of great interest due to their larvicidal properties. Some algal species provide nutritious food for larvae, while others produce allelochemicals that are toxic to mosquito larvae. In this article, we reviewed the existing literature on the larvicidal potential of extracts of micro- and macroalgae, transgenic microalgae, and nanoparticles of algae on mosquitoes and their underlying mechanisms. The results of many publications show that the toxic effects of micro- and macroalgae on mosquitoes vary according to the type of extraction, solvents, mosquito species, exposure time, larval stage, and algal components. A few studies suggest that the components of algae that have toxic effects on mosquitoes show through synergistic interaction between components, inhibition of feeding, damage to gut membrane cells, and inhibition of digestive and detoxification enzymes. In conclusion, algae extracts, transgenic microalgae, and nanoparticles of algae have shown significant larvicidal activity against mosquitoes, making them potential candidates for the development of new mosquito control products.

Pathogenicity of an Entomopathogenic Nematode, Steinernema carpocapsae on Alphitobius diaperinus (Coleoptera: Tenebrionidae) Strains From Turkey.

Alphitobius diaperinus Panzer (Coleoptera: Tenebrionidae) is an insect pest in poultry production systems. This insect has developed resistance to many chemical insecticides. As an alternative to chemicals, entomopathogenic nematodes (EPNs) are one of the most commonly used agents against several pest arthropods. The pathogenicity of the EPN Steinernema carpocapsae Weiser on four field strains of lesser mealworm, A. diaperinus, from Turkey was studied. In the experiments, larvae of A. diaperinus were found to be more sensitive than adults to S. carpocapsae infection. In terms of LC50 values in both larval and adult insects, Balikesir strain was found to be the most susceptible, Manisa strain the most resistant. The calculated LC50 values for adults were 85.9, 205.6, 135.4, and 418.8 IJs/ml, and for larvae 31.2, 39.8, 34.8, and 70.9 IJs/ml for the Balikesir, Canakkale, Izmir, and Manisa strains, respectively. This is the first report about the pathogenicity of EPNs against larvae and adults of lesser mealworm A. diaperinus strains from Turkey. We conclude that S. carpocapsae can be used as a control agent for lesser mealworms.

Insecticidal activity of major lichen compounds, (-)- and (+)-usnic acid, against the larvae of house mosquito, Culex pipiens L.

In this research, (-)-usnic acid and (+)-usnic acid, commonly encountered lichen secondary metabolites, were evaluated for their insecticidal effects against the larvae of Culex pipiens L. (Diptera: Culicidae) under laboratory conditions. Both compounds showed strong larvicidal activity and caused 100% mortality on third-fourth larval stages of the species at 24 h at the doses of 5 and 10 ppm. Bioassays with (-)- and (+)-usnic acids against larvae of C. pipiens revealed that the LC50 values were 0.8 and 0.9 ppm, respectively. The results suggest that lichen compounds could be useful in the search of new insecticides.