The efficacies of 5 insecticides against hard ticks Hyalomma asiaticum, Haemaphysalis longicornis and Rhipicephalus sanguineus

Preparation of Emamectin Benzoate·Hexaflumuron Granules Based on Response Surface Methodology

In order to obtain particles with an optimal loading rate and encapsulation efficiency and to explore the effects of sodium alginate, carboxymethyl chitosan, and bentonite on the particle loading rate and encapsulation rate, the preparation parameters of particles were optimized by the response surface method. A series of particles with constantly changing components were prepared, and the particle loading rate and encapsulation rate were determined. The release experiment of granules in different mass release media was implemented, and the optimal loading rate and encapsulation efficiency of particles were used to control the fall armyworm (FAW). The results showed that when the amount of sodium alginate was 1.83%, that of carboxymethyl chitosan was 0.41% and that of bentonite was 0.37%. The maximum theoretical value based on the response surface simulation was 92.63%, and the actual value at this ratio was 91.61%, which was 98.90% of the theoretical value. The release assay indicated that the mechanism of particle release in 2, 4, and 6 mL of the release medium was non-Fickian diffusion, and the controlled mechanism in 25 mL of the medium was Fickian diffusion. The beads were spread directly into maize leaf whorls in field production; at 14 days after application, the efficacy reached 91.28-98.82%. The combination of emamectin benzoate and hexaflumuron granules has a good control effect on the FAW.

Baseline susceptibility of Haemaphysalis longicornis to organophosphate, carbamate, and pyrethroid acaricides

BACKGROUND

The Asian longhorned tick, Haemaphysalis longicornis, continues to expand its range in North America, and synthetic acaricides are likely to play an increasing role in managing this species. Acaricide resistance is common in some tick species that infest livestock. However, baseline acaricide susceptibility has not previously been examined in this invasive tick.

RESULTS

We used a standard larval packet test to evaluate the susceptibility of the Asian longhorned tick to acaricides currently or formerly used in tick control: propoxur, carbaryl, bifenthrin, permethrin, and coumaphos. Discriminating concentrations were estimated at 6.5, 27.9, 988, 2242, and 808 ppm, respectively. The half-maximal lethal concentration (LC50 ) values for propoxur, carbaryl, permethrin and coumaphos were compared with data available for other tick species and showed that H. longicornis was more susceptible to propoxur, carbaryl and coumaphos, and had a similar susceptibility to permethrin.

CONCLUSIONS

The results indicate that resistance to these acaricides is not currently a concern for H. longicornis in the United States. However, responsible integrated management and early detection of resistance can help ensure the long-term efficacy of products used for controlling this tick species. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Molecular identification and functional analysis of Niemann-Pick type C2 proteins，carriers for semiochemicals and other hydrophobic compounds in the brown dog tick, Rhipicephalus linnaei

Ticks are important vectors of many pathogens with tremendous impact on human and animal health. Studies of semiochemical interactions and mechanisms underlying chemoreception can provide important tools in tick management. Niemann-Pick type C2 (NPC2) proteins have been proposed as one type of chemoreceptor in arthropods. Here, we cloned two NPC2 genes in the brown dog tick, Rhipicephalus linnaei, the tropical lineage previously named R. sanguineus sensu lato and characterized them functionally. R.linNPC2a and R.linNPC2b genes were found to be expressed at each developmental stage with the highest level in adult males. By using quantitative real-time PCR we revealed expression in multiple tissues, including midgut, ovary, salivary glands and legs. Ligand binding analysis revealed that R.linNPC2b bound a wide spectrum of compounds, with β-ionone, α-amylcinnamaldehyde, 2-nitrophenol and benzaldehyde displaying the strongest binding affinity (Ki < 10 μM), whereas R.linNPC2a showed a more narrow ligand binding range, with intermediate binding affinity to α-amylcinnamaldehyde and 2-nitrophenol (Ki < 20 μM). Molecular docking indicated that the amino acid residue Phe89, Leu77 and Val131 of R.linNPC2a and Phe70, Leu132 and Phe73 of R.linNPC2b could bind multiple ligands. These residues might thus play a key role in the identification of the volatiles. Our results contribute to the understanding of olfactory mechanisms of R. linnaei and can offer new pathways towards new management strategies.

Bio-efficacy of permethrin/tetramethrin and lambda-cyhalothrin treatments in habitats of hard ticks (Acari, Ixodidae) populations with confirmed Borrelia spp. infection

The aim of the study was to evaluate the bio-efficacy of two different acaricides against mobile stages of hard ticks Ixodes ricinus, Dermacentor marginatus, and Haemaphysalis punctata in their natural habitats. The study was conducted during 2020 and 2021 at localities populated by I. ricinus as the predominant species, at which the presence of Borrelia afzelii, Borrelia garinii, and Borrelia lusitaniae was confirmed. During the first investigation year, a combination of two pyrethroids, permethrin, and tetramethrin, with an insecticide synergist piperonyl butoxide (trade name: Perme Plus®) was tested. At the first evaluation, 24 h after the treatment with Perme Plus®, the efficacy expressed as a reduction rate of the population density was within the interval of satisfying performance (70-90%) at all localities, while the highest efficacy (97.8%) was recorded on the 14th post-treatment day. In the second investigation year, the formulation based on lambda-cyhalothrin (trade name: Icon® 10CS) was used. On the first post-treatment evaluation day, satisfying effects were also demonstrated. The highest recorded efficacy rate of lambda-cyhalothrin (94.7%) was recorded on the 14th post-treatment day. Both tested acaricides manifested satisfying initial acaricidal effects against mobile stages of ticks and provided long-term effects. Comparison of the regression trend lines of population reduction revealed that satisfying effects of treatment with Perme Plus® lasted until the 17th post-treatment day, while in the case of Icon® 10CS, the residual effects were significantly prolonged (30 days).

Joint toxicity of insecticides against Hyalomma asiaticum

Hyalomma asiaticum, a hematophagous ectoparasite, causes severe economic losses. We studied the acute toxicity of five pesticides (three single-agent and two combination preparations) to this organism. Engorged larval ticks were immersed in ten serial concentrations of each insecticide and observed for 20 days. The LC₅₀ values of the five insecticides and the cotoxicity coefficients (CTCs) of the two mixtures were estimated for H. asiaticum. The CTCs of lambda-cyhalothrin + etoxazole and lambda-cyhalothrin + fipronil were 128.83 and 331.58, respectively, each demonstrating synergism. The results indicated that these two mixtures were more effective than individual insecticides, and this study suggests a substitutional approach to the control of ticks.

The control of Hyalomma ticks, vectors of the Crimean–Congo hemorrhagic fever virus: Where are we now and where are we going?

At a time of major global, societal, and environmental changes, the shifting distribution of pathogen vectors represents a real danger in certain regions of the world as generating opportunities for emergency. For example, the recent arrival of the Hyalomma marginatum ticks in southern France and the concurrent appearance of cases of Crimean–Congo hemorrhagic fever (CCHF)—a disease vectored by this tick species—in neighboring Spain raises many concerns about the associated risks for the European continent. This context has created an urgent need for effective methods for control, surveillance, and risk assessment for ticks and tick-borne diseases with a particular concern regarding Hyalomma sp. Here, we then review the current body of knowledge on different methods of tick control—including chemical, biological, genetical, immunological, and ecological methods—and the latest developments in the field, with a focus on those that have been tested against ticks from the genus Hyalomma. In the absence of a fully and unique efficient approach, we demonstrated that integrated pest management combining several approaches adapted to the local context and species is currently the best strategy for tick control together with a rational use of acaricide. Continued efforts are needed to develop and implement new and innovative methods of tick control.

Disease-bearing Hyalomma ticks are an increasingly emerging threat to humans and livestock worldwide. Various chemical, biological, genetic, and ecological methods for tick control have been developed, with variable efficiencies. Today, the best tick control strategy involves an integrated pest management approach.

Field applications of granular and liquid pyrethroids, carbaryl, and IGRs to control the asian longhorned tick (Haemaphysalis longicornis) and impacts on nontarget invertebrates

Few documented control strategies exist for the invasive tick, Haemaphysalis longicornis, despite its potential to reach extremely high numbers and vector human and animal pathogens. In 2020, we evaluated the effects of single applications of five granular and liquid acaricides on H. longicornis in a public park in northern New Jersey. Acaricides tested included pyrethroids (lambda-cyhalothrin, bifenthrin), a carbamate (carbaryl), and the insect growth regulators (IGRs) pyriproxyfen and novaluron. We also monitored the impact of each treatment on non-target soil and above-ground invertebrate species using pitfall and sticky traps, respectively. We recorded over 70,000 H. longicornis ticks in the study area from July to October 2020. An average of 99% control was achieved with lambda-cyhalothrin spray and 95% with granular bifenthrin. In contrast, granular carbaryl did not significantly reduce any life stages of H. longicornis. The IGR (pyriproxyfen/novaluron) resulted in a significant 45% reduction of the larval stage following treatments in July. No other stages were significantly impacted by pyriproxyfen alone or in combination with novaluron. Analysis of non-target species revealed that the community composition of soil-dwelling arthropods was strongly impacted by pyrethroid treatments and, to a lesser extent, by the carbamate treatment. The granular pyrethroid bifenthrin had more pronounced effects and impacted a broader range of non-target groups in the pitfall traps than the liquid pyrethroid lambda-cyhalothrin. Arthropod groups that were negatively impacted included Isopoda, Formicidae, Coleoptera, Araneae, Acari, and Grylloidea. Collembola numbers, however, were elevated in both pyrethroid treatments. The community composition of arthropods collected on the above-ground sticky traps was strongly impacted only in the liquid lambda-cyhalothrin treatment. The primary groups impacted in the sticky trap analysis were Collembola and Hemiptera. Community composition in traps remained distinct in the pyrethroid treatments through the entire survey period up to 62 days post-treatment. The results of this study indicate that pyrethroid acaricides were highly effective at controlling H. longicornis, while other compounds, including carbaryl and IGRs, did not achieve consistent levels of control. Further research is needed to find effective and environmentally sustainable alternatives. Integrated management programs can include the judicious use of pyrethroids to control H. longicornis.

Seasonal distribution of Haemaphysalis longicornis (Acari: Ixodidae) and detection of SFTS virus in Gyeongbuk Province, Republic of Korea, 2018

The seasonal distribution of hard ticks was investigated in 2018 in Gyeongbuk Province, Republic of Korea. Ticks were assayed for severe fever with thrombocytopenia syndrome virus (SFTSV). Ticks were collected monthly using CO₂-baited traps from April to November in four habitats (grasslands, grave sites, hiking trails, and mixed forests). Based on morphological and molecular identification, Haemaphysalis longicornis was the most commonly collected species, followed by H. flava and Ixodes nipponensis. Ticks were more commonly collected in grassland habitats, followed by the grave sites, hiking trails, and mixed forests. Peak numbers of nymphs and adults of H. longicornis occurred in May and June, respectively, and Haemaphysalis larvae were collected from August to October. A total of 9/187 (4.8%) pools were positive for SFTSV between June and October in 2018. Phylogenetic analysis of partial fragments of the SFTSV obtained in this study showed that all positive virus samples clustered into genotype B.

Glutathione S-transferases play a role in the detoxification of flumethrin and chlorpyrifos in Haemaphysalis longicornis

Background

Haemaphysalis longicornis is a tick of importance to health, as it serves as a vector of several pathogens, including Theileria orientalis, Babesia ovata, Rickettsia japonica and the severe fever with thrombocytopenia syndrome virus (SFTSV). Presently, the major method of control for this tick is the use of chemical acaricides. The glutathione S-transferase (GST) system is one mechanism through which the tick metabolizes these acaricides. Two GSTs from H. longicornis (HlGST and HlGST2) have been previously identified.

Results

Enzyme kinetic studies were performed to determine the interaction of acaricides with recombinant H. longicornis GSTs. Recombinant HlGST activity was inhibited by flumethrin and cypermethrin, while recombinant HlGST2 activity was inhibited by chlorpyrifos and cypermethrin. Using real-time RT-PCR, the upregulation of the HlGST gene was observed upon exposure to sublethal doses of flumethrin, while the HlGST2 gene was upregulated when exposed to sublethal doses of chlorpyrifos. Sex and strain dependencies in the induction of GST gene expression by flumethrin were also observed. Knockdown of the HlGST gene resulted in the increased susceptibility of larvae and adult male ticks to sublethal doses of flumethrin and the susceptibility of larvae against sublethal doses of chlorpyrifos was increased upon knockdown of HlGST2.

Conclusions

HlGST could be vital for the metabolism of flumethrin in larvae and adult male ticks, while HlGST2 is important in the detoxification of chlorpyrifos in larval ticks.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-3044-9) contains supplementary material, which is available to authorized users.