Efficacy of λ-cyhalothrin, amitraz, and phoxim against the poultry red mite Dermanyssus gallinae De Geer, 1778 (Mesostigmata: Dermanyssidae): an eight-year survey

Hearing of malaria mosquitoes is modulated by a beta-adrenergic-like octopamine receptor which serves as insecticide target

Malaria mosquitoes acoustically detect their mating partners within large swarms that form transiently at dusk. Indeed, male malaria mosquitoes preferably respond to female flight tones during swarm time. This phenomenon implies a sophisticated context- and time-dependent modulation of mosquito audition, the mechanisms of which are largely unknown. Using transcriptomics, we identify a complex network of candidate neuromodulators regulating mosquito hearing in the species Anopheles gambiae. Among them, octopamine stands out as an auditory modulator during swarm time. In-depth analysis of octopamine auditory function shows that it affects the mosquito ear on multiple levels: it modulates the tuning and stiffness of the flagellar sound receiver and controls the erection of antennal fibrillae. We show that two α- and β-adrenergic-like octopamine receptors drive octopamine's auditory roles and demonstrate that the octopaminergic auditory control system can be targeted by insecticides. Our findings highlight octopamine as key for mosquito hearing and mating partner detection and as a potential novel target for mosquito control.

Profiling of Dermanyssus gallinae genes involved in acaricide resistance

The poultry red mite (PRM), Dermanyssus gallinae, is a major threat for the poultry industry worldwide. Chemical compounds have been extensively used for PRM control, leading to selection of resistant mites. Molecular mechanisms of resistance have been investigated in arthropods, showing the role of target-site insensitivity and enhanced detoxification. Few studies are available about those mechanisms in D. gallinae, and none have yet focused on the expression levels of detoxification enzymes and other defense-related genes through RNA-seq. We tested PRM populations from Italy for their susceptibility to the acaricidal compounds phoxim and cypermethrin. Mutations in the voltage-gated sodium channel (vgsc) and in acetylcholinesterase (AChE) were investigated, detecting mutations known to be associated with acaricide/insecticide resistance in arthropods, including M827I and M918L/T in the vgsc and G119S in the AChE. RNA-seq analysis was performed to characterize metabolic resistance in fully susceptible PRM and in cypermethrin-resistant PRM exposed and unexposed to cypermethrin as well as phoxim resistant PRM exposed and unexposed to phoxim. Detoxification enzymes (including P450 monooxygenases and glutathione-S-transferases), ABC transporters and cuticular proteins were constitutively overexpressed in phoxim and cypermethrin resistant mites. In addition, heat shock proteins were found constitutively and inductively upregulated in phoxim resistant mites, while in cypermethrin resistant mites esterases and an aryl hydrocarbon receptor were constitutively highly expressed. The findings suggest that acaricide resistance in D. gallinae is due to both target-site insensitivity and overexpression of detoxification enzymes and other xenobiotic defense-related genes, which is mostly constitutive and not induced by treatment. Understanding the molecular basis of resistance could be useful to screen or test PRM populations in order to select targeted acaricides and to avoid the abuse/misuse of the few available compounds.

Acaricide resistance and novel photosensitizing approach as alternative acaricides against the camel tick, Hyalomma dromedarii

The control of the camel tick, Hyalomma dromedarii is very crucial. This study evaluated the novel toxicity of photosensitizers and Phoxim insecticide against H. dromedarii males using the adult immersion tests. Ticks were subjected to sunlight for 10 min post-treatment (PT). The optical characters of the applied materials were determined by UV-Vis spectroscopy (250-900 nm wavelengths). The intensity of spectra decreased as dye concentration decreased. The optical bandgap energies of the dyes at different concentrations were not changed as the concentration changed and decreased as the absorption peak of individual dyes red-shifted. The mortalities 72 h PT reached 42.2%, 44.4%, 51.1%, 71.1%, 46.7%, 48.9%, 44.4%, and 55.6% for chlorophyllin, echinochrome, field stain, methylene blue, phthalocyanine, rhodamine 6G, riboflavin, and safranin, respectively. Methylene blue recorded the highest median lethal concentration (LC₅₀ = 127 ppm) followed by safranin, field stain, rhodamine 6G, phthalocyanine, echinochrome riboflavin, and chlorophyllin (LC₅₀ = 209, 251, 271, 303, 324, 332, and 362 ppm, respectively, 72 h PT). Their median lethal time, LT₅₀, values PT with 240 ppm were 45, 87, 96, 72, 129, 115, 131, and 137 h, respectively. The relative toxicities of the LC₅₀ values 72 h PT showed that chlorophyllin, echinochrome, field stain, methylene blue, phthalocyanine, rhodamine 6G, riboflavin, and safranin were 3.2, 3.6, 4.6, 9.1, 3.8, 4.3, 3.5, and 5.6 times, respectively, more effective than Phoxim. Methylene blue, safranin, and field stain showed a broad absorbance area indicating a large photoactivity and better phototoxicity and could be used as alternative agents to synthetic acaricides.

Evaluation of the in vitro acaricidal activity of Chinese herbal compounds on the poultry red mite (Dermanyssus gallinae)

The poultry red mite Dermanyssus gallinae is an economically important pest in poultry farms worldwide, but an effective treatment option is lacking. The current study determined the effectiveness of six Chinese herbal medicines [Syzygium aromaticum (clove), Hibiscus syriacus (Hibiscus), Illicium verum (star anise), Leonurus artemisia (motherwort), Cinnamomum cassia (cinnamon), and Taraxacum sp. (dandelion)] against D. gallinae. Alcohol extracts were prepared via the solvent extraction method and the phenol, flavonoid, and tannin contents were determined. These active components were highest in S. aromaticum and lowest in H. syriacus, I. verum. No tannin content was detected in L. artemisia. All extracts showed contact toxicity against D. gallinae at a test concentration of 1 g/mL, with S. aromaticum and L. artemisia resulting in 100% mortality. S. aromaticum, L. artemisia, and I. verum showed the best efficacy (LC₅₀ 0.159, 0.200, and 0.292 g/mL, respectively). Different combinations of extracts showed an additive effect of I. verum LC₉₀ + L. artemisia LC₉₀. The acaricidal efficacy of this combination was tested against different developmental stages of D. gallinae, being most efficacious against nymphal and larval D. gallinae, with a corrected mortality rate of 100%. However, inhibition of egg hatching was only 53.69%. Taken together, these results highlight I. verum LC₉₀ + L. artemisia LC₉₀ as a promising compound with severe contact toxicity against D. gallinae. Given the wide cultivation of these species and their extensive use in foodstuffs and cosmetics as flavors and fragrances, they could be a cheap, readily available ecofriendly alternative to pesticides currently used in poultry farms.

Miticidal activity of fenazaquin and fenpyroximate against Varroa destructor, an ectoparasite of Apis mellifera

BACKGROUND

The Varroa mite (Varroa destructor) is an ectoparasite that can affect the health of honey bees (Apis mellifera) and contributes to the loss of colony productivity. The limited availability of Varroacides with different modes of action in Canada has resulted in the development of chemical resistance in mite populations. Therefore, an urgent need to evaluate new potential miticides that are safe for bees and exhibit high efficacy against Varroa exists. In this study, the acute contact toxicity of 26 active ingredients (19 chemical classes), already available on the market, was evaluated on V. destructor and A. mellifera under laboratory conditions using an apiarium bioassay. In this assay, groups of Varroa-infested worker bees were exposed to different dilutions of candidate compounds. In semi-field trials, Varroa-infested honey bees were randomly treated with four vetted candidate compounds from the apiarium assay in mini-colonies.

RESULTS

Among tested compounds, fenazaquin (quinazoline class) and fenpyroximate (pyrazole class) had higher mite mortality and lower bee mortality over a 24 h exposure period in apiariums. These two compounds, plus spirotetramat and spirodiclofen, were selected for semi-field evaluation based on the findings of the apiarium bioassay trials and previous laboratory studies. Consistent with the apiarium bioassay, semi-field results showed fenazaquin and fenpyroximate had high efficacy (>80%), reducing Varroa abundance by 80% and 68%, respectively.

CONCLUSION

These findings suggest that fenazaquin would be an effective Varroacide, along with fenpyroximate, which was previously registered for in-hive use as Hivastan. Both compounds have the potential to provide beekeepers with an alternative option for managing Varroa mites in honey bee colonies. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Dermanyssus gallinae: the long journey of the poultry red mite to become a vector

The possibility that Dermanyssus gallinae, the poultry red mite, could act as a vector of infectious disease-causing pathogens has always intrigued researchers and worried commercial chicken farmers, as has its ubiquitous distribution. For decades, studies have been carried out which suggest that there is an association between a wide range of pathogens and D. gallinae, with the transmission of some of these pathogens mediated by D. gallinae as vector. The latter include the avian pathogenic Escherichia coli (APEC), Salmonella enterica serovars Enteritidis and Gallinarum and influenza virus. Several approaches have been adopted to investigate the relationship between D. gallinae and pathogens. In this comprehensive review, we critically describe available strategies and methods currently available for conducting trials, as well as outcomes, analyzing their possible strengths and weaknesses, with the aim to provide researchers with useful tools for correctly approach the study of the vectorial role of D. gallinae.

Biochemical and molecular mechanisms of acaricide resistance in Dermanyssus gallinae populations from Turkey

The poultry red mite, Dermanyssus gallinae, is the most important blood sucking ectoparasite of egg laying hens and causes economic losses in poultry farms worldwide. Although various management methods exist, the control of poultry red mites (PRMs) mainly relies on acaricides such as pyrethroids and organophosphates (OPs) in many regions of the world. However, repeated use of these synthetic chemicals has resulted in resistance development causing control failure of PRM. In this study, we investigated acaricide resistance mechanisms of Turkish PRM populations. First, we obtained the COI sequence from 30 PRM populations from different regions in Turkey and identified four different COI haplotypes. Toxicity assays showed that four field-collected PRM populations were highly resistant to the pyrethroid alpha-cypermethrin, with resistance ratios (RRs) varying between 100- and 400-fold, while two of these populations had a RR of more than 24-fold against the OP acaricide phoxim. Biochemical assays showed a relatively higher activity of glutathione-S-transferases and carboxyl-cholinesterases, two well-known classes of detoxification enzymes, in one of these resistant populations. In addition, we also screened for mutations in the gene encoding the voltage-gated sodium channel (vgsc) and acetylcholinesterase 1 (ace-1), the target-site of pyrethroids and OPs, respectively. In all but two PRM populations, at least one vgsc mutation was detected. A total of four target-site mutations, previously associated with pyrethroid resistance, M918T, T929I, F1534L, F1538L were found in domain II and III of the VGSC. The T929I mutation was present in the vgsc of almost all PRM populations, while the other mutations were only found at low frequency. The G119S/A mutation in ace-1, previously associated with OP resistance, was found in PRM for the first time and present in fourteen populations. Last, both alive and dead PRMs were genotyped after pesticide exposure and supported the possible role of target-site mutations, T929I and G119S, in alpha-cypermethrin and phoxim resistance, respectively. To conclude, our study provides a current overview of resistance levels and resistance mutations in Turkish PRM populations and might aid in the design of an effective resistance management program of PRM in Turkey.

Electrochemical application of cobalt nanoparticles-polypyrrole composite modified electrode for the determination of phoxim

In this study, cobalt nanoparticles (CoNPs) were synthesized and cobalt nanoparticles modified glassy carbon electrode (CoNPs/GCE) was prepared by drop coating the nanoparticles on glassy carbon electrode. After preparing polypyrrole modified glassy carbon electrode (PPy/GCE) using electropolymerization of pyrrole in LiClO4 solution, cobalt nanoparticles-polypyrrole composite modified glassy carbon electrode (CoNPs/PPy/GCE) was fabricated by drop coating the CoNPs on the PPy/GCE. Different characterization techniques such as scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, FTIR spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry were used to study the morphological structure and electrochemical behavior of the sensors. The results demonstrated that PPy chains interacted with CoNPs through donor-acceptor bonds. Among all the electrodes, CoNPs/PPy/GCE exhibited highest electroactive surface area and lowest electron transfer resistance towards phoxim. Under the optimal conditions, the sensor showed linear relationship between the reduction peak current and the concentration of phoxim in the range of 0.025 μM-12 μM with the detection limit as 4.5 nM. Besides, the composite electrode demonstrated excellent reproducibility, good stability and selectivity towards the possible interfering substances. All of these properties made CoNPs/PPy/GCE a suitable electrochemical sensor for the electrochemical determination of phoxim in water samples using square wave voltammetry.

Importance and Impact of the Poultry Red Mite (Dermanyssus gallinae) in Layer Farms - Analysis of Farmers’ Perception

Poultry red mite (PRM), Dermanyssus gallinae, causes egg drop production, anemia and can be a vector in transmitting diseases. The PRM control mainly focuses on usage of the conventional chemical biocides. The objective of this study was to analyze the farmers’ perception regarding the impact, management and control of PRM in Macedonian layer farms. The data were collected with direct on-site visits using a unified questionnaire. In total, 29 poultry farms (28% of farms in the country), all with conventional cages, were part of this study. The data were analyzed by descriptive statistics, inferential statistics and Naïve Bayes Classifier technique. In 30% of the poultry farms the farmers had observed that the flock was infested with PRM. In total, 32 different treatments against PRM were reported from the farmers, and three of them were non-biocide treatments. The most used biocides (17% of the farms) were crude oil, Formalin, Neopitroid® and disinfectants. The highest agreement regarding biocides application among the farms (38%) was before the production starts. Most of the farmers applied biocides routinely, before the infestation is evident (75%). The median costs for PRM treatment were 175€ per flock, higher in the infested farms 493±677€ compared to non - infested 100±71€, p<0.05. None of the Macedonian farmers included in the study was using monitoring method for PRM infestation, contributing to poor data records. This study highlights the need of developing unified strategy for PRM control included in the Integrated Pest Management in poultry layer farms.

Acaricidal Activity of Annonaceae Plants for Dermanyssus gallinae (Acari: Dermanyssidae) and Metabolomic Profile by HPLC-MS/MS

The poultry red mite Dermanyssus gallinae (De Geer) is the most important haematophagous ectoparasite in the poultry industry. The use of synthetic acaricides for this control is presenting risks related to human food. In this sense, plant secondary metabolites are promising for controlling this pest. Thus, this study aimed to evaluate the acaricidal activity of Duguetia lanceolata A.St.-Hil. (stem bark), Xylopia emarginata Mart. (stem bark), and Xylopia sericea A.St.-Hil. (stem bark and fruits) against D. gallinae. Additionally, the secondary metabolite profile of the X. emarginata was analysed by UFLC-DAD-ESI(+)-MS/MS (micrOTOF-QII) and data analysis was performed using the Molecular Networking. In a topical application test, all plant species tested showed bioactivity, in that order of toxicity with the respective probability survival: X. emarginata (stem bark) (0.28) > X. sericea (stem barks) (0.35) > X. sericea (fruits) and D. lanceolata (stem bark) (0.47). The most promising results were found for X. emarginata (LC₅₀ = 331.769 μg/cm²). It is noteworthy that the LC₅₀ of the insecticide cypermethrin was 1234.4 μg/cm², which was 73% higher than that of X. emarginata. The metabolomic profile of X. emarginata revealed the presence of alkaloids, amides, terpenoids, and phenolic compounds. This is the first report of X. emarginata acaricidal activity against D. gallinae and exploratory chemical analysis by untargeted metabolomics and the molecular network of this plant.