Acaricidal Efficacy Research Articles

In vitro evaluation of the composition and acaricidal efficacy of Urtica fissa leaf ethyl acetate extract against Sarcoptes scabiei mites.

In veterinary medicine, natural products provide an alternative to chemical agents for mite management. Inthe present study, the acaricidal efficacy ofUrtica fissa leaf ethyl acetate extract against Sarcoptes scabiei mites was examined. The chemical composition ofthe extract was determined using liquid chromatography-mass spectrometry (LC-MS) analysis. The ethyl acetate extract was found tobe extremely toxic tomites ataconcentration of100mg/ml (m/v), killing all S.scabiei within two hours. The median lethal time (LT50) values for ethyl acetate extract concentrations of25, 50, and 100mg/ml against S.scabiei were 1.706, 1.204, and 0.750h, respectively. Themedian lethal dosage (LC50) for S.scabiei was 19.14mg/ml attwo hours. The chemical composition oftheethyl acetate extract was evaluated using LC-MS, showing that the major components were schaftoside (8.259%), carnosol(6.736%), prostaglandinA2 (5.94%), 13(S)-HpOTrE (4.624%), nandrolone (4.264%), 1H-indole-3-carboxaldehyde (4.138%), 9-oxoODE (3.206%), and stearidonic acid (2.891%). Inconclusion, these findings indicate that Urtica fissa contains promising new acaricidal compounds capable ofsuccessfully controlling animal mites.

Comparison of the efficacy of different methods to apply acaricides for control of Rhipicephalus (Boophilus) microplus

The present study compared the efficacy of different methods to apply an acaricide formulation to control Rhipicephalus (Boophilus) microplus. To compare the methods, an acaricide blend containing three active ingredients (a pyrethroid and two organophosphates) was used. In experiment 1 (farm 1: Goiânia, GO, Brazil), three methods were tested: a backpack sprayer (BS), power sprayer (PS) and spray race (SR). In experiment 2 (farm 2: São José do Rio Pardo, SP, Brazil), two methods were tested: BS and PS. In both experiments, 10 cattle with similar tick burdens were used. On day 0 in both experiments, the animals were treated with the acaricide. On day +1 (only in experiment 1), +3, +7, +14, +21, +28 and +35 (only in experiment 2), tick counts were performed to determine the control efficacy. The time application, pressure (KPa), volume applied (L) and ergonomic aspects of each spraying system were also evaluated. The adult immersion test (AIT) using three different acaricide blends (combinations of pyrethroid + organophosphate) was performed to compare the susceptibility of strains of each farm. In experiment 1, all treatments significantly reduced (p < 0.05) the number of ticks on the animals, and PS resulted in the greatest acaricide efficacy since day +1. In experiment 2, both treatments (PS and BS) reduced (p < 0.05) the tick burden, and as observed in experiment 1, PS resulted in the best reduction. The application times were 4.5, 150 and 330 s, while pressures were 306.8, 4,826.3 and 220.6 KPa for SR, PS and BS, respectively. In the AIT, the efficacy values were between 99.8 and 100% for the tick strain form farm 1 (Goiânia), while for tick strain from farm 2 (São José do Rio Pardo), the efficacy was between 67.2 and 80.9%. We conclude that the sprayer methods chosen influences the efficacy of the acaricide. All sprayer methods were efficient for acaricide application; the best efficacy was obtained using the PS, while the SR resulted in good efficacy and lower application time. The strain from farm 2 was less susceptible to all acaricides tested.

Prevalence of cattle ixodid ticks and acaricides efficacy evaluation in Amibara district of Afar Region, Ethiopia.

A cross sectional and randomized controlled trial study was conducted starting from July 2021 to July 2022 to determine the prevalence of ixodid ticks, and evaluate the efficacy of commonly used acaricides (amitraz 12.5% and diazinon 60%) in vitro and in vivo on cattle ticks in Amibara district. A total of 372 cattle were visited randomly from six kebeles of the district which were selected based on their livestock population. A total of 4330 adult ticks were collected and identified to the species level with stereomicroscope. For the invitro acaricide efficacy test, 90 engorged female ticks were collected from infested herds and grouped into three, each group having ten engorged ticks; two groups for the two test acaricides and the third groups were control to evaluate these acaricides in the laboratory. All the groups were replicated three times and incubated for seven days with similar temperature and humidity. Thirty-six infested cattle were selected and again grouped into three randomly, 12 each for the invivo test. The first groups of animals were sprayed with amitraz, the second with diazinon and the third groups were left untreated. Ticks were counted and recorded before, day 3, day 7, day 14 and day 21 of spraying. A total of 360 (96.7%) of the visited cattle were infested with ticks. Amblyomma. Rhipicephallus, Hyalomma and Bophillus were the genera of ticks identified with a prevalence of 44.9%, 41.4%, 7.5% and 6.2% respectively. A total of 15 species of ixodid ticks were identified from which Rhipicephallus pulchellus (39.86%) was dominant followed by Amblyomma lepidum (26.65%) and Amblyomma gemma (14.36%). Diazinon 60% EC and amitraz 12.5% were significantly inhibited the egg laying ability of engorged ticks' in vitro with percent inhibition of 100% and 99.1% respectively. On live animal, both acaricides showed statistically significant difference from the control group (p- value <0.05) with maximum 97.37% (amitraz) and 93.33% (diazinon) at day 7 and minimum 73.3% (amitraz) and 73.7% (diazinon) efficacy. However, there was no statistically significant difference on egg laying inhibition and tick count reduction between the two acaricides (p-value >0.05). Therefore, awareness should be created about the high prevalence as well as the application, dosage and dilution of the acaricides to pastoralists, community animal health workers and para veterinarians in the study area. Cattle owners, veterinarians and concerned government officials should address infested herds with manufacturer recommended dosage of these acaricides to control the tick infestation.

Haematopinus suis Infestation in Pig Farms in Busogo Sector, Rwanda.

Haematopinus suis(H. suis) is a common ectoparasite of pigs and is economically important worldwide. H. suis is responsible for anemia and poor feed conversion rate that lead to poor growth in pig husbandry. This study assessed the prevalence and risk factors of H. suis in pigs through a cross-sectional survey in Busogo sector of Musanze district. Fifty-five (55) pigs, representing 10% of 555 pigs from 20 farms, were examined physically for the presence of H. suis, and a total number of 559 H. suis were collected from them in Busogo sector of Musanze district. Data were analyzed using the Statistical Package for the Social Sciences (SPSS). Results showed that out of 55 pigs, a total number of 35 pigs (63.6%), were found infested with H. suis in Busogo sector of Musanze district. The infestation by H. suis was associated with the farming system, animal breeds, animal's category, sex, pig hygiene, and piggery hygiene. Results showed a high (P < 0.05) prevalence in pigs reared in the intensive system (91.4%), whereas large whites were the most affected breed (60%). The prevalence of H. suis varied significantly (P < 0.05) among sexes, and females were the most affected (60%). Results related to pig hygiene revealed that all farmers were practicing washing skin three times per week, whereas only 60.0% of them were removing the bedding in their piggery. The study concluded that H. suis is present and remains a problem in the study area. Therefore, the study recommends to create farmer's awareness on the disease in pigs and its impact through training. Researchers should continue further studies on H. suis prevention with appropriate pig husbandry and management practices and the efficacy of acaricides used.

Essential Oils for a Sustainable Control of Honeybee Varroosis.

The Varroa destructor parasite is the main obstacle to the survival of honey bee colonies. Pest control mainly involves the use of synthetic drugs which, used with the right criteria and in rotation, are able to ensure that infestation levels are kept below the damage threshold. Although these drugs are easy to use and quick to apply, they have numerous disadvantages. Their prolonged use has led to the emergence of pharmacological resistance in treated parasite populations; furthermore, the active ingredients and/or their metabolites accumulate in the beehive products with the possibility of risk for the end consumer. Moreover, the possibility of subacute and chronic toxicity phenomena for adult honeybees and their larval forms must be considered. In this scenario, eco-friendly products derived from plant species have aroused great interest over the years. In recent decades, several studies have been carried out on the acaricidal efficacy of plant essential oils (EOs). Despite the swarming of laboratory and field studies, however, few EO products have come onto the market. Laboratory studies have often yielded different results even for the same plant species. The reason for this discrepancy lies in the various study techniques employed as well as in the variability of the chemical compositions of plants. The purpose of this review is to take stock of the research on the use of EOs to control the V. destructor parasite. It begins with an extensive discussion of the characteristics, properties, and mechanisms of action of EOs, and then examines the laboratory and field tests carried out. Finally, an attempt is made to standardize the results and open up new lines of study in future.

Protective Efficacy of Multiple Epitope-Based Vaccine against Hyalomma anatolicum, Vector of Theileria annulata and Crimean-Congo Hemorrhagic Fever Virus.

Hyalomma anatolicum is the principal vector for Theileria annulata, T. equi, and T. Lestoquardi in animals and the Crimean-Congo hemorrhagic fever virus in humans. Due to the gradual loss of efficacy of the available acaricides against field tick populations, the development of phytoacaricides and vaccines has been considered the two most critical components of the integrated tick management strategies. In the present study, in order to induce both cellular and humoral immune responses in the host against H. anatolicum, two multi-epitopic peptides (MEPs), i.e., VT1 and VT2, were designed. The immune-stimulating potential of the constructs was determined by in silicoinvestigation on allergenicity (non-allergen, antigenic (0.46 and 1.0046)), physicochemical properties (instability index 27.18 and 35.46), as well as the interaction of constructs with TLRs by docking and molecular dynamics analysis. The immunization efficacy of the MEPs mixed with 8% MontanideTM gel 01 PR against H. anatolicum larvae was determined as 93.3% and 96.9% in VT1- and VT2-immunized rabbits, respectively. Against adults, the efficacy was 89.9% and 86.4% in VT1- and VT2-immunized rabbits, respectively. A significant (p < 0.001) reduction in the anti-inflammatory cytokine (IL-4) and significantly higher IgG response was observed in a VT1-immunized group of rabbits as compared with the response observed in the control group. However, in the case of the VT2-immunized rabbits, an elevated anti-VT2 IgG and pro-inflammatory cytokine (IL-2) (>30 fold) along with a decreased level of anti-inflammatory cytokine IL-4 (0.75 times) was noted. The efficacy of MEP and its potential immune stimulatory responses indicate that it might be useful for tick management.

Poultry red mite eradication potential of ivermectin and allicin combination treatment.

Existing treatments against poultry red mite (PRM; Dermanyssus gallinae) infestation have reduced efficacy or exhibit hazardous effects on chickens. Considering the economic importance of chickens, development of a safe and effective method for exterminating PRMs is necessary. Ivermectin and allicin are effective against some ectoparasites; however, their acaricidal efficacies against PRMs remain unknown. To evaluate individual and combined efficacies of ivermectin and allicin in exterminating PRMs. Different concentrations (0.10-1.0mg/mL) of ivermectin (1mL) were applied via dropping method in different insect culture dishes (ICDs), prior to transferring PRMs. For the spraying method, PRMs were transferred to ICDs, before spraying ivermectin (1mg/mL) solution (1mL). Further, the acaricidal effect of allicin on PRMs was evaluated by applying different concentrations (0.25-1.0mg/mL) of allicin (1mL). The combined acaricidal effects of ivermectin and allicin were analysed using four concentration combinations. PRM death rates were determined after 2h, 24h, 2 days, 5 days and 7 days of drug application. Ivermectin application (1mg/mL) exterminated 64% and 100% of PRMs on 1 and 5 days, respectively, and prevented their revival. Further, 0.5mg/mL ivermectin and 1mg/mL allicin individually exterminated 98% and 44% of PRMs, respectively, within 7 days of treatment. In combination, 0.5mg/mL ivermectin and 0.5mg/mL allicin exterminated 100% of PRMs within 5 d of treatment. The most effective combination was 0.25mg/mL ivermectin + 1.00mg/mL allicin. The efficacy of ivermectin-allicin combination in exterminating PRMs was demonstrated. This novel approach could be optimised for industrial applications.

Acaricides containing zein nanoparticles: A tool for a lower impact control of the cattle tick Rhipicephalus microplus

Nanoformulations containing zein nanoparticles (ZN) can promote the stability and protection of molecules with acaricidal activity. The present study sought to develop nanoformulations with ZN associated with cypermethrin (CYPE) + chlorpyrifos (CHLO) + a plant compound (citral, menthol or limonene), characterize them, and verify their efficacy against Rhipicephalus microplus ticks. Additionally, we aimed to assess its safety in nontarget nematodes found in soil at a site subjected to contamination by acaricides. The nanoformulations were characterized by dynamic light scattering and nanoparticle tracking analysis. Nanoformulations 1 (ZN+CYPE+CHLO+citral), 2 (ZN+CYPE+CHLO+menthol), and 3 (ZN+CYPE+CHLO+limonene) were measured for diameter, polydispersion, zeta potential, concentration, and encapsulation efficiency. Nanoformulations 1, 2, and 3 were evaluated in a range from 0.004 to 0.466 mg/mL on R. microplus larvae and caused mortality > 80% at concentrations above 0.029 mg/mL. The commercial acaricide Colosso® (CYPE 15 g + CHLO 25 g + citronellal 1 g) was evaluated also from 0.004 to 0.512 mg/mL and resulted in 71.9% larval mortality at 0.064 mg/mL. Formulations 1, 2, and 3 at 0.466 mg/mL showed acaricidal efficacy of 50.2%, 40.5%, and 60.1% on engorged females, respectively, while Colosso® at 0.512 mg/mL obtained only 39.4%. The nanoformulations exhibited long residual period of activity and lower toxicity to nontarget nematodes. ZN was able to protect the active compounds against degradation during the storage period. Thus, ZN can be an alternative for the development of new acaricidal formulations using lower concentrations of active compounds.

Synthesis of Carvacrol-Loaded Invasomes Nanoparticles Improved Acaricide Efficacy, Cuticle Invasion and Inhibition of Acetylcholinestrase against Hard Ticks.

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.

Phytochemical Profile of Foeniculum vulgare Subsp. piperitum Essential Oils and Evaluation of Acaricidal Efficacy against Varroa destructor in Apis mellifera by In Vitro and Semi-Field Fumigation Tests.

Varroatosis is an important parasitic disease of Apis mellifera caused by the mite Varroa destructor (V. destructor). The parasite is able to transmit numerous pathogens to honeybees which can lead to colony collapse. In recent years, the effectiveness of authorized drug products has decreased due to increasing resistance phenomena. Therefore, the search for alternatives to commercially available drugs is mandatory. In this context, essential oils (EOs) prove to be a promising choice to be studied for their known acaricide properties. In this research work, the acaricide activity of EO vapours isolated from the epigeal part (whole plant) of fennel (Foeniculum vulgare sbps. piperitum) and its three fractions (leaves, achenes and flowers) against V. destructor was evaluated. The effectiveness of fumigation was studied using two methods. The first involved prolonged exposure of mites to oil vapour for variable times. After exposure, the five mites in each replicate were placed in a Petri dish with an Apis mellifera larva. Mortality, due to chronic toxicity phenomena, was assessed after 48 h. The second method aimed to translate the results obtained from the in vitro test into a semi-field experiment. Therefore, two-level cages were set up. In the lower compartment of the cage, a material releasing oil vapours was placed; in the upper compartment, Varroa-infested honeybees were set. The results of the first method showed that the increase in mortality was directly proportional to exposure time and concentration. The whole plant returned 68% mortality at the highest concentration (2 mg/mL) and highest exposure time (48 h control), while the leaves, achenes and flowers returned 64%, 52% and 56% mortality, respectively. In the semi-field experiment, a concentration up to 20 times higher than the one used in the in vitro study was required for the whole plant to achieve a similar mite drop of &gt;50%. The results of the study show that in vitro tests should only be used for preliminary screening of EO activity. In vitro tests should be followed by semi-field tests, which are essential to identify the threshold of toxicity to bees and the effective dose to be used in field studies.

Molecular characterization of Hyalomma dromedarii and evaluation of acaricidal potential of herbal methanolic extracts against H. dromedarii larvae in comparison to synthetic acaricides.

The present study had two aims: molecular characterization of Hyalomma dromedarii infesting one-humped camels of Haryana (North India), and assessment of the acaricidal potential of herbal methanolic extracts against H. dromedarii larvae in comparison to synthetic acaricides. Phylogenetics and population neutrality indices were assessed by targeting partial amplification of mitochondrial 16S rDNA sequences. Larval packet test (LPT) was performed to evaluate the acaricidal efficacy of herbal extracts (Ferula asafoetida and Trachyspermum ammi) and synthetic acaricides (deltamethrin and fipronil). Phylogenetic studies established the collected ticks to be H. dromedarii, exhibiting a homology of 99.8-100%. However, the present study isolates formed a different sub-clade compared to H. dromedarii sequences from Egypt, Senegal, Tunisia and Saudi Arabia. Nucleotide and haplotype diversity values were indicative of demographic expansion and low gene flow. Negative values of Tajima's D (-0.612) and Fu and Li's Fst (-0.479) highlighted deviations from neutrality and emphasized recent population expansion. The median lethal concentration (LC50) values recorded for T. ammi, F. asafoetida and their combination were 3.68, 2.87 and 2.59mg/mL, respectively, whereas the 90% lethal concentration (LC90) values were 4.09, 3.58 and 3.35mg/mL, respectively. It was also observed that the H. dromedarii population under study was completely susceptible to both the formulated synthetic acaricides. In conclusion, combination of methanolic extracts of F. asafoetida and T. ammi could provide a potential substitute to toxic synthetic chemical acaricides and might prove a valuable component of integrated tick management strategies.

Identification of effective insecticides to manage Petrobia latens outbreaks in winter wheat

Petrobia latens (Müller) is a sporadic, but important pest of winter wheat in Oklahoma. Outbreaks are associated with prevalent hot, dry conditions (Jepson et al. 1975; Dhooria 2016). Because outbreaks are sporadic, updated data on acaricide efficacy against P. latens is sparse, and growers need to know what products are available to effectively control them when outbreaks occur (Depew 1968; Henderson &amp; Tilton 1955; Saxena &amp; Rawat 1969). We conducted two studies in established winter wheat to evaluate selected insecticides (bifenthrin @ 0.02 kg ai/ha, dimethoate @ 0.28 kg ai/ha, gamma cyhalothrin @ 0.015 kg ai/ha, lambda cyhalothrin @ 0.03 kg ai/ha, and zeta-cypermethrin @ 0.028 kg ai/ha) for their effectiveness at controlling P. latens. The first study (field 1) was conducted in a wheat field at Feekes growth stage 3.0 (Feekes 1941), and the second in a wheat field (Field 2) at Feekes growth stage 4.0. Mite populations in Field 1 averaged 421 mites per m2 and 1694 per m2 in Field 2. Growth stage affected control, with % control ranging from 48% to 64% in Field 1, while % control ranged from 81% to 88% in Field 2.

Temperature Predicts the Population of Aceria cajani Chan. (Acari: Eriophyidae) and Efficacy of Insecticides and Acaricides in its Control on Pigeonpea [Cajanus cajan (L) Millsp.

Background: The pigeonpea eriophyid mite, Aceria cajani Chan., vector of sterility mosaic disease in pigeonpea, causes economic damage of up to 90% during the early stages of crop growth. The major element in deploying management practice is to know the population dynamics of the pest. Generally, the vectors of disease causing agents were managed with the synthetic chemical. So we have taken studies to know efficacy of insecticides and acaricides in its control on pigeonpea. Methods: The population dynamics of A. cajani Chan. was monitored in field plots from January 2021 to December 2021. For efficacy of insecticides and acaricides studies in control of A. cajani a completely randomized design was organized. Twelve treatments (insecticides/acaricides) were tested against A. cajani on pigeonpea [var. ICP 8863 (Shree Maruti]. Result: This study found that mite population reached a peak in the summer (March) and another peak in the post-monsoon period (October), whereas the lowest populations were recorded in winter (January). Correlation studies exhibited a significant positive correlation with both maximum and minimum temperature. The insecticide and acaricide trials on A. cajani found that all chemicals used were effective and entomopathogenic formulations were comparatively less effective.

In-vitro Acaricidal Study of Calotropis Gigantea Methanolic Extracts against (Rhipicephalus (B.) microplus) Ticks in Udaipur, Rajasthan, India

The present research was conducted to find out acaricidal efficacy of methanolic extracts of Calotropis gigantea against Rhipicephalus (Boophilus) microplus ticks in Udaipur (Rajasthan). Larval packet Test (LPT) and Adult Immersion Test (AIT) were used to evaluate acaricidal efficacy. A total of four concentrations of the Calotropis gigantea extract (12.5%, 25%, 50%, and 100%) were used along with one control group with twice replications for each concentration were used in the bioassay. The Highest efficacy in both in-vitro tests (AIT and LPT) was recorded in 100% methanolic extracts of Calotropis gigantea. The Calotropis gigantea methanolic extracts displayed the highest IO% at 100% concentration, which was determined to be 67.46% in AIT. The methanolic extracts at 100% concentration had a minimum reproductive index of 0.16. During the study, it was clear that AIT had a lower reproductive index and a higher percent oviposition inhibition. Calotropis gigantea methanolic extracts in LPT demonstrated the highest efficacy at 100% concentration, which was of 64%. The Larval mortality increased trend with increasing concentrations of plant extracts.

Laboratory and field efficacy of terpene combinations (carvacrol, thymol and menthol) against the poultry red mite (Dermanyssus gallinae)

In this study, we evaluated the efficacy of combinations of the terpenes carvacrol, thymol, and menthol on Dermanyssus gallinae under in vitro (direct contact and vapour efficacy assays) and in-use conditions. Combinations investigated in vitro included carvacrol-menthol, thymol-menthol, carvacrol-thymol, and carvacrol-thymol-menthol. Results from contact efficacy studies showed that carvacrol-thymol-menthol was the most efficacious compared to the other combinations (P < 0.05), killing 100 % of the mites when at a concentration of 0.5 μg/mL. Thymol-menthol showed the weakest acaricidal activity with an approximate 80 % mortality rate at a concentration of 2 μg/mL. Based on the results of the vapour efficacy assay, all tested combinations appear to exert their acaricidal efficacy not only through direct contact, but also by fumigant action. A subsequent in-field efficacy investigation in a cage system laying farm was carried out to confirm the miticidal activity of the carvacrol-thymol-menthol combination. A formulation based on the triple combination of carvacrol-thymol-menthol diluted 1:40 in water was sprayed, with 1-week interval, in an 8000-laying hen farm, in presence of hens. The number of mites were counted by monitoring traps for 21 days through the study. The number of mites in the treated group decreased until day 5 after the first spray, but increased on days 5 and 7. However, after the second spray on day 7, the number of mites showed a significant decrease on day 10. This terpene-based combination which showed promising in vitro and in field miticidal activity can be a step forward in greening the future of pest management, also producing residue-free eggs.

Acaricidal Activities of Dioscorea japonica Thunb. (Dioscoreales: Dioscoreaceae) Extract and its Constituents Against the Two-spotted Spider Mite, Tetranychus urticae Koch (Trombidiformes: Tetranychidae).

The acaricidal activities of 86 plant extracts were investigated under laboratory conditions. The ethanol extract of Dioscorea japonica Thunb. root showed the strongest acaricidal activity, with 89.3% mortality against two-spotted spider mite, Tetranychus urticae Koch adults at a 2 mg/ml concentration. Bioassay-guided isolation of D. japonica root extract using silica gel open column chromatography, gas chromatography (GC), and gas chromatography-mass spectrometry (GC-MS) identified palmitic acid as the primary active compound. The acaricidal activities of palmitic acid against T. urticae were 91.2% and 69.7% at concentrations of 1 and 0.5 mg/ml, respectively. Among nine saturated fatty acids with carbon chains ranging from C8 to C26, the most vigorous acaricidal activity was observed with octanoic acid, followed by palmitic acid, and decanoic acid at a 1 mg/ml concentration. The acaricidal activity of the other fatty acids was less than 40% mortality at a 1 mg/ml concentration. These results indicate that a suitable carbon length is essential for fatty acids to exhibit acaricidal activity. The acaricidal efficacy of Eungjinssag (EJSG), an organic agricultural material authorized for the management of mites in the Republic of Korea, was compared to D. japonica root extract. At concentrations above 1 mg/ml, the acaricidal activity of D. japonica root extract was stronger than that of EJSG. The results of this study show that D. japonica root extract and palmitic acid are promising candidates as new environmentally-friendly control agents against two-spotted spider mite, which is one of the most severely damaging agricultural arthropod pests.

Interaction between anti-tick vaccine and a macrocyclic lactone improves acaricidal efficacy against Rhipicephalus (Boophilus) microplus (Canestrini) (Acari: Ixodidae) in experimentally infested cattle

The southern cattle fever tick (SCFT) Rhipicephalus (Boophilus) microplus, is considered the most important ectoparasite of livestock in the world because of high financial losses associated with direct feeding and transmission of the hemoparasites Babesia bovis, B. bigemina, and Anaplasma marginale. Unfortunately, SCFT in many parts of the world have evolved resistance to all market-available pesticides thus driving development of new control technologies. Vaccination against ticks using the tick gut protein Bm86 has been shown to be effective against acaricide-resistant ticks. This technique has been successfully implemented in Puerto Rico for the control of acaricide-resistant R. microplus on dairy and beef cattle. Observations from Puerto Rico indicate a potentially positive interaction between anti-tick vaccination when used in conjunction with systemic acaricide treatment. In this project, controlled animal studies were completed directly comparing efficacy of anti-tick vaccination with and without systemic acaricide. Results show that the Bm86 anti-tick vaccine in combination with the macrocyclic lactone, Moxidectin, expressed a synergistic interaction, providing greater and longer efficacy than either treatment alone.

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.

Phytochemical investigation and evaluation of acaricidal activities of Datura stramonium fruits against Rhipicephalus microplus

Aim: The present study focused on the evaluation of acaricidal efficacy of ethanolic extract of fruits of Datura stramonium against cattle tick Rhipicephalus microplus in-vitro. The ethanolic extract of fruits of Datura stramonium were analysed for the presence of phytochemicals responsible for antitick activities. Methodology: The fruits of Datura stramonium were dried, blended, powdered and extracted in ethanol using Soxhlet’s apparatus. In-vitro tests like Adult Immersion Test and Larval Packet Test were utilized to assess the effect of plant extract by utilizing engorged R. microplus female. Reproductive Index, Inhibition of oviposition, adult and larval mortality of female ticks were observed. The phytochemicals present in the ethanolic fruits extract of D. stramonium were assessed by Gas chromatography-Mass spectroscopy and Fourier Transform Infra-red Spectroscopy. Results: The present study indicated anti tick activities of ethanolic extract of Datura stramonium fruit against Rhipicephalus microplus by reporting a mortality of 66.67%, Reproductive Index (0.11-0.16), Inhibition of oviposition ( 70.62%) and larval mortality (65%) at 100 mg ml-1 and LC50 value was determined to be 61.66 mg ml-1. There was dose dependant mortality of adult and larva and inhibition of reproduction. The ethanolic fraction's spectral examination revealed 31 components, with the presence of 2(4H)-Benzofuranone, 5,6,7,7a-(7.24), Hexadecanoic acid, methyl ester (9.16), 9,12,15-Octadecatrienoic acid, methyl ester (9.35), 9,12,15-Octadecatrienoic acid (15.17), 2-Propenoic acid, 3-phenyl-, methyl ester (32.87) as major phytocompounds. Interpretation: These results showed that ethanolic extract of Datura stramonium fruits are source of phytochemicals with antitick activities. The findings would be useful to the pharmaceutical industries for developing of ecologically friendly natural acaricides. Key words: Acaricides, Datura stramonium, Ethanolic extract, Rhipicephalus microplus, Ticks

Acaricidal activity of carvacrol and thymol on acaricide-resistant Rhipicephalus microplus (Acari: Ixodidae) populations and combination with cypermethrin: Is there cross-resistance and synergism?

This study evaluated the acaricidal activity of thymol and carvacrol on Rhipicephalus microplus populations with different resistance profiles and investigated the synergistic effect of combinations of these monoterpenes with cypermethrin. The adult immersion test (AIT) was used to characterize the susceptibility of tick populations (45 field populations) to synthetic acaricides: deltamethrin, amitraz and chlorfenvinphos. The larval packet test (LPT) was used to determine the LC50 values for thymol (25 tick populations) and carvacrol (20 tick populations). The susceptible strain Porto Alegre (POA) was used as a reference for calculating the resistance ratio (RR). Subsequently, larval immersion tests (LIT) were performed with combinations of cypermethrin with thymol or carvacrol to assess a synergistic effect. In the AIT, deltamethrin showed efficacy > 90% in one (2.2%) population tested (mean: 12.1 and 11.1 for populations 1–25 and 26–40, respectively), whereas amitraz and chlorfenvinphos showed efficacy > 90% for two (4.4%) populations (mean: 61.3 and 47.3 for populations 1–25 and 26–40, respectively) and eight (17.7%) populations (mean: 69.7 and 59.7 for populations 1–25 and 26–40, respectively). In the LPT, the LC50 values for thymol and carvacrol varied from 0.67 to 2.12 mg/mL and 0.55–3.21 mg/mL, with an average LC50 for populations of 1.49 and 1.75 mg/mL, respectively. For thymol, no resistance was observed in any of the populations, values of RR50 > 1.5. There was no correlation between the LC50 values for thymol and the efficacy of the chemical acaricides tested. Regarding carvacrol, for only one tick population had the value of RR50 > 1.5, indicating an incipient resistance. No correlation was observed between the LC50 values for carvacrol and the efficacy of tested acaricides. The combination of thymol and carvacrol with cypermethrin showed a synergistic effect in the resistant population (Jaguar – thymol 4.19 and carvacrol 3.67), and no synergistic interaction were showed in the susceptible population. Answering the questions we conclude that: 1 - The comparison between the LC50 values for thymol and carvacrol in field populations and the susceptible strain POA suggests the absence of cross-resistance (ticks and terpenes), and the differences between the LC50 values for thymol and carvacrol in the different R. microplus populations are inherent to the characteristics of each population tested; 2 - the combination of thymol or carvacrol with cypermethrin showed a synergistic effect with different activity according to the population of ticks.