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The parasitic mite Varroa destructor and the associated viruses it transmits are responsible for most instances of honey bee colony losses in the United States. As such, beekeepers utilize miticides to control Varroa populations. Widespread resistance has developed to the miticides fluvalinate and coumaphos. However, Varroa has largely maintained susceptibility to amitraz despite a long and extensive use history. Anecdotal reports of reduced amitraz effectiveness have been a widely discussed contemporary issue among commercial beekeepers. Amitraz resistance was measured by in vitro bioassays with technical amitraz as well as Apivar® efficacy tests. Amitraz resistance was evaluated in commercial beekeeping operations in Louisiana, New York, and South Dakota with a long history of amitraz use. This research shows that amitraz remains an effective Varroa control product in many operations. However, apiaries across operations displayed a wide range of amitraz resistance from no resistance to high resistance that resulted in Varroa control failure. The resistance ratios from in vitro amitraz bioassays were correlated with reduced Apivar® efficacy, demonstrating bona fide cases of Varroa control failures due to amitraz resistance. Therefore, amitraz resistance monitoring protocols need to be developed. A resistance monitoring network should be established to ensure the sustainability of miticide use for Varroa control.

Tick control mainly depends on using chemical acaricides that have led to the emergence of resistant tick populations along with environmental hazards. Natural alternatives including essential oils are now widely used to avoid the undesirable effects of chemicals on human, animals and environment. In this study, three commercial oils (myrrh, patchouli, and cypress) and their nanoemulsions (NEs) were tested against Rhipicephalus sanguineus sensu lato unfed adults. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) were used to characterize the nanoemulsions. Four concentrations with three replicates were used in the bioassay of oils and NEs against ticks using an adult immersion test. Furthermore, a toxicity study of the three oils and their NEs using normal fibroblast cells (BJ-1) was performed. TEM revealed particle size ranges from 29 to 211 nm with spherical droplets. The droplet size and polydispersity index were (29.30 nm & 0.367), (211.6 nm & 0.221) and (164.2 nm & 0.237) for myrrh NE, patchouli NE, and cypress NE, respectively. Myrrh and patchouli oils recorded high acaricidal activity followed by cypress oil with LC 50 value 5 days after treatment of 9.01, 12.40, and 15.21%, respectively. The acaricidal efficacy of oil was potentiated in the NEs form which was proved by the reduction in LC 50 values that were recorded 7 days after treatment 4.17, 8.57, and 5.04%, for myrrh, patchouli, and cypress NE, respectively. As an alternative for lab animals, we applied the cytotoxicity of myrrh, patchouli, and cypress on normal fibroblast cells. The oils showed low cytotoxic activity of 10.6, 21.5, and 23.6% for Myrrh, Patchouli, and Cypress, respectively. The nanoemulsion was revealed to be safe for normal cells up to a concentration of 0.62% (cytotoxicity%= 24.4, 34.4, and 16.3%, respectively), and the moderate cytotoxic effect appeared at around a concentration of 1.25% (cytotoxicity%= 42.2%, 57.0%, and 36.8% respectively). In conclusion, the three oils and their NEs have good acaricidal activity against Rhipicephalus sanguineus unfed adults. Further toxicity studies on mammals are needed to ensure the safe use of these formulations for the control of ticks on infested animals.

Chemical analysis shows that honey bees (Apis mellifera) and hive products contain many pesticides derived from various sources. The most abundant pesticides are acaricides applied by beekeepers to control Varroa destructor. Beekeepers also apply antimicrobial drugs to control bacterial and microsporidial diseases. Fungicides may enter the hive when applied to nearby flowering crops. Acaricides, antimicrobial drugs and fungicides are not highly toxic to bees alone, but in combination there is potential for heightened toxicity due to interactive effects. Laboratory bioassays based on mortality rates in adult worker bees demonstrated interactive effects among acaricides, as well as between acaricides and antimicrobial drugs and between acaricides and fungicides. Toxicity of the acaricide tau-fluvalinate increased in combination with other acaricides and most other compounds tested (15 of 17) while amitraz toxicity was mostly unchanged (1 of 15). The sterol biosynthesis inhibiting (SBI) fungicide prochloraz elevated the toxicity of the acaricides tau-fluvalinate, coumaphos and fenpyroximate, likely through inhibition of detoxicative cytochrome P450 monooxygenase activity. Four other SBI fungicides increased the toxicity of tau-fluvalinate in a dose-dependent manner, although possible evidence of P450 induction was observed at the lowest fungicide doses. Non-transitive interactions between some acaricides were observed. Sublethal amitraz pre-treatment increased the toxicity of the three P450-detoxified acaricides, but amitraz toxicity was not changed by sublethal treatment with the same three acaricides. A two-fold change in the toxicity of tau-fluvalinate was observed between years, suggesting a possible change in the genetic composition of the bees tested. Interactions with acaricides in honey bees are similar to drug interactions in other animals in that P450-mediated detoxication appears to play an important role. Evidence of non-transivity, year-to-year variation and induction of detoxication enzymes indicates that pesticide interactions in bees may be as complex as drug interactions in mammals.

Ticks are blood-feeding ecto-parasites that have a cosmopolitan distribution in tropical and subtropical regions of the world. Ticks cause economic losses in the form of reduced blood, meat and dairy products, as well as pathogen transmission. Different acaricides such as organochlorines, organophosphates, formamidines (e.g. amitraz), synthetic pyrethroids, macrocyclic lactones, fipronil, and fluazuron are currently used sequentially or simultaneously to control tick infestations. Most acaricide treatments now face increasingly high chances of failure, due to the resistance selection in different tick populations against these drugs. Acaricide resistance in ticks can be developed in different ways, including amino acid substitutions that result in morphological changes in the acaricide target, metabolic detoxification, and reduced acaricide entry through the outer layer of the tick body. The current literature brings a plethora of information regarding the use of different acaricides for tick control, resistance selection, analysis of mutations in target sites, and resistance mitigation. Alternatives such as synergistic use of different acaricides, plant-derived phytochemicals, fungi as biological control agents, and anti-tick vaccines have been recommended to avoid and mitigate acaricide resistance. The purpose of this review was to summarize and discuss different acaricides applied for tick control, their mechanisms of action and resistance selection, genetic polymorphisms in their target molecules, as well as the approaches used for diagnosis and mitigation of acaricide resistance, specifically in Rhipicephalus microplus ticks.

Ticks are among the most significant ectoparasites of livestock and humans, posing serious health and economic risks. The growing resistance to conventional acaricides highlights the need for safer and more effective alternatives. This study aimed to evaluate the acaricidal efficacy of different ivermectin (IVM) nanoformulations against different developmental stages of Rhipicephalus sanguineus tick. Different ivermectin nanoformulations were fabricated and evaluated for their physicochemical properties. An in vitro study was performed using larval, nymphal, and adult immersion tests, followed by an in vivo trial against unfed adults using the most effective formulation. All nanoformulations showed particle sizes from 450 to 650 nm and a polydispersity index range from 0.34 to 0.65. IVM spanlastics exhibited the smallest particle size, highest encapsulation efficiency (92%), and a sustained release profile. Based on LC 50 values, IVM spanlastics showed superior acaricidal activity against larvae (LC 50 : 0.05%), nymphs (LC 50 : 0.09%), and unfed adults (LC 50 :0.16%); followed by IVM-SeNPs, where the LC 50 values were 0.10, 0.23, and 0.38% for larvae, nymphs, and unfed adults, respectively. The in vivo study of IVM spanlastics demonstrated 100% mortality of adult ticks within four days after application. IVM spanlastics could be topically applied as an alternative to conventional injectable IVM to control R. sanguineus ticks. Further toxicological studies are necessary to ensure the safety of these formulations for environmental and veterinary use.

The acaricide propargite has been widely used for over 50 years without significant resistance issues. Addressing to the propargite defects of poor crop safety, thirty-six novel halogenated propargite analogues were designed, synthesized, and characterized using 1 H NMR, 13 C NMR spectroscopy, and HRMS. All target compounds were screened for activity against adult Tetranychus cinnabarinus (spider mites) and Myzus persicae (aphids). Two compounds exhibiting higher insecticidal activity were further evaluated for crop safety on cowpea seedlings. Structural modifications, such as replacing the tert -butyl group on the propargite benzene ring with chlorine or trifluoromethoxy, and substituting the propargyl group with fluorinated alkyl groups (e.g., 2-fluoroethyl or 3,3,3-trifluoropropyl), significantly enhanced both acaricidal and aphicidal activity. Compound 5.16 demonstrated superior acaricidal activity (LC 50 : 14.85 mg L -1 ) on Tetranychus cinnabarinus and excellent crop safety on cowpea seedlings. Additionally, Compound 5.32 exhibited both acaricidal (LC 50 : 14.32 mg L -1 ) and aphicidal activity, which is unusual in this chemical class. The compounds 5.16 and 5.32 could be used as promising leads for the discovery of novel acaricides or insecticides.

Recent declines in honey bees for crop pollination threaten fruit, nut, vegetable and seed production in the United States. A broad survey of pesticide residues was conducted on samples from migratory and other beekeepers across 23 states, one Canadian province and several agricultural cropping systems during the 2007–08 growing seasons. We have used LC/MS-MS and GC/MS to analyze bees and hive matrices for pesticide residues utilizing a modified QuEChERS method. We have found 121 different pesticides and metabolites within 887 wax, pollen, bee and associated hive samples. Almost 60% of the 259 wax and 350 pollen samples contained at least one systemic pesticide, and over 47% had both in-hive acaricides fluvalinate and coumaphos, and chlorothalonil, a widely-used fungicide. In bee pollen were found chlorothalonil at levels up to 99 ppm and the insecticides aldicarb, carbaryl, chlorpyrifos and imidacloprid, fungicides boscalid, captan and myclobutanil, and herbicide pendimethalin at 1 ppm levels. Almost all comb and foundation wax samples (98%) were contaminated with up to 204 and 94 ppm, respectively, of fluvalinate and coumaphos, and lower amounts of amitraz degradates and chlorothalonil, with an average of 6 pesticide detections per sample and a high of 39. There were fewer pesticides found in adults and brood except for those linked with bee kills by permethrin (20 ppm) and fipronil (3.1 ppm). The 98 pesticides and metabolites detected in mixtures up to 214 ppm in bee pollen alone represents a remarkably high level for toxicants in the brood and adult food of this primary pollinator. This represents over half of the maximum individual pesticide incidences ever reported for apiaries. While exposure to many of these neurotoxicants elicits acute and sublethal reductions in honey bee fitness, the effects of these materials in combinations and their direct association with CCD or declining bee health remains to be determined.

A novel sanitizer tablet containing clove essential oil (CO) microemulsion was developed. A preformulation study using nuclear magnetic resonance and thermal analyses showed component compatibility. The main components of the samples remained intact despite a color change, probably due to a strong acid-base interaction between eugenol and diethanolamine. The CO microemulsion showed acaricidal and larvicidal activities superior to the commercial product, with product efficacy of 99.9% and larvae mortality of 94%. Optimal spray-drying conditions were achieved with inlet and outlet temperatures of 50°C and 40°C, respectively, an aspiration rate of 1 m 3 min⁻ 1 , and a 0.25 L h⁻ 1 injection flow. The feed suspension comprised 50% (v/v) liquid soap, 37.5% (v/v) water, 12.5% (v/v) ethanol, and 5.0% (w/v) silica. This formulation and processing parameters allowed for successful free-flow powder formation, providing a suitable matrix for incorporating the CO microemulsion via wet granulation without heating. Finally, sanitizer tablets produced from such granules resulted in a uniform product with low weight variation (coefficient of variation of 0.15%), eugenol content of 95.5% ± 3.3, and friability of 0.58%. Furthermore, the tablets showed rapid aqueous dispersion, forming a colloidal system with particle sizes of 221 nm and a zeta potential of -17.2 mV. Antimicrobial activity tests demonstrated the effectiveness of the sanitizer tablet against bacteria and fungi, exhibiting comparable antimicrobial potency to isolated CO. Hence, the sanitizer tablet developed represents a promising candidate as a practical and efficient solution for pest control, offering strong antimicrobial and acaricidal activity.

Rhipicephalus microplus , a tick species, causes significant economic losses in livestock and presents control challenges due to the emergence of resistance to conventional acaricides. This underscores the urgent need for effective and eco-friendly alternatives. This study evaluates the acaricidal potential of Cirsium arvense using adult immersion and larval packet tests. In silico molecular docking techniques were employed to identify biologically active compounds within C. arvense . Using Chem-Draw Ultra software (version 12.0.2, 2010), we illustrated 25 compounds derived from the plant, which were subsequently tested as ligands in docking experiments against Subolesin. Among the tested compounds, Apigenin 7-O-glucosideand Pectolinarigenin 7-glucoside exhibited significant inhibitory effects on Subolesin, with docking scores of -6.6 and − 6.3 kcal/mol, respectively. In contact bioassays using Cirsium arvense extract, various concentrations (2.5, 5, 10, 20, and 40 mg/mL) were evaluated. The results indicated an LC50 of 2.907 mg/mL and an LC90 of 47.725 mg/mL after 24 h of exposure. Notably, at the highest concentration of 40 mg/mL, the extract significantly reduced egg-laying activity in adult female ticks, yielding an oviposition index of 0.09 ± 0.02, which corresponds to a 75.68 ± 0.44% reduction in reproductive capacity. Additionally, larval mortality reached 88.33 ± 2.90%, indicating that higher concentrations not only increased larval mortality but also substantially decreased the reproductive capacity of the ticks. These findings suggest that bioactive components from Cirsium arvense show promise as candidates for the control of R. microplus . Further research is warranted to evaluate their efficacy as alternative or complementary strategies to synthetic acaricides.

The most common hard tick in Egypt is Hyalomma dromedarii as a one of the most dangerous ectoparasites. The current study aims to detect the chemical composition of Syzygium aromaticum bud ethanolic extract using GC-MS and some phytochemical analysis in addition to investigating its acaricidal activity on H . dromedarii engorged females through biological and biochemical studies. The GC-MS revealed the presence of eugenol, eugenol acetate and D-(-)-fructofuranose as the most active compounds, and it appeared to be rich in alkaloids, flavonoids, phenolic compounds, tannins and terpenoids. At high concentration, the extract caused mortality to reach 100% after 35 days of treatment in engorged females, with LC 50 reached 100.22 and 0.83 mg/mL after the 3rd and 5th week (half and end of examined period) following treatment, respectively. The blood digestion was affected by significantly decreasing in their body weights. Furthermore, the extract showed a decrease in their oviposition, hatchability, and fertility. The extract at 100 mg/mL caused a reduction in ovary total protein content with disappearance of some protein bands using SDS-PAGE, compared with the control group. Overall, the current study revealed the effectiveness of S . aromaticum extract as a bio-acaricide for controlling H . dromedarii and it recommended numerous additional field studies to assess its effectiveness under different conditions.