Acaricide Resistance Research Articles

Toxicity evaluation and chemical composition of Capsicum frutescens for natural control of Asian blue tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

BackgroundIndiscriminate use of synthetic acaricides in the management of veterinary parasites has led to environmental pollution, acaricidal resistance and their residues in the animal products. These problems are directly demanded an alternative acaricidal source for the ticks control and that should be cost-effective, eco-friendly and target specific. The current study demonstrated the acaricidal effects of Capsicum frutescens (fruits) against the cattle tick Rhipicephalus (Boophilus) microplus. In adult immersion test, the effects of the treatment on engorged females were assessed by measuring egg mass production, estimated reproductive factor, and % inhibition of reproduction.ResultsMethanol extract was observed the most effective against adults with LC50 617.54 ppm and LC90 1040.41 ppm. The other target extracts (petroleum ether and hexane) were less effective to the engorged females of R. microplus. Chemical analysis of the potent extract was elucidated by Gas Chromatography–Mass Spectrometry analysis and Cis-13-octadecenoic acid was observed as main compound (43.54%). The simultaneous evaluation of the qualitative chemical screening of the methanol extract showed the presence of tannins, saponins, carbohydrates, steroids, terpenoids, flavonoids, and alkaloids.ConclusionThe study concludes that the methanol extract of C. frutescens fruits revealed the significant acaricidal properties and may be used as safe alternative for tick management.

Acaricidal and Repellent Effects of Essential Oils against Ticks: A Review.

Tick control is a priority in order to prevent the transmission of vector-borne diseases. Industrial chemical acaricides and repellents have been the most efficient tools against hard ticks for a long time. However, the appearance of resistances has meant the declining effectiveness of the chemicals available on the market. The trend today is to develop alternative control methods using natural products to replace nonefficient pesticides and to preserve the efficient ones, hoping to delay resistance development. Traditional in vitro evaluation of acaricidal activity or resistance to synthetic pesticides have been reviewed and they mainly focus on just one species, the one host tick (Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)). Recent reports have called for the standardization of natural product components, extraction techniques, and experimental design to fully discover their acaricidal potential. This study reviews the main variables used in the bibliography about the efficiency of natural products against ticks, and it proposes a unification of variables relating to ticks, practical development of bioassays, and estimation of ixodicidal activity.

A gene drive does not spread easily in populations of the honey bee parasite Varroa destructor

Varroa mites (Varroa destructor) are the most significant threat to beekeeping worldwide. They are directly or indirectly responsible for millions of colony losses each year. Beekeepers are somewhat able to control varroa populations through the use of physical and chemical treatments. However, these methods range in effectiveness, can harm honey bees, can be physically demanding on the beekeeper, and do not always provide complete protection from varroa. More importantly, in some populations varroa mites have developed resistance to available acaricides. Overcoming the varroa mite problem will require novel and targeted treatment options. Here, we explore the potential of gene drive technology to control varroa. We show that spreading a neutral gene drive in varroa is possible but requires specific colony-level management practices to overcome the challenges of both inbreeding and haplodiploidy. Furthermore, continued treatment with acaricides is necessary to give a gene drive time to fix in the varroa population. Unfortunately, a gene drive that impacts female or male fertility does not spread in varroa. Therefore, we suggest that the most promising way forward is to use a gene drive which carries a toxin precursor or removes acaricide resistance alleles.

Cypermethrin and ivermectin resistance in field populations of Rhipicephalus sanguineus sensu lato (Latrielle, 1806) collected from dogs in south India.

The abuse of acaricides for control of Rhipicephalus sanguineus sensu lato ticks led to a strong selection pressure for acaricide resistance. Data on acaricide resistance in R. sanguineus s.l. populations from India is meager though veterinarians frequently report treatment failures. The present study was aimed to characterize the level of resistance in R. sanguineus s.l. against most commonly used drugs, cypermethrin and ivermectin in Andhra Pradesh, south India. Fourteen adult female tick populations were collected from naturally infested dogs at veterinary clinics, residence and stray dog in nine state municipal corporations/municipalities. Information on the history of dog treatment with acaricides was obtained by interviewing dog owners. The larval packet test (LPT) and larval immersion test (LIT) were used on the larvae of ticks to test for resistance to cypermethrin and ivermectin, respectively. Mortality data of each tick population was analyzed by probit analysis. Corresponding to the most susceptible population, thirteen (92.6%) and six (42.9%) tick populations were regarded as resistant to cypermethrin and ivermectin, respectively. The phenotypic level of cypermethrin (resistance ratios at LC50% varied from 1.55 to 13.29) and ivermectin (resistance ratios at LC50% ranged from 1.16 to 4.79) resistance varied distinctly between the populations. Additionally, all the populations were tested using PCR to demonstrate the frequency of the point mutation in sodium channel gene that corresponds with resistance of R. sanguineus s.l. to cypermethrin. A nucleotide substitution (T2134C) on domain III segment VI of the sodium channel gene was noticed in phenotypically resistant tick populations on DNA sequencing. Ivermectin resistance in the brown dog ticks is reported for the first time from India.

Acaricide resistance in Rhipicephalus appendiculatus ticks collected from different farming systems in Zimbabwe.

The larval packet test (LPT) was used to investigate resistance in Rhipicephalus appendiculatus ticks to the amidine (amitraz) and organophosphate (chlorfenvinphos) chemical acaricides in different farming systems in Mashonaland West Province in Zimbabwe. The study results showed emerging resistance (ER) to amitraz in small-scale and commercial farming systems. The tick populations in communal farming systems were susceptible to both acaricides. A similar trend was observed for chlorfenvinphos, where ER was observed in the small-scale farming systems compared to communal and commercial farms. Furthermore, resistance ratios (RR) were higher for amitraz as compared to chlorfenvinphos. This study suggests that management practices, acaricide formulations, applications on cattle, intensity, and frequency of use could be pre-disposing factors for the emerging resistance towards amitraz observed in R. appendiculatus ticks found in small-scale and commercial farming systems. Amitraz is the most common and frequently used acaricides in all farming systems, and hence, resistance is developing much faster than organophosphates. There is a need to investigate further acaricide use and management practices in Zimbabwe's cattle farming systems to develop practical strategies for prevention and management of tick acaricide resistance.

Acaricide resistance in Panonychus citri and P. ulmi (Acari: Tetranychidae): Molecular mechanisms and management implications

The European red mite, Panonychus ulmi (Koch), and the citrus red mite, P. citri (McGregor) (Acari: Tetranychidae), are destructive mite pests in pome/stone fruit orchards and citrus groves, respectively, the management of these two spider mites species has relied largely on the use of synthetic acaricides. However, frequent, long-term use of acaricides has caused rapid development of resistance in P. ulmi and P. citri populations worldwide. Levels of resistance in P. ulmi and P. citri are exceeded only by that in the two-spotted spider mite, Tetranychus urticae Koch. Recent research on T. urticae has provided new insights into the molecular mechanisms of acaricide resistance. The molecular basis of resistance in P. ulmi and P. citri populations has been less thoroughly studied. In this brief review, the current understanding of the molecular mechanisms of toxicokinetic and toxicodynamic resistance of P. ulmi and P. citri to acaricides, as well as implications of the findings for the resistance management, are discussed.

Rearing of Hyalomma marginatum (Acarina: Ixodidae) under laboratory conditions in Morocco

Hyalomma marginatum Koch is one of the main tick vectors of human and animal tick-borne diseases. The objective of this study was to establish standard procedures for rearing H. marginatum under laboratory conditions. Such laboratory tick populations are required to study acaricide resistance of Hyalomma ticks. In our rearing program, larvae and nymphs were fed on New Zealand white rabbits, whereas adults were fed on sheep. Non-parasitic stages were held at 18 and 28 °C to study the effect of temperature on development and survival. In our experiments, H. marginatum ticks have maintained the characteristics of a two-host life cycle. The engorged larvae did not detach and moulted on the rabbit, after which the emerged nymphs continued to feed on the same animal. The life cycle duration of H. marginatum was influenced by temperature, with each non-parasitic stage—i.e., larva and nymph molting—developing faster at 28 than at 18 °C; preoviposition and oviposition periods were shorter at 28 than at 18 °C. At 18 °C, no eggs hatched. The whole cycle from the collection of an engorged field tick until the emergence of second-generation larvae took 189 days. One such tick on average results in 3500 eggs which over time, taking into account the losses at each developmental stage, develop into 1200 adult ticks. Rearing these ticks a second generation therefore could result in millions of larval ticks.

Potential causes of Acaricide Resistance in Rhipicephalus and Amblyomma Ticks (Acari: Ixodidae) in Namwala District, Zambia

Acaricide resistance in ticks poses a great threat to livestock production in many parts of the world where ticks are a problem. The objectives of this study were to screen for acaricide resistance in Rhipicephalus and Amblyomma ticks using phenotypic and molecular assays, and to assess current tick control practices used by cattle farmers in the traditional sector of Namwala District. The larval packet test was used to screen for acaricide resistance in ticks covering concentrations up to twice the discriminatory dose for amitraz, diazinon and cypermethrin. Genetic mutations associated with resistance to amitraz (A22C-T8P and T65C-L22S), and organophosphates/ pyrethroids (G1120A) were screened using polymerase chain reaction and sequencing. Information on tick control practices at the household level was collected using a semi-structured questionnaire. Intermediate resistance (21-50%) to amitraz and cypermethrin was detected in both Rhipicephalus and Amblyomma ticks, with both tick genera showing susceptibility to diazinon (<10%). None of the ticks in this study had the reported acaricide resistance-conferring molecular markers that were screened for. The findings suggest that the resistance detected in the studied tick population may be due to other mechanisms yet to be identified. Tick control practices observed amongst the farmers, such as incorrect use of acaricide concentrations and rotations, could be fuelling the development of acaricide resistance. Considering that acaricide treatment is the mainstay of tick control in the country, it is thus critical to comprehensively unravel the factors contributing to treatment failure as this would allow for the application of appropriate remedial actions for effective tick control in Zambia.

Optimizing long-acting acaricide use for integrated tick management of Rhipicephalus australis-infesting cattle in New Caledonia.

The tick Rhipicephalus australis, formerly known as Rhipicephalus microplus, is the most economically important ectoparasite of livestock in New Caledonia, affecting cattle health and production. Decades of control attempts based on the application of chemical acaricides have exerted a strong selective pressure on R. australis populations, some of which have evolved resistance to these treatments. Research to develop integrated tick control programs is now focused on decreasing applications of chemicals. This study reports the implementation of a method of pasture and herd management involving minimal strategic use of long-acting acaricides, here defined as those having substantial efficacy against larvae for several weeks. Diverse parameters concerning the utilization of long-acting acaricides in association with pasture and herd management on 21 New Caledonian farms over a 5-year period were analyzed to optimize their strategic use. Longer larval acaricidal effect was achieved with a commercial pour-on formulation of fluazuron than with a commercial injectable (subcutaneous) formulation containing 3.15% ivermectin. Pasture and herd management allowed an increase in the delay between a long-lasting acaricide application and the subsequent acaricide treatment from 11.0weeks to 17.7weeks. However, if ticks were detected and reported by producers on the day of a long-acting acaricide application, the delay to the following treatment was reduced from 18.5weeks to 11.2weeks. The impact of a long-acting acaricide treatment on larval populations in pastures was greatest with a stocking rate of 5 animals per hectare grazing during 1week. These results provide science-based evidence to cattle producers for adaptive integrated tick management in order to delay the development of acaricide resistance.

Rhipicephalus Tick: A Contextual Review for Southeast Asia.

Rhipicephalus species are distributed globally with a notifiable presence in Southeast Asia (SEA) within animal and human populations. The Rhipicephalus species are highly adaptive and have established successful coexistence within human dwellings and are known to be active all year round, predominantly in tropical and subtropical climates existing in SEA. In this review, the morphological characteristics, epidemiology, and epizootiology of Rhipicephalus tick species found in SEA are reviewed. There are six commonly reported Rhipicephalus ticks in the SEA region. Their interactions with their host species that range from cattle, sheep, and goats, through cats and dogs, to rodents and man are discussed in this article. Rhipicephalus-borne pathogens, including Anaplasma species, Ehrlichia species, Babesia species, and Theileria species, have been highlighted as are relevant to the region in review. Pathogens transmitted from Rhipicepahalus ticks to host animals are usually presented clinically with signs of anemia, jaundice, and other signs of hemolytic changes. Rhipicephalus ticks infestation also account for ectoparasitic nuisance in man and animals. These issues are discussed with specific interest to the SEA countries highlighting peculiarities of the region in the epidemiology of Rhipicephalus species and attendant pathogens therein. This paper also discusses the current general control strategies for ticks in SEA proffering measures required for increased documentation. The potential risks associated with rampant and improper acaricide use are highlighted. Furthermore, such practices lead to acaricide resistance among Rhipicephalus species are highlighted.

Toxicity of chitosan derivatives to Varroa destructor (Anderson and Trueman) and their effects on immune gene expression in honey bees

Varroasisis caused by Varroa destrucor (Anderson and Trueman) is considered the most dangerous honey bee disease. V. destructor mites parasitize both brood and adults, causing considerable losses to the colony population. The control of Varroa mites is highly dependent on the application of synthetic acaricides, however, acaricide resistance can develop. To eliminate the risk of Varroa mite resistance and to reduce residues in hive products, organic-based substances for Varroa mite control are being applied. In the present study, the acaricidal activity of N-alkyl and O-acyl chitosan derivatives against Varroa mites and their side effects on honey bees have been evaluated. Chitosan has been extracted from the corpses of honey bees. The yield, degree of deacetylation, and molecular weight of chitosan from the chitin of honey bee corpses were determined as 89%, 90%, and 20 kDa, respectively. Varroa mite mortalities were observed between 6.28-84.38% and 0.00-90.47% by N-alkyl and O-acyl chitosan derivatives, respectively. The best derivatives against Varroa mite were N-(3-phenylbutyl)chitosan (NAC-5) and O-(heptanoyl)chitosan (OAC-4). The results showed that different lethal concentrations of NAC-5 and OAC-4 had side effects against honey bees less than 26%. No significant difference was found between honey bee mortalities at 24, 48, and 72 hours post-treatment, while mortalities significantly differed between 4, and 24 h post-treatment. Immune gene expression in honey bees exposed to a lethal concentration of NAC-5and OAC-4 showed that the expressions of AmHym, AmBask, and AmSpz were significantly lower compared with those of control honey bees.

Acaricide Efficacy and Resistance in South Carolina Tomato Populations of Twospotted Spider Mite

Twospotted spider mite, Tetranychus urticae Koch (Trombidiformes: Tetranychidae) is a key pest of vegetable crops in the southeastern US. Spider mites can cause significant yield loss in tomato due to reduced photosynthetic capacity and direct feeding damage. Use of acaricides is the primary control method, but acaricide resistance is a serious concern. We sought to characterize efficacy of acaricides registered for use on tomato by conducting 2 field trials in South Carolina in 2015 and 2016. The most effective treatments were abamectin, fenpyroximate, and cyflumetofen. Bifenazate and bifenthrin had lower efficacy than other products, and acaricide resistance was a suspected cause. Therefore, 3 spider mite populations were collected from grower fields in 2017, subjected to concentration-response screening, and compared to a known-susceptible population. Probit analysis revealed that all populations were resistant to bifenthrin at levels that would likely result in field failure. All populations were resistant to abamectin, with the LC50 of 1 population above field rate. Resistance to acequinocyl and spiromesifen also was present in all populations, but LC50 values were well below field rate. Based on our results and known non-target effects of bifenthrin and abamectin on predatory mites, growers should avoid using these products for spider mite management. Poor performance of bifenazate in the efficacy study could not be attributed to resistance, although it is possible that the populations from the efficacy study were resistant and those screened for resistance were not. Many acaricides registered in tomato appear to be effective for mite management in South Carolina.

First tick and tick damage perception survey among sedentary and transhumant pastoralists in Burkina Faso and Benin.

BackgroundTranshumance, a main ancestral animal production strategy of the West African Countries (WAC), can favour the spread of vectors and vector‐borne diseases within and/or across countries. Transhumance has been implicated in such spread as well as that of related tick‐borne diseases (TBD).Methods and principal findingsUsing a questionnaire survey and statistical modelling, this study explores the perception of herders about ticks and TBD in cattle, their practices in tick control and the social groups involved in cattle farming in eastern Burkina Faso (46 random herds) and in the northern Benin (44 random herds). Results show that most of the herders (79%) are from the Fulani social group. The principal and secondary activities of herders are respectively cattle farming and agriculture. The mean age of pastoralists is between 40 and 50 years depending on the province of origin and 60% of the surveyed herds practice internal or transboundary transhumance. Herders have a clear knowledge of different genus of ticks except the genus Rhipicephalus. Their knowledge of TBD is very limited. These results also reveal that herders in Benin use less acaricides treatment calendar compared with those in Burkina Faso. Transhumant pastoralists (i.e. transhumant cattle farmers) plan more acaricide treatment and have more cows with lost teats (i.e. tick damage) than the sedentary ones. In addition, amitraz appears to be the main acaricide compound used by herders for tick control (68%) but its use is inappropriate and its source is frequently the unregulated market.Conclusions and significanceAll of these findings can induce acaricide resistance especially as the inefficacy of amitraz against Rhipicephalus (Boophilus) microplus has already been reported in previous studies. Such results would help to elaborate suitable strategies of control and prevention of ticks and TBD in Burkina Faso and Benin.

Delta class glutathione S-transferase (TuGSTd01) from the two-spotted spider mite Tetranychus urticae is inhibited by abamectin

GSTs (Glutathione S-transferases) are known to catalyze the nucleophilic attack of the sulfhydryl group of reduced glutathione (GSH) on electrophilic centers of xenobiotic compounds, including insecticides and acaricides. Genome analyses of the polyphagous spider mite herbivore Tetranychus urticae (two-spotted spider mite) revealed the presence of a set of 32 genes that code for secreted proteins belonging to the GST family of enzymes. To better understand the role of these proteins in T. urticae, we have functionally characterized TuGSTd01. Moreover, we have modeled the structure of the enzyme in apo form, as well as in the form with bound inhibitor. We demonstrated that this protein is a glutathione S-transferase that can conjugate glutathione to 1-chloro-2,4-dinitrobenzene (CDNB). We have tested TuGSTd01 activity with a range of potential substrates such as cinnamic acid, cumene hydroperoxide, and allyl isothiocyanate; however, the enzyme was unable to process these compounds. Using mutagenesis, we showed that putative active site variants S11A, E66A, S67A, and R68A mutants, which were residues predicted to interact directly with GSH, have no measurable activity, and these residues are required for the enzymatic activity of TuGSTd01. There are several reports that associate some T. urticae acaricide resistance with increased activity of GSTs . However, we found that TuGSTd01 is not able to detoxify abamectin; in fact, the acaricide inhibits the enzyme with Ki = 101 μM. Therefore, we suggest that the increased GST activity observed in abamectin resistant T. urticae field populations is a part of the compensatory feedback loop. In this case, the increased production of GSTs and relatively high concentration of GSH in cells allow GSTs to maintain physiological functions despite the presence of the acaricide.

Acaricidal activity of Alstonia scholaris and Sida cordifolia leaf extracts against Hyalomma anatolicum ticks

Development of acaricidal resistance and environmental pollution has driven need for eco-friendly pesticides and herbal acaricides. Leaf extracts of Alstonia scholaris and Sida cordifolia in four different solvents were used in the range of 0.25-8.0% for larval immersion test against unfed larvae of Hyalomma anatolicum. Mortality rates of larval ticks were in dose-dependent manner ranged from 0.5 to 100% for A. scholaris and from 0.8 to 100% for S. cordifolia. Acetone extract of A. scholaris and methanolic extract of S. cordifolia were most effective against larval ticks with LC50 values of 0.71% and 0.42%, respectively. Significant larvicidal activity of A. scholaris and S. cordifolia leaf extracts against unfed larvae of H. anatolicum qualify them as green pesticides which could be combined with other tools for integrated pest management.

Government Assistance To Farmers Against Tick-Borne Diseases During The COVID-19 lockdown

Ticks are responsible for transmitting viral, bacterial, and protozoal diseases to humans and animals and also cause significant economic damage to the livestock industry. The owner of the farmhouse prefers to use acaricides, a key component of tick control strategies. However, the indiscriminate and irresponsible use of acaricides has a detrimental effect on the increase in the contamination of the environment, acaricide resistance in ticks, and its residues in milk and meat of the animal. There is now ample evidence that vaccination can provide significant immunity to tick and tick-borne diseases [1]. The COVID-19 virus, like its predecessor, the SARS virus (and other emerging diseases), is thought to have spread to humans through animal markets of Wuhan a central city in China [2]. Fortunately, the ticks do not spread this virus, but the COVID-19 virus is responsible for all those factors that can cause it to spread rapidly to animals.

Analysis of Genetic Diversity in Indian Isolates of Rhipicephalus microplus Based on Bm86 Gene Sequence.

The control of cattle tick, Rhipicephalus microplus, is focused on repeated use of acaricides. However, due to growing acaricide resistance and residues problem, immunization of animals along with limited use of effective acaricides is considered a suitable option for the control of tick infestations. To date, more than fifty vaccine candidates have been identified and tested worldwide, but two vaccines were developed using the extensively studied candidate, Bm86. The main reason for limited vaccine commercialization in other countries is genetic diversity in the Bm86 gene leading to considerable variation in vaccine efficacy. India, with 193.46 million cattle population distributed in 28 states and 9 union territories, is suffering from multiple tick infestation dominated by R. microplus. As R. microplus has developed multi-acaricide resistance, an efficacious vaccine may provide a sustainable intervention for tick control. Preliminary experiments revealed that the presently available commercial vaccine based on the BM86 gene is not efficacious against Indian strain. In concert with the principle of reverse vaccinology, genetic polymorphism of the Bm86 gene within Indian isolates of R. microplus was studied. A 578 bp conserved nucleotide sequences of Bm86 from 65 R. microplus isolates collected from 9 Indian states was sequenced and revealed 95.6–99.8% and 93.2–99.5% identity in nucleotides and amino acids sequences, respectively. The identities of nucleotides and deduced amino acids were 94.7–99.8% and 91.8–99.5%, respectively, between full-length sequence (orf) of the Bm86 gene of IVRI-I strain and published sequences of vaccine strains. Six nucleotides deletion were observed in Indian Bm86 sequences. Four B-cell epitopes (D519-K554, H563-Q587, C598-T606, T609-K623), which are present in the conserved region of the IVRI-I Bm86 sequence, were selected. The results confirm that the use of available commercial Bm86 vaccines is not a suitable option against Indian isolates of R. microplus. A country-specific multi-epitope Bm86 vaccine consisting of four specific B-cell epitopes along with candidate molecules, subolesin and tropomyosin in chimeric/co-immunization format may provide a sustainable option for implementation in an integrated tick management system.

Efficacy of commercially available chemical compound used against management of tick infestation in Mhow, Madhya Pradesh

The study was conducted to determine the efficacy of commercially available chemical compound used in management of tick infestation in this area where the Rhipicephalus microplus is the most prevalent species of ticks. The most important chemical compound used for controlling ticks in this area is cypermethrin, deltamethrin and amitraz. This is happen because cheap and easy availability of these compound. The engorged female R. microplus tick sample was collected from unorganised dairy farm of Mhow districts in Madhya Pradesh. The Adult Immersion Test (AIT) and larval packet test (LPT) was performed for the characterization of resistance in field tick population. The slope of mortality, lethal concentration for 50 % (LC50), and resistance ratios (RR) were determined from the regression graphs of probit mortality of ticks plotted against log concentrations of chemical compound used in study. The resistant ration (RR) of cypermethrin was in the range of 0.76 to 1.45. Most of the population were found susceptibly in LPT and AIT and the slope value was recorded lower than the susceptible reference strain. In case of deltamethrin, the resistance ratio (RR) was in the range of 22.35 to 34.64 at level II and III and the slop value of field population was found comparatively low than susceptible reference strain. In amitraz, the resistance ratio (RR) was obtained as 2.23.On the basis of RR the tested tick showed resistance in adult stage at level I. The AIT bioassay was used for the characterization of resistance in field tick population. Efficacy of chemical compound was recorded on basis of resistance ratio and level of resistance was assessed. The data on field status of acaricide resistance in Mhow block of Madhya Pradesh state will be helpful to adopt suitable strategy to overcome the process of development of resistance in ticks.

Mechanisms and management of acaricide resistance for Tetranychus urticae in agroecosystems

The two-spotted spider mite, Tetranychus urticae Koch, is a constant threat to sustainable production of numerous economically important crops globally. Management of T. urticae is heavily reliant on the application of synthetic acaricides. However, T. urticae has rapidly developed resistance to most of the acaricides available for its control due to its very broad host plant range, extremely short lifecycle, high fecundity, arrhenotokous parthenogenesis, and overwintering strategy. Despite the recent progress in identifying genetic changes/markers associated with resistance toward some commonly used acaricides for T. urticae, there is still limited studies that select and apply these markers in field populations to guide sustainable pest management strategy design. Temporal and spatial characterization of acaricide-resistant phenotypes and their underlying mechanisms are crucial for the design and implementation of successful and sustainable integrated mite management programs. This review highlights the current acaricide resistance status of field-collected T. urticae populations and the underlying molecular mechanisms of resistance. Our review found that some genetic mutations in target sites and/or overexpression of metabolic genes confer resistance in geographically exclusive populations, while some resistance markers appear to be specific to populations at biogeographical areas. Thus, there is a need for locally based coordinated efforts to understand the mechanisms of resistance present in endemic T. urticae populations. Moreover, we discuss a prospective template for designing an effective acaricide resistance management program within various agroecosystems.

Transcriptome analysis revealed that multiple genes were related to the cyflumetofen resistance of Tetranychus cinnabarinus (Boisduval)

Metabolic resistance is one of the main causes of acaricide resistance. Many previous studies focused on the function of specific genes in insecticides/acaricides resistance. However, during the development of resistance, the overall dynamic of expression levels of detoxification enzyme genes in mites is still unclear. Tetranychus cinnabarinus, a major agricultural pest, which is notorious for developing resistance to acaricides rapidly. In this study, a field susceptible strain (YS) was continuously selected for 16, 25 and 32 generations, and developed to low resistance (7.83-fold, L), medium resistance (17.23-fold, M) and high resistance (86.05-fold, H), respectively. Transcriptome sequencing was performed in YS, L, M and H strains. Overall, compared with YS strain, the number of differential expression genes increased slightly with the development of cyflumetofen-resistance. As for detoxification genes, the median of fold change of up-regulated P450、CCE and GST genes was higher than those of all up-regulated genes in three resistance level, but only the number and the median of fold change of up-regulated P450 genes was increased slightly with the development of resistance. In addition, synergism experiments also proved that P450 and GST genes were the major contributors to the metabolic resistance of cyflumetofen of T. cinnabarinus. These results showed that the resistance of T. cinnabarinus to cyflumetofen was related to many resistant genes, among which P450 genes could play crucial roles in cyflumefen resistance.