Research Overview on Occurrence and Control of Tetranychus urticae Koch in China

Tetranychus urticae Koch;Insecticide resistance;Chemical control This paper elaborates the occurrence factors and damage characteristics of Tetranychus urticae Koch in China,and emphatically summarizes three main control strategies of T.urticae,namely agricultural control,chemical control and biological control,as well as research progress in its resistance mechanisms.The problems existing in controlling T.urticae and its resistance management strategies are put forward,to provide a theoretical basis for the resistance management and comprehensive control of T.urticae.

桑树(Morus alba)朱砂叶螨(Tetranychus cinnabarinus)实验种群的温度效应

采用生命表分析、生存分析、“王-兰-丁”模型及线性模型等分析方法，对15-28℃温区的5个恒温处理朱砂叶螨（Tetranychus cinnabarinus）实验种群进行了系统研究。结果表明，此温区内，种群在生殖、发育和生存3方面，有明显的温度效应：内禀增长力、周限增长力、净增殖力和平均日产卵量、世代平均周期、及种群倍增时间的倒数呈线性增长；而平均寿命、最大死亡年龄，随温度升高而递减；性比和实际产卵天数对温度不敏感。种群在生殖、发育和生存三者之间，采取了较为“折衷”的策略：8℃为发育临界点；13℃左右为生殖和种群增长临界温度；22℃左右为生殖和种群增长最适温度；30℃左右为发育最适温度。

Studies on Acaricidal Bioactivities of Artemisia annua L.Extracts Against Tetranychus cinnabarinus Bois.(Acari:Tetranychidae)

The aim of this study was to determine the best extraction technique, the most suitable solvent, the optimal plant parts, and the acaricidal activities of Artemisia annua L. The petroleum ether （30-60℃）, petroleum ether （60-90℃）, ethanol, acetone, and water parallel and sequenced extracts were obtained from the leaves, stems and roots of different period of A. annua L. in April, May, June, July and September respectively. And then the acaricidal bioactivities against Tetranychus cinnabarinus of all extracts were determined by the slide-capillary method in the laboratory. The results indicated that the acaricidal bioactivities elevated as the development of A. annua plant at the concentration of 5 mg mL-L The general tendency exhibited the sequence of July 〉 June 〉 May 〉 April, but September decreased comparing to July. However, the most effective extracts in five months were all acetone parallel extract of A. annua leaf, and the corrected mortalities treated after 48 h ranged from 74 to 100%. The median lethal concentrations （LC50） against T. cinnabarinus of acetone parallel extracts ofA. annua leaves in September, July, June, May and April were 0.5986, 0.4341, 0.8376, 0.9443 and 1.3817 mg mL^-1, respectively, treated after 48 h. The 13 groups were isolated from acetone extracts ofA. annua leaves in July by column chromatography, both the 1 lth and 12th groups exhibited strong bioactivities. The median lethal concentrations of the 1 lth and 12th groups against T. cinnabarinus were 0.3683 and 0.1586 mg mL^-1, respectively. The acetone parallel extract ofA. annua leaf in July was the most toxic to T. cinnabarinus and the corrected mortality was 100% after 48 h. The acetone parallel extract of the 1 lth and 12th groupswere the most active components, acted as the emphases in further study.

Acaricidal activity of different extracts from Syzygium cumini L.Skeels(Pomposia) against Tetranychus urticae Koch

Objective:To investigate the acaricidal activity of different extracts from Syzygium cumini(S.cumini)(Pomposia)againsst Tetranyckus urticae Koch(71 urticae)and the biochemical changes in antioxidants enzymes.Methods:Six extracts of S.cumini(Pomposia)at concentrations of 75,150 and 300μg/mL were used to control T.urticae(Koch).Results:The ethanol extract showed the most efficient acaricidal activity agent against T.urticae(98.5%)followed by hexane extract(94.0%),ether and ethyl acetate extract(90.0%).The LC_(50)values of the promising extract-were 85.0,101.0,102.0 and 98.0μ/mL,respectively.The activities of enzymes including ascorbate peroxidase(APX),peroxidase(POD),superoxide dismutase(SOD)and catalase(CAT)in susceptible mites were increased.The activities of all antioxidant enzymes reach the maximum value in mites at LC_(50)with ethanol and ethyl acetate extracts,respectively.Conclusions:The extract of S.cumini has acaricidal acivity against T.urticae,and the ethanol extract is the most efficient.

Resistance Selection of Tetranychus cinnabarinus to Three Acaricides and Its Management Strategy

The effects of retarding resistance evolution of mixing and sequencing acaricides were studied based on the resistance selection of three acaricides to Tetranychus cinnabarinus in the laboratory. Tetrany-chus cinnabarinus was continuously selected with fenpropathrin, abamectin and pyridaban for 28, 30 and 31 generations, respectively, and resistance factor increased to 65.6, 7.2 and 1.2 time, accordingly. Results of cross-resistance determination suggested that there were no cross-resistance existed among the three acaricides. Analysis of resistance selection and estimation of realized heritability (h2) of resistance to three single and two mixed acaricides showed that a mixture of fenpropathrin+abamectin would slow resistance development compared with a sequence of fenpropathrin followed by abamectin while the mixture of pyridaben+abamectin and the sequence of pyridaben followed by abamectin would effectively retard resistance evolution.

Resistance Selection of Tetranychus cinnabarinus to Fenpropathrin and Genetic Analysis

The resistant inheritance mode of Tetranychus cinnabarinus to fenpropathrin were studied based on the resistance selection in laboratory. After 40 generations selection, T. cinnabarinus developed 68.5-fold resistance to fenpropathrin. The methods of cross and back-cross between resistant （R） and sensitive （S） strains were used for exploring the inheritance mode of the resistance of this mite to fenpropathrin. The log （Lc）-p equation of F1 got from obverse （SR） and reverse （RS） crosses was intermediate between S and R and inclined to S, the dominant indices DSR and DRS were -0.83 and -0.29, respectively, which indicated that the resistance is controlled by the incompletely recessive gene; the 95% confidence limit of this two dominant indices do not superpose showing DSR and DRS have significant difference and the maternal or external karyon effect may be existed in resistance inheritance; the back-cross results of heterozygote F1 with its parents suggested that the separation of progenies F2 （SR♀× S ♂ and RS ♀ × R ♂） was consistent with Mendel＇s single gene inheritance model.

The influence of Tetranychus cinnabarinus-induced plant defense responses on Aphis gossypii development

Carmine spider mites （Tetranychus cinnabarinus） and cotton aphids （Aphis gossypii） are both serious pests of cotton, and cause reductions in yields of this key agricultural crop. In order to gain insights into how plant defense responses induced by one herbivore species affect the behavior and performance of another, we examined how infestation with T. cinnabarinus influences the development of A. gossypfi using cotton as a model. In this study, we measured the activities of several important biochemical markers and secondary metabolites in the leaves of cotton seedlings responding to infestation by T. cinnabarinus. Furthermore, the influences of T. cinnabarinus infestation on the development ofA. gossypfi in cotton were also examined. Our data showed that the activities of several key defense enzymes, including phenylalanine ammonia-lyase （PAL）, peroxidase （POD）, lipoxygenase （LOX）, and polyphenol oxidase （PPO）, were substantially increased in cotton seedlings responding to spider mite infestation. Further, the contents of gossypol and condensed tannins, key defensive compounds, were significantly enhanced in leaves of cotton seedlings following T. cinnabarinus infestation. Moreover, the T. cinnabarinus-induced production of defense enzymes and secondary metabolites was correlated with infestation density. The developmental periods of A. gossypii on cotton seedling leaves infested with T. cinnabarinus at densities of 10 and 15 individuals cm-2 were 1.16 and 1.18 times that of control, respectively. Meanwhile, the mean relative growth rates of A. gossypfi on cotton leaves infested with T. cinnabarinus at densities of 8, 10 and 15 individuals cm-2 were significantly reduced. Therefore, these data suggested that the developmental periods of A. gossypfi were significantly lengthened and the mean relative growth rates were markedly reduced when cotton aphids were reared on plants infested with high densities of spider mites. This research sheds light on the role that inducible defense responses played in plant-mediated interspecific interactions between T. cinnabarinus and A. gossypfi.

Identification of the key chitinase genes in Tetranychus cinnabarinus (Boisduval) based on the expression and sequence characteristic analysis

Chitin is an important content in the exoskeletons of arthropods, and its hydrolyzation is catalyzed by chitinases during the process of molting, thus, the chitinases are considered as ideal target to interfere the growth of arthropods. This study intends to clarify the characteristic of the chitinases during the development of Tetranychus cinnabarinus, and screen out important genes as potential control targets. The results showed that the total enzyme concentration of chitinases was significantly higher in larva, the first and second nymph than that in egg and adult. Base on the transcriptome data, six unigenes encoding chitinases were identified and their expression patterns in different developmental stages were detected. The expressions of TcCHIT1 and TcCHITIO showed high abundance during the molting process and their expression change during the developmental stages was consistent with the enzyme concentration. The full-length of these two genes were further cloned, and the structural characteristics of their proteins were analyzed by constructing the three-dimensional structure model. The results provide basic information to understand the characteristic of chitinases in T. cinnabarinus and might be considered as target for control.

Resistance Selection Against Abamectin in Tetranychus cinnabarinus(Boisduval) and Changes in Its Detoxification Enzyme Activity

The susceptible strain of Tetranychus cinnabarinus (Boisduval) was collected from the cassava germplasm resource garden of Guangxi South Subtropical Agricultural Science Research Institute and raised for 15 generations,during which resistance selection against avermectin was performed through the indoor spraying of avermectin,thereby obtaining an avermectin-resistance strain (Ab-R) with a resistance ratio of 3.25.After the indoor resistance selection,the determination of detoxification enzyme activity in the Ab-R and SS strains showed that the specific activity of carboxylesterases (CarE),glutathione-s-transferases (GSTs) and multi-functional oxidase (MFO) in Ab-R15 was 1.27,1.69 and 1.92 times of that in SS,respectively.In addition,the specific activity of MFO in Ab-R5,Ab-R10 and Ab-R15 was significantly different from that in SS;there was no significant difference in the specific activity of CarE compared with SS when screened to the F10 generation;and when screened to the F5 generation,there was no significant difference in the specific activity of GSTs compared with SS.The results showed that the significant increase in MFO activity was an important cause of resistance to avermectin in T.cinnabarinus,and CarE and GSTs were also involved in the formation of avermectin-resistant strains.

Efficacy Tests of Nine Insecticides on Tetranychus truncatus Ehara

[Objectives] This study was conducted to screen out pesticides that are highly effective against Tetranychus truncatus Ehara. [Methods] Nine kinds of pesticides were used to control pests on soybean. A petri dish efficacy test was first performed in laboratory,then a leaf efficacy test was performed in a greenhouse,and finally,three kinds of agents with good efficacy in the two tests were selected for field control tests. [Results] The indoor and outdoor test results showed that abamectin was the best agent,which showed efficacy higher than 96%,followed by bifenthrin,whose efficacy was higher than 93%. It can be seen that abamectin is the best choice for the prevention and control of T. truncatus,and bifenthrin can also be used according to the situation. [Conclusions] This study provides a theoretical basis for the control of T. truncatus.

Action modes of Aloe vera L. extracts against <i>Tetranychus cinnabarinus</i>Boisduval (Acarina: Tetranychidae)

Objective: This paper mainly determined the action modes of extract of Aloe vera L. against Tetranychus cinnabarinus Boisduval. Methods: The different action modes, contact action, repellent, fumigant, and oviposition inhibition property of the acetone extract of Aloe vera L. leaf against the carmine spider mite Tetranychus cinnabaribus (Boisduval) (Acarina: Tetranychidae) were investigated at 26°C ± 1°C, 75% - 80% relative humidity, and 14:10 light: day cycle in the laboratory. Results: Based on the established toxicity regression line of the Aloe vera L. acetone extract against female adult mites, the median lethal concentrations (LC50) were 0.836 and 0.167 mg/mL for 48 and 72 h, respectively. With processing time increased, the contact acaricidal activity increased and the repellent activity gradually decreased. The main modes of action of the extract against female adult mites were contact and repellent, and preferable effects were observed on adult mites. These results indicate that A. vera L. extract contains acaricidal and repellent bioactive components that may be useful in future control of the phytophagous mites.

Evaluation of Resistance of 84 Cassava Germplasms to Tetranychus cinnabarinus (Boisduval)

[Objective]The resistance to Tetranychus cinnabarinus(Boisduva)of 84 cassava gemplasms resources from the nursery of Guangxi Institute of Southern Tropical Agricultural Sciences was eraluated.[Method] Thuree random leaves were taken from Casiva plants separately from the upper,middle and lower parts,9 leaves from each plant to investigate the damage degree and calculate the mite damage index.[Result]The Tesults showed that among the 84 cassava gemplasms,6 were resistant(R),39 moderately resistant(MR),31 sensitive(S),and 8 highly sensitive(HS)Six germplasms such as Guiken 09-11 and SC5 could be used as breeding materials with resistance,and the vanietics with large planting area in Guangxi such as GR3,SC201,GR911,SC205 and SC11 were all moderately rsistant.The resistance of edible Cassava vanieties was poor,among which GR891 and South Asia Cassava No.1 have the lowest resistance.[Conclusion]No conelation was found between mite damage index of Ca8-sava germplasm and plant type,number of branches,lobe shape,leaf length,leaf width and leaf thicknes.

Effects of Two Silicon Fertilizers on Maize Growth and Tetranychus truncatus Ehara

[ Objectives] This study was conducted to investigate the effect of silicon fertilizer on maize growth and Tetranychus truncatus Ehara. [ Methods ] Yougui and Guishen were selected and sprayed onto maize for 1, 2 and 3 times, forming difference treatments. [ Results ] Spraying the two kinds of silicon fertilizers for different times promoted the growth of plant height, leaf length, leaf width and leaf thickness of maize, increased chlorophyll contents in maize leaves and yield of single ear, and also adversely affected T. truncatus （i. e. , increased the death rate of T. truncatus）. The more the treatment times of silicon fertilizer, the more remarkable the effect, and the higher the adverse effect on T. truncatus. [ Conclusions] In production, spraying silicon fertilizer onto maize for 2 -3 times could realize the purposes of increasing maize yield and alleviating the danlage by T. truncatus.

The Effect of Lion’s Ear (<i>Leonotis nepetifolia</i>) and African Basil (<i>Ocimum gratissimum</i>) Plant Extracts on Two-Spotted Spider Mites (<i>Tetranychus urticae</i>) for Improved Yield and Quality of French Beans

An experiment to evaluate the bio-control potential of Leonotis nepetifolia and Ocimum gratissimum plant extracts against two-spotted spider mites on French beans was conducted in the field. Five plant extract concentrations (1.5%, 3.0%, 6.0% and 12.0% w/v) were applied with water and Abamectin 0.6 ml/L as controls. Mite counts were done before and after treatment application and expressed as corrected percent efficacy. The impact of the mites on the French beans was evaluated by recording percent leaf reduction and quality and quantity by number of pods, pod length, diameter and yield. There was a dose dependent response in percent mite and leaf reduction, number of pods and yield. Treatments applied at 12% w/v indicated higher mite reduction (82.75%) for L. nepetifolia and 69.06% for O. gratissimum compared to abamectin (65.76%). The lowest percent leaf reduction of 1.71% for L. nepetifolia 0.39% for O. gratissimum and abamectin (20.46%) was also at 12% w/v. Similarly, the highest number of pod (61.00) for L. nepetifolia, 48.67 for O. gratissimum compared to 28.33 abamectin and yield (0.88 kg) for L. nepetifolia and 0.90 kg for O. gratissimum was also recorded at 12% w/v compared to 0.36 kg for abamectin. There were no significant differences in pod diameter and pod length between the extracts concentrations and abamectin. The study demonstrated the efficacy of L. nepetifolia and O. gratissimum in managing two-spotted spider mite and subsequent increase in French bean yield under field conditions.

The dynamic changes of genes revealed that persistently overexpressed genes drive the evolution of cyflumetofen resistance in Tetranychus cinnabarinus

Changes in gene expression are associated with the evolution of pesticide resis-tance in arthropods.In this study,transcriptome sequencing was performed in 3 different resistance levels(low,L;medium,M;and high,H)of cyflumetofen-resistant strain(YN-CyR).A total of 1685 genes,including 97 detoxification enzyme genes,were upregulated in all 3 stages,of which 192 genes,including 11 detoxification enzyme genes,showed a continuous increase in expression level with resistance development(L to H).RNA in-terference experiments showed that overexpression of 7 genes(CYP392A1,TcGSTd05,CCE06,CYP389A1,TcGSTz01,CCE59,and CYP389C2)is involved in the development of cyflumetofen resistance in Tetranychus cinnabarinus.The recombinant CYP392A1 can effectively metabolize cyflumetofen,while CCE06 can bind and sequester cyflumetofen in vitro.We compared 2 methods for rapid screening of resistance molecular markers,in-cluding short-term induction and 1-time high-dose selection.Two detoxification enzyme genes were upregulated in the field susceptible strain(YN-S)by induction with 20%lethal concentration(LC2o)of cyflumetofen.However,16 detoxification enzyme genes were up-regulated by 1-time selection with LCso of cyflumetofen.Interestingly,the 16 genes were overexpressed in all 3 resistance stages.These results indicated that 1685 genes that were upregulated at the L stage constituted the basis of cyflumetofen resistance,of which 192 genes in which upregulation continued to increase were the main driving force for the de-velopment of resistance.Moreover,the 1-time high-dose selection is an efficient way to rapidly obtain the resistance-related genes that can aid in the development of resistance markers and resistance management in mites.

Temperature-dependent development of Neoseiulus barked （Acari： Phytoseiidae） on Tetranychus urticae （Acari： Tetranychidae） at seven constant temperatures

The effect of seven constant temperatures of 15, 20, 25, 27, 30, 35 and 37℃ on developmental time ofNeoseiulus barkeri Hughes were determined in laboratory conditions under 65% - 5% RH and a photoperiod of 12 ： 12 （L ： D） h on nymphal stages of Tetranychus urticae Koch. Total developmental time of females （from egg to adult emergence） at the above-mentioned temperatures was 26.59, 14.43, 6.32, 5.64, 4.59, 3.98 and 4.67 days, respectively. Developmental rate of the N. barkeri increased as temperature increased from 15 to 35℃, but declined at 37℃. A linear and two nonlinear models were fitted to developmental rate of immature stages ofN. barkeri to predict the developmental rate as a function of temperature, as well as to estimate the thermal constant （K） and critical temperatures （i.e., Tmin, Topt and Tmax）. The estimated values of the Tmin and K for total developmental time using the linear model were 12.07℃ and 86.20 degree-days （DD）, respectively. The Trnin and Tmax estimated by the Sharpe-Schoolfield-Ikemoto （SSI） model were 11.90℃ and 37.41℃, respectively. The estimated Topt for overall immature stage development ofN. barkeri by the Lactin and SSI models were 33.89℃ and 24.51℃, respectively. Based on the biological criteria of model evaluation, the linear and SSI models were found to be the best models for describing the developmental rate of overall immature stages of N. barkeri and estimating the temperature thresholds.

Toxicity, inheritance and biochemistry of clofentezine resistance in Tetranychus urticae

This study evaluates the toxicological and biochemical response of two-spotted spider mites to clofentezine selection pressure. The mortality rate of Tetranychus urticae in adult females depends on increased clofentezine concentration and clofentezine was found to be effective against females. The resistance rate of the CUM strain selected 12 times once per generation with clofentezine was increased from 1.28- to 105.27-fold. The interaction of some synergists with clofentezine was analyzed in the clofentezine-resistant CLOF 12 strain. Synergists had no effect on clofentezine toxicity. The clofentezine-resistant CLOF 12 strain showed resistance against chlorpyrifos, abamectin, propargite, fenpyroximate and amitraz. The modes of inheritance of resistance to clofentezine were found to be incompletely dominant and not sex-linked. Esterase enzyme activity was detected both by gel electrophoresis and microplate reader methods, while glutathione S-transferase （GST） and monooxygenase （P450） activity were detected only by the microplate reader method. During the selection period the esterase, the GST and the P450 enzymes activities were raised from 7.69, 7.09 and 0.003 3 to 18.40, 13.11 and 0.003 7 milli-optical density/rain/rag proteins, respectively. An increase was observed in the band intensity of esterases and esterase enzymes may play a role in clofentezine resistance in T. urticae.

Molecular characterization of two novel esterase genes from carmine spider mite, Tetranychus cinnabarinus （Acarina： Tetranychidae）

Two novel esterase complementary DNAs were identified and cloned from the insecticide-susceptible strain of Tetranychus cinnabarinus （Boisduval） （Acarina： Tetrany- chidae）, which were designated as TCE1 and TCE2, respectively. The cDNA of TCE1 gene contained an open reading frame （ORF） of 1701 bp encoding 567 amino acids, and a predicted molecular weight of 62.75 kDa, the cDNA of TCE2 contained an ORF of 1680 bp encoding 560 amino acids, and a predicted molecular weight of 63.14 kDa. TCE1 and TCE2 were submitted to GenBank, accession number EU 130461 and EU 130462. The well-conserved sequence motif, GXSXG, used as a signature pattern in the esterase fam- ily are present in both TCE1 and TCE2 （GQSAG in TCE1, whereas GESAG in TCE2）, indicating that these two genes are predicted to be esterases. Comparison of the deduced amino acid sequence with the published mite esterase sequence coming from Boophilus microplus showed that TCE1 shares 33.98% identity and TCE2 shares 33.46% identity. TCE1 and TCE2 share 46.4% identity. Quantitative real-time polymerase chain reaction revealed that expression level of the TCE2 gene was relatively higher than that of the TCE1 in all instars examined except the protonymph, and the expression level of these two esterase genes in adults of T. cinnabarinus was significantly higher than that in any other instars, respectively. T. cinnabarinus is an important agricultural mite pest and esterases are important in the metabolisms of insects and mites; the genomic information obtained in this study will contribute to esterase molecular biological study on mite pest species.

Co-infection of Wolbachia and Spiroplasma in spider mite Tetranychus truncatus increases male fitness

Wolbachia and Spiroplasma are intracellular bacteria that are of great interest to entomologists,because of their ability to alter insect host biology in multiple ways.In the spider mite Tetranychus truncatus,co-infection of Wolbachia and Spiroplasma can induce cytoplasmic incompatibility(CI)and fitness costs;however,lttle is known about the effect of co-infection at the genetic level and the molecular mechanisms underlying CI.In this study,we explored the influence of the two symbionts on male mite host fitness and used RNA sequencing to generate the transcriptomes of T truncatus with four different types of infection.In total,we found symbiont-infected lines had a higher hatch proportion than the uninfected line,and the development time of the uninfected line was longer than that of the other lines.Co-infection changed the expression of many genes related to digestion detoxification,reproduction,immunity and oxidation reduction.Our results indicate that co-infection of Wolbachia and Spiroplasma confers multiple effects on their hosts,and helps iluminate the complex interactions between endosymbionts and arthropods.

Frequencies and mechanisms of pesticide resistance in Tetranychus urticae field populations in China

The two-spotted spider mite Tetranychus urticate is an important agricultural pest worldwide.It is extremely polyphagous and has developed resistance to many pesticides.Here,we assessed the pesticide resistance of seven field populations of T.urticae in China,their target site mutations and the activities of their detoxification enzymes.The results showed that abamectin and the traditional pesticides pyridaben,profenofos and bifenthrin had higher resistance or lower toxicity than more recently developed pesticides including chlorfenapyr,spinetoram,cyflumetofen,cyenopyrafen,bifenazate and B-azolemiteacrylic.The frequency of point mutations related to abamectin resistance,G314D in the glutamate-gated chloride channel 1(GluCl1)and G326E in GluC13,ranged 47%-70%and 0%-97%,respectively.The frequency of point mutations in A1215D and F1538I of the voltage-gated sodium channel gene(VGSC),which may increase resistance to pyrethroids,ranged 88%-100%and 10%-100%,respectively.For target sites related to organophosphate resistance,mutation frequencies ranged 25%-92%for G119S and 0%-23%for A201S in the acetycholinesterase gene(Ace).Mutation G126S in the bifenazate resistance-related cytochrome b gene(Cytb)was observed in three of the seven T.urticae populations.Higher activities of detoxification enzymes(P450,GST,CarEs and UGTs)were observed in two T.urticae populations,with significant difference in the XY-SX population.These results provide useful information on the status of pesticide resistance of T.urticae in China and suggest that T.urticae field populations may have multiple resistance mechanisms.