Monitoring of resistance to spirodiclofen and five other acaricides in Panonychus citri collected from Chinese citrus orchards

BACKGROUND: Citrus red mite, Panonychus citri (McGregor), is one of the most important pesticide‐resistant pests in China. In order better to understand its resistance status, six populations of the mite were collected from Chinese citrus orchards for monitoring of resistance to spirodiclofen and another five acaricides. RESULTS: All the samples collected in the field in 2006 were susceptible to spirodiclofen. However, the LC₅₀ values in populations sampled in 2009 ranged from 3.29 to 418.24 mg L^?1 spirodiclofen, a 127‐fold difference between the least and most sensitive populations. Compared with a susceptible strain, 50‐fold and 90.8‐fold resistance to spirodiclofen was detected in populations sampled from Pinghe and Fuzhou in 2009, as well as cross‐resistance to spirotetramat. The LC₅₀ values for abamectin, fenpropathrin, hexythiazox and pyridaben in the collected samples ranged from 0.041 to 3.52 mg L^?1, from 23.91 to 696.16 mg L^?1, from 13.94 to 334.19 mg L^?1 and from 48.90 to 609.91 mg L^?1 respectively. CONCLUSION: Great variations in resistance to the tested acaricides were observed among the sampled populations. The Pinghe population developed resistance to all the acaricides tested. The Jianning population was susceptible to most acaricides tested, except pyridaben. Resistance management strategies were conducted on the basis of these observations. Copyright © 2010 Society of Chemical Industry     

Untersuchungen zur Akarizidresistenz an Populationen der Obstbaumspinnmilbe, Panonychus ulmi KOCH (Acari: Tetranychidae) aus dem Bodenseegebiet

One of the major acarine pest species of deciduous fruit trees like apple and plum is the European red mite, Panonychus ulmi KOCH (Acari: Tetranychidae). Feeding damage by P. ulmi results in leaf bronzing followed by an early defoliation and a reduction in yield, which is usually prevented by the application of acaricides. A problem often associated with mite control is the (sometimes rapid) development of resistance due to their high reproductive potential, a short life cycle allowing numerous generations per season and frequent applications of acaricides. Therefore a resistance monitoring is considered to be an essential part within resistance management strategies where only compounds providing full efficacy at recommended rates should be used. Once a new acaricide is considered for market introduction a so-called baseline susceptibility study is requested by the European authorities. Such a baseline study was also conducted for the new acaricidal compound spirodiclofen (Envidor^®), which is known to inhibit lipid biosynthesis and particularly active against juvenile stages of tetranychid mite pests such as P. ulmi. However, a strong reduction of female adult fecundity results in excellent residual efficacy. Here we report on the baseline susceptibility of 15 European red mite populations against spirodiclofen, which were collected in 2005 in apple orchards at Lake Constance, Germany. The baseline data were combined because of a low population-to-population variation in response to spirodiclofen and a composite dose effect calculation revealed a diagnostic concentration (LC₉₅) of 5?mg/liter (ppm) for future monitoring purposes in P. ulmi larvae. Furthermore we checked the susceptibility of the very same field populations against pyridaben, hexythiazox and abamectin. This helps to identify candidates for a balanced resistance management strategy avoiding the implication of cross-resistance issues.     

Genetic and biochemical analysis of a laboratory‐selected spirodiclofen‐resistant strain of Tetranychus urticae Koch (Acari: Tetranychidae)

BACKGROUND: Spirodiclofen is a selective, non‐systemic acaricide from the new chemical class of tetronic acid derivatives. In order to develop strategies to minimise resistance in the field, a laboratory‐selected spirodiclofen‐resistant strain of the two‐spotted spider mite, Tetranychus urticae Koch, was used to determine genetic, toxicological, biochemical and cross‐resistance data. RESULTS: Selecting for spirodiclofen resistance in the laboratory yielded a strain (SR‐VP) with a resistance ratio of 274, determined on the larval stage. The egg stage remained far more susceptible. No cross‐resistance was found against other established acaricides, except for spiromesifen. Based on synergist experiments and enzyme assays, it appeared that especially P450 monooxygenases, but also esterases and glutathione‐S‐transferases, could be involved in the metabolic detoxification of spirodiclofen. Genetic analysis showed that the resistance is inherited as an intermediate trait under control of more than one gene. CONCLUSIONS: Resistance to spirodiclofen exceeded by far the recommended field rate. A good acaricide resistance management programme is necessary to prevent fast resistance build‐up in the field. Spirodiclofen can be used in alternation with most established acaricides, except for other tetronic acid derivatives. Without selection pressure, resistance tends to be unstable and can decrease in the presence of susceptible individuals owing to the intermediate, polygenic inheritance mode. Copyright © 2009 Society of Chemical Industry     

Acaricide resistance and resistance mechanisms in Tetranychus urticae populations from rose greenhouses in the Netherlands

BACKGROUND: Spider mites are important crop pests that rapidly develop resistance to acaricides. To investigate whether acaricide resistance is a threat to greenhouse rose culture in the Netherlands, the susceptibility of 15 strains of Tetranychus urticae was tested to several currently used acaricides, and resistance mechanisms were investigated. RESULTS: Although the observed levels of susceptibility differed between strains and acaricides, resistance was detected in most strains. The activity of detoxifying enzymes was significantly increased in most field‐collected strains, and a number of amino acid substitutions known to be involved in resistance were detected. CONCLUSIONS: Resistance levels to traditional acaricides such as bifenthrin and abamectin were prominent, and might result in control failure under field conditions. Resistance to more recently registered compounds was detected in several populations. Resistance levels were generally unstable in the laboratory without selection pressure. The toxicological, biochemical and genetic data in this study will be essential in devising an efficient resistant management for Dutch rose culture. Copyright © 2011 Society of Chemical Industry     

Spirodiclofen and spirotetramat bioassays for monitoring resistance in citrus red mite, Panonychus citri (Acari: Tetranychidae)

BACKGROUND: Citrus red mite, Panonychus citri (McGregor), is a key pest of San Joaquin Valley California citrus. Spirodiclofen was registered for mite control in 2007, and spirotetramat for scale control in 2008. Because of the potential for resistance to spirodiclofen to develop in spider mites, and cross‐resistance to spirotetramat used for other citrus pests, bioassay methods for resistance monitoring were developed. RESULTS: The responses of four populations of adult female, egg and larval stages of P. citri to spirodiclofen were compared to determine the most robust bioassay method for this pesticide. Adult females responded with a higher LC₉₉ and larval stages exhibited higher control mortality and a lower slope of response compared with the egg stage. Thus, the egg stage was found to be the most suitable stage for testing. Egg production and egg shape were significantly affected by spirodiclofen treatment of adult female mites. Bioassays with the related compound spirotetramat revealed that P. citri egg hatch was less affected by this compound, requiring the assessment of mortality to be extended to 11 days after treatment when the hatched larvae succumbed to the pesticide. Discriminating concentrations of 10 ppm for spirodiclofen and 31.6 ppm for spirotetramat in an 11 day bioassay were tested against eight field populations of P. citri, and 99–100% mortality resulted. CONCLUSION: These results provide a baseline for the response of P. citri to spirodiclofen and spirotetramat that will aid resistance management in California citrus. Copyright © 2011 Society of Chemical Industry     

三种杀螨剂对山楂叶螨的毒力评价

为筛选出高效防治山楂叶螨Amphitetranychus viennensis Zacher的杀螨剂,利用玻片浸渍法和叶片残毒法测定了3种杀螨剂对其3种螨态的室内毒力,并对不同浓度杀螨剂的田间防效进行了测定。结果表明:240 g/L螺螨酯、110 g/L乙螨唑和43%联苯肼酯中仅联苯肼酯对山楂叶螨雌成螨有毒力,其LC50为37.65 mg/L;3种杀螨剂均能毒杀卵及幼螨,毒力大小依次为乙螨唑联苯肼酯螺螨酯;同一杀螨剂对幼螨的毒力均高于对卵的毒力。240 g/L螺螨酯和110 g/L乙螨唑对山楂叶螨的总体防效较好,除螺螨酯4 000倍液处理的防效在药后30 d达到最大97.11%外,其余各处理均在药后15 d达到最大,防效为88.76%~96.14%;但二者速效性较差,药后1~7 d防效均低于对照;而螺螨酯4 000、5 000倍液处理及乙螨唑5 000倍液处理的持效性较好,药后30 d防效仍有97.11%、90.90%和93.06%,均显著高于对照。43%联苯肼酯对山楂叶螨的总体防效在3种杀螨剂中最高,其1 800、2 500倍液处理分别在药后7 d和3 d时防效达到最大99.79%和98.64%;1~7 d防效为97.45%~99.79%,显著高于其余杀螨剂和对照;30 d时防效分别达98.14%和96.19%,速效性和持效性均较好。表明螺螨酯和乙螨唑对山楂叶螨的持效性较好,联苯肼酯则有良好的速效性和持效性,可以按照其不同特点推广应用。     

Pyrethroid resistance in the tomato red spider mite, Tetranychus evansi, is associated with mutation of the para-type sodium channel

BACKGROUND: The tomato red spider mite, Tetranychus evansi (Baker and Pritchard), is a serious pest of solanaceous crops in many African countries. In this study an investigation has been conducted to establish whether mutation of the para‐type sodium channel underlies pyrethroid resistance in T. evansi strains collected in Southern Malawi. RESULTS: Two T. evansi strains from Malawi showed tolerance to the organophosphate chlorpyrifos and resistance (20–40‐fold) to the pyrethroid bifenthrin, but were susceptible to two contemporary acaricides (abamectin and fenpyroximate) in insecticide bioassays. Cloning of a 3.1 kb fragment (domains IIS5 to IVS5) of the T. evansi para gene from pyrethroid‐resistant and pyrethroid‐susceptible strains revealed a single non‐synonymous mutation in the resistant strains that results in an amino acid substitution (M918T) within the domain II region of the channel. Although novel to mites, this mutation confers high levels of resistance to pyrethroids in several insect species where it has always been associated with another mutation (L1014F). This is the first report of the M918T mutation in the absence of L1014F in any arthropod species. Diagnostic tools were developed that allow sensitive detection of this mutation in individual mites. CONCLUSION: This is the first study of pyrethroid resistance in T. evansi and provides contemporary information for resistance management of this pest in Southern Malawi. Copyright © 2011 Society of Chemical Industry     

乙唑螨腈与螺螨酯混用对柑橘全爪螨的田间防治效果评价

柑橘全爪螨 Panonychus citri 是一种重要的世界性害螨, 已对多种常用杀螨剂产生了不同程度的抗性?为有效控制该害螨的危害, 本研究于2017年-2018年通过田间小区试验评价了30%乙唑螨腈·螺螨酯SC?30%乙唑螨腈SC?240 g/L螺螨酯SC?1.8%阿维菌素EC及43%联苯肼酯SC对柑橘全爪螨的防治效果及其对柑橘树的安全性?研究结果表明:试验浓度下, 叶面喷施1次上述药剂均对柑橘树安全?30%乙唑螨腈·螺螨酯SC及30%乙唑螨腈SC能有效控制柑橘全爪螨危害, 速效性好, 持效期长达30 d, 药后1~30 d的防治效果分别为76.55%~100%和81.21%~98.30%?240 g/L螺螨酯SC和43%联苯肼酯SC对柑橘全爪螨的控制作用较好, 速效性一般而持效期可达30 d, 药后1~30 d的防治效果分别为69.15%~91.55%和64.63%~88.46%?1.8%阿维菌素EC难以控制柑橘全爪螨危害, 速效性较差, 持效期约15 d; 药后1~30 d对该害螨的防治效果为57.08%~83.39%?综上所述, 在柑橘生产实践中, 为有效控制柑橘全爪螨为害, 应于害螨初发期叶面喷施1次30%乙唑螨腈·螺螨酯SC 75 mg/kg或30%乙唑螨腈SC 100 mg/kg?     

Acaricide toxicity and resistance in larvae of different strains of Tetranychus urticae and Panonychus ulmi (Acari: Tetranychidae)

The toxicities of eight structurally different acaricidal compounds to six‐legged larvae (first motile stage) of three laboratory strains of the two‐spotted spider mite, Tetranychus urticae, and the European red mite, Panonychus ulmi, were evaluated following spray application. The larvae of five field‐derived strains of T urticae originating from France, Italy, Brazil, California and Florida were also tested for their susceptibilities to discriminating concentrations of several acaricides resulting in 95% mortality when applied to the organophosphate‐resistant laboratory reference strain WI. The spray bioassay used was robust and gave repeatable results with a wide range of acaricidal compounds, irrespective of their mode of action (ovo‐larvicides or primarily acting on motile life stages). Compounds tested were abamectin, azocyclotin, chlorpyrifos, clofentezine, deltamethrin, fenpyroximate, hexythiazox and pyridaben. Larvae of one of the laboratory strains of T urticae, AK, originally collected in Japan in 1996 and maintained without further selection pressure, exhibited 2000‐ and >4000‐fold resistance to the mitochondrial electron transport inhibitors pyridaben and fenpyroximate, respectively. Another strain of T urticae, AU, obtained from Australia and maintained in the laboratory under selection with hexythiazox and clofentezine since 1987 showed >770‐ and >1000‐fold resistance to clofentezine and hexythiazox, respectively. The same resistance pattern was observed against larvae of a laboratory strain of P ulmi, CE, also selected with hexythiazox. Larvae of one of the field‐derived strains of T urticae, BR, showed a lower susceptibility to a number of compounds, whilst the others were susceptible to all compounds except the organophosphates. © 2001 Society of Chemical Industry     

Resistance of Bemisia tabaci (Homoptera: Aleyrodidae) to insecticides in southern Spain with special reference to neonicotinoids

The tobacco whitefly, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) which occurs in various parts of the world, has developed a high degree of resistance against several chemical classes of insecticide, including organophosphates, carbamates, pyrethroids, insect growth regulators and chlorinated hydrocarbons. The present studies were done in order to monitor the susceptibility of whitefly populations in southern Spain to insecticides commonly used there. Systemic bioassays using Spanish field populations of B tabaci collected in 1994, 1996 and 1998 indicated an increase, albeit a slow one, in resistance to imidacloprid over this period. Comparative studies of other neonicotinoids using the same bioassay revealed a high degree of cross‐resistance to acetamiprid and thiamethoxam. Leaf‐dip bioassays with adult females from these populations revealed a high level of resistance to cyfluthrin, endosulfan, monocrotophos, methamidophos, and pymetrozine, each at 200 mg litre⁻¹. Buprofezin and pyriproxyfen were tested against second‐instar nymphs and eggs, respectively. Buprofezin also showed a lower efficacy against ESP‐98, a strain of B tabaci received from Almeria in 1998, but pyriproxyfen resistance was not obvious when tested against eggs of strain ESP‐98. Field trials in 1998 revealed good efficacy of imidacloprid in one farm in the Almeria region and two greenhouses in Murcia and Sevilla, but a loss of activity by imidacloprid in another farm in the Almeria region. Cross‐resistance between imidacloprid and thiamethoxam was also confirmed under field conditions. © 2000 Society of Chemical Industry     

苹果全爪螨抗药性研究进展

苹果全爪螨是重要的蔷薇科果树害虫之一, 具有体型小、繁殖快、世代周期短等生物学特点。该螨以若螨和成螨取食苹果叶片和嫩芽, 影响果树生长发育, 造成果实品质和产量下降, 自20世纪60年代开始其在我国果园的发生逐年加重。国内外对苹果全爪螨的防治主要采用化学杀螨剂, 由于化学杀螨剂长期不规范的使用, 致使该螨对多种类型的化学杀螨剂产生了抗药性。本文总结了苹果全爪螨的发生、为害、抗药性现状及其抗性机理, 同时结合国内外苹果全爪螨抗药性和防治相关研究, 提出该螨抗药性治理策略, 以期为其防治提供参考。     

Development of strategies for monitoring indoxacarb and gel bait susceptibility in the German cockroach (Blattodea: Blattellidae)

BACKGROUND: Advion^® cockroach gel bait (6 g kg^?1 indoxacarb) is in widespread use for Blattella germanica (L.) control in the United States. However, baseline susceptibility levels to indoxacarb in German cockroach field populations are not known. Hence, this research sought to develop monitoring strategies to estimate the susceptibility of German cockroach populations to indoxacarb. RESULTS: Four bioassays were evaluated: topical lethal dose (LD), formulated gel bait lethal time (LT), vial lethal concentration (LC) and gel bait matrix LD. Of these methods, the vial LC and gel bait matrix LD bioassays were the most economical and relevant assessment strategies. For indoxacarb susceptibility monitoring, a two‐tiered approach was developed that utilizes diagnostic concentrations and doses in vial LC (30 and 60 µg vial^?1) and gel bait matrix LD (1.0, 1.5 and 2.5 µg insect^?1) formats. CONCLUSIONS: A two‐tiered susceptibility monitoring strategy was developed that includes testing field populations at diagnostic concentrations and doses in first‐tier vial LC bioassays and second‐tier gel bait matrix LD bioassays. The vial method facilitates rapid identification of field strains with reduced susceptibility. The feeding bioassay effectively simulates field exposure to Advion^® and therefore has utility for secondary confirmation of susceptibility shifts and identification of behavioral resistance (i.e. bait aversion). Copyright © 2010 Society of Chemical Industry     

Het voorkomen van resistentie tegen organische fosforverbindingen bij de bonespintmijt (Tetranychus urticae) in Aalsmeer

Samenvatting Bij een onderzoek naar de gevoeligheid voor acariciden van spintpopulaties, afkomstig van verschillende bedrijven in Aalsmeer, bleek in 20 van de 22 onderzochte gevallen een resistentie te bestaan tegen organische fosforverbindingen. Deze resistentie bleek ook te bestaan ten opzichte van organische fosforverbindingen, die nooit eerder tegen de onderzochte spintpopulaties gebruikt waren. De resistentie tegen demeton (Systox) bleek bij enkele populaties niet even groot.Tegen acariciden op basis van gechloreerde koolwaterstoffen zoals kelthane en chloorbenzilaat, werd nog geen resistentie bij de onderzochte populaties aangetroffen.Een onderzoek naar de gevoeligheid voor acariciden van spintpopulaties, welke in de directe omgeving buiten de kassen op onkruiden e.d. voorkomen, leidde tot de conclusie dat resistente spintmijten niet buiten de kas voorkomen. De resistentie van spintpopulaties is op de verschillende bedrijven in Aalsmeer zelfstandig spontaan opgetreden. Er bleek geen correlatie te bestaan tussen de verschillende waardplanten (roos, anjer enGerbera) en het optreden van resistentie.Summary During the year 1958 the susceptibility to acaricides of a number of populations of the two-spotted spider mite (Teranychus urticae Auct.) occurring in several nurseries in Aalsmeer (fig. 5) was studied at the Experimental Station for Floriculture at Aalsmeer, The Netherlands.The susceptibility of a population was examined by placing 50 adult female mites on a bean plant, treated with an acaricide. The percentage mortality was determined after four days.In these experiments both spider mite populations in the greenhouses (on roses, carnations andGerbera) and those in the open air near the greenhouses (on weeds) were studied. Fig. 1 gives the susceptibility of the different populations for water, parathion, diazinon, demeton (Systox) and kelthane. Of the 22 populations from glasshouses 20 proved to be resistant to organic P-compounds. Of those collected from weeds growing outside the greenhouses, not a single one proved to be resistant, so that it may be taken for granted that the resistant red spider mite, found in the greenhouse, does not survive outside.A number of populations were examined for their susceptibility to some other acaricides (fig. 2). In this experiment the resistance to those organic P-compounds with which the populations had never been treated before, such as phosdrin, thiometon and phenkapton was observed. It clearly illustrates that there is no question of resistance to a definite acaricide, but to the group of organic P-compounds. Resistance to demeton did not prove to be equally strong for every population.In all cases examined chlorinated hydro-carbons, such as kelthane and chlorobenzilate, proved to be normally active. Resistance to this group of acaricides has not yet been found in Aalsmeer.A special case is stated in fig. 3, where the spider mite population in a cucumberhouse, in which no chemical control had been applied, is compared with a population on nettles outside the glasshouse and a resistant population in a rosehouse of the same nursery.An experiment, repeated on several dates over a period of 13 months (fig. 4), shows that there was no important shift in the susceptibility of the population studied. It is clear that the resistance of two-spotted spider mites to organic P-compounds has been developed in Aalsmeer independently in more than twenty separate glasshouses.In no case the host plant (carnation, rose,Gerbera) proved to have an appreciable influence on the appearence of resistance.     

杀螨剂对朱砂叶螨的毒力测定和对加州新小绥螨的安全性评价

为评价杀螨剂对朱砂叶螨的毒力和对加州新小绥螨的安全性，本文采用玻片浸渍法、叶片残毒法和浸叶法测定了乙唑螨腈、丁氟螨酯、乙螨唑、哒螨灵、螺螨酯和联苯肼酯对朱砂叶螨的毒力，并对这6种杀螨剂对加州新小绥螨卵孵化率和雌成螨存活率进行了测定。结果表明，6种杀螨剂用叶片残毒法测定的毒力大于玻片浸渍法测定的毒力。朱砂叶螨雌成螨对螺螨酯和乙螨唑不敏感，其余4种杀螨剂都表现出较高的毒性。哒螨灵田间使用剂量显著降低加州新小绥螨雌成螨存活率，10倍田间使用剂量处理24 h后死亡率达100%。乙螨唑和哒螨灵田间使用剂量处理后加州新小绥螨卵仅有1%和0.33%的孵化率。因此，建议应用加州新小绥螨防治害螨时，应尽量避免哒螨灵和乙螨唑的施用。     

Chlorfenapyr resistance in the spider mite Tetranychus urticae: stability, cross-resistance and monitoring of resistance

The two-spotted spider mite, Tetranychus urticae Koch, is a key pest of many agricultural crops. Studies of stability of resistance, cross-resistance relationships and monitoring of chlorfenapyr resistance were carried out with T. urticae to provide basic information necessary to define effective acaricide resistance management strategies for this pest. Chlorfenapyr resistance was shown to be stable in the absence of selection pressure under laboratory conditions. The activities of seven different acaricides against chlorfenapyr-resistant and -susceptible strains of T. urticae were evaluated. The results indicated possible positive cross-resistance between chlorfenapyr and the acaricides abamectin, propargite and etoxazole. No cross-resistance was detected for the acaricides milbemectin, fenpyroximate and diafenthiuron. A possible negatively correlated cross-resistance was observed between chlorfenapyr and spiromesifen. The evaluation of 21 T. urticae populations from several crops in the States of São Paulo, Mato Grosso, Goiás, and Bahia, in Brazil, indicated that the susceptibility of mites to chlorfenapyr was variable, with percentages of resistant mites ranging from 0.0 to 86.5%. The highest resistance frequencies were observed in ornamental plants in the State of São Paulo. Some populations from cotton and papaya also presented high frequencies of chlorfenapyr resistance. This is the first report on chlorfenapyr resistance in T. urticae on cotton and papaya in Brazil. Strategies for the management of acaricide resistance are discussed.     

Pyrethroid insecticide resistance in British populations of the cabbage whitefly, Aleyrodes proletella

BACKGROUND: The cabbage whitefly, Aleyrodes proletella L., is emerging as a significant pest of field brassica crops in certain regions of the United Kingdom. In order to investigate the contribution of pesticide resistance to this phenomenon, A. proletella populations were sampled from five different areas in England in 2008 and 2009. Adult residual leaf‐dip bioassays were carried out using pyrethroid and neonicotinoid insecticides. RESULTS: Significant resistance to pyrethroids was found in multiple samples collected from two areas. No evidence of cross‐resistance to neonicotinoids was found in a subset of the pyrethroid‐resistant populations. While the patterns of resistance to different pyrethroids were broadly correlated, the magnitude of resistance factors differed substantially. Survival of strains at a putative diagnostic concentration of lambda‐cyhalothrin was found to provide a guide to their LC₅₀. Significant differences in LC₅₀ were found when different brassica crops were used in the bioassay, although the resistance patterns between strains were maintained. CONCLUSION: Reduced susceptibility to multiple pyrethroid insecticides exists in populations of A. proletella in the United Kingdom, corresponding to recent major outbreaks. The mechanism(s) of resistance are yet to be determined, but molecular structural differences in pyrethroids probably influence the magnitude of cross‐resistance within this group of insecticides. Copyright © 2011 Society of Chemical Industry     

Pyrethroid resistance discovered in a major agricultural pest in southern Australia: the redlegged earth mite Halotydeus destructor (Acari: Penthaleidae)

BACKGROUND: The redlegged earth mite (Halotydeus destructor Tucker) is an important pest of field crops and pastures. Control of this pest relies heavily on chemicals, with few genuine alternatives presently available. Pesticide responses of H. destructor from the field with reported chemical control failures were compared with mites from susceptible 'control' populations. Toxicology bioassays were conducted on adult mites across multiple generations. RESULTS: Very high levels of resistance to two synthetic pyrethroids, bifenthrin and alpha-cypermethrin, were detected in this species for the first time. For bifenthrin, LC(50) estimates showed a difference in resistance of greater than 240 000-fold. Resistance to alpha-cypermethrin was almost 60 000-fold. This resistance was shown to be heritable, persisting after several generations of culturing. There was no evidence that resistance to organophosphorus chemicals had evolved, which is likely to be a direct consequence of the history of chemical applications these mites have experienced. CONCLUSION: These results highlight the need for more judicious management decisions in order to control pest species in a sustainable manner. The implications of these findings in regard to the management and future research of the redlegged earth mite are discussed.     

Acaricide mode of action

The last few years have seen the introduction of an unprecedented number of new classes of acaricides with novel or under-exploited modes of action, discovered by traditional screening. Acaricide research has uncovered several unrelated compounds that possess improved properties. Pyridaben, acequinocyl, diafenthiuron, etoxazole, spirodiclofen and bifenazate, in particular, are acaricides that are safe to beneficials, have low mammalian toxicity and short environmental persistence. Many of the new acaricides appear to affect mitochondrial respiration, and previously unknown targets affecting mite growth and development have been identified, offering new opportunities for mite control.     

The effectiveness of various acaricides against resistant and susceptible carmine spider mites

Two colonies of the carmine spider mite,Tetranychus cinnabarinus (Boisd.), were raised on beans in the laboratory. One originated from roses in a greenhouse which had received acaricidal treatments, and the other fromViola odorata L. in a garden where no pesticides had been used. Laboratory evaluation indicated that the greenhouse strain was highly resistant to dicofol (Kelthane) and bromopro-pylate (Neoron), moderately resistant to propargite (Omite), and slightly resistant to cyhexatin (Plictran); in the garden strain, there was no resistance to any of these acaricides. On a strain of carmine spider mites which was identified and defined as resistant, several acaricides were evaluated in the laboratory for their contact toxicity to the mite by the slide dip method, and for their contact plus stomach toxicity by exposing the mites to sprayed leaves. Some of these acaricides were later tested in the field on two undetermined populations. Cyhexatin, triazophos (Hostathion), fentrifanil (PP-199) and R-28627 killed more than 90% of the mites by both methods and were effective in the field. NC-13292 was an ovicide only. Proclonol (R-8284) had a good effect in the slide dip method but was not so effective in the leaf exposure test. The compounds tested were phytotoxic to rose foliage only, but triazophos burned all the crops tested.     

Transovarial biotransference of etoxazole through a terrestrial trophic web

BACKGROUND: Transovarial transport is defined as the passage of chemicals from the maternal body to eggs within the ovaries. Little is known about the effects of transovarial transport on non‐target species. This study evaluates etoxazole (a transovarial acaricidal compound) on a terrestrial trophic web consisting of a ubiquitous phytophagous mite, Tetranychus urticae Koch, and three species of predatory mites. RESULTS: Predatory mite females that consumed eggs laid by etoxazole‐treated T. urticae also produced infertile eggs. There was a negative relationship between the proportion of etoxazole‐treated T. urticae females and the instantaneous rate of predatory mite increase at the population level (r² = 0.86). Reduced fertility of etoxazole‐treated T. urticae females continued for 18 days following application. Eggs laid by etoxazole‐treated T. urticae females remained toxic to predatory mite females for 42 days after treatment. CONCLUSIONS: Transovarial transport could lead to magnification in the ecosystem by enhancing both bioavailability and movement of an active ingredient. The potential for enhancement of residual activity by terrestrial organisms and its significance once reaching the food web should be taken into account for new classes of acaricides and insecticides. Copyright © 2012 Society of Chemical Industry