Genetics of hexythiazox resistance in two spotted spider mite,Tetranychus urticae Koch

Genetic analysis of the QRPH strain of two spotted spider mite Tetranychus urticae Koch indicates that hexythiazox resistance in that strain is not sex linked and has a dominance factor of 0.152 (incomplete dominance). Hexythiazox resistance appears to be controlled by a single gene.This work contributes in part for the fulfilment of the requirements of the degree of PhD at the University of Sydney.     

Clofentezine and fenbutatin oxide resistance in the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae) from deciduous fruit tree orchards in Western Australia

The resistance status of Tetranychus urticae Koch to the miticides clofentezine and fenbutatin oxide was investigated in deciduous fruit tree orchards in Western Australia. Mites were collected from 30 orchards across three fruit growing regions and subjected to discriminating–dose assays. There was a significant relationship between clofentezine (=;0.64) and fenbutatin oxide (V=;0.44) use and the proportion of resistant mites in each sample. Improved clofentezine models were obtained when the Perth Hills region (V=;0.90) was modelled separately from Donnybrook and Manjimup (V=;0.80). Clofentezine could be expected to fail in the latter regions after four sprays and in the former region after only one spray. The relatively low pest status of T. urticae in Western Australia did not delay the clofentezine resistance. For any given number of spray applications the response of T. urticae to fenbutatin oxide was more variable than it was to clofentezine.     

二斑叶螨滞育特性的初步研究

诱导滞育实验表明 :短日照和低温是诱导二斑叶螨发生滞育的主要因子。测定我国天水种群 ,在 15℃条件下 ,诱导其滞育的临界日照长度为 9小时 4 2分 ,在每日 8小时光照条件下 ,诱导其滞育的临界温度为 15.5℃。解除滞育实验表明 :在每日 13小时的光照条件下 ,温度越高 ,解除越冬雌成螨滞育的速度越快 ;低温处理滞育雌成螨的时间越长 ,解除其滞育的速度也越快。     

The Effects of Clofentezine on Life-table Parameters in Two-spotted Spider Mite Tetranychus urticae

Sublethal effects of the growth inhibitor, clofentezine, on life-table parameters of Tetranychus urticae Koch females treated at different developmental stages with a concentration causing >90% mortality were investigated. Females which survived treatment as 'early' (0-24 h old) eggs produced 12% more offspring than the untreated females during the first five days of oviposition. This resulted in a significant rise in the intrinsic rate of increase (rj): 0.324, compared to 0.299 in the untreated females. This effect may be interpreted as hormoligosis. Clofentezine treatment at any other developmental stage of T. urticae significantly decreased both longevity and fertility of female survivors. Females which survived treatment either as 'late' (72-96 h old) eggs or larvae had 2.6 times lower net reproductive rate (R0) than the untreated females, and the rj values were significantly lower: 0.242 and 0.215, respectively (0.285 in the untreated females). Females which survived treatment either as protonymphs or deutonymphs had 3.9 times and 6 times lower R0, respectively. Corresponding rj values were 0.178 and 0.146, respectively (0.247 in the untreated females). The clofentezine treatment at all stages influenced the age distribution of survivors. The sublethal effects of clofentezine and their impact on T. urticae management are discussed.     

二斑叶螨生物学研究

作者于1994—1995年对生活在花生和苹果叶上的二斑叶螨的生物学进行了研究。研究结果表明,以花生叶片为食科,该螨在25℃、30℃恒温条件和26．5℃-29．1℃变温条件下,其发育历期分别为11．04天,7．96天和8．64天。雌成螨在25℃、30℃恒温条件和23．8℃-30℃变温条件下,寿命分别是13．14天、10．5天和12．43天;产卵量分别是37．75粒、60,42粒和54．62粒。以苹果叶为食科,该螨在25℃、28℃和30℃恒温条件下,其发育历期分别是11．48天、9．56天和8．63天;雌成螨在25℃、30℃恒温条件和24.4℃-28．1℃变温条件下,其寿命分别为16．75天、14．78天和11.56天;产卵量分别是20粒、31.08粒和33．21粒。在花生上,该螨卵发育的起始温度是6．44℃,有效积温是69．79日度;虫期发育的起始温度是14．65℃．有效积温是74.98日度。在苹果上,卵发育的起始温度是4．61℃,有效积温是82,67日度,虫期发育的起始温度是12．41℃,有效积温是93．99日度。     

不同葫芦科作物对二斑叶螨的抗性评价

【目的】二斑叶螨Tetranychus urticae Koch是世界性重大农业害螨,葫芦科作物是其重要寄主植物。为明确不同葫芦科作物对二斑叶螨生长发育的抗性/适合性,开展了二斑叶螨在葫芦科作物上的产卵和取食选择性研究。【方法】选择苦瓜、葫芦、南瓜、丝瓜、西瓜、甜瓜和黄瓜作为供试寄主植物,室内采用离体叶片和室外采用活体植株比较了二斑叶螨对7种作物的取食选择性及其种群生存与繁殖动态。【结果】供试7种葫芦科作物中,二斑叶螨对黄瓜的选择率最高,为35.49%,其次为甜瓜和西瓜;二斑叶螨在南瓜和黄瓜叶碟上的生存率和繁殖率高,12 h单雌产卵数分别为9.72粒和7.83粒;在葫芦和苦瓜叶碟上,二斑叶螨48 h螨口减退率达47.5%和32.5%,表现为较低的取食和生存适合度,同时葫芦和苦瓜活体植株上二斑叶螨繁殖率显著低于其他5种葫芦科作物。【结论】二斑叶螨在黄瓜、西瓜和甜瓜上的种群发育适合度高,在葫芦和苦瓜上适合度低。这一结果可为田间防控二斑叶螨生态措施的制定及开展葫芦科作物抗螨性机理和抗螨育种提供科学依据。     

二点叶螨对甲氰菊酯、氧乐果和四螨嗪抗药性的选育、衰退和恢复

以兰州吐鲁沟公园的二点叶螨Tetranychus urticae 为敏感品系,分别用氧乐果、甲氰菊酯、四螨嗪喷雾处理15次,其抗性水平分别为38.5、479.8和67.3倍。将抗性品系分别与敏感品系进行杂交和回交的结果表明：抗氧乐果品系的显性系数DRS（R♀×S♂）为0.4700、D_SR（S♀×R♂）为0.4749;抗甲氰菊酯品系的DRS（R♀×S♂）为0.5155, DSR为0.5237;抗四螨嗪品系的DRS为0.3134, DSR为0.2466。表明二点叶螨对这3种药剂的抗性均是由单个不完全显性基因所控制。在连续10个月不接触药剂的情况下,3个抗性品系的抗药性都有下降,抗氧乐果品系的抗性下降最快,只有敏感品系的抗性倍数的3.6倍;抗甲氰菊酯种群的抗性下降较慢,为敏感品系的95.9倍。再经甲氰菊酯、氧乐果、四螨嗪分别连续15次喷雾处理后,3个抗性种群的抗性水平又再度回升,抗甲氰菊酯品系回升较快,抗性为敏感品系的523.5倍,抗四螨嗪品系次之,抗氧乐果的品系抗性恢复最慢。     

二点叶螨对甲氰菊酯、氧乐果和四螨嗪抗药性的选育、衰退和恢复

以兰州吐鲁沟公园的二点叶螨Tetranychusurticae为敏感品系 ,分别用氧乐果、甲氰菊酯、四螨嗪喷雾处理 15次 ,其抗性水平分别为 38 5、 479 8和 6 7 3倍。将抗性品系分别与敏感品系进行杂交和回交的结果表明 :抗氧乐果品系的显性系数DRS (R♀×S♂ )为 0 470 0、DSR (S♀×R♂ )为 0 4749;抗甲氰菊酯品系的DRS (R♀×S♂ )为 0 5 15 5 ,DSR 为0 5 2 37;抗四螨嗪品系的DRS为 0 3134 ,DSR 为 0 2 46 6。表明二点叶螨对这 3种药剂的抗性均是由单个不完全显性基因所控制。在连续 10个月不接触药剂的情况下 ,3个抗性品系的抗药性都有下降 ,抗氧乐果品系的抗性下降最快 ,只有敏感品系的抗性倍数的 3 6倍 ;抗甲氰菊酯种群的抗性下降较慢 ,为敏感品系的 95 9倍。再经甲氰菊酯、氧乐果、四螨嗪分别连续15次喷雾处理后 ,3个抗性种群的抗性水平又再度回升 ,抗甲氰菊酯品系回升较快 ,抗性为敏感品系的 5 2 3 5倍 ,抗四螨嗪品系次之 ,抗氧乐果的品系抗性恢复最慢。     

Demography of the twospotted spider mite,Tetranychus urticae Koch

Summary A simple life table model was constructed for Tetranychus urticae in which daily survivorship of eggs and motil stages, fecundity, and development time was altered to assess the impact of each parameter on the intrinsic rate of increase. r. Interpretation of the trade-offs focused on management considerations.A second aspect of the study concerned age and stage structure in mite populations including the time path of convergence to a stable age distribution and the effect of changes in birth and death rates on the age profile. The stable stage distributions of 7 tetranychid mite species were computed using 25 separate life tables. In spite of the wide range of r-values induced by different experimental conditions, all of the stage distributions were quite similar averaging roughly 66% eggs, 26% immatures, and 8% adults. Several population studies were cited which reported stage distributions of growing mite populations. The empirical evidence suggested that natural mite populations are often quite near this stable distribution.A practical problem involving the extent to which hormoligosis (insecticide stimulation) affects mite population growth rate was addressed using the life table model and laboratory data from controlled studies. The findings suggested that mite populations treated with insecticide may attain a 1.4- to a 4.2-fold difference in population size relative to an untreated population after 2 generations and over a 1,300-fold potential difference after 10 generations.     

Phenotypic- and Genotypic-Resistance Detection for Adaptive Resistance Management in Tetranychus urticae Koch

Rapid resistance detection is necessary for the adaptive management of acaricide-resistant populations of Tetranychus urticae. Detection of phenotypic and genotypic resistance was conducted by employing residual contact vial bioassay (RCV) and quantitative sequencing (QS) methods, respectively. RCV was useful for detecting the acaricide resistance levels of T. urticae, particularly for on-site resistance detection; however, it was only applicable for rapid-acting acaricides (12 out of 19 tested acaricides). QS was effective for determining the frequencies of resistance alleles on a population basis, which corresponded to 12 nonsynonymous point mutations associated with target-site resistance to five types of acaricides [organophosphates (monocrotophos, pirimiphos-methyl, dimethoate and chlorpyrifos), pyrethroids (fenpropathrin and bifenthrin), abamectin, bifenazate and etoxazole]. Most field-collected mites exhibited high levels of multiple resistance, as determined by RCV and QS data, suggesting the seriousness of their current acaricide resistance status in rose cultivation areas in Korea. The correlation analyses revealed moderate to high levels of positive relationships between the resistance allele frequencies and the actual resistance levels in only five of the acaricides evaluated, which limits the general application of allele frequency as a direct indicator for estimating actual resistance levels. Nevertheless, the resistance allele frequency data alone allowed for the evaluation of the genetic resistance potential and background of test mite populations. The combined use of RCV and QS provides basic information on resistance levels, which is essential for choosing appropriate acaricides for the management of resistant T. urticae.     

Tebufenpyrad (Pyranica®) resistance detected in two-spotted spider mite Tetranychus urticae Koch (Acari: Tetranychidae) from apples in Western Australia

A strain (WA) of Tetranychus urticae Koch was collected from apples in Western Australia following a reported field-control failure of tebufenpyrad. The WA strain had been exposed to five tebufenpyrad applications over four seasons. The tebufenpyrad resistance in the WA strain was confirmed at 63.29× which is the first reported instance of tebufenpyrad resistance in T. urticae. The tebufenpyrad resistance in T. urticae conferred a >210× cross-resistance to pryidaben, a 24.60× cross-resistance to fenpyroximate and a 2.20× cross-resistance to chlorfenapyr.Exp Appl Acarol 22: 633–641 © 1998 Kluwer Academic Publishers     

Wolbachia-induced 'hybrid breakdown' in the two-spotted spider mite Tetranychus urticae Koch

The most common post-zygotic isolation mechanism between populations of the phytophagous mite Tetranychus urticae is 'hybrid breakdown', i.e. when individuals from two different populations are crossed, F1 hybrid females are produced, but F2 recombinant male offspring suffer increased mortality. Two-spotted spider mites collected from two populations, one on rose and the other on cucumber plants, were infected with Wolbachia bacteria. These bacteria may induce cytoplasmic incompatibility in their hosts: uninfected (U) females become reproductively incompatible with infected (W) males. We report on the effect of Wolbachia infections in intra- and interstrain crosses on (i) F1 mortality and sex ratios (a test for cytoplasmic incompatibility), and (ii) the number of haploid offspring and mortality in clutches of F1 virgins (a test for hybrid breakdown). U x W crosses within the rose strain exhibited partial cvtoplasmic incompatibility. More interestingly, F2 males suffered increased mortality, a result identical to the hybrid breakdown phenomenon. The experiments were repeated using females from the cucumber strain. In interstrain U x W and U x U crosses, hybrid breakdown was much stronger in the former (80 versus 26%). This is the first report of a Wolbachia infection causing a hybrid breakdown phenotype. Our results show that Wolbhachia infections can contribute to reproductive incompatibility between populations of T. urticae.     

Inbreeding depression in an arrhenotokous mite (Tetranychus urticae Koch)

Five generations of inbreeding by sibmating in an arrhenotokous mite (Tetranychus urticae Koch) caused depression as measured in the hatchability of the eggs. It appeared that mainly the haploid eggs were affected.

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Zusammenfassung Inzucht über 5 Generationen verursachte bei einer arrhenotoken Spinnmilbe (Tetranychus urticae Koch) eine an der Schlüpffähigkeit der Eier gemessene Depression. Es schien, daß davon hauptsächlich die haploiden Eier betroffen waren.

     

Resistance to tedion in haploid and diploid offspring of Tetranychus urticae Koch

The susceptibility to Tedion of haploid and diploid-haploid mixtures of eggs of Tetranychus urticae Koch was examined. It was concluded for a normal susceptible strain that haploid eggs are more susceptible to Tedion than diploid eggs. This difference in tolerance between haploid and diploid eggs could not be established for a strain resistant to Tedion.Mass crosses between the susceptible and the resistant strain were made. Susceptible females, mated by resistant males, produce susceptible haploid and resistant diploid offspring. Resistant females, mated by susceptible males, gave a resistant offspring. Both sexes can also transmit resistance to Tedion. As there was a difference in tolerance between diploid offspring in the reciprocal crosses, it is assumed that either a maternal or a cytoplasmic component is also present in the genetical mechanism of Tedion-resistance.

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Zusammenfassung Es wurde die Empfindlichkeit haploider und diploid-haploider Gemische von Eiern von Tetranychus urticae Koch gegenüber Tedion untersucht. Für einen normal empfindlichen Stamm wurde aus toxikologischen Daten und einer Verschiebung des Geschlechterverhältnisses erschlossen, daß haploide Eier gegenüber Tedion empfindlicher sind als diploide. Dieser Toleranzunterschied zwischen haploiden und diploiden Nachkommen konnte bei einem gegen Tedion resistenten Stamm nicht nachgewiesen werden.Es wurden Massenkreuzungen zwischen empfindlichen und resistenten Stämmen durch-geführt. Empfindliche Weibchen, mit resistenten Männchen gepaart, produzierten empfindliche haploide und resistente diploide Nachkommen. Resistente Weibchen, mit empfindlichen Männchen gepaart, ergaben eine resistente Nachkommenschaft. Beide Geschlechter können also die Resistenz gegen Tedion übertragen. Da bei den reziproken Kreuzungen ein Toleranzunterschied zwischen den diploiden Nachkommen auftritt, wird angenommen, daß in dem genetischen Mechanismus der Tedion-Resistenz auch eine mütterliche oder eine zytoplasmatische Komponente vorhanden ist.

     

Effect of clofentezine-hexythiazox resistance on life-table attributes of Tetranychus urticae Koch (Acari: Tetranychidae)

Life-table parameters of clofentezine-hexythiazox susceptible, resistant and back-crossed hybrid strains of Tetranychus urticae were studied to aid resistance management. Mean egg production (±s.e.) for the QRPH strain was 102.99 (13.452) and significantly more (P<0.05) than for strains S 67.18 (8.370) and S^QRPH 50.98 (6.180) which were not significantly different from each other. We consider the elevated level of egg production evident in the QRPH strain to be evidence of coadaption. The relative fitness of the resistant strain would make resistance management difficult.This work contributes in part for the fulfilment of the requirements of the degree of PhD at the University of Sydney.     

Toxicity of methyl ketones from tomato trichomes to Tetranychus urticae Koch

The two methyl ketones, 2-tridecanone and 2-undecanone, are constituents of type VI glandular trichomes of the wild tomato, Lycopersicon hirsutum f. glabratum (PI 134417). They are known to cause mortality in several herbivorous insect species. In this study we investigated the effects of these chemicals on two strains of the two-spotted spider mite, Tetranychus urticae Koch, collected from tomato and cucumber crops in Dutch greenhouses. The two ketones were tested separately, in combination in the ratio found in L. hirsutum f. glabratum and in several other ratios to detect any synergistic interaction between them. We measured both the direct contact and residual toxicity, as well as the viability of the eggs produced by ketone-treated females. The methyl ketones can be considered as quite toxic to spider mites because their LC50 values were comparable to that found for the formulated acaricide amitraz. 2-Tridecanone was slightly more toxic than 2-undecanone but only in the tomato strain. Synergistic effects were not detected. In the bio assays for the residual effects of the two methyl ketones no significant mortality occurred but the mites avoided feeding on the treated surface and the eggs were laid almost exclusively on the untreated area. Furthermore, there was no significant egg viability for most of the treatments and when some egg viability occurred, it was not correlated to the dose of the chemical. Based on published data on the levels of methyl ketones in the trichome tips of wild and cultivated tomato (L. hirsutum f. glabratum and Lycopersicon esculentum Mill, respectively) it was calculated how many contacts are required to reach the LD50 (ng a.i. per mite). It appeared that on wild tomato just a few contacts suffice, but many are needed on cultivated tomato. Nevertheless, it seems justified to conclude that even in cultivated tomato, 2-tridecanone represents a naturally occurring acaricide. The cucumber and tomato strains of the two-spotted spider mite did not differ in their response to the methyl ketones. Because this is surprising, given the selection pressures on their respective host plants, we formulated two hypotheses, one explaining the absence of a difference due to cross-resistance and another one proposing that bioaccumulation obscures the underlying differences between the strains. This revised version was published online in November 2006 with corrections to the Cover Date.     

The formation of collective silk balls in the spider mite Tetranychus urticae Koch

Tetranychus urticae is a phytophagous mite that forms colonies of several thousand individuals. These mites construct a common web to protect the colony. When plants become overcrowded and food resources become scarce, individuals gather at the plant apex to form a ball composed of mites and their silk threads. This ball is a structure facilitating group dispersal by wind or animal transport. Until now, no quantitative study had been done on this collective form of migration. This is the first attempt to understand the mechanisms that underlie the emergence and growth of the ball. We studied this collective behaviour under laboratory conditions on standardized infested plants. Our results show that the collective displacement and the formation of balls result from a recruitment process: by depositing silk threads on their way up to the plant apex, mites favour and amplify the recruitment toward the balls. A critical threshold (quorum response) in the cumulative flow of mites must be reached to observe the emergence of a ball. At the beginning of the balls formation, mites form an aggregate. After 24 hours, the aggregated mites are trapped inside the silk balls by the complex network of silk threads and finally die, except for recently arrived individuals. The balls are mainly composed of immature stages. Our study reconstructs the key events that lead to the formation of silk balls. They suggest that the interplay between mites' density, plant morphology and plant density lead to different modes of dispersions (individual or collective) and under what conditions populations might adopt a collective strategy rather than one that is individually oriented. Moreover, our results lead to discuss two aspects of the cooperation and altruism: the importance of Allee effects during colonization of new plants and the importance of the size of a founding group.     

Differences among plant species in acceptance by the spider mite Tetranychus urticae Koch

Abstract:  The spider mite Tetranychus urticae Koch has a broad range of host plants. However, the spider mite does not accept all plants to the same degree because of differences in nutritive and toxic constituents. Other factors, such as the induction of secondary metabolites, the morphology of a leaf surface and the presence of natural enemies, also play an important role in plant acceptance. We compared plants from various families in their degree of acceptance by the spider mite, to get an indication of the plant's direct defence. Glycine max (soybean), Humulus lupulus (hop), Laburnum anagyroides (golden chain) and Nicotiana tabacum (tobacco) were highly accepted by the spider mites. Different glandular hair densities among tobacco cultivars did not affect their suitability towards spider mites significantly. Solanum melalonga (eggplant), Robinia pseudo-acacia (black locust), Vigna unguiculata (cowpea) and Datura stramonium (thorn apple) were accepted by the spider mites to a lesser degree. Vitis vinifera (grapevine) was poorly accepted by the spider mite. It might be that the food quality of the leaves was not high enough to arrest the spider mites. Also, Capsicum annuum (sweet pepper) and especially Ginkgo biloba (ginkgo) were poorly accepted by the spider mite, probably because of the presence and concentration of certain of the secondary metabolites in the leaves. The spider mites accepted all the plants belonging to the Fabaceae for feeding, but those belonging to the Solanaceae showed a larger variance in spider mite acceptance varying from well accepted (tobacco) to poorly accepted (sweet pepper).