Demographic examination of sex ratio in the two-spotted spider mite, Tetranychus urticae

Primary sex ratio of arrhenotokous tetranychid mites depends on the age-specific schedule of ratios of progeny produced by individual females. Since primary sex ratio is conditional upon female age and since the proportion of females of a given age in a population is influenced by the rate of increase, both the agespecific ratio of males to females and the overall ratio of males to females depends on the rate of increase. We given an expression for this dependence and compare it to experimental results for the two-spotted spiter mite. These results imply that there is no standard sex ratio of spider mites because of interpopulation variation in rates of increase.

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Résumé Le taux sexuel des acariens tétranychidés arrhénotoques est défini comme le rapport de la somme des nombres de mâles sur la somme des nombres de femelles pour chaque âge de la distribution en âges. Comme le taux sexuel primaire dépend de l'âge de la femelle et comme la proportion de femelles d'un âge donné dans la population est influencée par le taux d'accroissement, alors le rapport mâle/femelle spécifique d'un âge déterminé et le rapport global mâle/femelle dépendent du taux d'accroissement. Nous avons cherché à exprimer cette dépendance et à la comparer aux résultats expérimentaux pour Tetranychus urticae. Ces résultats signifient qu'il n'y a pas de taux sexuel caractéristique de Tétranyques par suite des variations du taux d'accroissement suivant les populations.

     

Comparison of methods for estimating the prevalence of Neozygites floridana in Tetranychus urticae populations infesting strawberries

Methods for measuring prevalence of Neozygites floridana in a Tetranychus urticae population collected from strawberries were developed and compared. T. urticae were extracted from leaves using a soapy water solution (0.5 ml washing detergent : 8 L water) and then placed into 80% alcohol for use in Methods 1 and 2. Method 1: N. floridana-sporulating T. urticae cadavers were observed and quantified under a compound microscope (40-80x). Method 2: Adult females were mounted in lactophenol cotton blue and observed for the presence or absence of N. floridana hyphal bodies under a microscope (200-400x). Method 3: Live T. urticae females were incubated at 25 degrees C and 75% RH and observed for mortality and N. floridana infection under a compound microscope (6.4-40x). Method 1 was the most time-efficient method and it also allows processing of samples as time permits. Method 2 quantified significantly higher fungal prevalence than Methods 1 and 3, but Method 2 is not considered to be reliable because hyphal bodies are difficult to detect. No significant differences were found between Methods 1 and 3.     

Effects of mating status and age on dispersal behavior in the twospotted spider mite, Tetranychus urticae in response to fenvalerate-treated leaf surfaces

Effects of variation in age and mating status on dispersal of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), from fenvalerate-treated leaf surfaces were investigated. Unmated and mated female mites, 1 to 6 days in age, were scored for walkoff and spindown dispersal response on bean leaves treated with a sub-lethal, residual dose of fenvalerate. Variation in mite age did not have a pronounced effect on dispersal response. Significant differences in dispersal response due to mating type were observed, yet the mean differences in dispersal response between unmated and mated females was generally small. Our data suggest that the current practice of using mated female mites of unknown age when testing for among-population differences in dispersal response, in most cases, provides an adequate estimate of population response when differences among treatments in dispersal response are large. However, when testing for within-population differences in dispersal response, small treatment effects may be more easily measured using a single age class of mites, because this could decrease within-treatment variance.     

Interactive effects of selected pesticides on the two-spotted spider mite and its fungal pathogen Neozygites floridana

Benomyl affected populations of Tetranychus urticae by interfering with the pathogenic fungus, Neozygites floridana. Benomyl delayed but prolonged spider mite outbreaks. Few mites were infected with the pathogen when benomyl was used. Reductions in mite populations treated with fentin hydroxide were associated with a high incidence of N. floridana infection. Benomyl did not affect sporulation of N. floridana but appeared to inhibit conidial germination or growth of the fungus.

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Résumé Le bénomyl a modifié les populations de Tetranychus urticae Koch en interférant avec son champignon pathogène, Neozygites floridana (Weiser & Muma). Le bénomyl retardait mais prolongeait les pullulations de l'acarien. Peu d'acariens étaient infectés par le champignon quand on utilisait du bénomyl. Les réductions des populations d'acariens traitées avec l'hydroxyde de fentine étaient associées à un haut niveau d'infection par N. floridana. Le bénomyl ne modifiait pas la sporulation de N. floridana mais semblait inhiber la germination des conidies ou la croissance du champignon.

     

Movement of the twospotted spider mite, Tetranychus urticae, among hosts in a corn-peanut agroecosystem

A 3 year study of spider mites in a corn-peanut agroecosystem indicated that the persistance and pest status of mite populations depended on dispersal among a succession of temporarily suitable cultivated and non-cultivated hosts. In the spring, mites crawled from overwintering sites in vegetation along field margins into both peanut and corn fields, but became established only in corn. Initiation of aerial dispersal from corn was coincident with and appeared dependent upon mites moving to the top of the corn canopy, where they were exposed to the wind. Mites were first observed in peanut immediately following the onset of aerial dispersal from corn, and these aerial dispersers were the primary source of subsequent mite infestations in peanut. As populations grew in peanut, mites dispersed into vegetation along peanut field margins and became the nucleus of populations which persisted over the winter. This pattern of host utilization was reinitiated in the spring if corn was planted adjacent to infested field borders. This pattern commonly occurs since corn is planted following peanut in the predominant crop rotation sequence in this area.

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Résumé Des populations d'acariens ont été étudiées pendant 3 ans sur maïs, arachide et végétation spontanée, dans 7 fermes commerciales de Chowan Co., Caroline du Nord. Les déplacements d'acariens parmi ces plantes ont été notés en fonction de la croissance de la population et de la phénologie des hôtes. Un schéma cohérent de croissance de la population d'acariens et de leurs mouvements en découle, dont seule la taille change suivant les fermes et les années. Les acariens provenant de populations hivernantes sur la végétation spontanée bordant les champs migrèrent dans les champs cultivés adjacents quelle qu'en soit la nature de la culture. Cependant, à cette époque, les populations d'acariens ne s'établissaient que dans le maïs. Dans le maïs, les acariens se répandirent à travers le champ et se multiplièrent sur des pieds particuliers jusqu'à ce qu'ils eussent atteint le sommet de la canopée du maïs. Les premiers acariens transportés par le vent ont été capturés la semaine suivant la première apparition d'acariens au sommet de la canopée du maïs et aussitôt après la découverte des premiers acariens dans les arachides voisines. Ceci suggère que les acariens dispersés par le vent sont à l'origine des contaminations ultérieures des arachides voisines. Plus tard dans la saison, les acariens se dispersèrent à partir de l'arachide vers les sites d'hibernation dans la végétation spontanée poussant autour du champ d'arachide. Puisque des champs semés en arachides sont généralement semés en maïs l'année suivante, les acariens se dispersant au printemps depuis les sites d'hibernation rencontrèrent souvent du maïs qu'ils colonisèrent. Ce cycle répétitif d'utilisation de l'hôte et de dispersion est considéré comme fortement responsable de la pérennité des acariens et de leur danger potentiel dans les agroécosystèmes à maïs-arachide, caractéristiques du canton de Chowan (N.C.).Les problèmes potentiels posés par les acariens sur arachide ont paru être liés à l'intensité de l'attaque d'acariens sur le maïs voisin, qui sert de réservoir pour les populations d'acariens. Ceci suggère que le contrôle des populations d'acariens sur maïs peut être une stratégie viable pour limiter les infestations ultérieures sur arachide et, en dernier lieu, les populations hivernantes.

     

Behavioral aspects of dicofol resistance in the twospotted spider mite Tetranychus urticae

Behavioral analysis of near-isogenic dicofol-resistant and dicofol-susceptible spider mites did not uncover behavior patterns, present in resistant individuals yet absent in susceptible individuals, that would have reduced exposure to dicofol. On the contrary, homozygous resistant individuals were more likely than homozygous susceptible individuals to remain in contact with treated leaf areas. In the case of dicofol resistance in twospotted spider mites, resistance appears to have resulted in the loss, rather than the acquisition, of behavioral traits that lessen exposure to pesticide. Therefore, we conclude that behavioral resistance does not play a major role in twospotted spider mite resistance to dicofol.Deux génotypes de T. urticae Koch (un sensible et un résistant) ont servi à étudier les aspects comportementaux de la résistance aux pesticides: la durée et la fréquence des comportements de nutrition, de marche et d'attente ont été mesurés chez cet acarien. Dans toutes les expériences, des femelles de mêmes âges avaient été placées sur des feuilles jeunes de haricot (Phaseolus vulgaris) portant des résidus de dicofol.3 séries d'expériences ont été réalisées pour examiner:

Comparative toxicity of some acaricides to the predatory mite, Phytoseiulus persimilis and the twospotted spider mite, Tetranychus urticae

The relative toxicity of someacaricides to the predatory mite, Phytoseiulus persimilis and the twospottedspider mite, Tetranychus urticae (Acari: Phytoseiidae, Tetranychidae) wasevaluated in laboratory. Five of theacaricides tested, including bifenazate,acequinocyl, chlorfenapyr, flufenoxuron andfenbutatin oxide, were much less toxic to adultfemales and immatures of P. persimilisthan to those of T. urticae, and adultfemale predators treated with these fiveacaricides produced 84±96% as many eggs as didcontrol females. Etoxazole did not seriouslyaffect the survival and reproduction of adultfemale predators but caused high mortalityrates in eggs and larvae of P.persimilis. Milbemectin and fenazaquin werevery toxic to adult females and immatures ofP. persimilis. Adult female predatorssurvived on a diet of spider mites treated withbifenazate, acequinocyl, chlorfenapyr,flufenoxuron and fenbutatin oxide, and theirfecundity, prey consumption and the sex ratioof the progeny were not substantially affected. Based on the results, bifenazate, acequinocyl,chlorfenapyr, flufenoxuron and fenbutatin oxideappeared to be the promising candidates for usein integrated mite management programs whereP. persimilis is the major naturalenemy.     

Resistance status of the carmine spider mite,Tetranychus cinnabarinus and the twospotted spider mite,Tetranychus urticae to selected acaricides on strawberries

The carmine spider mite, Tetranychus cinnabarinus (Boisduval) and the twospotted spider mite, Tetranychus urticae Koch, are serious pests of strawberries and many other horticultural crops. Control of these pests has been heavily dependent upon chemical acaricides. Objectives of this study were to determine the resistance status of these two pest species to commonly used acaricides on strawberries in a year‐round intensive horticultural production region. LC₉₀ of abamectin for adult carmine spider mites was 4% whereas that for adult twospotted spider mites was 24% of the top label rate. LC_90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 0.5%, 0.5%, 1.4% and 83% of their respective highest label rates for carmine spider mite eggs, 0.7%, 2.7%, 12.1% and 347% of their respective highest label rates for the nymphs. LC_90s of spiromesifen, etoxazole, hexythiazox and bifenazate were 4.6%, 11.1%, 310% and 62% of their respective highest label rates for twospotted spider mite eggs, 3%, 13%, 432,214% and 15% of their respective highest label rates for the nymphs. Our results suggest that T. cinnabarinus have developed resistance to bifenazate and that the T. urticae have developed resistance to hexythiazox. These results strongly emphasize the need to develop resistance management strategies in the region.     

Field predation of twospotted spider mite in a New Zealand strawberry crop

Predation by naturally occurring predatory arthropods was investigated to explain variations in population numbers of twospotted spider mite (Tetranychus urticae Koch) between first and second season strawberry crops. Araneomorph spiders. European harvestman [Phalangium opilio (L.)], Tasmanian lacewing [Micromus tasmaniae (Walker)] and Pacific damsel bug [Nabis kinbergii Reuter] were the only predators found in high numbers. However, spiders and harvestment were more prevalent than lacewings and nabids. Laboratory feedings trials indicated spiders build horizontal webs in the plants and prey predominantly on small flying insects that shelter in the crops. Similar feeding trials cofirmed the palatability of TSSM to spiders and harvestmen. Immunological testing for proteins of TSSM, aphids, Collembola and leafrollers in the intestines of field collected European harvestman, spiders, Tasmanian lacewing and Pacific damsel bug confirmed European harvestman includes TSSM in its diet, but not in large enough quantities to exert a significant regulating pressure on TSSM populations. Lacewings and nabids include TSSM in their diets but only in very small quantities (2% and 1% respectively). Spiders do not take TSSM unless they drop or spin down onto the spider webbing. The immunological testing also showed European harvestman to be a polyphagous and opportunistic feeder. Prey residues were detected more frequently in harvestmen intestines at times of prey abundance which indicated a seasonality to harvestmen diet.      

Effects of triflumuron on the two-spotted spider mite,Tetranychus urticae (Acari: Tetranichydae)

The effects of triflumuron on the mortality, fecundity, and fertility of the two-spotted spider mite, Tetranychus urticae, were evaluated in the laboratory. No differences in toxicity for larvae, protonymphs and deutonymphs were observed, but immature stages were 3.8-times more susceptible than adults at the LC₅₀. The compound exhibited a direct contact ovicidal activity influenced by eggs age. 48–72 hold eggs were significantly more sensitive than eggs of the other age classes. No hatch inhibition was observed in eggs laid by treated adult females using a sublethal dose at two physiological times (<12 and 48–72h old). However, fecundity decreased in younger treated females, but it increased in the older-ones. The toxicity for immatures and eggs, and the sublethal effects described suggest that triflumuron could be an interesting incorporation in integrated pest programs of T. urticae. This revised version was published online in July 2006 with corrections to the Cover Date.     

Within-plant and within-leaf dispersion pattern of two-spotted spider mite,Tetranychus urticae Koch (Acari: Tetranychidae) on okra

Tetranychus urticae distribution on spatial scale both within leaf and within plant was assessed by the index of dispersion (Id), Lloyd's mean crowding index (Imc), Lloyd's patchiness index (Ip) and Morisita's index (I _δ). Id values in all leaves and leaf parts promised aggregated distribution regardless of leaf position and leaf areas. The values of Imc estimated were all larger than the mean. The value of Ip and I _δ  also indicated increased degree of aggregation and clumping in all leaves and leaf areas. While pattern of distribution is same in all the leaves and leaf parts, population estimated is high in young fully opened top leaves than the grown-up middle and bottom leaves. Within the young leaf, top area of upper side of the leaf housed relatively increased number of T. urticae than bottom area of upper side of the leaf. Because young fully opened leaves consistently contained major proportion of mites (48.33%), particularly the top leaf area (79.62%), these leaves and leaf areas can be used as sampling unit for population estimation to minimise the time spent on sampling. However, it warrants future research for predictive models to associate a number of mites of top leaf to other leaves and top area to other areas. Further, releasing predators in young fully opened leaves may increase predator efficiency if supplementary studies on predator–prey relationship on spatial scale are triggered.     

Effects of pesticides on spin down and webbing production by the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae)

Spin down in response to pesticides is a known phenomenon. This study aimed at investigating the effects of varying acaricide concentrations and acaricidal combinations on the rate of spin down and thread length, the fate of mites after spinning down and, thus, the implications of spin down in the context of mite control and the relationship between webbing and the efficacy of ovicides. In response to cyhexatin at a concentration of up to 100 mg dm-3 the rate of spin down did not change, but in response to higher concentrations it occurred earlier and ceased before the end of the experiment. The mean thread length did not vary with the concentration of acaricide and, whilst the proportion of mites spinning down increased with a cyhexatin concentration of up to 10 mg dm-3, it did not increase further with higher concentrations thereafter. It is therefore postulated that at any given time only a certain proportion of mites have a propensity to spin down. In combination with cyhexatin, only amitraz (at low concentrations) increased the proportion of mites spinning down, but amitraz (at higher concentrations), flubenzimine and permethrin all inhibited spin down, which may be a useful attribute in pesticide formulations. With regard to the fate of mites after spinning down, they were able to climb back up threads, but the proportion doing so was too small to be of practical importance. Mites which spin down and remain at the end of a thread die, but those which reached another leaf were able to spin down again and were more likely to do so if the leaf bore a cyhexatin residue. Mites reaching another leaf are also able to lay eggs, the number being greater if the leaf which they reach is untreated. Spin down is therefore likely to be of significant advantage to Tetranychus urticae in avoidance of the effects of acaricides. Finally, some eggs were observed to be laid on webbing and not to come into direct contact with clofentezine residues. The use of a fine water spray to simulate dew increased the ovitoxicity of clofentezine, probably by resuspension of the pesticide, but not of amitraz, which inhibits webbing production. The avoidance of acaricides should be added to the several known advantages of webbing production for spider mites. It is concluded that, all other factors being equal, pesticide formulations which inhibit spin down and webbing production are likely to be more effective in control programmes than those which stimulate such behaviour.     

Population response of the twospotted spider mite,Tetranychus urticae, to host phenology in corn and peanut

In northeastern North Carolina, outbreaks ofTetranychus urticae Koch on commercial corn and peanut plantings were observed to coincide with flowering and fruiting of the crop host. In greenhouse studies, when equal mite numbers were started on plants in either vegetative or reproductive growth stages, populations increased significantly more after 3–4 weeks on reproductive plants of both corn and peanut. This direct response of mite populations to differences in plant phenology appears to be an important component in the population dynamics ofT. urticae. The importance of this effect in understanding mite outbreaks on corn and peanut is discussed, especially in reference to the corn-peanut agroecosystem in North Carolina.

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Réponse de populations deTetranychus urticae Koch., aux phénologies du maïs et de l'arachide

Résumé Les populations de tétraniques sont souvent associées à la floraison et à la fructification des plantes attaquées. Dans les agrosystèmes maïsarachide du N.E. de la Caroline du Nord, l'augmentation rapide de populations deT. urticae a été observée lors de la maturation des épis mâles du maïs et du maximum de floraison de l'arachide. Bien que ces observations suggèrent une relation causale avec la phénologie des plantes hôtes, il est difficile de déterminer dans les conditions de la nature si l'augmentation des populations d'acariens sur les stades reproducteurs des plantes est due à une réponse à la phénologie des cultures ou à une autre cause, comme le passé de la population ou une immigration. Des expériences ont été réalisées dans une serre pour mettre en évidence l'action de la phénologie du maïs et de l'arachide sur les populations d'acariens en maîtrisant ces autres hypothétiques facteurs. Des effectifs identiques d'acariens femelles ont été libérés sur des plantes à des stades tant végétatifs que reproductifs, et ensuite laissés sans interventions pendant plusieurs semaines, au bout desquelles les effectifs sur chaque plante ont été dénombrés. Sur les deux hôtes, les populations sur plante à un stade reproducteur avaient augmenté significativement plus que sur les plantes de même espèce à un stade végétatif. Ces résultats montrent queT. urticae répond directement à des différences entre plantes à un stade végétatif et à un stade reproductif. Cette réponse semble jouer un rôle important dans la dynamique des populations deT. urticae.

     

Predation risk affects diapause induction in the spider mite Tetranychus urticae

Whenever diapause induction triggers movement into another microhabitat or the development of protective morphological structures, this may also alter predation risk. If the risk of being eaten is lower in the diapause phase, then there may be selection favouring diapause induction in response to predators or their cues. In this article, we studied the effect of the predatory mite Typhlodromus pyri on diapause induction in the spider mite Tetranychus urticae. We used a Greek strain because under long-night photoperiods and low temperature only part of the population enters diapause, thereby leaving room for the impact of another factor. In spider mite groups under predation, the percentage diapause induction increased whenever night-lengths were such that diapause was induced (13–16 h of night). Given this diapause induction in response to predation risk, the question arises whether entering diapause helps spider mites to escape from predation and contribute more offspring to the spring generation next year.     

Ambulatory dispersal and life history response to food deprivation in twospotted spider mites

A major life history characteristic of the twospotted spider mite, Tetranychus urticae Koch, is the ability to disperse between different hosts. This may be done by aerial or ambulatory means. Although there have been a number of studies dealing with mite dispersal, most have been qualitative in nature and examine only the overall process. In this study we measure the ambulatory dispersal capabilities of twospotted spider mite adult females and males, as well as that of deutonymphs, protonymphs and larvae at distances up to 480 cm. Additionally, for adult females only vertical (upwards and downwards) distances of up to 240 cm were measured. We also measured the influence of food deprivation on spider mite longevity and fecundity by depriving mites of food for one, two or three days immediately after ecdysis at 24 or 30 °C, or food deprivation for one, two or three days (at 24 °C) after feeding as adults for five days. Dispersal efficiency, defined as the percentage of individuals successfully crossing the test distance, generally increased with time and decreased with distance. As expected, dispersal efficiency was shown to be related to stage, with adults the most efficient and larvae the least. Food deprivation studies revealed that at 24 °C mites were capable of withstanding two days without food before longevity and fecundity began to decrease. Tetranychus urticae Koch est caractérisé par son aptitude à la dispersion sur différents hôtes. Nous examinons 2 aspects de celle-ci: 1) aptitude à la dispersion à faible distance en rampant; 2) effet de la perte de contact avec l'hôte (par suite de la dispersion) sur la survie et la fécondité. En ce qui concerne la dispersion à faible distance, la mesure a porté sur l'aptitude de chaque stade à parcourir différentes distances jusqu'à 480 cm. De plus, pour les femelles la mesure a concerné seulement la dispersion verticale jusqu'à 240 cm. L'efficacité de la dispersion était plus élevée sur les faibles distances; l'aptitude à la dispersion était liée au stade, les adultes étant meilleurs que les larves. Les effets de la privation de nourriture ont été en particulier:

Effects of mite age, mite density, and host quality on aerial dispersal behavior in the twospotted spider mite

Mite age, population density, and host leaf quality affect various life history traits in spider mites. We investigated the effects of these factors on the aerial dispersal behavior of adult female twospotted spider mites,Tetranychus urticae Koch (Acari: Tetranychidae). The proportion of adult females exhibiting the dispersal behavior dropped significantly with age following adult emergence, particularly in the first 3 days. Sixty to eighty percent of female mites 2-days old or younger displayed the behavior under test conditions, whereas less than 20% of female mites older than 3-days-old showed the behavior. Younger adult females also exhibited shorter latency for the behavior, although this trend was not as clear. Leaf quality experienced during deutonymph development had no effect on the behavior adults subsequently displayed. On the other hand, adult females that fed on poor quality leaves after emergence were twice as likely to display the behavior (90% vs. 45%), and with shorter latency (37 vs. 77 min), than those that fed on high quality leaves. When newly emerged adult females encountered high mite density and dry leaves, the incidence of the behavior increased (69% vs. 47%) and latency decreased (69 vs. 93 min) compared to mites that encountered low density on well watered leaves. Our results suggest that both starvation and desiccation of adult females may enhance their dispersal behavior.     

Host specificity of the cassava green mite pathogen Neozygites floridana

Tests were conducted on the hostspecificity of a Brazilian isolate of thefungus Neozygites floridana, a potentialbiological control agent for the cassava greenmite, Mononychellus tanajoa, in Africa.Five insect and two mite species, mostly fromthe cassava agroecosystem, were evaluated forsusceptibility to N. floridana, namelyEuseius concordis, E. citrifolius, Phenacoccus herreni, Stethorus sp., Aleurothrixus aepim, Apoanagyrusdiversicornis, and Bombyx mori.Individuals of each species were exposed tocapilliconidia (the infective stage of thefungus). None of the tested individuals wasfound with hyphal bodies (the vegetative stageof the fungus), whereas 73 to 94% of thecassava green mites in the controls becameinfected. Non-germinated capilliconidia were,however, found attached to several individualsin most species. N. floridana appears tobe safe for exportation. Further evaluation ofits performance against M. tanajoa inAfrica is therefore desirable.     

Identification of Wolbachia-responsive microRNAs in the two-spotted spider mite,Tetranychus urticae

Background

The two-spotted spider mite, Tetranychus urticae, is infected with Wolbachia, which have the ability to manipulate host reproduction and fitness. MicroRNAs (miRNAs) are small non-coding RNAs that are involved in many biological processes such as development, reproduction and host-pathogen interactions. Although miRNA was observed to involve in Wolbachia-host interactions in the other insect systems, its roles have not been fully deciphered in the two-spotted spider mite.

Results

Small RNA libraries of infected and uninfected T. urticae for both sexes (in total four libraries) were constructed. By integrating the mRNA data originated from the same samples, the target genes of the differentially expressed miRNAs were predicted. Then, GO and pathway analyses were performed for the target genes. Comparison of libraries showed that Wolbachia infection significantly regulated 91 miRNAs in females and 20 miRNAs in males, with an overall suppression of miRNAs in Wolbachia-infected libraries. A comparison of the miRNA and mRNA data predicted that the differentially expressed miRNAs negatively regulated 90 mRNAs in females and 9 mRNAs in males. An analysis of target genes showed that Wolbachia-responsive miRNAs regulated genes with function in sphingolipid metabolism, lysosome function, apoptosis and lipid transporting in both sexes, as well as reproduction in females.

Conclusion

Comparisons of the miRNA and mRNA data can help to identify miRNAs and miRNA target genes involving in Wolbachia-host interactions. The molecular targets identified in this study should be useful in further functional studies.

Electronic supplementary material

The online version of this article (doi:10.1186/1471-2164-15-1122) contains supplementary material, which is available to authorized users.     

UV radiation elevates arylalkylamine N-acetyltransferase activity and melatonin content in the two-spotted spider mite, Tetranychus urticae

Ultraviolet (UV) radiation produces reactive oxygen species (ROS) in mammals, where melatonin plays the role of a ROS scavenger. The melatonin synthetic enzyme arylalkylamine N-acetyltransferase (NAT) is a significant element in a possible ROS removal system. Changes in NAT activity and melatonin content were determined in the two-spotted spider mite Tetranychus urticae by irradiating it with monochromatic light using the Okazaki Large Spectrograph at the National Institute for Basic Biology, Okazaki, Japan. The NAT activity and melatonin content were suppressed by blue light (450nm). No effects of red light (650nm) on the NAT activity and melatonin content were observed. UV radiation had intensity-dependent dual effects on the NAT activity and melatonin content. In the UV-B (300nm) treatment, the NAT activity and melatonin content were suppressed at the intensity below 1mumolm(-2)s(-1) but elevated when the intensity was as high as 10mumolm(-2)s(-1). In the UV-A (350nm) treatment, the melatonin content was elevated when the intensity was as high as 10mumolm(-2)s(-1), though the NAT activity and melatonin content were suppressed at the intensity below 10 and 1mumolm(-2)s(-1), respectively. Elevation of the NAT activity and melatonin content by high intensity UV irradiation may indicate that the UV signals initiate melatonin synthesis for ROS removal in mites.     

New report of Neozygites sp. infecting red spider mite Tetranychus urticae infesting French bean from Eastern Plateau and Hill region,India

An anamorphic entomopathogenic fungus Neozygites sp. belonging to the Family Neozygitaceae was found infecting the tetranychid mites Tetranychus urticae Koch (Acari: Tetranychidae) of French bean (Phaseolus vulgaris L.) for the first time in Eastern Plateau and Hill region of India in the month of October 2011. The report of entomopathogenic fungus could be of help in managing acaricide resistant mites.