The population dynamics of Trialeurodes vaporariorum (Westwood) in fields grown with French bean (Phaseolus vulgaris L.) were followed at two different locations in Kenya with the purpose of studying the interplay between local and regional dynamics. The fields were surrounded by two types of window traps which provided data on the relative rates of whiteflies arriving and leaving the fields. These data were supplemented with density estimates of adult whiteflies within the fields obtained by means of pot traps. Whiteflies arrived five days after the crop germinated, causing a quick increase in the proportion of infested plants, which reached 98% of all plants one month after germination, corresponding to ca 6 adult whiteflies per plant. Flight activity had two daily peaks, one around 12 hours and one about 16 hours. Activity level was found to increase with temperature (up to 27.5oC) and solar radiation (up to 0.73 kW/m2) and to decrease with wind speed. Immigration rate at first increased with crop age, but reached a maximum of approximately 1.5 whiteflies arriving per plant per day once the crop had reached maturity. A simple statistical model was fitted to sampling data of the number of whiteflies per plant (Nt). The model has three predictor variables: t which is the number of days since germination of the crop, Co(t) and Ci(t) which are the cumulated catches of whiteflies obtained from the outer and inner side, respectively, of the window traps from day 0 and until day t. The model explained 66% of variation in Nt, but surprisingly the model showed that Nt was positively associated with Ci, but negatively associated with Co. A possible explanation for this counterintuitive result is that Ci reflects trivial (non dispersal) flights, which is likely to be correlated with the population size, whereas Co reflects the emigration rate, which tends to increase when the whitefly population declines as a result of reduced food quality due to aging or overexploitation. If there are no other suitable fields in the vicinity, a fraction of the emigrating whiteflies will return to the original field to be caught at the outer side of the window traps. Such captures thus represent “false” immigrants.

Nationwide occurrence of Bemisia tabaci Q biotype was identified from 2005 May to 2007 Dec. in total 28 cities/counties of 9 provinces such as Goyang (Kyung-gi), Gangnung (Gang-won), Jincheon (Chung-buk), Buyeo (Chung-nam), Seongju (Kyung-buk), Geoje (Kyung-nam), Bukjeju (Jeju). Host plants of the scale of B. tabaci Q biotype were over 15 crops of tomato, sweet pepper, hot pepper, eggplant, etc. and total 12 species of weeds such as Veronica persica, Ipomoea lacunosa, Conyza sumatrensis, I. hederacea, Xanthium canadense, Humulus japonicus, Boehmeria nivea, Artemisia vulgaris, Paederia scandens, Acalypha austeralis, Brassica juncea, Rumex crispus. For molecular identifying Bemisia tabaci B and Q biotypes, and Trialeurodes vaporariorum, for which it is difficult to distinguish morphologically, sequences of mitochondrial 16S rDNA and CO I (Cytochromoxidase I) gene were analyzed and restriction enzymes were selected for biotypespecific cleaved bands. As the results, Hinf I for 16S rDNA and Vsp I for CO I gene made specific band patterns for the B and Q biotypes in gel electrophoresis. Thus these methods were able to identify those biotypes and species without DNA sequence analysis. Populations of the Q biotype were collected in each regions of Korea from 2005 to 2007, and they were genetically compared using CO I gene sequences. Thus the populations were divided by three different groups which were introduced over 3-4 times before 2007 from different population sources. Geoje and Jeju were suggested as the first regions of introduction. Especially the populations in the first introduced regions were highly homologous with the Q biotype of Japan. In addition, infection pattern of secondary symbionts in populations of the B and Q biotypes in Korea were different from the Israeli populations. Thus it is suggested that Japan is the main source of B. tabaci Q biotype introduced to Korea. In addition, populations of the both of B and Q biotype in Korea were infected by Haemiltonella, which is more effectively related to the transmission of tomato yellow leaf curl begomovirus (TYLCV). Therefore it is needed to monitor continuously if the outbreak of begomovirus vectored by B. tabaci. In this molecular phylogenetic analysis, it was shown that the population of B. tabaci Q biotype in weed plants near greenhouse was introduced to crop plants in greenhouse. Therefore we understand that weed control is important to inhibit recurrence of B. tabaci in greenhouse. Three species of begomovirus, sweet potato leaf curl virus (SPLCV), tobacco leaf curl virus (TLCV), and TYLCV, were reported after introduction of B. tabaci in Korea. Especially Korean government removed all plants in the first TYLCV-occurred greenhouse in 2008. Multiplex PCR diagnosis between TLCV and TYLCV was developed for the more rapid and accurate monitoring. TLCV and TYLCV strains occurred in Korea were highly homologous with strains of Japan. Therefore these results support our suggestion that Japan is the main source of B. tabaci Q biotype introduced to Korea.

The sweet potato whitefly Bemisia tabasi is one of the most important pests of various horticultural crops. In addition, B. tabaci is a vector of many plant-pathogenic viruses and cause a serious secondary damage to crop plants. Association of plant-pathogenic virus with vector insects is known to be effective on the transmission capacity, fecundity, longevity of vectors including whiteflies. However, the interactive mechanisms between virus and vector insects are still poorly understood. Recently, a serious damage caused by virus disease together with B. tabasi emergence was identified at tomato glasshouse in Tongyoung. We detected the signals of Tomato Yellow Leaf Curl Virus (TYLCV) in tomato leaves and vector whiteflies using PCR amplification and confirmed its presence by those sequence comparison. To determine the effects of TYLCV acquisition on physiological status of vector whiteflies, transcript levels of genes that associated with metamorphosis, metabolism, stress and immune processes were compared between TYLCVinfected whiteflies and non-infected ones. Generally, the transcript levels of virus-infected whiteflies were lower than those of non-infected ones. In addition, the associations of endosymbiont levels within whiteflies were discussed in aspect of the acquisition and transmission of TYLCV.

Dongbu HiTek had a focal group depth interview with pesticide sales dealers and farmers in 2007. With results, dealers assessed a white fly as a most difficult pest in up-land crop cultivation, and answered the increase and change of pests and pathogen from climate change as a most concerned event. Farmers pointed that important jobs in vegetable cultivation were the control of pest and pathogen (34%) and the prevention of pest and pathogen (24%). And difficult works was the control of pest and pathogen (24%), and the climate change (18%). When choosing the insecticide, the long lasting activity (44%) and the completeness of control (34%) were the important factors. Among customers’ claims related with white fly, claims on insufficient efficacy was dominant and occupied 86% in spite of efforts of producers, and it reflected that commercial agrochemicals did not meet the expectation level of the farmers. Common agrochemicals for the control of white fly are Neo-Nicotinoids in Korea today and CGAR of it is about 13% average increased per year from 2003. As Bio Type Q showed higher resistant level to the Neo Nicotinoids than other Bio type (Nauen et al. 2002), Bio Type Q would spread easily and counter-plan is needed.. Market size of agrochemical for white fly is assumed to be about 9.6 million US dollars. The market size is smaller than that of aphids or lepidopterous pests, but the market would increase because of suffering and failure in control due to resistance and resurgence problems. As the increase of vegetable consuming, host crop for the white fly is also increasing. As green house cultivation area of host vegetable increases, natural enemies to foreign invading pest like sweet potato white fly are limited. Also it is important that that management of pest and pathogen in green house environment. It is essential to build pest management model and to develop and commercialize agrochemicals according to the critical customer (farmer) requirement.

In 2005, the invasion of Bemisia tabaci Q-type was detected at first in the southern part of Korea. And then the pest has been spread rapidly over the nation, and it has attacked various fruit vegetables including yellow melon, tomato, sweet pepper, and so on. During three years since 2005, many kinds of predators and parasitoids have been applied to establish the biological control program to solve the Bemisia tabaci problem. Parasitoids were regarded as promising natural enemies, at first. However, Encarsia formosa famous for the parasitoid of greenhouse whitefly is not so effective to control Bemisia tabaci. Although other parasitoids, Eretmocerus eremicus and Eretmocerus mundus, were introduced successively, application results of them were not satisfactory. Owing to the difficulties in settling the parasitoids on crops, total cost of biological control program tends to be increased by the iterative periodic release. On the other hand, it was great that the application result of predatory mite, Amblyseius swirskii. Laboratory experiments show that the mite can consume large amount of Bemisia tabaci eggs. In addition, the mite can survive and reproduce without prey. Plant-associated materials such as pollens are sufficient for the development and reproduction of the mite. Field observations reveal that just onetime release after the first blossom is enough for the preventive treatment. The mite is especially so effective on the pollen-rich crops such as sweet pepper. Flowers and leaves are infested by the mite in a brief instant. While flower-dwelling mites take a role of natural enemy of thrips, leaf-dwelling mites effectively suppress the density of Bemisia tabaci. Anyway, curative treatment of the mite is not desirable, for it usually do not feed on other stage of Bemisia tabaci except fresh eggs within one or two days. It is also unfortunate that the mite seldom moves on tomato. It is even reluctant to go out from distribution box. When we put some mites on a leaf of tomato, they usually aggregated in a point. Sticky trichomes and semiochemicals might be engaged in such phenomena. In addition, the mite seems to be suffered by high temperature. So the density of Bemisia tabaci could be increased continuously in summer season, regardless of the presence of the predatory mite. In recent, we keep an eye on another predatory bug, Nesidiocoris tenuis, as a biological control agent against whiteflies on tomato. Nesidiocoris tenuis is an active and aggressive natural enemy. It likes to eat whitefly eggs, larvae and pupae. It can also feeds on aphids and mites. Once established in tomato greenhouse, whiteflies were overwhelmed by the predator. In our observation, Bemisia tabaci could be successfully controlled by the predator without any pesticide application, during about a half year from early spring to mid summer. However, we should take precaution against the side effects of Nesidiocoris tenuis, which is ironically known as a serious pest on tomato. From time to time, growing points of tomato could be disappeared by the damage of Nesidiocoris tenuis. So we need to control the density of the bug under the economic threshold. Owing to the bug, the production of sesame could be decreased remarkably. To avoid side effects, Nesidiocoris tenuis should be handled by the experts who know well about the ecological characteristics of it. In the case of yellow melon, biological control of any pest is not easy task. Without pesticide, yellow melon is frequently damaged destructively by aphids, mites and whiteflies. However, the temperature in greenhouse is too high to release and augment ordinary natural enemies. We just regard Nesidiocoris tenuis as a promising natural enemy of whiteflies on yellow melon, because it is resistant to high temperature. Many trials and errors might be required to establish reliable strategy to solve the problem caused by Bemisia tabaci. And it should be continued that the efforts for the integrated pest management based on biological control.

Identifying effective chemical control agents of Bemisia tabaci biotype B and Q is an important step toward IPM strategy. Until 2008, only 10 chemical agents were registered for B. tabaci. From the laboratory screening of 60 insect- and acaricides, 18 chemicals for egg, 10 for nymph and 8 for adult stage were found effective (>90% mortality). Also ten chemicals were less toxic to B. tabaci. Among ten chemicals, some conventional insecticides need further careful resistance monitoring. Field trials with some of the selected chemicals open the possibility to chemical control of B. tabaci biotype Q. Further consideration of non-target effects and resistance development has to be exerted before registration process.

To establish a rapid diagnosis method for the monitoring of acaricide resistance in the two-spotted spider mite, Tetranychus urticae, we evaluated the performance of residual contact vial (RCV) method as a routine bioassay for T. urticae by using two widely used acaricides, abamectin and tebupenpyrad. Appropriate concentrations of test acaricides were dissolved in acetone and evenly coated (100 μl) onto the inside wall of a 4-ml glass vial using a rolling machine. The average survival times in untreated control vial was longer than 12 hrs in the absence of food or water regardless of cap being closed or open. Webbing behavior of mites inside the vial, which may interfere with maximum chemical contact, began to be observed from 8 hrs post treatment. The minimum concentrations causing 100% mortality within 8 hrs posttreatment in a susceptible strain of T. urticae were determined to be 30 and 60 ppm in abamectin and tebupenpyrad, respectively. Dose-response curve was significantly affected by temperature in both acaricides, in which the knockdown rate increased greatly as temperature increased. The endpoint mortality at 6-8 hrs posttreatment, however, was not significantly affected by temperature. Nymphal stage of mites showed more rapid intoxication response than adults but endpoint mortality at 6-8 hrs posttreatment was not substantially different between developmental stages. When compared with the results from conventional spray method, RCV method showed moderate to high correlation coefficients (r=0.51~0.98), suggesting that it is a reliable in determining susceptibility of T. urticae. The vial-coated pesticides were stable at least one year when stored at -20°C as determined by LC-MS/MS analysis. Moreover, there was no significant difference in the bioassay results in repeated experiments with three different persons, indicative of high reproducibility of RCV. The RCV diagnostic kit, when used by farmers on site, should provide crucial and essential information for the selection of most suitable acaricides for different field populations of T. urticae.

Oriental persimmon, Diospyros kaki Thunb., endemic to East Asia is one of the major fruit crops in Korea. We conducted the faunal survey of mites on persimmon trees in Korea from June to September 2006, especially focusing on herbivorous and predacious mites. Mites of Tetranychidae and Tenuipalpidae were dominantly collected as herbivores, while those of Phytoseiidae and Stigmaeidae were predominant as predators. All identified tenuipalpid mites were Tenuipalpus zhizhilashviliae Reck. Most of the collected tetranychid mites were found to belong to the genus Tetranychus. To clarify the species identity, additional collections of tetraychid mites during summer 2007 on sweet persimmon were made. The mites were identified as Tetranychus urticae Koch. Four phytoseiid species, Neoseiulus womersleyi (Schicha), Amblyseius eharai Amitai and Swirski, Phytoseius (Dubininellus) rubii Xin, Liang and Ke and Typhlodromus (Anthoseius) vulgaris Ehara were collected. Among them, A. eharai was the most dominant species. Seventeen populations of two spotted mites (TSM) were observed 3 times per month from May to October to figure out their fluctuations at the site of individual farmer’s orchard from Sacheon, Sancheong, and Jinju in Gyeongsangnam- do and Gwangyang, Gurye, and Suncheon in Jeollanam-do. Among them, only 2 sites were properly managed, 5 sites were required to control but the farmers had little information on the mite and its damage, though 10 orchards were not in jeopardy. Number of TSM reached more than 400 at its maximum when 100 leaves were randomly observed at orchards from Sacheon, Okgok, and Muncheok, showing remarkably discolored leaves. For the control of TSM in fields by chemical means, it was tried to select an effective miticides in persimmon fields. Control activity of spiromesifen 20SC showed 99.0% and 98.1% and the activity of acequinocyl 15SC showed 90.8% and 99.0% in Jinju and Sacheon at 20 days after treatment, respectively. It was tried to understand the cause of the fluctuations of TSM populations on the viewpoints of pesticide spray, density of predacious mites, rainfalls, and weeds in the persimmon orchards. Various factors considered to contribute to the cause of population fluctuations, depending upon the situations of each orchard. To develop as a potential resource of biological control agents, it was tried to find out winter spatial distribution and movement of Amblyseius eharai (Acari: Phytoseiidae) on persimmon trees in Korea using artificial materials. We attached Phyto traps and urethane foam on persimmon trees in early November 2007 in Sacheon, Korea to estimate overwintering ecology of the predominant phytoseiid species Amblyseius eharai on persimmon. Most of A. eharai were found on the samples of branches, such as pedicel. In early spring, A. eharai was abundantly collected in the weekly and long-term traps before the leaf extension of persimmon trees, which additionally enhanced the possibility that A. eharai overwintered on the trees.

Tetranychus evansi Baker & Pritchard occurs on solanaceous plants, and causes serious damage to a variety of crops in Africa and Europe; it has not been reported from Japan. Tetranychus takafujii Ehara & Ohashi was found on Solanum nigrum L. in Japan in 2001 and described as a new species in 2002. It is considered to be a Solanaceae-specialist too and it is feared to become a severe pest on solanaceous crops, once it invades them. Because T. takafujii is morphologically very similar to T. evansi, doubt has arisen about the difference between these two species. Here we avoid the issue of taxonomy and focus on a solution for the potential problems that may arise when either of the species invades solanaceous crops. The present study determines the susceptibility of three T. takafujii populations from Japan and six T. evansi populations from various countries to 11 acaricides. The LC50-values of all nine populations tested were lower than the recommended concentration of every acaricide. These results suggest that mites from all nine populations can be controlled with acaricides when they occur on crops.

Tetranychus evansi Baker & Pritchard occurs on solanaceous plants, and causes serious damage to various crops in Africa and Europe. Tetranychus takafujii Ehara & Ohashi was found on Solanum nigrum L. in Japan in 2001 and described as a new species in 2002. However, because T. takafujii is very similar to T. evansi in morphology, doubt has arisen about the difference between these two species, although there is no report discussing their taxonomic status. Tetranychus takafujii is specialized on solanaceous plants and it is possible that this species gets out of hand after invasion of solanaceous agricultural crops. To evaluate its potential severity as a pest, it is necessary to assess its performance on a variety of food plants in a carefully controlled laboratory set-up. The present study determined the development on 21 crops and weeds, and the reproduction on Solanum nigrum of a Japanese T. takafujii population and six T. evansi populations from abroad. Four plants (potato, horsenettle, pear and cucumber) served as host plant for all seven populations and most larvae successfully reached adulthood. Life-history parameters, such as the rate of development and the intrinsic rate of natural increase (rm), became higher with temperature increasing from 15 to 35°C. The rm-value at 25°C was similar among all populations tested and it was close to the value obtained in T. takafujii [Kotsubo et al. (2004) J. Acarol. Soc. Jpn. 13: 71-76]. This indicates that T. takafujii has the potential to become a serious pest on solanaceous crops, just the same as T. evansi in Africa and Europe.

Temperature is an important inorganic factor which affects on every aspect in life of phytoseiid mites in general including N. californicus in this study. Cumulative and short-term effects of temperature through different life stages (immature, mating and oviposition periods) on mating duration and total fecundity of N. californicus were investigated at temperatures of 18, 25, 30 and 350C with a photoperiod of 16L:8D. Throughout experiments, females mated once and egg production was observed until they stop oviposition.

Effects of starving treatment on the gravid females of N. californicus were investigated at 20°C and 85% RH. When the females were reared without prey and water just after they laid the first egg under the abundant prey condition, they laid 1.8 eggs and survived for 4.3 d. In order to investigate the process of oogenesis in the body of the starved females, females just after laying the first egg were reared for 0, 12, 24, 36, 48, 72, and 96 hr without prey and water, and were then prepared for internal observation. In the body of females of 0hrstarvation, an egg with eggshell and two oocytes were observed in the ventral and dorsal regions, respectively. Larger oocyte had 2 roundish nuclei and abundant yolk granules, and was enveloped with vitelline membrane. These 2 nuclei were not fused but were just conjugated. Smaller oocyte had a nucleus, but did not form yolk granules and vitelline membrane. Females of 12hrstarvation had an egg in the ventral region and an oocyte in the dorsal region of the body. Females of 24hr-starvation maintained an oocyte in the dorsal region of the body, but did not have an egg in the ventral region. The oocyte was filled with abundant yolk granules, and held 2 irregular-shaped nuclei. Females starved more than 36hr also maintained only an oocyte in the dorsal region of the body. Only an irregular-shaped nucleus was observed in the oocyte. These micrographs suggested that (1) gravid females maintained an oocyte in the dorsal region after laying 2 eggs during starving treatment, (2) the oocyte was not absorbed during starvation, (3) the oocyte advanced vitellogenesis and the fusion of 2 nuclei, and (4) the oocyte was not enveloped with eggshell and did not start embryogenesis. It is also assumed that the sperm penetrated into the oocyte without yolk granules, although the penetration was not observed in this study.

There are many related studies; however, almost all of them focus on higher taxonomic tendencies, ignoring a difference in the reaction for each species. In this study, we measured relative basal area (RBA) as the index for invasion of broad-leaved trees into eight Larch plantations, and investigated the relationship between RBA and composition and abundance of oribatid mites community. As a result, we found 49 families, 60genus, 89 species, 24,368 adult and larvae and nymphs, 56,364. The degree of invasion of broad-leaved trees did not affect significantly total abundance and number of species for oribatid mites observed. While, those measurements significantly correlated with the total amount of litter, including conifer and broad-leaves. We also found that there are many oribatid mite species showing habitat preference relating to a kind of litter.

Fine structures on a plant leaf, such as trichomes or leaf domatia, are considered to affect plant mite community. However, so far, few empirical studies has determined mite fauna and its seasonal dynamics on plants bearing such fine structures on leaf surface. Viburnum erosum var. punctatum is a deciduous shrub, which has dense stellate hairs and hair tufts (domatia) on the abaxial surface of leaf. In this study, to determine the effects of such structures on fauna of leaf mites, we investigated seasonal dynamics of leaf mites on V. erosum in comparison with those on the other 13 tree or shrub species in secondary forests in Kyoto, the central part of Japan. Some mites remained on V. erosum leaves all over the season, with the density of all mite species reaching the maximum, 39.5 individuals per leaf, in June. The density on V. erosum was 10 times higher than on the other target plant species. Phytoseiid mites belonging to Phytoseius stably occurred for most seasons, from May to October, and the density reached the maximum, 2.2 individuals per leaf, in July. Mites of Tydeoidea and Astigmata were frequently observed in the leaf domatia of V. erosum, whereas they were rarely observed on the other plant species. These results indicate that V. erosum harbor more unique and more abundant mite community on its leaf surface, compared to its sympatric tree and shrub species.

In the preceding symposium, we presented the result of the phylogenetic analysis of Stigmaeopsis spider mites (Acari: Tetranychidae) in Japan using sequence data of the Cytochrome Oxidase subunit I (COI) region of mitochondria DNA. We analyzed haplotypes representing S. longus, S. celarius, S. takahashii and S. saharai, which inhabit bamboo species of the genera Sasa and Phyllostachys (Poaceae; Bambusoideae), and two forms of S. miscanthi (HG and LW) living on Miscanthus sinensis (Poaceae; Panicoideae). Both neighborjoining and maximum-likelihood methods revealed that Stigmaeopsis consists of seven monophyletic groups, in which two forms of S. miscanthi form two distinct monophyletic groups, whereas four species of bamboo-inhabiting species comprise a polyphyletic assembly. These results imply a mismatch between diagnostic morphological characters (i.e. the length of dorsal setae) and their phylogenetic lineages for bamboo-inhabiting species, requiring re-evaluation of the use of these characters. In addition, our results indicate that plural lineages coexist in a single habitat at various regions, suggesting that differentiated lineages secondarily encounter around southwestern Japan. Interestingly, the result of phylogenetic analysis on mitochondrial COI and nuclear ITS1 region was, in part, inconsistent in internal branches. In this symposium, I re-analyzed more these data by phylogenetic network analysis. Based on the results, I make some inference about the process of habitat expansion of these mites.

Halacarid mites inhabit mainly in the bottom of the sea and their body lengths are approximately 0.5 mm. Few biological information about halacarids have been obtained. The phylogenetic study of halacarid mites has not been progressed and the phylogenetic relationship within the family Halacaridae is still unknown. Particularly there is no molecular study to infer phylogenetic relationship within the family. In the annual meeting of Acarological Society of Japan 2007, we developed the method for molecular analysis of 28S nuclear ribosomal gene in haracarid mites. Subsequently, we have further progressed the technique of the molecular analysis to infer the phylogenetic relationship of haracarids. The aim of the present study is to elucidate the phylogenetic position of the subfamily Rhombognathinae on the bases of molecular data. Halacarid specimens which were obtained from seaweeds and sandy segment at Japanese seacoasts, consist of eight genera in five subfamilies: Halacarinae (Halacarus sp., Agauopsis spp., Thalassarachna spp.), Halixodinae (Badyagaue sp., Agaue sp.), Copidgnathinae (Copidognathus spp.), Actacarinae (Actacarus spp.) and Rhombognathinae (Rhombognathus spp.). The template DNA was extracted and 28S nuclear ribosomal gene of the DNA was amplified by PCR reactions. And we determined approximately 400 base pair length of the gene. To construct phylogenetic trees by neighbor-joining method we calculated genetic distances of each operational taxonomic unit considering 1) transversions and 2) transitions and transversions based on Tamura - Nei model by using MEGA ver. 4 (Tamura et al. 2007). As a result, we got two trees both showing two main clusters. One of them includes only one subfamily Rhombognathinae and another consist of Halacarinae, Copidgnathnae, Actacarinae and Halixodinae. Rhombognathinae was greatly differentiated from the other subfamilies. Thus, Rhombognathinae possibly is a distinct taxon phylogenetically and this result supports the monophyletic nature obtained previously by morphological analysis.