Permethrin resistance variation and susceptible reference line isolation in a field population of the mosquito,Culex quinquefasciatus （Diptera： Culicidae）

This study examines the genetic variations and mechanisms involved in the development of permethrin resistance in individual mosquitoes from a field population of Culex quinquefasciatus, HAmCq^G0, and characterizes susceptible reference lines of mosquitoes with a similar genetic background to the field HAmCq^G0 strain. Six upregulated cytochrome P450 genes, CYP9M10, CYP9J34, CYP6P14, CYP9J40, CYP6AA7, and CYP4C52v1, previously identified as being upregulated in the larvae of resistant HAmCq68 mosquitoes were examined in the larvae of 3 strains （susceptible S-Lab, parental HAmCq^G0 and permethrin-selected highly resistant HAmCq68） and 8 HAmCq^G0 single- egg raft colonies, covering a range of levels of susceptibility/resistance to perrnethrin and exhibiting different variations in the expression of A and/or T alleles at the L-to-F kdr locus of the sodium channel. The 2 lines with the lowest tolerance to permethrin and bearing solely the susceptible A allele at the L-to-F kdr locus of the sodium channels, from colonies Cx_SERC5 and Cx_SERC8, showed lower or similar levels of all 6 of the P450 genes tested compared with the S-Lab strain, suggesting that these 2 lines could be used as the reference mosquitoes in future studies characterizing insecticide resistance in HAmCq mosquitoes. This study also provides a detailed investigation of the mechanisms involved in insecticide resistance in individuals within a population： individuals with elevated levels of resistance to permethrin all displayed one or more potential resistance mechanisms-either elevated levels of P450 gene expression, or L-to-F mutations in the sodium channel, or both.     

The mitochondrial genome of the plant bug Apolygus lucorum （Hemiptera： Miridae）＂ Presently known as the smallest in Heteroptera

The complete mitochondrial （mt） genome of the plant bug, Apolygus lucorum, an important cotton pest, has been sequenced and annotated in this study. The entire circular genome is 14 768 bp in size and represents the smallest in presently known heteropteran mt genomes. The mt genome is encoding for two ribosomal RNA （rRNA） genes, 22 transfer RNA （tRNA） genes, 13 protein coding genes and a control region, and the order, content, codon usage and base organization show similarity to a great extent to the hypothetical ancestral model. All protein coding genes use standard initiation codons ATN. Conventional stop codons TAA and TAG have been assigned to the most protein coding genes; however, COIII, ND4 and ND5 genes show incomplete terminator signal （T）. All tRNA genes possess the typical clover leaf structure, but the dihydrouridine arm of tRNAser（A6N） only forms a simple loop. Secondary structure models of rRNA genes are generally in accordance with the former models, although some differences exist in certain parts. Three intergenic spacers have never been found in sequenced mt genomes of Heteroptera. The phylogenetic study based on protein coding genes is largely congruent with previous phylogenetic work. Both Bayesian inference and maximum likelihood analyses highly support the sister relationship ofA. lucorum and Lygus lineolaris, and Miridae presents a sister position to Anthocoridae.     

Accumulation of cadmium and its effects on growth, development and hemolymph biochemical compositions in Boettcherisca peregrina larvae （Diptera： Sarcophagidae）

Newly emerged larvae of the fleshfly, Boettcherisca peregrina were exposed to two different CdCl2 concentrations of 100μg/g and 400 mg/g diet fresh weight （DFW）. They were administered in the diets until the end of larval stage. Cd-exposed larvae accumulated significant amounts of Cd and this accumulation increased with the exposure dose and time. The body weights were lightened and lengths of larvae were shortened considerably after Cd exposure, especially at the higher Cd concentration. The total larval duration was also extremely affected due to Cd exposure. The average duration was prolonged significantly by 14 h at the lower Cd concentration, while it was increased by 33.7 h over controls at the higher Cd concentration. A significant decrease in contents of either soluble proteins, total lipids or caloric values in the hemolymph occurred due to Cd exposure throughout the entire tested period but after 120 h of Cd exposure. In contrast, when exposed to Cd with its higher concentration, total sugar contents in the hemolymph were increased strikingly over the whole tested time, except after 96 h of Cd exposure, while they were not apparently altered except after 24 h of Cd exposure at the lower concentration. Thus, it is suggested that Cd exposure shows significant adverse impact on the growth and development, as well as metabolism, in larvae of this fleshfly, depending on its exposure time and dose.     

Detection of food source by PCR analysis of the gut contents of Aldrichina grahami （Aldrich） （Diptera： Calliphoridae） during post-feeding period

The last meal of sarcophagous maggots may be useful in identifying the species on whose flesh they have fed （the＂host＂species）. The DNA profile of the host species may indeed be detectable in the＂last meal＂. In this paper, mitochondrial DNA analysis of gut contents was used to identify the prior host of post-feeding larvae of Aldrichina grahami （Aldrich） （Diptera： Calliphoridae）. A modified logistic equation was fitted to estimate the probability of identifying the host under five different constant temperatures （16, 20, 24, 28 and 32 ℃）. Our results shows that the detected time ranged from a maximum of 24 h at 32℃ to 42 h at 16℃ and a minimum of 12 h at 32~C to 30 h at 16℃. Furthermore, the host detection time was also calculated to give the maximal time after larval hatching from the egg. These results indicate that, in criminal cases where the maggots stray from the corpse, the last meal of the larvae should not be overlooked as potentially critical evidence.     

Influence of rice black streaked dwarf virus on the ecological fitness of non-vector planthopper Nilaparvata lugens （Hemiptera： Delphacidae）

Rice black streak dwarf virus （RBSDV） is transmitted by the small brown planthopper （SBPH）, Laodelphax striatellus （Fallen）. Non-vector rice brown planthopper （BPH）, Nilaparvata lugens （Stal）, shares the same host rice plants with SBPH in paddy fields. The changes in nutritional composition of rice plants infected by RBSDV and the ecological fitness of BPH feeding on the infected plants were studied under both artificial climate chamber and field conditions. Contents of 16 detected amino acids and soluble sugar in RBSDV infected rice plants were higher than those in the healthy ones. On the diseased plants BPH had significantly higher nymphal survival rates, nymphal duration of the males, weight of the female adults, as well as egg hatchability compared to BPH being fed on healthy plants. However, there was no obvious difference in female nymph duration, longevity and fecundity. Defense enzymes （superoxidase dismutase, SOD and catalase, CAT） and detoxifying enzymes （carboxylesterase, CAE and glutathione S-transferase, GST） in BPH adults fed on diseased plants had markedly higher activities. The results indicate rice plants infected by RBSDV improved the ecological fitness of the brown planthopper, a serious pest but not a transmitter of the RBSDV virus.     

Development of setal patterns in embryonic and adult aphids of the Hormaphidinae （Hemiptera： Aphididae）

The elementary traits and diversity of embryonic setal patterns of 31 species of 22 genera, in three tribes of Hormaphidinae are studied. The embryonic setal patterns to every species are provided. Based on the parsimony principle and the developmental principle, these patterns are analyzed in each tribe following the terminology of Richards （1965）. It is suggested that the setal patterns of abdominal tergites are the most important characters in embryonic and adult setal patterns. In conclusion, neoteny is a phylogenetic trend in the Hormaphidinae. Nipponaphidini and Hormaphidini have more typical neoteny in each genus and more diversity in different types of adult viviparous females than Cerataphidini, by showing more frequent and various protopatterns or mesopatterns.     

Biological and biochemical characterization of a red-eye mutant in Nilaparvata lugens （Hemiptera： Delphacidae）

A red-eye colony was established in our laboratory in brown planthopper （BPH）, Nilaparvata lugens （Stal）, a major rice pest in Asia. Except for the red-eye phenotype, no other differences were observed between the wild-type （brown eye） and the mutant-type （red eye） in external characters. Genetic analysis revealed that the red-eye phenotype was controlled by a single autosomal recessive allele. Biological studies found that egg produc- tion and egg viability in the red-eye mutant colony were not significantly different from those in the wild-type BPH. Biochemical analysis and electronic microscopy examination revealed that the red-eye mutants contained decreased levels of both xanthommatin （brown） and pteridine （red） and reduced number of pigment granules. Thus, the changes of amount and ratio of the two pigments is the biochemical basis of this red-eye mutation. Our results indicate that the red-eye mutant gene （red） might be involved in one common gene locus shared by the two pigments in pigment transportation, pigment granule formation or some other processes.     

Role of venom and ovarian proteins in immune suppression of Ostrinia furnacalis （Lepidoptera： Pyralidae） larvae parasitized by Macrocentrus cingulum （Hymenoptera： Braconidae）, a polyembryonic parasitoid

Venom and ovarian proteins in braconid and ichneumonid wasps play an important role in the successful parasitism of their host, especially for immune suppression immediately after oviposition. In this study, we compared the effect of venom and ovarian proteins collected from the female wasps of Macrocentrus cingulum, a polyembryonic parasitoid of the larvae of Ostriniafunacalis, on the encapsulation capacity of Sephadex A- 25 beads at 4 h and 24 h post-injection both in vivo and in vitro. The results showed that the ovarian proteins significantly interfered with the encapsulation capacity of hemocytes in a dose-dependent manner. Spreading and viability of hemocytes in O. furnacalis was not disrupted by venom and ovarian proteins at various concentrations injected. It seems likely that the ovarian proteins from M. cingulum play a role in suppressing the encapsulation capacity of host hemocytes.     

Evaluations of larvicidal activity of medicinal plant extracts to Aedes aegypti （Diptera： Culicidae） and other effects on a non target fish

A preliminary study was conducted to investigate the effects of the extracts of 112 medicinal plant species, collected from the southern part of Thailand, on Aedes aegypti. Studies on larvicidal properties of plant extracts against the fourth instar larvae revealed that extracts of 14 species showed evidence of larvicidal activity. Eight out of the 14 plant species showed 100% mosquito larvae mortality. The LC50 values were less than 100μg/mL （4.1μg/ mL-89.4μg/mL）. Six plant species were comparatively more effective against the fourth instar larvae at very low concentrations. These extracts demonstrated no or very low toxicity to guppy fish （Poecilia reticulata）, which was selected to represent most common non-target organism found in habitats ofAe. aegypti, at concentrations active to mosquito larvae. Three medicinal plants with promising larvicidal activity, having LC50 and LC50 values being 4.1 and 16.4 μg/mL for Mammea siamensis, 20.2 and 34.7 μg/mL forAnethum graveolens and 67.4 and 110.3μg/mL forAnnona muricata, respectively, were used to study the impact of the extracts on the life cycle ofAe. aegypti. These plants affected pupal and adult mortality and also affected the reproductive potential of surviving adults by reducing the number of eggs laid and the percentage of egg hatchability. When each larval stage was treated with successive extracts at the LC50 value, the first instar larvae were found to be very susceptible to A. muricata and the second instar larvae were found to be susceptible to A. graveolens, while the third and fourth instar larvae were found to be susceptible to M. siamensis. These extracts delayed larval development and inhibited adult emergence and had no adverse effects on P. reticulata at LC50 and LC50 values, except for the M. siamensis extract at its LC50 value.     

Centers of endemism and diversity patterns for typhlocybine leafhoppers （Hemiptera： Cicadellidae： Typhlocybinae） in China

This study identifies ＇centers of endemism＇ for typhlocybine leafhoppers in China, revealing diversity patterns and congruence of patterns between total species rich- ness and endemism. Distribution patterns of 774 Typhlocybinae （607 described and 167 undescribed species） were mapped on a 1.5° × 1.5° latitude/longitude grid. Total species richness, endemic species richness and weighted endemism richness were calculated for each grid cell. Grid cells within the top 5% highest values of weighted endemism richness were considered as ＇centers of endemism＇. Diversity patterns by latitude and altitude were obtained through calculating the gradient richness. A congruence of diversity patterns between total species richness and endemism was confirmed using correlation analysis. To investigate the bioclimatic factors （19 variables） contributing to the congruence be- tween total species richness and endemism, we compared the factor＇s difference between non-endemic and endemic species using the Kruskal-Wallis test. Eleven centers of en- demism, roughly delineated by mountain ranges, were identified in central and southern China, including the south Yunnan, Hengduan Mountains, Qinling Mountains, Hainan Is- land, Taiwan Island and six mountain areas located in western Sichuan, northwest Fujian, southeast Guizhou, southeast Hunan, central and western Guangdong, and north Zhejiang. Total species richness and endemic species richness decreased with increased latitude and had a consistent unimodal response to altitude. The proportions of endemism decreased with increased latitude and increased with rising altitude. Diversity patterns between total species richness and endemism were highly consistent, and ＇Precipitation of Coldest Pe- riod＇ and ＇Temperature of Coldest Period＇ may contribute to the congruence of pattern. Migration ability may play a role in the relationship of endemism and species richness; climate, environment factors and important geologic isolation events can also play crucial effect     

Evolutionary relationships of Pemphigus and allied genera （Hemiptera： Aphididae： Eriosomatinae） and their primary endosymbiont,Buchnera aphidicola

Aphids harbor primary endosymbionts, Buchnera aphidicola, in specialized cells within their body cavities. Aphids and Buchnera have strict mutualistic relationships in nutrition exchange. This ancient association has received much attention from researchers who are interested in endosymbiotic evolution. Previous studies have foundparallel phylogenetic relationships between non-galling aphids and Buchnera at lower taxonomic levels （genus, species）. To understand whether relatively isolated habitats such as galls have effect on the parallel relationships between aphids and Buchnera, the present paper investigated the phylogenetic relationships of gall aphids from Pemphigus and allied genera, which induce pseudo-galls or galls on Populus spp. （poplar） and Buchnera. The molecular phylogenies inferred from three aphid genes （COI, COII and EF-la） andtwo Buchnera genes （gnd, 16S rRNA gene） indicated significant congruence between aphids and Buchnera at generic as well as interspecific levels. Interestingly, both aphid andBuchnera phylogenies supported three main clades corresponding to the galling locations of aphids, namely leaf, the joint of leaf blade and petiole, and branch of the host plant.The results suggest phylogenetic conservatism of gall characters, which indicates gall characters are more strongly affected by aphid phylogeny, rather than host plants.     

Life history and life table analysis of the whitefly predator Delphastus catalinae （Coleoptera： Coccinellidae） on collards

Abstract The ladybeetle, Delphastus catalinae (Horn), is one of the most commonly used predacious natural enemies being commercially reared for controlling whiteflies, including Bemisia tabaci (Gennadius) biotype B (= B. argentifolii Bellows & Perring), on various ornamental and vegetable crops under greenhouse conditions. The development, survivorship, and fecundity of D. catalinae feeding on B. tabaci biotype B on collard plants were determined in the laboratory, and the age-specific life table parameters were analyzed based on the life history data. Developmental time was 4.0, 1.9, 1.1, 1.4, 5.2, and 5.3 days for eggs, first, second, third, fourth instars, and pupae, respectively, with an average of 18.9 days from oviposition to adult emergence for both sexes, 19.0 days for females, and 18.8 days for males. Adult longevities averaged 146.6 days for both sexes, 122.6 days for females, and 170.5 days for males. After an average 4.9 days preoviposition period, females laid a mean of 5.6 eggs per day over a 97.0-day period. Net reproductive rate ( R ₀) and gross reproductive rate (ΣM m_x ) were estimated by life table analysis at 276.8 and 325.1, respectively. Generation time (T) and doubling time (DT) were 35.6 and 4.8 days respectively, and the intrinsic rate of natural population increase ( r_m ) was estimated at 0.158, or l = 1.171 for the finite rate of increase. The r_m value of D. catalinae is similar to or higher than those of the whitefly feeding on most vegetable and ornamental crops, indicating that the ladybeetle is capable of regulating populations of B. tabaci biotype B and other whiteflies under greenhouse conditions.     

Foliar persistence and residual activity of methoxyfenozide against beet armyworm （Lepidoptera： Noctuidae）

A greenhouse study was conducted to investigate the persistence of methoxyfenozide in pepper （Capsicum annuum L.） foliage. An aqueous suspension of methoxyfenozide was sprayed on pepper plants at concentrations of 72 and 144 mg of active ingredient （a.i.）/L. Foliage was collected at different intervals of time （0, 3, 5, 10, 20, 30, 40, and 50 days） after the treatment, and the methoxyfenozide residue was measured by high-performance liquid chromatography. The foliage was also used in bioas- says to determine the residual toxicity on and the consumption rate of the third-instar larvae of the beet armyworm, Spodoptera exigua （Htibner） （Lepidoptera： Noctuidae）. The methoxyfenozide concentrations observed after 50 days had decreased to 19 and 69μg/g per sample, corresponding to a loss of 61% and 28% from the application concentrations of 72 and 144 mg a.i./L, respectively. When fitting a first-order kinetics degradation model, the half-life （DT50） of this compound was 76 days. Both application concentrations of methoxyfenozide caused a high mortality rate （〉97%） when the larvae were fed the pepper foliage collected at all of the time intervals. Lastly, at all of the time points, the consumption rate by the larvae was reduced to between 57% and 92% for both concentrations that were bioassayed. Our results indicate that, under the present greenhouse conditions, the degradation of methoxyfenozide was slower than that reported by other authors and that its residues were highly toxic to S. exigua larvae. The implications of these results for the management programs of this pest are discussed.     

The current and future potential geographic range of West Indian fruit fly,Anastrepha obliqua （Diptera： Tephritidae）

The West Indian fruit fly, Anastrepha obliqua （Macquart）, is one of the most important pests throughout the Americas. CLIMEX 3.0 and ArcGIS 9.3 were used to model the current and future potential geographical distribution of this pest. Under current climatic conditions, A. obliqua is predicted to be able to establish throughout much of the tropics and subtropics, including not only North and South America, where it has been reported, but also southern Asia, northeastern Australia and Sub-Saharan Africa. The main factors limiting the pest＇s range expansion may be cold stress. Climate change expands the potential distribution of A. obliqua poleward as cold stress boundaries recede, but the predicted distribution in northwestern Australia and northern parts of Sub-Saharan Africa will decrease because of heat stress. Considering the widely suitable range for A. obliqua globally and in China, enhanced quarantine and monitoring measures should be implemented in areas that are projected to be suitable for the establishment of the pest under current and future climatic conditions.     

Phylogenetic analysis of Toxicodendron （Anacardiaceae） and its biogeographic implications on the evolution of north temperate and tropical intercontinental disjunctions

Toxicodendron is a genus in the Rhus complex of Anacardiaceae with a disjunct distribution between eastern Asia and North America, extending to southeastern Asia and the neotropics. Nuclear （internal transcribed spacer, external transcribed spacer, and NIA-i3） and chloroplast （ndhF and trnL-F） sequences were used to construct phylogenetic relationships of Toxicodendron. Phylogenetic analysis of these data strongly support Toxieodendron as a monophyletic group distinct from other genera of the Rhus complex, and the phylogeny does not fully corroborate classification at the sectional level. Two temperate disjunct lineages were detected, one from section Toxicodendron and the other between the eastern North American Toxicodendron vernix and the eastern Asian Toxicodendron vernieifluum. Their divergence times were estimated to be 13.46 （7.95-19.42） and 7.53 （2.76-12.86） mya, respectively. The disjunction between section Griffithii （taxa from warm temperate to tropical Asia） and Toxieodendron striatum （from the neotropics） was supported and their divergence time was estimated to be 20.84 （11.1 6-30.52） mya in the early Miocene. Our biogeographic results and the paleontological data support the Bering land bridge as the most likely route to explain the temperate disjunctions, yet the tropical disjunction in Toxicodendron seems to be best explained by the North Atlantic land bridge hypothesis.     

Effects of photoperiod and temperature on diapause induction in Conogethes punctiferalis （Lepidoptera： Pyralidae）

The yellow peach moth, Conogethes punctiferalis （Guenee）, a multivoltine species that overwinters as diapausing larvae, is one of the most serious insect pests on maize in China. Effect of photoperiod and temperature on larval diapause was examined under empirical laboratory conditions. Short-day treatments caused larval diapause at 25℃, and the critical photoperiod was between 12 and 13 h （or 12 h 51 min） light per day. No sensitive instar was identified for diapause induction under alternated short- （L ： D 11 ： 13 h） and long-day （L ： D 14 ： 10 h） treatments at different larval stages. However, accumulative treatment of three instars and 10 d under short-day treatment was required for the induction of 50% larval diapause. All larvae entered diapause at 20℃, whereas less than 3% did so at 30℃, irrespective of the long- or short-day treatment. Furthermore, under the short-day treatment, more than 90% of larvae went into diapause with temperatures ≤ 25℃, but less than 17% did so at 28℃. In contrast, under the long-day treatment, less than 19% of larvae went into diapause with temperatures ≥23 ℃. The forward shift （5℃） of critical temperature under the long-day regime demonstrated the compensatory effect of temperature and photoperiod on diapause induction. In conclusion, C. punctiferalis had a temperature-dependent type Ⅰ photoperiodic diapause response; there was no sensitive instar for diapause determination, but the photoperiodic accumulation time countermeasures both of the short-day cycles and the number ofinstars exposed, and the photoperiodic diapause response, was a temperature-compensated phenomenon.     

Description of a New Species of the Genus Brachytarsophrys Tian and Hu, 1983 （Amphibia： Anura： Megophryidae） from Southern China Based on Molecular and Morphological Data

A new species, Brachytarsophrys popei sp. nov., is described based on a series of specimens collected from Mount Jinggang, Jiangxi Province, Taoyuandong Nature Reserve, Hunan Province and Nanling Nature Reserve, Guangdong Province, China. The new species can be easily distinguished from other known congeners by morphology, morphometrics and molecular data of the mitochondrial 16S rRNA gene. It is characterized by its relatively small size with 86.2 mm in snout-vent length in adult female and 70.7 mm-83.5 mm in males; vomerine teeth bearing on two markedly elevated ridges, which projecting behind far beyond the posterior level of the choanae, widely separated by a distance nearly 1.5 times length of one; margin of tongue de~ply notched behind; toes about one-third to two-thirds webbed in males, at most one-third webbed in female; the webs extending as a wide fringes along either side of toes; upper eyelid with tubercles, one of which is enlarged and becoming a remarkably prominent, bluntly conical light- yellow horn; black tiny nuptial spines on the dorsal surface of the first finger and second finger base, single vocal sac in males; gravid females bear pure yellowish oocytes; tadpoles with a transverse white stripe on ventral surface and two longitudinal white stripes along the sides of body. The new species represents the fifth known Brachytarsophrys species.     

Addition of Ptyas nigromarginata （Blyth, 1854） （Squamata： Colubridae） to the Snake Fauna of Thailand with Preliminary Remarks on Its Distribution

The first record of Ptyas nigromarginata(Blyth,1854) from Thailand and a new record from China are reported.Literature and internet sources were searched for previous records of this species to establish its geographic and altitudinal distributions in Asia.The distribution in India was adapted to the new state division of the northern part of the country.The results show that the species almost exclusively occurs in hill evergreen and montane forests of the Himalayan foothills and mountain ranges continuous with it,at altitudes of 1000–2300 m above sea level.     

Aphis （Hemiptera： Aphididae） species groups found in the Midwestern United States and their contribution to the phylogenetic knowledge of the genus

A phylogeny of the genus Aphis Linnaeus, 1 758 was built primarily from specimens collected in the Midwest of the United States. A data matrix was constructedwith 68 species and 41 morphological characters with respective character states of alate and apterous viviparous females. Dendrogram topologies of analyses performed usingUPGMA （Unweighted Pair Group Method with Arithmetic Mean）, Maximum Parsimony and Bayesian analysis of Cytochrome Oxidase I, Elongation Factor 1-α and primary endosymbiont Buchnera aphidicola 16S sequences were not congruent. Bayesian analysis strongly supported most terminal nodes of the phylogenetic trees. The phylogeny wasstrongly supported by EFI-α, and analysis of COl and EFI-α molecular data combined with morphological characters. It was not supported by single analysis of COI or Buch-hera aphidicola 16S. Results from the Bayesian phylogeny show 4 main species groups： asclepiadis,fabae, gossypii, and middletonii. Results place Aphis and species of the generaProtaphis Bōrner, 1952, Toxoptera Koch, 1856 and Xerobion Nevsky, 1928 in a monophyletic clade. Morphological characters support this monophyly as well. The phylogenyshows that the monophyletic clade of the North American middletonii species group belong to the genus Protaphis： P. debilicornis （Gillette ＆ Palmer, 1929）, comb. nov., P. echinaceae（Lagos and Voegtlin, 2009）, comb. nov., and P. middletonii （Thomas, 1879）. The genus Toxoptera should be considered a subgenus of Aphis （stat. nov.）. The analysis also indicatesthat the current genus Iowana Frison, 1954 should be considered a subgenus of Aphis （stat. nov.）.     

The integrated use of chemical insecticides and the entomopathogenic nematode,Steinemema carpocapsae （Nematoda： Steinernematidae）, for the control of sweetpotato whitefly,Bemisia tabaci （Hemiptera： Aleyrodidae）

The integration of chemical insecticides and infective juveniles of the entomopathogenic nematode Steinernema carpocapsae （Wesier） （Nematoda： Steinernematidae）, to control second instars of the sweetpotato whitefly, Bemisia tabaci Gennadius （Hemiptera： Aleyrodidae） was investigated. Using a sand bioassay, the effects of direct exposure of S. carpocapsae for 24 h to field rate dilutions of four insecticides （spiromesifen, thiacloprid, imidacloprid and pymetrozine） on infectivity to Galleria mellonella larvae were tested. Although all chemicals tested, except spiromesifen, produced acceptable nematode infectivity rates, they were all significantly less than the water control. The effect of insecticide treatment （dry residues of spiromesifen, thiacloprid and pymetrozine and soil drench of imidacloprid） on the efficacy of the nematode against B. tabaci was also investigated. Nematodes in combination with thiacloprid and spiromesifen gave higher B. tabaci mortality （86.5% and 94.3% respectively） compared to using nematodes alone （75.2%） on tomato plants. There was no significant difference in B. tabaci mortality when using the chemicals imidacloprid, pymetrozine and spiromesifen in conjunction with nematodes compared to using the chemicals alone. However, using thiacloprid in combination with the nematodes produced significantly higher B. tabaci mortality than using the chemical alone. The integration of S. carpocapsae and these chemical agents into current integrated pest management programmes for the control of B. tabaci is discussed.