The whitefly, Bemisia tabaci (Gennadius) is documented as a major pest on soybean. It was reported that whitefly response towards its hosts and their cultivars varies, and is mediated through various host-related factors. Considering the significance of leaf morphological characteristics in influencing the host–whitefly responses, the present investigation was conducted in screen-house conditions to study the prevailing variations in leaf morphological characteristics of soybean genotypes and their role in governing the adult whitefly attractiveness and oviposition preference. In the multiple-choice test, the whitefly population (eggs, nymphs and adults) was found to be lowest in moderately resistant genotypes (SL 1028 and SL 1074) compared to highly susceptible (DS 3105) and susceptible genotypes (SL 688, SL 958 and SL 1113). The foliar trichomes were characterized using scanning electron microscopy and leaf area, leaf lamina thickness and leaf shape data were acquired using standard procedures. To determine the factors involved in the resistance/susceptible responses towards whitefly, Pearson correlation was applied between the morphological characteristics and the whitefly population. The results show that the leaf area, trichome density, trichome length and trichome angle showed a significant positive correlation with the whitefly population, whereas leaf lamina thickness was negatively correlated. Thus, for developing whitefly-resistant germplasm, breeders should choose genotypes having narrow and thick leaves with sparse, short and flat trichomes.

Bemisia tabaci is a complex of species, which is considered the most common and important pest of a wide range of crops belonging to many different botanical families. In Argentina, this species is recognized as a vector of geminiviruses, and Middle East-Asia Minor 1, Mediterranean, New World and New World 2 have been found to coexist in the same area. Landscape elements, like habitat patch area and isolation, define the habitat configuration and have a direct effect on insect populations between and within host patches. In this paper, we analyse the effect of potato patch configuration on the distribution and abundance of B. tabaci. Potato patches were identified using Landsat TM5 and TM7 images, and a supervised classification was performed to quantify the spatial distribution of the patches in the whole study area. Potato patch metrics were estimated using Fragstats 4.4. Generalized linear mixed models were employed to analyse the relationship between whiteflies and landscape configuration, through a multimodel inference approach, finding that B. tabaci abundance and landscape metrics were very variable. After a multimodel selection process, we found that perimeter-to-area ratio and Euclidean distance between patches were the variables that best explained whitefly abundance in potato patches. Implications of these findings are discussed.

The Bemisia tabaci species complex is one of the most important pests of open field and protected cropping globally. Within this complex, one species (Middle East Asia Minor 1, B. tabaci MEAM1, formerly biotype B) has been especially problematic, invading widely and spreading a large variety of plant pathogens, and developing broad spectrum pesticide resistance. Here, we fit a CLIMEX model to the distribution records of B. tabaci MEAM1, using experimental observations to calibrate its temperature responses. In fitting the model, we consider the effects of irrigation and glasshouses in extending its potential range. The validated niche model estimates its potential distribution as being considerably broader than its present known distribution, especially in the Americas, Africa and Asia. The potential distribution of the fitted model encompasses the known distribution of B. tabaci sensu lato, highlighting the magnitude of the threat posed globally by this invasive pest species complex and the viruses it vectors to open field and protected agriculture.

The tomato Mi-1 gene mediates plant resistance to whitefly Bemisia tabaci, nematodes, and aphids. Other genes are also required for this resistance, and a model of interaction between the proteins encoded by these genes was proposed. Microarray analyses were used previously to identify genes involved in plant resistance to pests or pathogens, but scarcely in resistance to insects. In the present work, the GeneChip™ Tomato Genome Array (Affymetrix®) was used to compare the transcriptional profiles of Motelle (bearing Mi-1) and Moneymaker (lacking Mi-1) cultivars, both before and after B. tabaci infestation. Ten transcripts were expressed at least twofold in uninfested Motelle than in Moneymaker, while other eight were expressed half or less. After whitefly infestation, differences between cultivars increased to 14 transcripts expressed more in Motelle than in Moneymaker and 14 transcripts less expressed. Half of these transcripts showed no differential expression before infestation. These results show the baseline differences in the tomato transcriptomic profile associated with the presence or absence of the Mi-1 gene and provide us with valuable information on candidate genes to intervene in either compatible or incompatible tomato–whitefly interactions.

Bemisia tabaci (Gennadius) represents a relatively large cryptic species complex. Australia has at least two native populations of B. tabaci sensu lato and these were first found on different host plants in different parts of Australia. The species status of these populations has not been resolved, although their mitochondrial sequences differ by 3.82–4.20%. We addressed the question of whether these AUSI and AUSII B. tabaci populations are distinct species. We used reciprocal cross-mating tests to establish whether the insects from these different populations recognize one another as potential mating partners. The results show that the two native Australian populations of B. tabaci have a mating sequence with four phases, each of which is described. Not all pairs in the control crosses mated and the frequency of mating differed across them. Some pairs in the AUSI-M × AUSII-F did mate (15%) and did produce female progeny, but the frequency was extremely low relative to controls. Microsatellite genotyping of the female progeny produced in the crosses showed these matings were successful. None of the AUSII-M × AUSI-F crosses mated although some of the males did search for females. These results demonstrate the critical role of the mate recognition process and the need to assess this directly in cross-mating tests if the species status of different populations is to be tested realistically. In short, AUSI and AUSII B. tabaci populations are distinct species because the individual males and females do not recognize individuals of the alternative population as potential mating partners.

The potential of the mirid predator Dicyphus hesperus Knight (Heteroptera: Miridae) as a biological control agent of the sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and the potato psyllid, Bactericera cockerelli Sulcer (Hemiptera: Psyllidae) in tomato was investigated in two experiments. The first experiment focused on the study of the life history traits of D. hesperus when fed on nymphs of the potato psyllid compared with the factitious prey Ephestia kuehniella Zeller (Lepidoptera: Pyrallidae) eggs. Although reproductive and development rates were higher on E. kuehniella eggs, the predator exhibited a good intrinsic rate of natural increase (rm) when feeding on B. cockerelli nymphs (rm: B. cockerelli 0.069 ± 0.0001; E. kuehniella 0.078 ± 0.0001), thus reflecting good potential as a biocontrol agent of this pest. The second experiment focused on the efficacy of D. hesperus as a biocontrol agent of the potato psyllid and the sweetpotato whitefly in a tomato greenhouse. Prey species were offered individually or together in a series of five treatments in greenhouse cages. Results showed that the predator was able to establish and suppress populations of both pests inhabiting tomato plants when pests occurred alone or together. Thus, D. hesperus was demonstrated to be a suitable biocontrol agent of these two important pests that could be used in tomato greenhouses.

Whitefly, Bemisia tabaci, is one of the most important pests of tomato, Solanum lycopersicum L. The Mi-1 gene mediates tomato resistance to the Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) species of B. tabaci, three species of root-knot nematodes, Meloidogyne spp., and the potato aphid, Macrosiphum euphorbiae. Tomato seedlings bearing the Mi-1 gene are resistant to nematodes soon after germination but resistance to aphids is developmentally regulated; a reliable conclusion about Mi-1 resistance to B. tabaci was not available to date. In the present work, 3-, 5- and 8-week-old plants of the tomato cultivars Motelle and Moneymaker (bearing and lacking the Mi-1 gene, respectively) were simultaneously tested under free-choice (antixenosis) and no-choice (antibiosis) conditions, to assess the real influence of plant age on the Mi-1-mediated resistance to the MED species of B. tabaci. Subsequently, plants of the same age but with different level of development were compared to check whether the plant size can also affect this tomato resistance. Obtained results demonstrated that Mi-1-mediated resistance to B. tabaci is developmentally regulated, as variations in the age of bearing-Mi-1 plants affects most infestation parameters tested. Differences between cultivars with and without the Mi-1 gene were significant for 8- but not for 3-week-old plants. For 5-week-old plants, differences between cultivars were less pronounced than in older plants, expressing an intermediate level of resistance in Motelle. Plant size also influenced whitefly infestation and reproductive activity on the resistant cultivar. However, plant age has more impact than plant size on the Mi-1-mediated resistance of tomato to B. tabaci.

Plant defense to pests or pathogens involves global changes in gene expression mediated by multiple signaling pathways. A role for the salicylic acid (SA) signaling pathway in Mi-1-mediated resistance of tomato (Solanum lycopersicum) to aphids was previously identified and its implication in the resistance to root-knot nematodes is controversial, but the importance of SA in basal and Mi-1-mediated resistance of tomato to whitefly Bemisia tabaci had not been determined. SA levels were measured before and after B. tabaci infestation in susceptible and resistant Mi-1-containing tomatoes, and in plants with the NahG bacterial transgene. Tomato plants of the same genotypes were also screened with B. tabaci (MEAM1 and MED species, before known as B and Q biotypes, respectively). The SA content in all tomato genotypes transiently increased after infestation with B. tabaci albeit at variable levels. Whitefly fecundity or infestation rates on susceptible Moneymaker were not significantly affected by the expression of NahG gene, but the Mi-1-mediated resistance to B. tabaci was lost in VFN NahG plants. Results indicated that whiteflies induce both SA and jasmonic acid accumulation in tomato. However, SA has no role in basal defense of tomato against B. tabaci. In contrast, SA is an important component of the Mi-1-mediated resistance to B. tabaci in tomato.

Insect species can respond adaptively to stress temperature conditions including both thermal limits and reaction norms. In this study, we considered two populations of the whitefly Bemisia tabaci (Gennadius), in which adaptive differentiation was detected for tolerance to upper thermal limits. These two populations are found in two regions of Colombia with climatic differences: the Caribbean region with high environmental temperatures and the Southwest region with lower temperature regimens. We assessed the thermal responses to a range of 1 h heat shocks (37, 39, 41, 43 and 44 °C) performed below the thermal limits for this species. Thermal responses were measured using three life-history traits involved in fitness: survival, fecundity and viability of the offspring after heat shocks. Survival or fecundity as a response to heat shocks did not differ among populations; however, there were significantly different responses for viability between populations. The Southwestern population showed higher viability responses to low heat shocks than the Caribbean population. This relationship suggests a potential trade-off, which appears to be associated with climatic regions. In addition, these results suggest that adaptation under thermal limits does not necessarily involve similar responses throughout the reaction norm. A potential ongoing evolutionary response is taking place through the thermal reaction norms for viability after the invasion by this pest in Colombia.

Bemisia tabaci Gennadius is a major pest on cotton and vegetable plants in Africa. It is considered as a cryptic species complex. Identification of the most damaging species such as the Middle East–Asia Minor 1 (B biotype) and Mediterranean (MED) (which contains the Q and Africa silverleaf (ASL) biotypes) species represents an important step towards the management of B. tabaci. Some data on the geographical distribution of the B. tabaci species complex exist in Burkina Faso, Benin and Togo, but data on the pest's invasion and displacement dynamics, in relation to time, are lacking. Here, molecular markers (mitochondrial cytochrome oxidase, mtCO1) were used to determine the identity of B. tabaci. Our results illustrate population dynamics on cotton and vegetable plants between 2007, 2009 and 2010. On cotton in southern Togo, ASL was predominant and found in sympatry with Q1. Its frequency decreased slightly over time, i.e. from 92% in 2009 to 90% in 2010. In Burkina Faso, Q1, Q3 and ASL biotypes showed different temporal and spatial distribution patterns. There, Q1 dominated on cotton plants throughout the study. This work provides relevant information about the population dynamics of B. tabaci MED species in two West African countries, Burkina Faso and Togo, in connection with pest management programmes.

Several whitefly species (Hemiptera: Aleyrodidae) are cosmopolitan phloem-feeders that cause serious damage in numerous agricultural crops. All whitefly species harbor a primary bacterial symbiont and a diverse array of secondary symbionts which may influence several aspects of the insect's biology. We surveyed infections by secondary symbionts in Bemisia tabaci (Gennadius), Trialeurodes vaporariorum (Westwood) and Siphoninus phillyreae (Haliday) from areas in the east cost of the Adriatic Sea. Both the Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) B. tabaci genetic groups were detected in Montenegro, whereas only the MED was confirmed in Croatia. Trialeurodes vaporariorum and S. phillyreae were found in all areas surveyed. MEAM1 and MED exhibited similarity to previously reported infections, while populations of T. vaporariorum from Montenegro harbored Rickettsia, Wolbachia and Cardinium in addition to previously reported Hamiltonella and Arsenopnohus. Siphoninus phillyreae harbored Hamiltonella, Wolbachia, Cardinium and Arsenophonus, with the latter appearing in two alleles. Multiple infections of all symbionts were common in the three insect species tested, with some reaching near fixation. Florescent in situ hybridization showed new localization patterns for Hamiltonella in S. phillyreae, and the morphology of the bacteriosome differed from that observed in other whitefly species. Our results show new infections with bacterial symbionts in the whitefly species studied. Infections with the same symbionts in reproductively isolated whitefly species confirm complex relationships between whiteflies and bacterial symbionts, and suggest possible horizontal transfer of some of these bacteria.

The whiteflies Bemisia tabaci Gennadius and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are two of the main pests in tomato crops. Their biological control in Mediterranean IPM systems is based on the predators Macrolophus pygmaeus (Rambur) and Nesidiocoris tenuis Reuter (Hemiptera: Miridae), as well as on the parasitoids Eretmocerus mundus (Mercet) and Encarsia pergandiella Howard (Hymenoptera: Aphelinidae). These natural enemies may interact with each other and their joint use could interfere with the biological control of those whitefly pests. Analysis of predator-prey interactions under field conditions is therefore essential in order to optimize whitefly control. Species-specific polymerase chain reaction (PCR)-primers were designed to detect DNA fragments of these whiteflies and parasitoids within both predator species in tomato greenhouses. We demonstrated that both predators feed on both whitefly species, as well as on both parasitoids under greenhouse conditions. Prey molecular detection was possible where prey abundance was very low or even where predation was not observed under a microscope. Whitefly DNA detection was positively correlated with adult whitefly abundance in the crop. However, a significant relationship was not observed between parasitoid DNA detection and the abundance of parasitoid pupae, even though the predation rate on parasitoids was high. This unidirectional intraguild predation (predators on parasitoids) could potentially reduce their combined impact on their joint prey/host. Prey molecular detection provided improved detection of prey consumption in greenhouse crops, as well as the possibility to identify which prey species were consumed by each predator species present in the greenhouse, offering a blueprint with wider applicability to other food webs.

Biology, morphometrics and analyses of non-specific esterases were carried out for populations of Bemisia tabaci (Gennadius) collected from leucaena [Leucaena leucocephala (Lam.) de Wit] in New Delhi, India and compared with those for cotton populations. The developmental periods of the egg, and the first to fourth instars of the leucaena populations were 6.7 ± 0.18, 4.2 ± 0.18, 3.8 ± 0.14, 3.0 ± 0.0 and 5.2 ± 0.18 days, respectively, with a total life-cycle duration of 22.9 ± 0.58 days; fecundity (62.60 ± 61.53 eggs per female) and longevity (male: 13.50 ± 0.12 days, female: 16.50 ± 0.12 days) were higher than those recorded for the cotton population, with a sex ratio (male:female) of 1:3.7 in cotton and 1:4 in leucaena. Morphometrics revealed significant differences in the length of egg, second, third and fourth instars (P < 0.05). Of the 62 measurements of the puparia analysed, 70% of those of the head, 44% of those of the thorax and 51% of those of the abdomen showed significant differences between the cotton and leucaena populations. Mapping of the host association of samples onto principal component ordination showed their significant separation according to host plants, with the first three principal components accounting for 66% of the total variation. The analysis of non-specific esterases showed two bands at Rm E0.18 and E0.23 in the cotton populations but not in the leucaena populations. So far, B. tabaci is known on leucaena only from Taiwan. The present study reports it as a new host record from India in addition to documenting the biology, morphometrics and esterases of this and a cotton population.

The whitefly Bemisia tabaci is a pest vector of begomoviruses on crops worldwide. Bemisia tabaci is composed of a complex of cryptic species which barely interbreed. An exception is the Ms from the South West Indian Ocean (SWIO), which crosses in low proportions with the exotic B. The Ms, together with B and Q is part of the same phylogenetic clad. To infer the genetic structure, the geographical range and putative origin of this putative species, microsatellite data and mitochondrial DNA (cytochrome oxydase I) sequences were analysed on an extensive sample set, including all the islands of the region and samples from mainland Africa. Only B and Ms populations were detected across these islands. The exotic B was found only on the islands of Réunion and Mauritius, whereas the Ms is found on all the SWIO islands. Very high isolation by distance was found for the Ms populations between islands of the SWIO, suggesting a long period of presence in this region. Ms populations from mainland Africa had a higher COI diversity than the Ms of the SWIO islands. This diversity is correlated with size and geological ages of the SWIO islands. The population genetic data obtained are in accordance with an origin of Ms in Africa, followed by its expansion and evolution across the SWIO islands prior to human arrival, confirming the status of Ms as indigenous in the SWIO islands.

It is often considered that reduced genetic variation due to bottlenecks and founder effects limits the capacity for species to establish in new environments and subsequently spread. The recent invasion (during the past five years) of an alien whitefly, one member of Bemisia tabaci cryptic species complex, referred to as Mediterranean (herein referred to as Q-type) in Shandong Province, China, provides an ideal opportunity to study the changes in genetic variation between its home range in the Mediterranean region and its invasion range. Using both the mitochondrial cytochrome oxidase I (mtCOI) and nuclear (microsatellite) DNA, we show that Q in Shandong likely originated in the western Mediterranean. We also found that the haplotype diversity was low compared with its presumed geographic origin, whereas microsatellite allele diversity showed no such decline. A key factor in invasions is the establishment of females and so bottleneck and founder events can lead to a very rapid and considerable loss of mitochondrial diversity. The lack of haplotype diversity in Shandong supports the interpretation that, at one or more points between the western Mediterranean and China, the invading Q lost haplotype diversity, most probably through the serial process of establishment and redistribution through trade in ornamental plants. However, the loss in haplotype diversity does not necessarily mean that nuclear allelic diversity should also decline. Provided females can mate freely with whichever males are available, allelic diversity can be maintained or even increased relative to the origin of the invader. Our findings may offer some explanation to the apparent paradox between the concept of reduced genetic variation limiting adaptation to new environments and the observed low diversity in successful invaders.

The degree of reproductive isolation between the B and Q biotypes of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is currently not clear. Laboratory experiments have shown that the two biotypes are capable of producing viable F1 hybrids but that these females are sterile as their F2 generation failed to develop, indicating, most likely, a post-zygotic reproductive barrier. Here, we confirm, by molecular and ecological tools, that the B and Q biotypes of Israel are genetically isolated and provide two independent lines of evidence that support the existence of a pre-zygotic reproductive barrier between them. Firstly, monitoring of mating behaviors in homogeneous and heterogeneous couples indicated no copulation events in heterogeneous couples compared to ∼50% in homogeneous B and Q couples. Secondly, we could not detect the presence of sperm in the spermathecae of females from heterogeneous couples, compared to 50% detection in intra-B biotype crosses and 15% detection in intra-Q biotype crosses. The existence of pre-zygotic reproductive barriers in Israeli B and Q colonies may indicate a reinforcement process in which mating discrimination is strengthened between sympatric taxa that were formerly allopatric, to avoid maladaptive hybridization. As the two biotypes continued to perform all courtship stages prior to copulation, we also conducted mixed cultures experiments in order to test the reproductive consequences of inter-biotype courtship attempts. In mixed cultures, a significant reduction in female fecundity was observed for the Q biotype but not for the B biotype, suggesting an asymmetric reproductive interference effect in favour of the B biotype. The long-term outcome of this effect is yet to be determined since additional environmental forces may reduce the probability of demographic displacement of one biotype by the other in overlapping niches.

Cotton leaf curl disease, a viral infection vectored by the whitefly Bemisia tabaci (Gennadius), is a major threat to the cotton industry in India and Pakistan. We examined the settling preferences of B. tabaci adults on infected versus healthy cotton plants under choice conditions. For experiments with plants at 20 and 35 days post-inoculation (DPI), whiteflies preferentially settled on healthy cotton plants after 8 and 1 h of release, respectively. Whiteflies, however, were unable to discriminate between virus-infected and healthy cotton plants at 5 DPI. Our results suggest that whiteflies' preference for healthy plants compared with diseased plants can lead to rapid virus spread in the field, resulting in higher crop losses.

We developed new methods for analyzing inheritance of insecticide resistance in haplodiploid arthropods and applied them to elucidate resistance of the whitefly Bemisia tabaci (Gennadius) to an insect growth regulator, pyriproxyfen. Two invasive biotypes of this devastating crop pest, the B biotype in Arizona and the Q biotype in Israel, have evolved resistance to pyriproxyfen. Here, we incorporated data from laboratory bioassays and crossing procedures exploiting haplodiploidy into statistical and analytical models to estimate the number of loci affecting pyriproxyfen resistance in strains of both biotypes. In tests with models of one to ten loci, the best fit between expected and observed mortality occurred with a two-locus model for the B biotype strain (QC-02) and for one- and two-locus models for the Q biotype strain (Pyri-R). The estimated minimum number of loci affecting resistance was 1.6 for the B biotype strain and 1.0 for the Q biotype strain. The methods used here can be applied to insecticide resistance and other traits in haplodiploid arthropods.

Bemisia tabaci, biotype B, commonly known as the silverleaf whitefly (SLW) is an alien species that invaded Australia in the mid-90s. This paper reports on the invasion ecology of SLW and the factors that are likely to have contributed to the first outbreak of this major pest in an Australian cotton cropping system. Population dynamics of SLW within whitefly-susceptible crop (cotton and cucurbit) and non-crop vegetation (sowthistle, Sonchus spp.) components of the cropping system were investigated over four consecutive growing seasons (September–June) 2001/02–2004/05 in the Emerald Irrigation Area (EIA) of Queensland, Australia. Based on fixed geo-referenced sampling sites, variation in spatial and temporal abundance of SLW within each system component was quantified to provide baseline data for the development of ecologically sustainable pest management strategies. Parasitism of large (3rd and 4th instars) SLW nymphs by native aphelinid wasps was quantified to determine the potential for natural control of SLW populations. Following the initial outbreak in 2001/02, SLW abundance declined and stabilised over the next three seasons. The population dynamics of SLW is characterised by inter-seasonal population cycling between the non-crop (weed) and cotton components of the EIA cropping system. Cotton was the largest sink for and source of SLW during the study period. Over-wintering populations dispersed from weed host plant sources to cotton in spring followed by a reverse dispersal in late summer and autumn to broad-leaved crops and weeds. A basic spatial source-sink analysis showed that SLW adult and nymph densities were higher in cotton fields that were closer to over-wintering weed sources throughout spring than in fields that were further away. Cucurbit fields were not significant sources of SLW and did not appear to contribute significantly to the regional population dynamics of the pest. Substantial parasitism of nymphal stages throughout the study period indicates that native parasitoid species and other natural enemies are important sources of SLW mortality in Australian cotton production systems. Weather conditions and use of broad-spectrum insecticides for pest control are implicated in the initial outbreak and on-going pest status of SLW in the region.

In addition to constitutive plant resistance against pests or pathogens, plants can activate protective mechanisms upon contact with an invader or a chemical elicitor. Studies on induced plant resistance to herbivores, especially piercing-sucking insects, are less abundant than those devoted to pathogens. Several experiments under controlled conditions have been conducted to demonstrate that infestations by Macrosiphum euphorbiae induce plant resistance to Bemisia tabaci in susceptible tomato plants. After three days of exposure to 20 apterous adult aphids, the plants acquired a transiently induced resistance to B. tabaci when aphid removal occurred one or 18 hours prior to B. tabaci infestation; the effect disappeared when four days passed between aphid and whitefly infestations. The resistance observed was both locally and systemically induced. Other assays were performed to evaluate the effect of preinfestation with ten adults of B. tabaci during 48 h on the tomato responses to two different clones (Sp and Nt) of M. euphorbiae. The numbers of nymph and adult aphids were counted after the same time interval as the pre-reproductive period and 20 (Sp clone) or 22 (Nt clone) days after adult aphid removal. The tomato responses induced by whitefly feeding depend on the aphid clone. For the Sp clone, the number of aphid nymphs ten days after adult removal was significantly higher on whitefly preinfested plants than on uninfested plants. However, no significant differences were observed when the aphid clone Nt was tested. The duration of plant response to a previous infestation by B. tabaci is apparently limited.