Ultrastructure, distribution, and transmission of endosymbionts in the whiteflyAleurochiton aceris Modeer (Insecta, Hemiptera, Aleyrodinea)

Summary The body of the whiteflyAleurochiton aceris contains specialized cells, termed mycetocytes, that enclose endosymbiotic microorganisms. The endosymbionts are transmitted from one generation to the next transovarially. In contrast to other insects, in whiteflies whole intact mycetocytes migrate into the ovaries, traverse the follicular epithelium, and reach the oocyte surface (i.e., perivitellin space). The migration of mycetocytes begins in the last instar, called puparium, from which imagines emerge. During this stage the cytoplasm of mycetocytes is tightly packed with pleomorphic bacteria and less numerous coccoid microorganisms. In adult females the mycetocytes gather extracellularly in the depression of the vitellarial oocyte. Till the end of oogenesis neither pleomorphic nor coccoid microorganisms are released from mycetocytes into the oocyte.     

Genetic diversity and geographic distribution of Bemisia tabaci and Trialeurodes vaporariorum in Costa Rica

The tobacco whitefly Bemisia tabaci (Gennadius) cryptic species complex and of the greenhouse whitefly Trialeurodes vaporariorum (Westwood) are extensively reported as destructive pests in vegetable crops worldwide. A survey was conducted in 2011 and 2012 to determine the occurrence and genetic diversity present in the populations of these whiteflies in the major vegetable production areas of Costa Rica. Insect samples were collected from sweet pepper (Capsicum annuum L.), tomato (Solanum lycopersicum L.), common bean (Phaseolus vulgaris L.) and weeds present in commercial crops either in open field or greenhouse conditions. PCR‐RFLP analysis of mitochondrial cytochrome c oxidase subunit 1 gene (mtCOI) sequences of 621 whitefly individuals confirmed the presence of the Mediterranean (MED) type of the B. tabaci and of T. vaporariorum in most sampled regions. Also, individuals of the Middle East‐Asia Minor 1 (MEAM1) type of the B. tabaci were observed in low numbers. Contingency analyses based on type of crop, geographical region, whitefly species, year of collection and production system confirmed that T. vaporariorum was the most frequent species in vegetable production areas in Costa Rica, both in greenhouses and in open fields. B. tabaci MED is likely spreading to new areas of the country, whereas B. tabaci MEAM1 was mostly absent or rarely found. Comparisons of mtCOI sequences from B. tabaci individuals revealed the presence of four B. tabaci sequence haplotypes (named MED‐i, MED‐ii, MEAM1‐i, MEAM1‐xviii) in Costa Rica, three of them identical to B. tabaci haplotypes previously reported in the Western Hemisphere and other parts of the world. Analysis of sequences of T. vaporariorum individuals revealed a more complex population with the presence of 11 haplotypes, two of which were identical to T. vaporariorum sequences reported from other countries.     

Effects of temperature on the growth and reproduction characteristics of Bemisia tabaci B‐biotype and Trialeurodes vaporariorum

The development period, survival rate, longevity and fecundity of two whiteflies, Bemisia tabaci B‐biotype and Trialeurodes vaporariorum (Homoptera: Aleyrodidae) were compared under different temperature laboratory conditions (15°C, 18°C, 21°C and 24°C). Egg development of B. tabaci B‐biotype was significantly longer compared with that of T. vaporariorum at 15°C, 18°C and 24°C. Significantly longer pseudo‐pupae development and lower survival rate were found in B. tabaci B‐biotype at 15°C compared with those at 18°C, 21°C and 24°C. Significantly higher fecundity was found in B. tabaci B‐biotype at 24°C compared with that at 15°C, 18°C and 21°C. However, the fecundity of T. vaporariorum was significantly lower at 24°C relative to that at 15°C, 18°C and 21°C. Significantly shorter 1st instar larval development was found in T. vaporariorum compared with that of B. tabaci at 15°C and 18°C. Significantly longer 2nd instar larval development was found in B. tabaci and T. vaporariorum at 15°C compared with that at 18°C, 21°C and 24°C. However, significantly shorter 3rd instar larval development was found in T. vaporariorum compared with that of B. tabaci at 15°C, 18°C and 24°C. The adaptive divergence of tolerance to relatively low temperature may be an important factor that results in the interspecific differentiation between the seasonal dynamics of these two whiteflies in China.     

Variation between laboratory populations in the performance of the parasitoid Encarsia formosa on two host species, Bemisia tabaci and Trialeurodes vaporariorum

We tested the hypothesis that populations of the parthenogenetic parasitic wasp Encarsia formosa Gahan (Hymenoptera: Aphelinidae) differed in their ability to use two different host species, Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and Trialeurodes vaporariorum Westwood (Homoptera: Aleyrodidae). Of the three wasp populations tested, two populations had been reared for many generations on B. tabaci and one population had been reared for many years on T. vaporariorum. Performance was measured by the number of whitefly nymphs that were successfully parasitized by individual wasps, and performance on either host was measured in separate experiments. There was variation between wasp populations in their performance on the host B. tabaci, with one wasp population reared for many years on this host performing considerably better than the other two populations. There were no significant differences between populations in their use of the preferred host, T. vaporariorum. The experiments were conducted in such a way that we could distinguish heritable differences between populations from environmentally-induced conditioning differences due to the immediate host from which an individual wasp enclosed. In either experiment there were no significant effects of conditioning, although there was a trend within each population for wasps conditioned on T. vaporariorum to have higher performance than those conditioned on B. tabaci. Thirdly, we conducted a selection experiment, initiated with wasps from a single population historically reared on T. vaporariorum, to measure the effect of laboratory rearing on different hosts for 17 generations. We did not see any difference in the performance of wasps on B. tabaci after this period of rearing on either of the two hosts. In summary, populations of E. formosa do differ in their relative performance on B. tabaci. The one population that was tested further did not show any response to selection by rearing, but the ability to respond to selection on performance may not be equal for all populations. The possibility that wasp populations have differential performance on particular hosts may affect the use of this species as a biological control agent.     

Cloning and expression of heat shock protein genes in two whitefly species in response to thermal stress

Two whitefly species, Trialeurodes vaporariorum and Bemisia tabaci biotype B were shown to have different temperature tolerance and seasonal dynamics. To determine whether this variation in thermal tolerance is related to different expression patterns of heat shock protein (hsp) genes during temperature stress, we obtained complete cDNA sequences for hsp90, hsp70 and hsp20, and analysed their expression profiles across temperature gradients by real‐time quantitative polymerase chain reaction (PCR). Six full‐length cDNAs were cloned and sequenced from these two species. The full‐length cDNAs of hsp90s contain 2166 and 2157 bp open‐reading frames (ORF) which encode proteins with calculated molecular weights of 83 013 and 82 857 Da in T. vaporariorum and B. tabaci, respectively. The 1947 and 1959 bp ORFs of whitefly hsp70s comprise 649 and 653 amino acids with the calculated masses of 70 885 and 71 008 Da in T. vaporariorum and B. tabaci, respectively. Both complete cDNAs of hsp20 of T. vaporariorum and B. tabaci contain 585 bp ORFs and deduced amino acid sequences had molecular weights of 21 559 and 21 539 Da, respectively. The hsp expression profile results showed that temperatures for onset (T_on) or maximal (T_max) induction of hsp expression in T. vaporariorum were generally 2–6°C lower than those in B. tabaci. These results suggest that the T_on (or T_max) of hsps can represent the differences in temperature tolerance of these two whitefly species, and may be used to determine their natural geographical distribution and natural population seasonal dynamics. Significant upregulation of most hsps were observed when temperature stress was lifted, except that hsp70 and hsp20 of B. tabaci did not respond to the cold stress, indicating that response to heat and cold stress may have a different genetic and physiological basis in two whitefly species. These results highlight the importance of understanding the complexity of the heat shock response across multiple isoforms while attempting to link them to whole‐organism traits such as thermal tolerance.     

Differential responses between a vector species Bemisia tabaci and a nonvector species Trialeurodes vaporariorum following ingestion of tomato yellow leaf curl virus

In transmitting plant viruses, insect vectors undergo physiological and behavioral alterations. The whitefly Bemisia tabaci is a vector of tomato yellow leaf curl virus (TYLCV), causing severe damages to various horticultural crop plants. To determine whether whitefly alteration is specific to vector species, the responses to TYLCV ingestion were compared between B. tabaci and Trialeurodes vaporariorum, a nonvector for TYLCV. The two species were reared on TYLCV‐infected and noninfected tomato, a host of TYLCV, and their longevity and fecundity were determined while rearing in either tomato or eggplant, a nonhost of TYLCV. TYLCV‐ingested B. tabaci increased their developmental rates but reduced fecundity when they were reared in either tomato or eggplant compared with those of TYLCV‐free ones. In contrast, TYLCV‐ingested T. vaporariorum did not show any of the aforementioned changes when reared on both plant species. In addition, TYLCV‐ingested B. tabaci increased their levels of three heat shock protein genes ( hsp20, hsp70, and hsp90) against thermal stress, whereas TYLCV‐ingested T. vaporariorum did not. The presence of TYLCV virions was identified in two colonies of both species via polymerase chain reaction analysis. TYLCV was detected in the whole body, saliva, and eggs of B. tabaci, while TYLCV was detected only in the whole body but not in the saliva and eggs of T. vaporariorum. The present results strongly indicated that TYLCV specifically manipulate physiological processes of the vector species, B. tabaci.     

The circulative pathway of begomoviruses in the whitefly vector Bemisia tabaci— insights from studies with Tomato yellow leaf curl virus

Our current knowledge concerning the transmission of begomoviruses by the whitefly vector Bemisia tabaci is based mainly on research performed on the Tomato yellow leaf curl virus (TYLCV) complex and on a number of viruses originating from the Old World, such as Tomato leaf curl virus, and from the New World, including Abutilon mosaic virus, Tomato mottle virus, and Squash leaf curl virus. In this review we discuss the characteristics of acquisition, transmission and retention of begomoviruses by the whitefly vector, concentrating on the TYLCV complex, based on both published and recent unpublished data. We describe the cells and organs encountered by begomoviruses in B. tabaci. We show immunolocalisation of TYLCV to the B. tabaci stylet food canal and to the proximal part of the descending midgut, and TYLCV‐specific labelling was also associated with food in the lumen. The microvilli and electron‐dense material in the epithelial cells of the gut wall were also labelled by the anti TYLCV serum, pointing to a possible virus translocation route through the gut wall and to a putative site of long‐term virus storage. We describe the path of begomoviruses in their vector B. tabaci and in the non‐vector whitefly Trialeurodes vaporariorum, and we follow the rate of virus translocation in these insects. We discuss TYLCV transmission between B. tabaci during mating, probably by exchange of haemolymph. We show that following a short acquisition access to infected tomato plants, TYLCV remains associated with the B. tabaci vector for weeks, while the virus is undetectable after a few hours in the non‐vector T. vaporariorum. The implications of the long‐term association of TYLCV with B. tabaci in the light of interactions of the begomovirus with insect receptors are discussed.     

Morphological variation inBemisia endosymbionts

Summary The ultrastructure of the endosymbionts of several populations of whitefly (Homoptera: Aleyrodidae) was examined using transmission electron microscopy. Consistent differences in morphology and relative number of endosymbionts were observed between species and biotypes of whitefly within the Bemisia taxon.Bemisia argentifolii (=B. tabaci B biotype) individuals from Hawaii, Florida, and Arizona contained two morphological types of microorganisms housed within the mycetocyte cells of immature whiteflies. In contrast, individuals from populations ofB. tabaci A biotype from Arizona and Mexico, andB. tabaci Jatropha biotype from Puerto Rico, consistently contained three distinct morphological types of microorganisms within their mycetocytes. Organisms fromB. tabaci A and Jatropha biotypes differed from each other in the relative frequency of each type of microorganism. These observations suggest that different whitefly biotypes may have variable combinations of micro-fauna, with some possibly unique to each group, and furthers the hypothesis that variation in whitefly endosymbionts may be associated with the development of biotypes.     

Fitness of Encarsia sophia (Hymenoptera: Aphelinidae) parasitizing Trialeurodes vaporariorum and Bemisia tabaci (Hemiptera: Aleyrodidae)

Abstract Fitness and efficacy of Encarsia sophia (Girault & Dodd) (Hymenoptera: Aphelinidae) as a biological control agent was compared on two species of whitefly (Hemiptera: Aleyrodidae) hosts, the relatively smaller sweetpotato whitefly, Bemisia tabaci (Gennadius) biotype ‘B’, and the larger greenhouse whitefly, Trialeurodes vaporariorum (Westwood). Significant differences were observed on green bean (Phaseolus vulgaris L.) in the laboratory at 27 ± 2°C, 55%± 5% RH, and a photoperiod of 14: 10 h (L: D). Adult parasitoids emerging from T. vaporariorum were larger than those emerging from B. tabaci, and almost all biological parameters of E. sophia parasitizing the larger host species were superior except for the developmental times of the parasitoids that were similar when parasitizing the two host species. Furthermore, parasitoids emerging from T. vaporariorum parasitized more of these hosts than did parasitoids emerging from B. tabaci. We conclude that E. sophia reared from larger hosts had better fitness than from smaller hosts. Those from either host also preferred the larger host for oviposition but were just as effective on smaller hosts. Therefore, larger hosts tended to produce better parasitoids than smaller hosts.     

The composition of external lipids from adult whiteflies,Bemisia tabaci and Trialeurodes vaporariorum

The total surface lipids, including the wax particles, of the adult whiteflies of Bemisia tabaci and Trialeurodes vaporariorum were characterized. At eclosion, there were similar amounts of long-chain hydrocarbons, aldehydes, alcohols and wax esters. Within a few hours post-eclosion, long-chain aldehydes and long-chain alcohols were the dominant surface lipid components, C₃₄ on B. tabaci and C₃₂ on T. vaporariorum. Hydrocarbons, mainly n-alkanes, were minor components of the surface lipids. The major wax esters were C₄₆ on B. tabaci and C₄₂ on T. vaporariorum. The major acid and alcohol moieties in the wax esters of B. tabaci were C₂₀ and C₂₆, respectively, and of T. vaporariorum were C₂₀ and C₂₂, respectively. Both B. tabaci and T. vaporariorum had a minor wax ester composed of the fatty acid C_18:1 esterified to the major alcohols, C₃₄ and C₃₂, respectively. Bemisia were readily distinguished from Trialeurodes based on the composition of their wax particles and/or their wax esters; however, no differentiating surface lipid components were detected between biotypes A and B of B. tabaci.     

The status ofBemisia tabaci (Hom.: Aleyrodidae),Trialeurodes vaporariorum (Hom.: Aleyrodidae) and their natural enemies in Crete

The non «B» biotype ofBemisia tabaci (Gennadius) is recorded for the first time in Crete in 1992, in the north east and south east of the island.Trialeurodes vaporariorum (Westwood) is the predominant whitefly on plants in the north and west of the island. Three surveys of Crete were made in 1992 and 1993 for natural enemies ofB. tabaci andT. vaporariorum and resulted in the collection of 4 species ofEncarsia, (plus a number of species that are unidentifiable at this time), anEretmocerus sp. (unidentifiable at this time) and a fungal pathogen,Paecilomyces farinosus (Dickson Ex Fries) Brown &; Smith.Encarsia adrianae was identified fromT. vaporariorum; which constitutes its most westerly distribution point and a new host record respectively.B. tabaci andT. vaporariorum were found on horticultural crops, ornamentals and weeds. Populations of both whitefly species were severely depleted on field hosts throughout the island during the winter of 1992/93. Climatic constraints, competition withT. vaporariorum in otherwise suitable niches, effective natural enemies and an observed low level of polyphagy may explain the present limited distribution of the non «B» biotype ofB. tabaci in Crete.     

Identification,comparison, and functional analysis of salivary phenol‐oxidizing enzymes in Bemisia tabaci B and Trialeurodes vaporariorum

The differences in the ability of the invading whitefly, Bemisia tabaci (Gennadius) (commonly known as biotype B and hereafter as B) and Trialeurodes vaporariorum (Westwood) (both Hemiptera: Aleyrodidae) to utilize salivary phenol‐oxidizing enzymes – polyphenol oxidase (PPO) and peroxidase (POD) to detoxify plant defensive phenolic compounds were explored. Polyphenol oxidase and POD were found in the saliva of both B and T. vaporariorum. For tomato colonies, the PPO and POD activities in the watery saliva of B were 2.27‐ and 1.34‐fold higher than those of T. vaporariorum. The PPO activities against specific phenolic compounds commonly found in plants were compared. The activities of those from B were significantly greater than those from T. vaporariorum. We also measured PPO activity in both species after they had fed on plants that were undamaged or had been previously damaged with either a plant pathogen [Phytophthora infestans (Mont.) de Bary (Peronosporales)] infection, mechanical damage, B infestation, or exogenous salicylic acid. For B, PPO activities in watery saliva increased 229, 184, 152, and 139% in response to the four treatments, whereas those of T. vaporariorum only increased 133, 119, 113, and 103%, respectively. Biotype B infestation significantly increased the total phenolic content of tomato leaves. Meanwhile, feeding on tomato infestation with B had no significant effect on the survival rate of B, but decreased the survival rate of T. vaporariorum significantly. These results suggest that B has stronger ability utilizing PPO to detoxify high concentrations of phenolics than T. vaporariorum, and this contributes to a significant advantage for B to hold high fitness on plants with induced resistance. Possible roles of salivary PPO in the competition between B and T. vaporariorum are discussed.     

Patterns of host cell inheritance in the bacterial symbiosis of whiteflies

Whiteflies possess bacterial symbionts Candidatus Portiera aleyrodidium that are housed in specialized cells called bacteriocytes and are faithfully transmitted via the ovary to insect offspring. In one whitefly species studied previously, Bemisia tabaci MEAM1, transmission is mediated by somatic inheritance of bacteriocytes, with a single bacteriocyte transferred to each oocyte and persisting through embryogenesis to the next generation. Here, we investigate the mode of bacteriocyte transmission in two whitefly species, B. tabaci MED, the sister species of MEAM1, and the phylogenetically distant species Trialeurodes vaporariorum. Microsatellite analysis supported by microscopical studies demonstrates that B. tabaci MED bacteriocytes are genetically different from other somatic cells and persist through embryogenesis, as for MEAM1, but T. vaporariorum bacteriocytes are genetically identical to other somatic cells of the insect, likely mediated by the degradation of maternal bacteriocytes in the embryo. These two alternative modes of transmission provide a first demonstration among insect symbioses that the cellular processes underlying vertical transmission of bacterial symbionts can diversify among related host species associated with a single lineage of symbiotic bacteria.     

Factors that affect the selection of tomato leaflets by two whiteflies,Trialeurodes vaporariorum and Bemisia tabaci (Homoptera: Aleyrodidae)

In Japan, although greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and sweet potato whitefly, Bemisia tabaci (Gennadius), co-occur on tomato plants under greenhouse conditions, the two whiteflies are distributed differently with regard to leaf position. To elucidate the factors that determine the leaf position of these whiteflies, we investigated traits for leaflets collected from three positions on tomato plants. Furthermore, we examined leaflet selection by and fertility of the two whiteflies under choice and non-choice conditions. In addition, the effect on whitefly behavior of volatile compounds released from leaflets was evaluated by use of a Y-tube olfactometer test. Nitrogen and carbon content were highest for upper leaflets. In choice tests, more T. vaporariorum and B. tabaci adults selected upper and middle leaflets, respectively. Similarly, they oviposited more eggs on upper and middle leaflets. In non-choice tests, T. vaporariorum oviposited more eggs on upper leaflets, but B. tabaci oviposited equally on each leaflet. In Y-tube olfactometer tests, more T. vaporariorum adults moved to upper leaflets whereas more B. tabaci adults moved to middle leaflets. These results suggest that different leaflet selection by adults of these two whiteflies is likely to be associated with the different volatile compounds emitted by tomato leaflets at each position.     

B型烟粉虱与温室白粉虱不同虫态的碱性磷酸酶性质比较

为了探明B型烟粉虱Bemisia tabaci B-biotype 和温室白粉虱Trialeurodes vaporariorum体内的碱性磷酸酶(alkaline phosphatase,ALP)在两者竞争替代中所起的作用,以对硝基苯磷酸二钠 (pNPP)为底物,采用个体测定和群体测定的方法,研究比较了2种粉虱不同虫态中该酶的性质。结果表明：2种粉虱的碱性磷酸酶比活力在整个发育历期均逐渐增加,成虫期达到最大。温室白粉虱2至4龄若虫（伪蛹）期的碱性磷酸酶比活力分别是B型烟粉虱对应龄期酶比活力的2.58、2.68和3.14倍; B型烟粉虱雌雄成虫的碱性磷酸酶比活力分别是温室白粉虱雌雄成虫酶比活力的1.24和1.26倍,且2种粉虱雌虫的酶比活力显著大于其雄虫。2种粉虱2龄若虫到成虫的碱性磷酸酶最适pH均为7.8,最适温度均为47℃;在1龄若虫中均未能检测到该酶活性。测定并比较2种粉虱不同虫态碱性磷酸酶动力学特征参数的结果显示,温室白粉虱碱性磷酸酶在3、4龄若虫的亲和力以及在2, 3, 4龄若虫的酶蛋白浓度均显著大于B型烟粉虱的对应值,而在成虫期2种粉虱的亲和力、酶蛋白浓度无差异,B型烟粉虱的活化能显著小于温室白粉虱。据此推测,B型烟粉虱利用碱性磷酸酶在若虫期进行组织骨化和生长发育不如温室白粉虱,但羽化为成虫后利用其进行解毒代谢则可能强于温室白粉虱。     

Beauveria bassiana ARP14 a potential entomopathogenic fungus against Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)

The sweet potato whitefly, Bemisia tabaci (Hemiptera: Aleyrodidae), and the greenhouse whitefly, Trialeurodes vaporariorum (Hemiptera: Aleyrodidae), are important pests of protected crops grown in warm climates. We compared efficacy of a new strain of the entomopathogenic fungus Beauveria bassiana (ARP14) isolated from Riptortus pedestris (Hemiptera: Alydidae) with a commercial strain (GHA) against different life stages of both B. tabaci and T. vaporariorum. Eggs, nymphs, and adults were exposed to 1 × 10⁸ conidia/mL of each strain using the leaf-dipping method. The mycosis rate of B. tabaci eggs (as a proportion) was relatively low (0.13 for B. bassiana ARP14 and 0.10 for B. bassiana GHA), while, for T. vaporariorum eggs, mycosis rate was 0.44 for B. bassiana GHA and 0.27 for B. bassiana ARP14. However, mycosis rate of 1st instars of both whiteflies was much higher than for eggs, for both strains (ARP14 and GHA). The developmental period of B. tabaci eggs exposed to ARP14 was significantly shorter than for either eggs treated with GHA or the control. For 2nd and 4th instar nymphs and adults of both whiteflies there were no differences in mycosis rates between the two B. bassiana strains. These results suggest that, B. bassiana ARP14 could be commercialized as a native biological control agent for control of B. tabaci and T. vaporariorum.     

Design and use of a simulation model to evaluate germplasm for antibiotic resistance to the greenhouse whitefly (Trialeurodes vaporariorum) and the sweetpotato whitefly (Bemisia tabaci)

SARAH (Software for theAssessment of antibioticResistance toAleyrodidae inHost plants) is a deterministic simulation model of whitefly population growth based on whitefly life-history components determined on individual plants. The life-history components recorded were oviposition rate, adult survival, pre-adult survival, developmental period, and sex ratio. The simulation model serves as a tool to combine these components and to obtain a single criterion for (antibiotic) resistance. The criterion used was the decrease in simulated intrinsic population growth rate, r _s , relative the r _s value determined on a susceptible control genotype. This model-based evaluation method was tested using the greenhouse whitefly,Trialeurodes vaporariorum Westwood, on tomato and the sweetpotato whitefly,Bemisia tabaci Gennadius, on tomato, eggplant, collard, and pepper. To study its consistency over time, the evaluation method was repeated six times forT. vaporariorum on a susceptible and a resistant tomato cultivar. Simulated intrinsic population growth rate was more consistent in indicating resistance than any of the individual life-history components. Of tenL. hirsutum accessions tested for resistance toT. vaporariorum, three exhibited r _s values that were significantly lower than those for the susceptible control. In addition, on these tenL. hirsutum accessions, a significant positive correlation was observed between r _s and sex ratio (# females/# males). Four host plant species (tomato, collard, eggplant, and pepper) were evaluated for resistance toB. tabaci. All life-history components and r _s values varied among host species, while a negative r _s value was observed forB. tabaci on pepper. A high correlation was found between results from a sensitivity analysis of SARAH and results from a sensitivity analysis of a validated whitefly population simulation model by Yanoet al. (1989a). Significant correlations were found for the relationships between oviposition rate, adult survival, or pre-adult survival and r _s , indicating that none of these life-history components can be omitted from the test procedure. This model-based evaluation method offers a standardized way to quantify levels of antibiotic resistance to whiteflies and will enhance efficiency in breeding programs.     

Comparison of the host-handling behavior of Eretmocerus mundus on Bemisia tabaci B biotype, Q biotype and Trialeurodes vaporariorum

Host-handling behaviors of Eretmocerus mundus (Mercet) (Hymenoptera: Aphelinidae) toward first to fourth instar nymphs of the Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) B and Q biotypes and of Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae) were compared under laboratory conditions. The host acceptance rates differed among host stages but not among host species or biotypes. In all host species and biotypes, the parasitoids stopped their host-handling behavior before oviposition more often with older hosts. The total host-handling time was longer for the fourth instars than for younger instars, mainly due to the longer oviposition times and probing times. E. mundus showed marking behavior for the B. tabaci B and Q biotypes, but not for T. vaporariorum. In conclusion, E. mundus could parasitize all whitefly biotypes and species used in this study, but both B. tabaci biotypes were more suitable hosts than T. vaporariorum. The younger instars were good oviposition targets in all hosts.     

Host preferences and biotic potential of <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> and <Emphasis Type="Italic">Bemisia tabaci</Emphasis> (Hemiptera: Aleyrodidae) in tomato and pepper

Whiteflies Bemisia tabaci (Gennadius) and Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae) are important pests in pepper (Capsicum annuum L.) and tomato (Solanum lycopersicum L.) crops in many countries. Contrary to what is observed for all other countries, in Uruguay, B. tabaci is mainly found on pepper and rarely on tomato, while T. vaporariorum is exclusively found on tomato. This study tested the oviposition preferences and biotic potential of these two whiteflies reared on both host plants. The developmental time, survival rates, longevity, fecundity and main population parameters were characterized. Both whitefly species showed different preference patterns regarding their host plants. T. vaporariorum preferred tomato instead of pepper to oviposit. Their developmental time is longer on pepper. B. tabaci preferred pepper, but the difference from tomato was not very strong. Pepper affects the biotic expression of T. vaporariorum negatively, while B. tabaci is able to develop equally on both host plants. These results show that the distribution differences of both whiteflies observed on both host plants could have a biological basis.     

Chromosome‐level genome assembly of the greenhouse whitefly (Trialeurodes vaporariorum Westwood)

The greenhouse whitefly, Trialeurodes vaporariorum Westwood, is an agricultural pest of global importance. Here we report a 787‐Mb high‐quality draft genome sequence of T. vaporariorum assembled from PacBio long reads and Hi‐C chromatin interaction maps, which has scaffold and contig N50 lengths of 70 Mb and 500 kb, respectively, and contains 18,275 protein‐coding genes. About 98.8% of the assembled contigs were placed onto the 11 T. vaporariorum chromosomes. Comparative genomic analysis reveals significantly expanded gene families such as aspartyl proteases in T. vaporariorum compared to Bemisia tabaci Mediterranean (MED) and Middle East‐Asia Minor 1 (MEAM1). Furthermore, the cytochrome CYP6 subfamily shows significant expansion in T. vaporariorum and several genes in this subfamily display developmental stage‐specific expression patterns. The high‐quality T. vaporariorum genome provides a valuable resource for research in a broad range of areas such as fundamental molecular ecology, insect–plant/insect–microorganism or virus interactions and pest resistance management.