Tabaci Middle East-Asia Minor 1 Research Articles

Monitoring the susceptibility of Bemisia tabaci Middle East-Asia Minor 1 (Hemiptera: Aleyrodidae) to afidopyropen, cyantraniliprole, dinotefuran, and flupyradifurone in south Florida vegetable fields.

Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) is a significant pest that damages a wide range of high-value vegetable crops in south Florida. This pest has demonstrated the ability to develop resistance to various insecticide groups worldwide. Monitoring the resistance levels of MEAM1 populations and maintaining baseline susceptibility data are crucial for the long-term effectiveness of insecticide management strategies. We conducted serial dilution bioassays on 15 field populations of MEAM1 collected in south Florida to assess their resistance to 4 key insecticides: afidopyropen, cyantraniliprole, dinotefuran, and flupyradifurone. To quantify resistance levels, resistance ratios (RR) were generated by comparing the LC50 values of field populations to those of a known susceptible MEAM1 colony reared in the laboratory. Our findings reveal that all field-collected populations were susceptible to dinotefuran (RR 1-8) and flupyradifurone (RR 2-8). While over 80% of the populations tested were susceptible to afidopyropen (RR 1-9), 2 populations exhibited low (RR 38) and moderate resistance (RR 51), respectively. In contrast, most of the populations (57%) showed low to moderate resistance to cyantraniliprole (RR 21-78), and the remaining populations were susceptible (RR 3-10). The 2 populations with resistance to afidopyropen also exhibited moderate resistance to cyantraniliprole. Further research in this direction can aid in refining insecticide resistance management programs in Florida and other regions where B. tabaci MEAM1 is a major pest. Exploring the implications of these findings will be essential for insecticide use and integrated pest management strategies in south Florida.

Discovery of Three Bemisia tabaci Effectors and Their Effect on Gene Expression in Planta.

Bemisia tabaci (whitefly) is a polyphagous agroeconomic pest species complex. Two members of this species complex, Mediterranean (MED) and Middle-East-Asia Minor 1 (MEAM1), have a worldwide distribution and have been shown to manipulate plant defenses through effectors. In this study, we used three different strategies to identify three MEAM1 proteins that can act as effectors. Effector B1 was identified using a bioinformatics-driven effector-mining strategy, whereas effectors S1 and P1 were identified in the saliva of whiteflies collected from artificial diet and in phloem exudate of tomato on which nymphs were feeding, respectively. These three effectors were B. tabaci specific and able to increase whitefly fecundity when transiently expressed in tobacco plants (Nicotiana tabacum). Moreover, they reduced growth of Pseudomonas syringae pv. tabaci in Nicotiana benthamiana. All three effectors changed gene expression in planta, and B1 and S1 also changed phytohormone levels. Gene ontology and KEGG pathway enrichment analysis pinpointed plant-pathogen interaction and photosynthesis as the main enriched pathways for all three effectors. Our data thus show the discovery and validation of three new B. tabaci MEAM1 effectors that increase whitefly fecundity and modulate plant immunity. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Transcriptome data reveal beneficial effects of Rickettsia (Rickettsiales: Rickettsiaceae) on Bemisia tabaci(Hemiptera: Aleyrodidae) through nutritional factors and defense mechanisms.

Whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a destructive insect pest of many crops. Rickettsia infection in different cryptic species of B. tabaci has been observed worldwide. Understanding the interactions between these 2 organisms is critical to developing Rickettsia-based strategies to control B. tabaci and thereby reduce the transmission of related vector-borne viruses. In this study, we investigated the effects of Rickettsia infection on the biological characteristics of the Middle East Asia Minor 1 (MEAM1) strain of B. tabaci through biological analysis of infected and uninfected individuals. The results of this study suggest that Rickettsia may confer fitness benefits. These benefits include increased fertility, improved survival rates, accelerated development, and resulted in female bias. We also investigated the transcriptomics impact of Rickettsia infection on B. tabaci by performing a comparative RNA-seq analysis of nymphs and adult females, both with and without the infection. Our analysis revealed 218 significant differentially expressed genes (DEGs) in infected nymphs compared to uninfected ones and 748 significant DEGs in infected female adults compared to their uninfected whiteflies. Pathway analysis further revealed that Rickettsia can affect many important metabolic pathways in whiteflies. The results suggest that Rickettsia plays an essential role in energy metabolism, and nutrient synthesis in the B. tabaci MEAM1, and depends on metabolites obtained from the host to ensure its survival. Overall, our findings suggest that Rickettsia has beneficial effects on B. tabaci and offered insights into the potential molecular mechanisms governing the interactions between Rickettsia and B. tabaci MEAM1.

Passionfruit severe leaf distortion virus: Expanded host range, response of Passiflora spp. plants to infection and transmission by Bemisia tabaciMEAM1

AbstractPassionfruit severe leaf distortion virus (PSLDV) is a begomovirus transmitted by Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1), associated with severe disease in passion flowers. This study aimed to evaluate the reaction of plants of different species of Passiflora to infection with PSLDV, expand the known host range of the virus and determine the minimum virus acquisition and inoculation access periods and the time of virus retention by B. tabaci MEAM1. Plants of Passiflora cincinnata, P. mucronata and P. malacophylla were not infected with PSLDV through transmission with B. tabaci MEAM1. When healthy plants of these species were fork grafted onto PSLDV‐infected plants of P. edulis, only plants of P. malacophylla remained uninfected and the virus was not detected by PCR, suggesting immunity to this begomovirus. Plants of Datura stramonium, Nicotiana benthamiana, N. clevelandii, N. tabacum ‘Xanthi’, Solanum lycopersicum (tomato cv. Compack) and several varieties of Manihot esculenta (cassava cvs IAC 118‐96, IAC 6‐01, Paranavaí, IAC 576, IAC 90 and IAC 14) were susceptible to infection with PSLDV through transmission with B. tabaci MEAM1. Adults of B. tabaci MEAM1 acquired PSLDV after 1 h of feeding on PSLDV‐infected plants of D. stramonium. They transmitted the virus to healthy plants after feeding on these plants for 1 h, although with low transmission rates. The retention time of PSLDV in the vector was 14 days.

A temperature-dependent phenology model for Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae).

The sweetpotato whitefly, Bemisia tabaci (Gennadius) Middle East-Asia Minor 1 (MEAM1), is widespread across tropical and subtropical regions, affecting hundreds of cultivated and wild plant species. Because the species transmits a variety of viruses, the whitefly has become one of the most economically significant insect pests in the world. Determining a pest's population growth potential as a function of temperature is critical for understanding a species population dynamics, predicting the potential range of the species and its associated diseases, and designing adaptive pest management strategies. The life history of B. tabaci MEAM1 was studied in life-table experiments at 7 constant temperatures ranging from 12 to 35 °C. Nonlinear equations were fitted to development, mortality, and reproduction data and compiled into an overall phenology rate-summation model using Insect Life Cycle Modeling (ILCYM) software, to simulate life-table parameters based on temperature. Life tables of B. tabaci MEAM1 observed at naturally variable temperature in La Molina, Lima, during different seasons, covering the entire temperature range of the species' predicted performance curve, were used to validate the model. Simulations predicted population growth within temperature between 13.9 and 33.4 °C, revealing a maximum finite rate of population increase (λ = 1.163), with a generation time of 33.3 days at 26.4 °C. Predicted species performance agreed well when compared against observed life tables and published data. The process-based physiological model presented here for B. tabaci MEAM1 should prove useful to predict the potential spatial distribution of the species based on temperature and to adjust pest control measures taking different population growth potentials due to prevailing temperature regimes into account.

Characterization of Soybean, Tomato, and Nicandra physalodes as Sources of Inoculum of Tomato Severe Rugose Virus to Tomato Crops.

Tomato severe rugose virus (ToSRV) is one of Brazil's main begomoviruses infecting tomatoes (Solanum lycopersicum). Recent studies indicate that soybean (Glycine max) crops harboring the whitefly Bemisia tabaci MEAM1 may have epidemiological significance by acting as an asymptomatic amplifier host for the virus. In this study, we gathered experimental greenhouse and field evidence of the role of soybeans in the epidemiology of the disease caused by ToSRV. Tomato and Nicandra physalodes, known as good sources of inoculum of this begomovirus, were used as references. The infection rates of soybean, tomato, and N. physalodes with ToSRV in greenhouse no-choice transmission tests with B. tabaci MEAM1 were 50%, 71.4%, and 64.2%, respectively. The transmission efficiencies of ToSRV to tomato when B. tabaci MEAM1 acquired the virus in ToSRV-infected soybean, tomato, and N. physalodes were 43%, 33%, and 20%, respectively. Leaves of ToSRV-infected soybean, tomato, and N. physalodes used as sources of inoculum had similar virus titers. In the host preference assay, viruliferous whiteflies preferred to land on tomato than soybean and N. physalodes, whereas aviruliferous whiteflies landed indistinctly on these plants. Under experimental field conditions, the transmission efficiency of ToSRV to tomato was higher when tomato was used as a source of inoculum, followed by N. physalodes and soybean. Considering that soybean is extensively cultivated in several Brazilian states that also grow tomatoes, it can serve as an efficient asymptomatic source of inoculum and support the recent hypothesis that it can also play, under certain conditions, a relevant role as an amplifier host in the epidemiology of the disease caused by ToSRV.

Differential Transcriptional Responses in Two Old World Bemisia tabaci Cryptic Species Post Acquisition of Old and New World Begomoviruses.

Begomoviruses are transmitted by several cryptic species of the sweetpotato whitefly, Bemisia tabaci (Gennadius), in a persistent and circulative manner. Upon virus acquisition and circulative translocation within the whitefly, a multitude of molecular interactions occur. This study investigated the differentially expressed transcript profiles associated with the acquisition of the Old World monopartite begomovirus, tomato yellow leaf curl virus (TYLCV), and two New World bipartite begomoviruses, sida golden mosaic virus (SiGMV) and cucurbit leaf crumple virus (CuLCrV), in two invasive B. tabaci cryptic species, Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED). A total of 881 and 559 genes were differentially expressed in viruliferous MEAM1 and MED whiteflies, respectively, compared with their non-viruliferous counterparts, of which 146 genes were common between the two cryptic species. For both cryptic species, the number of differentially expressed genes (DEGs) associated with TYLCV and SiGMV acquisition were higher compared with DEGs associated with CuLCrV acquisition. Pathway analysis indicated that the acquisition of begomoviruses induced differential changes in pathways associated with metabolism and organismal systems. Contrasting expression patterns of major genes associated with virus infection and immune systems were observed. These genes were generally overexpressed and underexpressed in B. tabaci MEAM1 and MED adults, respectively. Further, no specific expression pattern was observed among genes associated with fitness (egg production, spermatogenesis, and aging) in viruliferous whiteflies. The weighted gene correlation network analysis of viruliferous B. tabaci MEAM1 and MED adults identified different hub genes potentially implicated in the vector competence and circulative tropism of viruses. Taken together, the results indicate that both vector cryptic species and the acquired virus species could differentially affect gene expression.

Differential Transmission of Old and New World Begomoviruses by Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) Cryptic Species of Bemisia tabaci.

Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED) are two of the most invasive members of the sweetpotato whitefly, Bemisia tabaci, cryptic species complexes and are efficient vectors of begomoviruses. Bemisia tabaci MEAM1 is the predominant vector of begomoviruses in open-field vegetable crops in the southeastern United States. However, recently B. tabaci MED also has been detected in the landscape outside of greenhouses in Florida and Georgia. This study compared the transmission efficiency of one Old-World (OW) and two New-World (NW) begomoviruses prevalent in the southeastern United States, viz., tomato yellow leaf curl virus (TYLCV), cucurbit leaf crumple virus (CuLCrV), and sida golden mosaic virus (SiGMV) between B. tabaci MEAM1 and B. tabaci MED. Bemisia tabaci MEAM1 efficiently transmitted TYLCV, CuLCrV, or SiGMV, whereas B. tabaci MED only transmitted TYLCV. Percent acquisition and retention of OW TYLCV following a 72 h acquisition access period was significantly higher for B. tabaci MED than B. tabaci MEAM1. In contrast, B. tabaci MEAM1 acquired and retained significantly more NW bipartite begomoviruses, CuLCrV or SiGMV, than B. tabaci MED. Quantitative analysis (qPCR) of virus DNA in whitefly internal tissues revealed reduced accumulation of CuLCrV or SiGMV in B. tabaci MED than in B. tabaci MEAM1. Fluorescent in situ hybridization (FISH) showed localization of CuLCrV or SiGMV in the midgut of B. tabaci MED and B. tabaci MEAM1. However, localization of CuLCrV or SiGMV was only observed in the primary salivary glands of B. tabaci MEAM1 and not B. tabaci MED. TYLCV localization was observed in all internal tissues of B. tabaci MEAM1 and B. tabaci MED. Overall, results demonstrate that both B. tabaci MEAM1 and B. tabaci MED are efficient vectors of OW TYLCV. However, for the NW begomoviruses, CuLCrV and SiGMV, B. tabaci MEAM1 seems to a better vector.

Natural Infection Rate of Known Tomato chlorosis virus-Susceptible Hosts and the Influence of the Host Plant on the Virus Relationship With Bemisia tabaci MEAM1.

Tomato chlorosis virus (ToCV; genus Crinivirus, family Closteroviridae) was identified in tomato crops in São Paulo State, Brazil, in 2006. Management strategies to control external sources of inoculum are necessary, because chemical control of the whitefly vector Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) has not efficiently prevented virus infections and no commercial tomato varieties or hybrids are resistant to this crinivirus. We first evaluated the natural infection rate of some known wild and cultivated ToCV-susceptible hosts and their attractiveness for B. tabaci MEAM1 oviposition. Physalis angulata was the most susceptible to natural infection in all six exposures in 2018 and 2019. No plants of Capsicum annuum 'Dahra' or Chenopodium album became infected. Solanum melongena 'Napoli' had only two infected plants of 60 exposed. Capsicum annuum and Chenopodium album were the least preferred, and Nicotiana tabacum and S. melongena were the most preferred for whitefly oviposition. In addition, from 2016 to 2019, we surveyed different tomato crops and the surrounding vegetation to identify ToCV in weeds and cultivated plants in the region of Sumaré, São Paulo State. Only S. americanum, vila vila (S. sisymbriifolium), and Chenopodium album were found naturally infected, with incidences of 18, 20, and 1.4%, respectively. Finally, we estimated the ToCV titer (U.S. and Brazilian isolates ToCV-FL and ToCV-SP, respectively) by quantitative reverse transcription PCR in different ToCV-susceptible host plants and evaluated the relationship between virus acquisition and transmission by B. tabaci MEAM1. The results clearly showed significant differences in ToCV concentrations in the tissues of ToCV-susceptible host plants, which appeared to be influenced by the virus isolate. The concentration of the virus in plant tissues, in turn, directly influenced the ToCV-B. tabaci MEAM1 relationship and subsequent transmission to tomato plants. To minimize or prevent damage from tomato yellowing disease through management of external sources of ToCV, it is necessary to correctly identify potentially important ToCV-susceptible hosts in the vicinity of new plantings.

Low Genetic Variability in Bemisia tabaci MEAM1 Populations within Farmscapes of Georgia, USA.

Simple SummarySweetpotato whitefly, Bemisia tabaci Gennadius, is a serious pest of many agricultural crops worldwide. Numerous studies have examined the genetic structure of whitefly populations separated by geographical barriers; however, very few have assessed the population structure of B. tabaci at a farmscape level. A farmscape in this study is defined as heterogenous habitat with crop and non-crop areas spanning approximately 8 square kilometers. To assess the roles of farmscapes as drivers of B. tabaci genetic variation, thirty-five populations of the sweetpotato whitefly were collected from crop and non-crop plant species from fifteen farmscapes. Using mitochondrial COI gene sequences (mtCOI) and six nuclear microsatellite markers, the genetic diversity and genetic differentiation among collected B. tabaci MEAM1 populations were examined. Haplotype analysis using mtCOI sequences revealed the presence of a single B. tabaci MEAM1 haplotype across farmscapes of Georgia. Results from microsatellite markers further showed no significant genetic structuring among populations that corresponded to plant species or farmscapes from which they were collected. Annual whitefly population explosions and subsequent dispersal might have facilitated the persistence of a single panmictic B. tabaci population over all sampled farmscapes in this region. Bemisia tabaci is a whitefly species complex comprising important phloem feeding insect pests and plant virus vectors of many agricultural crops. Middle East–Asia Minor 1 (MEAM1) and Mediterranean (MED) are the two most invasive members of the B. tabaci species complex worldwide. The diversity of agroecosystems invaded by B. tabaci could potentially influence their population structure, but this has not been assessed at a farmscape level. A farmscape in this study is defined as heterogenous habitat with crop and non-crop areas spanning ~8 square kilometers. In this study, mitochondrial COI gene (mtCOI) sequences and six microsatellite markers were used to examine the population structure of B. tabaci MEAM1 colonizing different plant species at a farmscape level in Georgia, United States. Thirty-five populations of adult whiteflies on row and vegetable crops and weeds across major agricultural regions of Georgia were collected from fifteen farmscapes. Based on morphological features and mtCOI sequences, five species/cryptic species of whiteflies (B. tabaci MEAM1, B. tabaci MED, Dialeurodes citri, Trialeurodes abutiloneus, T. vaporariorum) were found. Analysis of 102 mtCOI sequences revealed the presence of a single B. tabaci MEAM1 haplotype across farmscapes in Georgia. Population genetics analyses (AMOVA, PCA and STRUCTURE) of B. tabaci MEAM1 (microsatellite data) revealed only minimal genetic differences among collected populations within and among farmscapes. Overall, our results suggest that there is a high level of gene flow among B. tabaci MEAM1 populations among farmscapes in Georgia. Frequent whitefly population explosions driven by a single or a few major whitefly-suitable hosts planted on a wide spatial scale may be the key factor behind the persistence of a single panmictic population over Georgia’s farmscapes. These population structuring effects are useful for delineating the spatial scale at which whiteflies must be managed and predicting the speed at which alleles associated with insecticide resistance might spread.

Spatial Distribution of Whitefly Species (Hemiptera: Aleyrodidae) and Identification of Secondary Bacterial Endosymbionts in Tomato Fields in Costa Rica.

In Costa Rica, tomato (Solanum lycopersicum Linnaeus) Linnaeus (Solanales: Solanaceae) is one of the crops most severely affected by the whiteflies (Hemiptera: Aleyrodidae) Trialeurodes vaporariorum (Westwood) and the Bemisia tabaci (Gennadius) species complex. The objective of this study was to monitor the spatial distribution and diversity of these species and to detect the presence of secondary bacterial endosymbionts in individuals collected in areas of intensive tomato production. In total, 628 whitefly individuals were identified to the species level using restriction analysis (PCR-RFLP) of a fragment of the mitochondrial cytochrome C oxidase I gene (mtCOI). Trialeurodes vaporariorum was the predominant species, followed by B. tabaci Mediterranean (MED). Bemisia tabaci New World (NW) and B. tabaci Middle East-Asia Minor 1 (MEAM1) were present in lower numbers. The mtCOI fragment was sequenced for 89 individuals and a single haplotype was found for each whitefly species. Using molecular markers, the 628 individuals were analyzed for the presence of four endosymbionts. Arsenophonus Gherna et al. (Enterobacterales: Morganellaceae) was most frequently associated with T. vaporariorum, whereas Wolbachia Hertig (Rickettsiales: Anaplasmataceae) and Rickettsia da Rocha-Lima (Rickettsiales: Rickettsiaceae) were associated with B. tabaci MED. This study confirmed that B. tabaci NW has not been completely displaced by the invasive species B. tabaci MED and B. tabaci MEAM1 present in the country. An association was found between whitefly species present in tomato and certain secondary endosymbionts, elevation was the most likely environmental factor to affect their frequency.

Transmission of the Bean-Associated Cytorhabdovirus by the Whitefly Bemisia tabaci MEAM1.

The knowledge of genomic data of new plant viruses is increasing exponentially; however, some aspects of their biology, such as vectors and host range, remain mostly unknown. This information is crucial for the understanding of virus–plant interactions, control strategies, and mechanisms to prevent outbreaks. Typically, rhabdoviruses infect monocot and dicot plants and are vectored in nature by hemipteran sap-sucking insects, including aphids, leafhoppers, and planthoppers. However, several strains of a potentially whitefly-transmitted virus, papaya cytorhabdovirus, were recently described: (i) bean-associated cytorhabdovirus (BaCV) in Brazil, (ii) papaya virus E (PpVE) in Ecuador, and (iii) citrus-associated rhabdovirus (CiaRV) in China. Here, we examine the potential of the Bemisia tabaci Middle East-Asia Minor 1 (MEAM1) to transmit BaCV, its morphological and cytopathological characteristics, and assess the incidence of BaCV across bean producing areas in Brazil. Our results show that BaCV is efficiently transmitted, in experimental conditions, by B. tabaci MEAM1 to bean cultivars, and with lower efficiency to cowpea and soybean. Moreover, we detected BaCV RNA in viruliferous whiteflies but we were unable to visualize viral particles or viroplasm in the whitefly tissues. BaCV could not be singly isolated for pathogenicity tests, identification of the induced symptoms, and the transmission assay. BaCV was detected in five out of the seven states in Brazil included in our study, suggesting that it is widely distributed throughout bean producing areas in the country. This is the first report of a whitefly-transmitted rhabdovirus.

Deep Sequencing of Small RNAs in the Whitefly Bemisia tabaci Reveals Novel MicroRNAs Potentially Associated with Begomovirus Acquisition and Transmission.

SummaryThe whitefly (Bemisia tabaci), a notorious insect vector, transmits hundreds of viruses causing serious yield losses in a diverse food and fiber crops including beans, cassava, cotton, cucurbits, pepper, sweet potato and tomato, and results in billions of U.S. dollars of economic losses annually worldwide. To investigate the molecular mechanisms regulating gene expression in whitefly that is associated with begomovirus transmission, we conducted small RNA sequencing and compared the microRNA (miRNA) profiles between viruliferous whiteflies feeding on tomato plants infected with a begomovirus, tomato yellow leaf curl virus (TYLCV), and those whiteflies feeding on uninfected plants. We uncovered a comprehensive microRNA genetic regulatory system in whiteflies that may be involved in virus acquisition and transmission. Interestingly, correlating the expression profile of miRNAs and their target transcript expression in our earlier transcriptome study, we found miRNA expression was inversely correlated with predicted target gene expression in over 50% of all cases. This fundamental understanding will help identify new target sequences that could be used to improve RNA interference technology for whitefly control. These analyses could also serve as a model to study gene regulation in other systems involving arthropod transmission of viruses to plants and animals.The whitefly Bemisia tabaci (Gennadius) is a notorious insect vector that transmits hundreds of plant viruses, affecting food and fiber crops worldwide, and results in the equivalent of billions of U.S. dollars in crop loss annually. To gain a better understanding of the mechanism in virus transmission, we conducted deep sequencing of small RNAs on the whitefly B. tabaci MEAM1 (Middle East-Asia Minor 1) that fed on tomato plants infected with tomato yellow leaf curl virus (TYLCV). Overall, 160 miRNAs were identified, 66 of which were conserved and 94 were B. tabaci-specific. Among the B. tabaci-specific miRNAs, 67 were newly described in the present study. Two miRNAs, with predicted targets encoding a nuclear receptor (Bta05482) and a very-long-chain (3R)-3-hydroxyacyl-CoA dehydratase 2 (Bta10702), respectively, were differentially expressed in whiteflies that fed on TYLCV-infected versus uninfected plants. To better understand the regulatory effects of identified miRNAs and their target genes, we correlated expression profiles of miRNAs and their target transcripts and found that, interestingly, miRNA expression was inversely correlated with the expression of ~50% of the predicted target genes. These analyses could serve as a model to study gene regulation in other systems involving arthropod transmission of viruses to plants and animals.

Phenolics, rather than glucosinolates, mediate host choice of Bemisia tabaci MEAM1 and MED on five cabbage genotypes

AbstractWorldwide, the most two important cryptic species of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) are MEAM1 (Middle East–Asia Minor 1, “B” biotype) and MED (Mediterranean, “Q” biotype). Although both B. tabaci MEAM1 and MED are polyphagous, they differ greatly in host choice and performance on various host plants. MEAM1 prefer to settle and perform better than MED on cabbage (Brassica oleracea), for example, but the underlying mechanism is largely unexplored. In the present study, we first measured the contents of the main secondary insect‐resistant substances (glucosinolates and phenolics) and main nutrients (soluble proteins, total amino acids and total nitrogen) in five cabbage genotypes. We then examined the settling and oviposition choices of MEAM1 and MED on the five cabbage genotypes, respectively. The settling and oviposition preferences of both MEAM1 and MED were negatively related to the content of total phenolics rather than to the content of glucosinolates or main nutrients. Furthermore, our results showed that MEAM1 ranked the host quality of the cabbage genotypes more accurately than MED. The results at least in part indicate that total phenolics rather than glucosinolates mediate the host choice of B. tabaci MEAM1 and MED on the five cabbage genotypes.

Competitive Displacement between Bemisia tabaci MEAM1 and MED and Evidence for Multiple Invasions of MED.

Despite the severe ecological damage and economic loss caused by invasive species, the factors contributing to successful invasion or displacement remain elusive. The whitefly, Bemisia tabaci (Gennadius), is an important invasive agricultural pest worldwide, causing severe damage to numerous crops by feeding or transmitting plant viruses. In this study, we monitored the dynamics of two invasive whitefly cryptic species, Middle East-Asia Minor 1 (MEAM1) and Mediterranean (MED), in Jiangsu, China, from 2005–2016. We found that B. tabaci MED quickly established and asserted dominance over MEAM1, resulting in their population displacement in Jiangsu in only three years (from 2005 to 2008). We further investigated the possible mechanisms underlying the successful invasion and competitive displacement from a genetic perspective. Based on sequencing of mitochondrial gene sequences from large numbers of whitefly samples, multiple invasion events of MED were validated by our genetic analyses. MED invaded Jiangsu starting from multiple introduction sites with secondary and/or subsequent invasive events. This may favor their invasion and displacement of MEAM1. This study advances our understanding of the mechanisms that enabled the successful invasion of MED.

Insecticide resistance status of Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae) in Australian cotton production valleys

AbstractThe whitefly Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1), previously known as B biotype, is a major agricultural pest with a reputation for developing resistance to insecticides. DNA‐based identification revealed that B. tabaci MEAM1 is the dominant species within Australian cotton cropping. Discriminating doses of 10 mg/L for pyriproxyfen and 300 mg/L for both diafenthiuron and bifenthrin were determined from bioassay data collected in 2010–2015. Resistance to these insecticides was tested in whitefly populations collected in 2017 from cotton crops in Queensland and New South Wales. This study reports on the presence of pyriproxyfen resistance in B. tabaci MEAM1 at seven locations in Queensland and New South Wales. One population from Goondiwindi was resistant to bifenthrin, whereas no populations tested had resistance to diafenthiuron. To determine the presence of resistance alleles to organophosphates and pyrethroids, reference populations of susceptible and resistant whiteflies (pyriproxyfen, bifenthrin and neonicotinoid) were tested. The resistance mutation L925I was found in a pyrethroid‐resistant population and in some individuals from the pyriproxyfen‐resistant population. The mutation F331W that confers organophosphate and carbamate resistance was found in all individuals tested including the susceptible reference population, indicative of a widespread distribution in Australian B. tabaci MEAM1. The cotton industry has revised the insecticide resistance management strategy for B. tabaci, to restrict the usage of pyriproxyfen to a single application within a 30‐day window. Our results argue against the use of organophosphate and carbamate insecticides in Australian cotton, because B. tabaci MEAM1 populations show significant resistance levels. Furthermore, both pesticide groups are highly disruptive to a diverse range of natural enemy populations, and as such, widespread use likely contributes to pest outbreaks.

Effect of host plant species of cotton whitefly Bemisia tabaci Middle East‐Asia Minor 1 (Hemiptera: Aleyrodidae) on the development, survival and reproduction of its predaceous ladybeetle Serangium japonicum (Coleoptera: Coccinellidae)

Abstract The ladybeetle Serangium japonicum has great potential to control the invasive pest Bemisia tabaci Gennadius Middle East‐Asia Minor 1 (MEAM1) in China. However, whether and how the host plant species of B. tabaci MEAM1 affect S. japonicum remains largely unexplored. The present study investigated the influence of five host plant species of B. tabaci MEAM1, namely tobacco, cucumber, cotton, tomato and eggplant, on the pre‐imaginal development, survival of immature stages, adult weight, adult acquired rate and fecundity of S. japonicum under laboratory conditions. The results obtained indicate that the developmental time from first instar to adult eclosion in S. japonicum was shortest when fed on B. tabaci MEAM1 reared on cotton and longest on cucumber. The survival rate of immature stages and the adult acquired rate were highest for cotton and tomato and lowest for tobacco. The fresh weight of adults and the number of eggs laid by S. japonicum were highest for cucumber and lowest for tobacco. The egg hatch rate was lowest for tobacco and highest for tomato. These findings support suggest that host plant species should be factored into integrated pest management to maximize control efficiency when utilizing S. japonicum to control B. tabaci MEAM1.

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.

Baseline susceptibility of Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae) in Australia to spirotetramat, cyantraniliprole and dinotefuran, with reference to pyriproxyfen cross‐resistance

AbstractSilverleaf whitefly, Bemisia tabaci (Gennadius) Middle East‐Asia Minor 1 (MEAM1), previously known as B biotype, is an agricultural pest of global significance and has developed resistance to many commonly used insecticides. Toxicity of spirotetramat, cyantraniliprole and dinotefuran to B. tabaci MEAM1 populations from eastern Australia was determined by laboratory bioassay, using either a foliar leaf dip or systemic uptake methodology. All field‐collected populations tested were susceptible to spirotetramat (12 tested from 2011 to 2015), cyantraniliprole (23 tested from 2014 to 2017) and dinotefuran (16 tested from 2015 to 2017). Based on LC50 values, there was a 2.1‐fold difference in the response of field populations to spirotetramat, a threefold difference in response to cyantraniliprole, while the response to dinotefuran varied depending on assay used, 1.8 vs. 2.6 with a foliar assay and systemic uptake assay, respectively. Testing of spirotetramat and cyantraniliprole against a pyriproxyfen‐resistant strain, AY09‐1R demonstrated no evidence of cross‐resistance to pyriproxyfen. When tested against dinotefuran, AY09‐1R had a resistance factor of two indicating possible weak cross‐resistance to pyriproxyfen, although it is also possible that the strain carries other forms of resistance given its origin. Discriminating doses of 100 mg/L for spirotetramat, 1 mg/L for cyantraniliprole and 60 mg/L (systemic) and 600 mg/L (foliar) for dinotefuran were calculated from the bioassay data. All three insecticides demonstrated good efficacy against silverleaf whitefly, and for the Australian cotton industry, they add three modes of action to the insecticide resistance management strategy, providing greater flexibility in control options. This study has established baseline toxicity data and discriminating doses for spirotetramat, cyantraniliprole and dinotefuran, which will serve as a useful reference for future monitoring and management of B. tabaci MEAM1 insecticide resistance in Australian cotton.

Infection dynamics of endosymbionts reveal three novel localization patterns of Rickettsia during the development of whitefly Bemisia tabaci.

The whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) is a severe agricultural pest that harbors at least seven endosymbionts. Many important aspects of the symbiosis mechanism between these bacterial endosymbionts and their hosts are poorly understood, such as endosymbiont proliferation dynamics, spatial distribution and titer regulation during host development. In this study, infection by bacterial endosymbionts in the whitefly B. tabaci Middle East-Asia Minor-1 (MEAM1, formerly B biotype) South China population, their infection titers in various stages of whitefly host development and their spatial localization were investigated. Results revealed that the MEAM1 B. tabaci harbors the primary symbiont Portiera and secondary symbionts Rickettsia and Hamiltonella. The titers of these three endosymbionts increased with the development of their B. tabaci host. Significant proliferation of Portiera and Hamiltonella mainly occurred during the second to fourth instar nymphal stages, while Rickettsia proliferated mainly during adult eclosion. Fluorescence in situ hybridization analysis of B. tabaci adults revealed three novel infection patterns of Rickettsia: assemblage in the bacteriocytes that scattered through the entire abdomen of the female host, localization in wax glands and localization in the colleterial gland. These novel infection patterns may help to uncover the function of Rickettsia in its insect hosts.