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The sweet potato (cotton) whitefly Bemisia tabaci is a major agricultural pest in various fields and vegetable crops worldwide. It causes extensive damage by direct feeding on plants, reducing quality, secreting honeydew and transmitting plant viruses. B. tabaci is known for its genetic diversity and considered a complex of biotypes or, as suggested, a complex of distinct cryptic species. Management of whiteflies relies mainly on the use of insecticides; however, its ability to develop resistance to major insecticide classes creates a serious challenge to farmers and pest control specialists. Among the cryptic species of B. tabaci , MED is considered more resistant than the MEAM1 to insecticides such as pyriproxyfen and neonicotinoids; however, in recent years there are other species of B. tabaci including MEAM1, Asia I and Asia II-1 that have developed high resistance to various groups of insecticides. Advanced methods based on molecular and gene sequence data obtained from resistant and susceptible field-collected B. tabaci populations resulted in a better understanding of resistance mechanisms in this pest. Several components of IPM-IRM (Integrated Pest Management-Insecticide Resistance Management) programs such as selective and biorational insecticides, insecticide rotation with different modes of action and nonchemical control methods are among the countermeasures of insecticide resistance management for this pest. In the current review, we concentrate on insecticide resistance and resistance management of B. tabaci, focusing on reports published mainly over the past 10 years.

In China, Tomato chlorosis virus (ToCV) and Tomato yellow leaf curl virus (TYLCV) are widely present in tomato plants. The epidemiology of these viruses is intimately associated with their vector, the whitefly ( Bemisia tabaci MED). However, how a ToCV+TYLCV mixed infection affects viral acquisition by their vector remains unknown. In this study, we examined the growth parameters of tomato seedlings, including disease symptoms and the heights and weights of non-infected, singly infected and mixed infected tomato plants. Additionally, the spatio-temporal dynamics of the viruses in tomato plants, and the viral acquisition and transmission by B. tabaci MED, were determined. The results demonstrated that: (i) ToCV+TYLCV mixed infections induced tomato disease synergism, resulting in a high disease severity index and decreased stem heights and weights; (ii) as the disease progressed, TYLCV accumulated more in upper leaves of TYLCV-infected tomato plants than in lower leaves, whereas ToCV accumulated less in upper leaves of ToCV-infected tomato plants than in lower leaves; (iii) viral accumulation in ToCV+TYLCV mixed infected plants was greater than in singly infected plants; and (iv) B. tabaci MED appeared to have a greater TYLCV, but a lower ToCV, acquisition rate from mixed infected plants compared with singly infected plants. However, mixed infections did not affect transmission by whiteflies. Thus, ToCV+TYLCV mixed infections may induce synergistic disease effects in tomato plants.

The whitefly, Bemisia tabaci MEAM1 Gennadius causes serious losses to Florida vegetable and ornamental production. In 2019, a maximum dose bioassay was administered to 20 field populations of B. tabaci MEAM1 collected from various economic and weed hosts across south Florida to assess insecticide efficacy. The maximum dose bioassay tests the top labeled rate of the insecticide against B. tabaci adults on treated cotton leaves in a Petri dish over a 72-h period. A susceptible laboratory colony of B. tabaci MEAM1 and a colony of B. tabaci MED were also tested. Survival over 72 h was used to produce an area under the maximum dose curve, which was used to compare insecticide effects on different populations. Overall, imidacloprid demonstrated the poorest efficacy, dinotefuran and flupyradifurone were the most effective, and bifenthrin, cyantraniliprole, and thiamethoxam tended to group together, providing intermediate control. Across populations tested, survival in whitefly adults treated with dinotefuran was 50% lower than whiteflies treated with imidacloprid, about 33% lower than whiteflies treated with thiamethoxam, bifenthrin, and cyantraniliprole, and 10% lower than whiteflies treated with flupyradifurone. Efficacy of bifenthrin was less than imidacloprid on some populations, particularly from the Homestead area. Imidacloprid and thiamethoxam had no effect on mortality of the MED population when it was tested after 22 mo in culture without exposure to insecticides, although 7 mo later, these materials resulted in some mortality for the MED population.

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.

The Bemisia tabaci species complex threatens worldwide agriculture. While host-plant resistance is sustainable and effective, it is a relatively unexplored strategy for whitefly control. Three alfalfa ( Medicago sativa L.) populations were developed and used in high-throughput B. tabaci MEAM1 nymph-mortality screens. The phenotypic resistance/susceptibility spectrum in these populations indicated that whitefly resistance to MEAM1 is multigenic. Alfalfa lines highly resistant (R1, R2, and R3) and susceptible (S1) to B. tabaci MEAM1 were identified and further characterized. When life history parameters for three B. tabaci species (MEAM1, MED and NW1) were assessed on the four lines, whitefly species-specific responses to R1, R2 and R3 plants were revealed. While nymph mortality was high for MEAM1 and NW1 on resistant alfalfa, MED nymph development was surprisingly unimpaired. In addition, significant differences in oviposition, host-choice and longevity were observed amongst the three B. tabaci species. Collectively, these data indicated that R1, R2 and R3 plants each express a unique set of antibiotic/antixenotic resistance traits providing a potent multigenic and multi-faceted resistance to whiteflies with each B. tabaci species displaying distinct behaviors on the resistant lines. Our nymph-mortality simulation models indicate that deployment of the nymph mortality-mediated resistance of R1 and R3 alfalfa could substantially suppress whitefly population expansion in the field.

Genome-wide analysis of Bemisia tabaci Asia II-1 unravelled for the first-time full-length sequences of 14 chemosensory proteins (CSPs), their exon-intron boundaries, insertion sites of retrotransposons, and clustering patterns on chromosomes. All the CSPs sans CSP6 have an N-terminal signal peptide. The presence of OS-D superfamily and PhBP domains in different CSPs suggests their roles in chemosensory signal transduction and pheromone binding. Motif analysis reveals the conservation and cohesiveness of CSPs in hemiptera. The phylogenetic analysis uncovers the evolutionary lineages of Hemipteran CSPs. RT-qPCR analysis showed spatial expression of CSPs in different body tissues of B. tabaci adults. In-silico docking analysis showed high-affinity binding of CSP 1 and 5 with two insecticides, imidacloprid and fipronil, with energy values ranging from − 5.8 to -9.3 kcal/mol, along with the details of interacting aminoacidic residues in the hydrophobic binding pockets of these two CSPs. Further functional validation was done through insecticide bioassays and RNAi. This study provides novel insights into the genomic architecture of CSPs in B. tabaci Asia II-1, and functional characterisation suggests that CSP1 and 5 genes may have indirect roles in insecticide resistance. It lays the foundation for further research on developing new control strategies for B. tabaci .

Characterizing the olfactory responses of insect pests is critical for developing biological control options and pest management strategies in the field. Such responses form the basis for evaluating interactions between plants and insects, as well as providing evidence to support the use of non-crop plant types in pest suppression tactics. To evaluate the potential aversion or attraction of Bemisia tabaci MED/Q to volatiles from various plants, behavioral responses of adult whitefly were observed in Y-type olfactometer tests (n = 30 individuals per trial, with 3 replicate trials per treatment combination; n = 4230 individuals in total). We quantified the potential repellent effects of the essential oils of Thymus pulegioides (‘thyme’) and Artemisia absinthium (‘wormwood’) on B. tabaci MED/Q. The essential oil of T. pulegioides as well as three of the four major subcomponents tested (thymol 36.18%, p-Cymene 10.85% and thymol methyl ether 7.45%, but not Carvacrol 13.43%) had significant repellent effects on B. tabaci MED/Q. Similarly, the essential oil of A. absinthium, as well as the two major subcomponents tested (Linalool 23.41% and (−)-β-Pinene 27.88%), had marginally significant repellent effects on B. tabaci MED/Q. In tests across increasing concentrations of these volatile compounds, repellent effects were typically only significant at the two highest concentrations tested. Overall, these results demonstrate that major constituents of certain aromatic plant oils have a strong repellent effect and contact toxicity on B. tabaci MED/Q. These findings have important implications for more environmentally friendly biological control options using aromatic plants to repel target pests in production crops.

Cruciferous plants in the order Brassicales defend themselves from herbivory using glucosinolates: sulfur-containing pro-toxic metabolites that are activated by hydrolysis to form compounds, such as isothiocyanates, which are toxic to insects and other organisms. Some herbivores are known to circumvent glucosinolate activation with glucosinolate sulfatases (GSSs), enzymes that convert glucosinolates into inactive desulfoglucosinolates. This strategy is a major glucosinolate detoxification pathway in a phloem-feeding insect, the silverleaf whitefly Bemisia tabaci , a serious agricultural pest of cruciferous vegetables. In this study, we identified and characterized an enzyme responsible for glucosinolate desulfation in the globally distributed B. tabaci species MEAM1. In in vitro assays, this sulfatase showed a clear preference for indolic glucosinolates compared with aliphatic glucosinolates, consistent with the greater representation of desulfated indolic glucosinolates in honeydew. B. tabaci might use this detoxification strategy specifically against indolic glucosinolates since plants may preferentially deploy indolic glucosinolates against phloem-feeding insects. In vivo silencing of the expression of the B. tabaci GSS gene via RNA interference led to lower levels of desulfoglucosinolates in honeydew. Our findings expand the knowledge on the biochemistry of glucosinolate detoxification in phloem-feeding insects and suggest how detoxification pathways might facilitate plant colonization in a generalist herbivore.

Tomato is affected by a large number of arthropod pests, among which the whitefly ( Bemisia tabaci ) is considered to be one of the most destructive. Several accessions of the wild species of Solanum galapagense , including accession LA1401, are considered resistant to whitefly ( B. tabaci ). This resistance has been associated with the presence of type IV glandular trichomes on the leaf surface. Our research aimed to study the inheritance of type IV glandular trichome density and its association with resistance to whitefly ( B. tabaci biotype B) in populations derived from the interspecific cross Solanum lycopersicum  ×  S. galapagense ‘LA1401.’ High estimates for both broad-sense and narrow-sense heritabilities of type IV glandular trichome densities suggest that inheritance of this trait is not complex. Whitefly resistance was associated with high density of type IV glandular trichomes. F 2 ( S. galapagense  ×  S. lycopersicum ) population plants selected for the highest densities of type IV glandular trichomes showed similar levels of resistance to those found in the donor of resistance LA1401.

Background Neonicotinoids are widely applied in the control of the destructive agricultural pest Bemisia tabaci , and resistance against these chemicals has become a common, severe problem in the control of whiteflies. To investigate the molecular mechanism underlying resistance against nenonicotinoids in whiteflies, RNA-seq technology was applied, and the variation in the transcriptomic profiles of susceptible whiteflies and whiteflies selected by imidacloprid, acetamiprid and thiamethoxam treatment was characterized. Results A total of 90.86 GB of clean sequence data were obtained from the 4 transcriptomes. Among the 16,069 assembled genes, 584, 110 and 147 genes were upregulated in the imidacloprid-selected strain (IMI), acetamiprid-selected strain (ACE), and thiamethoxam (THI)-selected strain, respectively, relative to the susceptible strain. Detoxification-related genes including P450s, cuticle protein genes, GSTs, UGTs and molecular chaperone HSP70s were overexpressed in the selected resistant strains, especially in the IMI strain. Five genes were downregulated in all three selected resistant strains, including 2 UDP-glucuronosyltransferase 2B18-like genes (LOC 109030370 and LOC 109032577). Conclusions Ten generations of selection with the three neonicotinoids induced different resistance levels and gene expression profiles, mainly involving cuticle protein and P450 genes, in the three selected resistant whitefly strains. The results provide a reference for research on resistance and cross-resistance against neonicotinoids in B. tabaci .