The sweetpotato whitefly, Bemisia tabaci, has been a destructive pest in China for over the past two decades. It is an extremely polyphagous insect, being recorded feeding on hundreds of host plants around the world. Potential host plants and natural enemies of B. tabaci in the south, southeast, middle, north and northwest of China were investigated during the last decade. In total 361 plant species from 89 families were recorded in our surveys. Plants in the families Compositae, Cruciferae, Cucurbitaceae, Solanaceae and Leguminosae were the preferred host species for B. tabaci, which therefore suffered much damage from this devastating pest due to their high populations. In total, 56 species of parasitoids, 54 species of arthropod predators and seven species of entomopathogenic fungi were recorded in our surveys. Aphelinid parasitoids from Encarsia and Eretmocerus genera, lady beetles and lacewings in Coleoptera and Neuroptera were found to be the dominant arthropod predators of B. tabaci in China. The varieties of host plant, their distribution and the dominant species of natural enemies of B. tabaci in different regions of China are discussed.

Reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) is a momentous technique for quantifying expression levels of the targeted genes across various biological processes. Selection and validation of appropriate reference genes for RT-qPCR analysis are a pivotal precondition for reliable expression measurement. Henosepilachna vigintioctopunctata is one of the most serious insect pests that attack Solanaceae plants in Asian countries. Recently, the transcriptomes of H. vigintioctopunctata were sequenced, promoting gene functional studies of this insect pest. Unfortunately, the reference genes for H. vigintioctopunctata have not been selected and validated. Here, a total of 7 commonly used reference genes, namely, Actin, GAPDH, RPL13, RPL6, RPL32, RPS18, and ATPB, were selected and assessed for suitability under four experimental conditions, namely, developmental stage, tissue, temperature, and host plant, using RefFinder, which integrates four different analytical tools (Normfinder, geNorm, the ΔCt method, and BestKeeper). The results displayed that RPL13 and RPS18 were the best suitable reference genes for each experimental condition. The relative transcript levels of 2 target genes, lov and TBX1, varied greatly according to normalization with the two most- and least-suited reference genes. Our results will be helpful for improving the accuracy of the RT-qPCR analysis for future functional investigations of target gene expression in H. vigintioctopunctata.

BACKGROUND: Nanoparticles can be used for effective pest management as a combined formulation of metal and some other material that has proven efficacy against a given pest. This study reports the synthesis, characterization and efficacy of Isaria fumosorosea-based zero-valent iron (ZVI) nanoparticles against sweet potato whitefly Bemisia tabaci (Gennadius). RESULTS:The I. fumosorosea-ZVI nanoparticles showed a characteristic surface plasmon absorption band at 470 nm during UV-visible spectroscopy. The scanning electron micrographs of nanoparticles showed spherical shaped nanoparticles with sizes ranging between 1.71 and 3.0 m. The EDX analysis showed the characteristic peak of iron at 0.6 and 6.8 KeV. The XRD analysis showed characteristic peaks at 44.72 ∘ , 65.070 ∘ , 82.339 ∘ and 82.65 ∘ . The bioassay results indicated that the percentage of larval mortality of B. tabaci challenged with I. fumosorosea ZVI nanoparticles was both concentration and age dependent. Isaria fumosorosea ZVI nanoparticles showed high pathogenicity against second and third instar nymphs, and pupae with LC 50 values of 19.17, 26.10 and 37.71 ppm, respectively. The LT 50 was lowest for second instar nymphs (3.15 days) and highest for pupae (4.22 days) when inoculated with a concentration of 50 ppm. CONCLUSION: Isaria fumosorosea ZVI nanoparticles can be an eco-friendly tool for effective B. tabaci management.

To efficiently prevent the occurrence and spread of HLB disease, it is critical to understand the ecological basis of vector outbreaks and disease incidence, especially under field conditions. Thus, this study has increased our understanding of the epidemiology of HLB transmitted by psyllids in nature.

BACKGROUNDRNA interference (RNAi) is a potential tool for plant protection against insect pests. The great challenge for effective pest control using RNAi in the field is the development of efficient and reliable methods for the production and delivery of double‐stranded RNA (dsRNA).RESULTSIn the present study, we investigated the potential of feeding in vitro synthesized or bacterially expressed dsRNA to populations of the 28‐spotted ladybeetle Henosepilachna vigintioctopunctata as a method of biological pest control. Ingestion of in vitro synthesized dsHvRPS18 or dsHvRPL13 led to significant down‐regulation of the ribosomal protein‐encoding genes HvRPS18 and HvRPL13, respectively, and significantly decreased the survival of H. vigintioctopunctata. Such silencing of HvRPS18 or HvRPL13 expression appeared to be partially dose‐dependent and also inhibited the growth of H. vigintioctopunctata and significantly suppressed the expression of digestive enzyme‐related genes. Finally, ingestion of bacterially expressed dsHvRPS18 or dsHvRPL13 induced significant mortality in the first and third instars, and in adults.CONCLUSIONThe effectiveness of RNAi‐based gene silencing in H. vigintioctopunctata provides a powerful reverse genetic tool for the functional annotation of its genes. This study demonstrates that HvRPS18 and HvRPL13 represent candidate genes for RNAi‐based biological control of H. vigintioctopunctata. © 2020 Society of Chemical Industry