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Thermal stress usually leads to excessive production of reactive oxygen species (ROS) in all aerobic organisms. Catalases (CAT) are the key antioxidant enzymes, which act as the first line of defense against ROS in the antioxidant pathway. The highly invasive and widely distributed whitefly Bemisia tabaci MED damages plants by feeding as well as by transmitting many plant viruses. Previous studies have shown that strong adaptability to high temperature helps explain the spread of MED around the world. However, the mechanism underlying high temperature adaptation of this pest is not well understood. In this study, six CAT genes were identified from the MED genome and transcriptome dataset, among which BtCAT1, BtCAT2, and BtCAT3 were found to be highly expressed in adults. The expression of BtCAT1, BtCAT2, or BtCAT3 increased with induction temperature and induction time. The MED was exposed with mean high temperature (30°C or 35°C) and a short-term extremely high temperature (39°C or 41°C) after the silencing of BtCAT1, BtCAT2, or BtCAT3 to significantly increased ROS levels by at least 0.5 times and significantly decreased survival rate and fecundity of MED adults. The ROS level in the treated specimens gradually returned to a normal level after 24 h at 25°C, but the survival rate still declined significantly. Taken together, our results demonstrate that CAT could help B. tabaci adapt to long-term mean high temperatures and short-term extremely high temperatures by eliminating excessive ROS. This article is protected by copyright. All rights reserved.

Uridine diphosphate (UDP)-glycosyltransferases (UGTs), which are major phase II detoxification enzymes, have been implicated in the glycosylation of lipophilic endobiotics and xenobiotics and thus potentially lead to the evolution of insecticide resistance. In this study, we identified and cloned two putative UGT genes from transcriptome data which are named UGT352A4 and UGT352A5. As demonstrated by qRT-PCR, two UGT genes were over-expressed in the thiamethoxam-resistant (THQR) strain relative to the susceptible (THQS) strain. Moreover, the induction experiment revealed that the expression of the UGT352A5 gene was significantly increased following exposure to thiamethoxam in the THQR strain. Furthermore, the expression of both UGT352A4 and UGT352A5 was downregulated after RNA interference, whereas only the silencing of UGT352A5 resulted in a noticeable increase in the mortality of THQR adults. Our results represent the first line of evidence showing that UGT352A5 might be responsible for conferring thiamethoxam resistance in B. tabaci. The results will be shed new insights for obtaining a better understanding of the role of UGTs in the evolution of insecticide resistance and developing new insect resistance management tactics within the sustainable integrated pest management framework.

The western flower thrips Frankliniella occidentalis, a worldwide agricultural pest, has developed resistance to an array of insecticides. Spinosad resistance confers an apparent fitness cost in F. occidentalis. In the present study, we compared the reproductive capacities, ovary development, and the expression of the vitellogenin (Vg) gene in spinosad-susceptible (Ivf03) and -resistant (NIL-R) near isogenetic lines of F. occidentalis in order to clarify the reason for the fitness cost in spinosad resistance.The NIL-R strain exhibited a 17.9% decrease in fecundity (eggs laid per female) as compared to the Ivf03 strain, and the ovariole was significantly shortened by 2.8% in the NIL-R strain relative to the Ivf03 strain. Compared to the Ivf03 strain, the expression levels of Vg mRNA and protein were downregulated by 33.7% and 32.9% in the NIL-R strain, respectively. Moreover, interference with the Vg gene significantly reduced the expression levels of Vg mRNA and protein, and decreased ovariole length, survival rates and the fecundity of both strains.The results indicate that the downregulated expression of Vg may contribute to the reduction of ovariole length and consequently to a fitness cost in spinosad-resistant F. occidentalis. The results not only increase our understanding of the evolution of insecticide resistance, but also could contribute to the formulation of control strategy of F. occidentalis. © 2022 Society of Chemical Industry.

Species displacement by the outcome of interspecific competition is of particular importance to pest management. Over the past decade, spinetoram has been extensively applied in control of the two closely related thrips Megalurothrips usitatus and Frankliniella intonsa worldwide, while whether its resistance is implicated in mediating interspecific interplay of the two thrips remains elusive to date.Field population dynamics (from 2017 to 2019) demonstrated a trend toward displacement of F. intonsa by M. usitatus on cowpea crops, supporting an existing interspecific competition. Following exposure to spinetoram, M. usitatus became the predominate species, which suggests the use of spinetoram appears to be responsible for mediating interspecific interactions of the two thrips. Further annual and seasonal analysis (from 2016 to 2020) of field-evolved resistance dynamics revealed that M. usitatus developed remarkably higher resistance to spinetoram compared to that of F. intonsa, implying a close relationship between evolution of spinetoram resistance and their competitive interactions. After 12 generations of laboratory selection, resistance to spinetoram in M. usitatus and F. intonsa increased up to 64.50-fold and 28.33-fold, and the average realized heritability (hCollectively, our results uncover the involvement of insecticide resistance in conferring displacement mechanism behind interspecific competition, providing a framework for understanding the significance of the evolutionary relationships among insects under ongoing changing environments. These findings also can be invaluable in proposing the most appropriate strategies for sustainable thrips control programs. © 2022 Society of Chemical Industry.

The possible advantage of cotton production established in low-lying land area over intensive culture pond was investigated by comparing the abundance of cotton spider mites on these plants to that in conventional production areas at the Jiangbei farm, Hubei Province, China. Cotton fields recently grown at low-lying land area supported significantly lower populations of cotton spider mites than conventional long established cotton fields. There were no significant differences in mite populations between cotton fields established in low-lying land area in the current year or 1 or 2 years earlier. The pest control advantage provided by pond areas was present whether or not acaricides were used. The total phenolic content of cotton leaves differed occasionally between treatments but did not seem to have affected the abundance of mites. The number of eggs, larva-nymph-adults, egg-larva-nymph-adults, the percentage of host plants colonized by cotton spider mites and the plant damage index were independent of the total phenolic content in leaves. The results are discussed in relation to integrated pest management and the mineral balance hypothesis.