Interspecific and intraspecific variation in susceptibility of two co-occurring pest thrips, Frankliniella occidentalis and Thrips palmi, to nine insecticides.

BACKGROUND: Field control of pest thrips mainly relies on insecticides, but the toxicity of insecticides can vary among thrips species and populations. In this study, we examined the susceptibility of multiple field populations of two thrips pests, Frankliniella occidentalis, and Thrips palmi, that often co-occur on vegetables, to nine insecticides belonging to seven subgroups. RESULTS: The highest level of variation in susceptibility among F. occidentalis populations was for spinetoram (73.92 fold difference between most resistant and most susceptible population), followed by three neonicotinoids (8.06-15.99 fold), while among T. palmi populations, it was also for spinetoram (257.19 fold), followed by emamectin benzoate, sulfoxaflor, and acetamiprid (23.64-45.50 fold). These findings suggest evolved resistance to these insecticides in some populations of the two thrips. One population of F. occidentalis had a particularly high level of resistance overall, being the most resistant for five of the nine insecticides tested. Likewise, a population of T. palmi had high resistance to all nine insecticides, again suggesting the evolution of resistance to multiple chemicals. For F. occidentalis, the LC95 values of most populations were higher than the field-recommended dosage for all insecticides except chlorfenapyr and emamectin benzoate. For several T. palmi populations, the LC95 values also tended to be higher than recommended dosages, except in the case of emamectin benzoate and spinetoram. CONCLUSIONS: Our study found interspecific and intraspecific variations in the susceptibility of two thrips to nine insecticides and multiple resistance in some populations, highlighting the need for ongoing monitoring and resistance management. © 2023 Society of Chemical Industry.

Variation in the toxicity of a novel meta-diamide insecticide, broflanilide, among thrips pest species and developmental stages.

BACKGROUND: Thrips pests cause increasing damage to crops around the world. Widespread usage of some insecticides against thrips has now led to the evolution of resistance to several active ingredients, and new insecticides are required. This study examined the toxicity of the novel insecticide broflanilide to multiple populations of several thrips pests. RESULTS: Bioassays showed that thrips populations had LC50 values ranging from 0.5 to almost 300 mg·L-1 . A population of Frankliniella occidentalis had the highest LC50 value at 290.63 mg·L-1 , while a population of Echinothrips americanus had the lowest LC50 value at 0.51 mg L-1 . LC50 values among seven populations of Thrips palmi ranged from 2.5689 to 23.6754 mg·L-1 , indicating intraspecific variation in toxicity. In this species, the toxicity of broflanilide was relatively higher in adults than in larvae. More than 90% of eggs of T. palmi could not develop into larvae when treated with 5-50 mg L-1 broflanilide. Compared to five commonly used insecticides, broflanilide showed relatively high toxicity to T. palmi. Field control tests with T. palmi showed that control efficacy (from 90.44% to 93.14%) was maintained from day three to day 14 after treatment with 22.5 and 45 ga.i hm-1 broflanilide. CONCLUSION: Broflanilide is potentially a useful insecticide for controlling Thrips hawaiiensis, Frankliniella intonsa, Megalurothrips usitatus. E. americanus, and some populations of T. palmi. However, the variation in toxicity of this insecticide to different species, populations, and developmental stages indicates that target species and life stages may need to be carefully considered. © 2022 Society of Chemical Industry.

Toxicity and Control Efficacy of an Organosilicone to the Two-Spotted Spider Mite Tetranychus urticae and Its Crop Hosts.

Organosilicone molecules represent important components of surfactants added to pesticides to improve pest control efficiency, but these molecules also have pesticidal properties in their own right. Here, we examined toxicity and control efficacy of Silwet 408, a trisiloxane ethoxylate-based surfactant, to the two-spotted spider mite (TSSM), Tetranychus urticae and its crop hosts. Silwet 408 was toxic to nymphs and adults of TSSM but did not affect eggs. Field trials showed that the control efficacy of 1000 mg/L Silwet 408 aqueous solution reached 96% one day after spraying but declined to 54% 14 days after spraying, comparable to 100 mg/L cyetpyrafen, a novel acaricide. A second spraying of 1000 mg/L Silwet 408 maintained control efficacy at 97% when measured 14 days after spraying. However, Silwet 408 was phytotoxic to eggplant, kidney bean, cucumber, and strawberry plants, although phytotoxicity to strawberry plants was relatively low and declined further seven days after application. Our study showed that while the organosilicone surfactant Silwet 408 could be used to control the TSSM, its phytotoxicity to crops should be considered.

Nanocarrier-delivered dsRNA suppresses wing development of green peach aphids.

RNA interference (RNAi) has developed rapidly as a potential "green" pest management strategy. At present, most studies have focused on the screening of aphid lethal genes, whereas only a few studies have been conducted on wing development, which is crucial for aphid migration and plant-virus dissemination. Here, the Myzus persicae genes vestigial (vg) and Ultrabithorax (Ubx) related to wing development, were cloned. These two genes were expressed in various tissues of 3rd-instar winged aphids. The mRNA level of vg was high in 3rd-instar nymphs, whereas the expression level of Ubx was high in adults. The nanocarrier-mediated delivery system delivered double-stranded RNAs for aphid RNAi using topical and root applications. The expression levels of vg and Ubx were downregulated by 44.0% and 36.5%, respectively, using the topical application. The simultaneous RNAi of the two target genes caused 63.3% and 32.2% wing aberration rates using topical and root applications, respectively. The current study provided a promising method for controlling aphid migration to alleviate the spread of insect transmitted plant diseases.

A novel plasmid-Escherichia coli system produces large batch dsRNAs for insect gene silencing.

BACKGROUND: RNA interference (RNAi)-based pest management requires efficient delivery and large-batch production of double-stranded (ds)RNA. We previously developed a nanocarrier-mediated dsRNA delivery system that could penetrate an insect's body and efficiently silence gene expression. However, there is a great need to improve the plasmid-Escherichia coli system for the mass production of dsRNA. Here, for efficient dsRNA production, we removed the rnc gene encoding endoribonuclease RNase III in E. coli BL21(DE3) and matched with the RNAi expression vector containing a single T7 promoter. RESULTS: The novel pET28-BL21(DE3) RNase III-system was successfully constructed to express vestigial (vg)-dsRNA against Harmonia axyridis. dsRNA was extracted and purified from cell cultures in four E. coil systems, and the yields of dsRNA in pET28-BL21(DE3) RNase III-, pET28-HT115(DE3), L4440-BL21(DE3) RNase III- and L4440-HT115(DE3) were 4.23, 2.75, 0.88 and 1.30 µg mL-1 respectively. The dsRNA expression efficiency of our novel E. coil system was three times that of L4440-HT115(DE3), a widely used dsRNA production system. The RNAi efficiency of dsRNA produced by our system and by biochemical synthesis was comparable when injected into Harmonia axyridis. CONCLUSION: Our system expressed dsRNA more efficiently than the widely used L4440-HT115(DE3) system, and the produced dsRNA showed a high gene-silencing effect. Notably, our pET28-BL21(DE3) RNase III-system provides a novel method for the mass production of dsRNA at low cost and high efficiency, which may promote gene function analysis and RNAi-based pest management. © 2020 Society of Chemical Industry.

[Clinical effect of double filtration plasmapheresis combined with glucocorticoid and immunosuppressant in treatment of children with severe Henoch-Schönlein purpura nephritis].

OBJECTIVE: To study the clinical effect and safety of double filtration plasmapheresis (DFPP) combined with double pulse therapy with methylprednisolone (MP) and cyclophosphamide (CTX) in the treatment of children with severe Henoch-Schönlein purpura nephritis (HSPN). METHODS: A total of 60 children with severe HSPN who were admitted to the hospital from January 2014 to March 2018 were enrolled and were randomly divided into an observation group and a control group (n=30 each). In addition to routine treatment, the children in the control group were given MP+CTX pulse therapy. Those in the observation group were given DFPP treatment in addition to the treatment in the control group, with three courses of treatment in total. After three courses of treatment, the two groups were compared in terms of 24-hour urinary protein, urinary microproteins, renal function parameters, adverse reactions, and clinical outcome. RESULTS: After three courses of treatment, the observation group had significantly greater reductions in 24-hour urinary protein, urinary albumin, urinary immunoglobulin G, urinary ß2-microglobulin, serum creatinine, and blood urea nitrogen than the control group (P<0.05). After the treatment ended, the observation group had a significantly shorter time to achieve remission than the control group (P<0.05). No serious adverse reactions, such as hemorrhagic cystitis, thrombocytopenia, and hemolysis, were observed, and there was no significant difference in the overall incidence rate of adverse reactions between the two groups (P>0.05). CONCLUSIONS: Compared with MP+CTX pulse therapy alone in the treatment of severe HSPN in children, DFPP combined with MP+CTX pulse therapy can further alleviate renal injury and improve clinical outcome and does not increase the incidence rate of adverse reactions.