The hibiscus bud weevil is an invasive pest that attacks tropical hibiscus. Its management has been challenging due to its cryptic adult and concealed immature stages. We evaluated the efficiency of ...four systemic insecticides (spirotetramat, chlorantraniliprole, flupyradifurone, and cyantraniliprole) against the pest using two approaches: one applied 4 weeks before infestation (prophylactic) and the other 1 week after (curative). The number of eggs, larvae, and feeding holes per sampled bud were recorded 7, 14, 21, and 28 days after the infestation (prophylactic), and after the application (curative), respectively. In general, a greater number of treatment effects were detected in the prophylactic approach in comparison with those in the curative. With the prophylactic approach, the mean number of larvae and feeding holes per actively growing bud was significantly greater for the control (water) than for all insecticides. Among fallen buds, chlorantraniliprole, cyantraniliprole, and spirotetramat had significantly fewer feeding holes than those in the control. With the curative approach, the mean number of feeding holes was greater in the control with no differences among insecticides. The prophylactic application can effectively suppress initial HBW infestation, in contrast to the curative application targeting already high populations. This provides the opportunity for reducing the impact of this regulated pest in areas of expansion.
Both Aedes aegytpi and Ae. albopictus are major vectors of 5 important arboviruses (namely chikungunya virus, dengue virus, Rift Valley fever virus, yellow fever virus, and Zika virus), making these ...mosquitoes an important factor in the worldwide burden of infectious disease. Vector control using insecticides coupled with larval source reduction is critical to control the transmission of these viruses to humans but is threatened by the emergence of insecticide resistance. Here, we review the available evidence for the geographical distribution of insecticide resistance in these 2 major vectors worldwide and map the data collated for the 4 main classes of neurotoxic insecticide (carbamates, organochlorines, organophosphates, and pyrethroids). Emerging resistance to all 4 of these insecticide classes has been detected in the Americas, Africa, and Asia. Target-site mutations and increased insecticide detoxification have both been linked to resistance in Ae. aegypti and Ae. albopictus but more work is required to further elucidate metabolic mechanisms and develop robust diagnostic assays. Geographical distributions are provided for the mechanisms that have been shown to be important to date. Estimating insecticide resistance in unsampled locations is hampered by a lack of standardisation in the diagnostic tools used and by a lack of data in a number of regions for both resistance phenotypes and genotypes. The need for increased sampling using standard methods is critical to tackle the issue of emerging insecticide resistance threatening human health. Specifically, diagnostic doses and well-characterised susceptible strains are needed for the full range of insecticides used to control Ae. aegypti and Ae. albopictus to standardise measurement of the resistant phenotype, and calibrated diagnostic assays are needed for the major mechanisms of resistance.
The objective of this work was to evaluate the effect of the hexane fraction of the crude extract of the fruits and seeds of Ricinus communis (HFFSRC) on eggs of Spodoptera cosmioides and Spodoptera ...frugiperda and on caterpillars of Spodoptera eridania, S. frugiperda, and S. cosmioides, under laboratory conditions through topical application and ingestion, as well as to identify the compounds in the hexane fraction through high-performance chromatography (HPLC-ESI-Q-TOF-MS/MS). To do so, three bioassays were conducted: (1) the effect of HFFSRC at 2% (20,000 mg·mLsup.−1) on eggs of S. cosmioides and S. frugiperda, (2) the lethal effect of HFFSRC at 2% applied topically, and (3) the lethal effect of HFFSRC at 2% applied to soybean-leaf discs on first-, second-, third-, and fourth-instar caterpillars of the three insect species. It was found that 2% HFFSRC had an ovicidal effect on S. frugiperda and S. cosmioides, completely reducing larvae hatching and the insecticidal effect for the four instars of the three insect species when applied topically and on food. Five compounds were identified in the HFFSRC: three flavonoids, one ricinoleic acid, and one cinnamic acid. HFFSRC at 2% had an acute ovicidal and insecticidal effect on caterpillars of the studied species, configuring itself as a potential insecticide.
Rotenone is a widely used botanical insecticide, which can inhibit the mitochondrial respiratory chain of various insect cells, while the mechanism of its toxicity to insect cells needs further ...investigation. The purpose of this study was to understand the toxicity level of low (0.2 µg/mL) and high (20 µg/mL) concentrations of rotenone in Spodoptera litura cells (SL-1) using trypan blue and Coomassie brilliant blue staining assays. Our study found that rotenone possessed cytotoxicity against SL-1 cells with varying effects of action between high and low concentrations. After low-concentration rotenone treatment, the SL-1 cells showed obvious aggregation time-dependently, with the fastest aggregation rate observed under the first 8 h of treatment time, but no such phenomenon was observed at high concentration. Furthermore, this aggregation phenomenon caused SL-1 cells to squeeze each other and led to the destruction of the cell membrane structure and function. Taken together, the results suggested that treatment with a low concentration of rotenone exhibited a chronic toxic effect that was significantly different from treatment with a high concentration of rotenone, which provides new insight into the cytotoxic mechanism of rotenone.
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