Insecticide Resistance and Control Failure Likelihood Analysis in Plutella xylostella (Lepidoptera: Plutellidae) Populations From Taiwan

The I4790K mutation of the ryanodine receptor is responsible for anthranilic diamide resistance in field populations of Plutella xylostella (Lepidoptera: Plutellidae)

Insecticide resistance in Plutella xylostella (Linnaeus) (Lepidoptera: Plutellidae) is a major constraint on the global production of cruciferous crops. For effective management of insecticide resistance, it is necessary to develop a molecular detection tool for predicting insecticide resistance levels based on the mutation frequency of target sites. In this study, a susceptible strain (SHggt) of P. xylostella was subjected to chlorantraniliprole and tetraniliprole selection under laboratory conditions to obtain the CHLSel and TETSel strains, respectively, to determine their resistance development, cross-resistance and mutation frequencies of the P. xylostella ryanodine receptor (PxRyR). In addition, the tetraniliprole resistance and the mutation frequencies of the PxRyR from 7 field populations were evaluated. Continuous selection over 30 generations resulted in resistance ratios (RRs) of 7,073.2-fold and 6,971.0-fold for the CHLSel and TETSel strains, respectively, and thousandfold increases in cross-resistance to unexposed diamides, e.g., cyantraniliprole and flubendiamide, were observed. For the field populations, three out of seven populations have developed more than thousandfold resistance to tetraniliprole. Among the three investigated target site mutations in PxRyR, only I4790K was detected in both laboratory-selected strains. However, 2 mutations, I4790K and G4946E, were detected in field populations. A positive correlation between RRs and K allele frequencies was observed in the laboratory-selected/relaxed strains and field populations of P. xylostella. These results suggest a possible link between the development of anthranilic diamide resistance and the frequency of the PxRyR I4790K mutation, which can be used to develop effective strategies for diamide resistance management in P. xylostella.

Chitosan-based insecticide formulations for insect pest control management: A review of current trends and challenges

Future agricultural practices necessitate green alternatives to replace hazardous insecticides while distinguishing between pests and beneficial insects. Chitosan, as a biological macromolecule derived from chitin, is biodegradable and exhibits low toxicity to non-target organisms, making it a sustainable alternative to synthetic pesticides. This review identifies chitosan-derivatives for insecticidal activity and highlights its efficacy including genotoxicity, defense mechanism, and disruption of insect's exoskeleton at different concentrations against several insect pests. Similarly, synergistic effects of chitosan in combination with natural extracts, essential oils, and plant-derived compounds, enhances insecticidal action against various pests was evaluated. The chitosan-based insecticide formulations (CHIF) in the form of emulsions, microcapsules, and nanoparticles showed efficient insecticide action on the targeted pests with less environmental impact. The current challenges associated with the field-trial application were also recognized, by optimizing potent CHIF-formulation parameters, scaling-up process, and regulatory hurdles addressed alongside potential solutions. These findings will provide insight into achieving the EU mission of reducing chemical pesticides by 50 %.

Identification and evaluation of cruciferous plant volatiles attractive to Plutella xylostella L. (Lepidoptera: Plutellidae)

BACKGROUND

The diamondback moth, Plutella xylostella, has developed resistance to almost all insecticides used for its control. The 'push-pull' method has been shown as an effective control strategy to address this resistance challenge of P. xylostella. The key focus of the strategy is the identification of attractive or repellent volatile components. The aim of this study was to identify attractive volatile compounds released from host plants. Identified compounds were applied in the biological control of this pest.

RESULTS

Nine active compounds released into the headspace of seven cruciferous plant species were identified using gas chromatography-electroantennographic detection and gas chromatography-mass spectrometry. Electroantennographic detection-active compounds included five green leaf volatiles (hexanal, trans-2-hexen-1-ol, cis-3-hexen-1-ol, cis-3-hexenyl acetate, and 1-penten-3-ol), three isothiocyanates (isopropyl isothiocyanate, allyl isothiocyanate, and butyl isothiocyanate), and nonanal. Except for nonanal, all the identified green leaf volatiles and isothiocyanates elicited strong electrophysiological and behavioral responses in P. xylostella. The strongest attractive compounds, trans-2-hexen-1-ol and isopropyl isothiocyanate, were further evaluated in oviposition and field-trapping assays. Results showed that they both lured female moths to lay eggs, and were highly attractive to P. xylostella adults in field, especially when used in combination with yellow and green sticky boards. However, a blend of the two compounds showed no synergistic effect, but rather an antagonistic effect.

CONCLUSIONS

Green leaf volatiles and isothiocyanates were identified as key olfactory cues for host selection of P. xylostella. Trans-2- hexen-1-ol and isopropyl isothiocyanate were identified as candidate attractive compounds to serve in a 'push-pull' strategy for P. xylostella control. © 2023 Society of Chemical Industry.

Development of a gold nanoparticle-based lateral flow immunoassay for the fast detection of diafenthiuron in cabbage and apples

Due to its unique insecticidal and acaricidal mechanism of action, and ability to mix with most insecticides and fungicides, diafenthiuron (DIAF) is widely used in the cultivation of fruits and vegetables. However, this insecticide can cause unacceptable harm to organisms, making the detection of DIAF residues in fruits and vegetables crucial. In this study, a novel hapten based on the structure of DIAF was utilized to prepare a monoclonal antibody (mAb) with high specificity and sensitivity. The half maximum inhibitory concentration (IC₅₀) of the anti-DIAF mAb was 20.96 μg kg^-1 as determined by ic-ELISA and little cross-reactivity with other analogues. Next, a GNP-based lateral flow immunoassay (LFIA) was developed to detect DIAF in cabbages and apples. The optimized LFIA, for cabbage samples, showed a visual limit of detection (vLOD), cut-off value and calculated limit of detection (cLOD) of 0.1 mg kg^-1, 10 mg kg^-1 and 1.5 μg kg^-1, respectively, and for apples 0.1 mg kg^-1, 5 mg kg^-1 and 3.4 μg kg^-1, respectively. Recovery rates in cabbage and apples were 89.4-105.0% and 105.3-112.0%, with a coefficient of variation of 2.73-5.71% and 2.15-7.56%, respectively. These results indicated that the established LFIA based on our anti-DIAF mAb was a reliable method for in situ rapid detection of DIAF in cabbage and apple samples.

Transcriptomics analysis of ethanol treatment of male Aedes aegypti reveals a small set of putative radioprotective genes

Introduction: Sterile Insect Technique (SIT) is based on releasing sterilized male insects into wild insect populations to compete for mating with wild females. Wild females mated with sterile males will produce inviable eggs, leading to a decline in population of that insect species. Sterilization with ionizing radiation (x-rays) is a commonly used mechanism for sterilization of males. Since irradiation can cause damage to both, somatic and germ cells, and can severely reduce the competitiveness of sterilized males relative to wild males, means to minimize the detrimental effects of radiation are required to produce sterile, competitive males for release. In an earlier study, we identified ethanol as a functional radioprotector in mosquitoes. Methods: Here, we used Illumina RNA-seq to profile changes in gene expression of male Aedes aegypti mosquitoes fed on 5% ethanol for 48 hours prior to receiving a sterilizing x-ray dose, compared to males fed on water prior to sterilization. Results: RNA-seq revealed a robust activation of DNA repair genes in both ethanol-fed and water-fed males after irradiation, but surprisingly few differences in gene expression between ethanol-fed and water-fed males regardless of radiation treatment. Discussion: While differences in gene expression due to ethanol exposure were minimal, we identified a small group of genes that may prime ethanol-fed mosquitoes for improved survivability in response to sterilizing radiation.