Identification and Functional Characterization of an Omega-Class Glutathione S-Transferase Gene PcGSTO1 Associated with Cyetpyrafen Resistance in Panonychus citri (McGregor).

Cyetpyrafen is a recently developed acaricide. The citrus red mite, Panonychus citri (McGregor), has developed significant resistance to cyetpyrafen. However, the molecular mechanism underlying the cyetpyrafen resistance in P. citri remains unclear. Glutathione S-transferases (GSTs) play a critical role in arthropod pesticide resistance. This study showed that GSTs were potentially related to the resistance of P. citri to cyetpyrafen through synergistic experiments and enzyme activity analysis. An omega-family GST gene, PcGSTO1, was significantly up-regulated in the egg, nymph, and adult stages of the cyetpyrafen-resistant strain. Additionally, silencing of PcGSTO1 significantly increased the mortality of P. citri to cyetpyrafen and recombinant PcGSTO1 demonstrated the ability to metabolize cyetpyrafen. Our results indicated that the overexpression of PcGSTO1 is associated with cyetpyrafen resistance in P. citri, and they also provided valuable information for managing resistance in P. citri.

Particle Size Effect of Cyetpyrafen Formulation in the Pesticide Transmission Process and Its Impact on Biological Activity.

Cyetpyrafen is a compound that lacks inherent uptake and systemic translocation activity. If mites do not come into direct contact with the pesticide solution on leaves, the efficacy cannot be achieved. Controlling the particle size can potentially play a crucial role in the manifestation of efficacy. In this study, high-throughput formulation technology was used to systematically screen a large number of adjuvants to obtain cyetpyrafen formulations. The particle size of the active ingredient in the formulation was measured. By examining the dynamic light scattering and contact angle, we simulated the actual process of the efficacy transmission of cyetpyrafen formulations against Tetranychus cinnabarinus. Our results showed that the activity of cyetpyrafen increases as the particle size decreases, suggesting that reducing the particle size can enhance the coverage and deposition on crop leaves, and further improve the dispersion efficiency and enhance spreading capabilities. Furthermore, controlling the particle size at 160 nm resulted in an LC50 value of 0.2026, which is approximately double than that of the commercial product. As a novel pesticide for mites, our study presents the most effective cyetpyrafen formulation in practice. Our findings provide valuable insights into controlling other mite species that pose a threat to agricultural products.

Novel Acaricidal Silico-Containing Pyrazolyl Acrylonitrile Derivatives Identified through Rational Carbon-Silicon Bioisosteric Replacement Strategy.

The identification of novel pyrazolyl acrylonitrile acaricides with improved properties is of great value for the control of phytophagous mites. A series of innovative silicon-containing pyrazolyl acrylonitriles were rationally designed by applying a bioisosteric carbon-silicon replacement strategy and prepared based on novel synthetic methodology. As a result of our research, we discovered compound A25 which possesses outstanding acaricidal activity. With an LC50 value of 0.062 mg/L, compound A25 was found to be 2.3-fold and 1.9-fold more potent than the commercial acaricides cyenopyrafen and cyetpyrafen, respectively. Enzymatic inhibitory assay indicated that the active principle M1 of compound A25 possesses an IC50 value of 2.32 µM against Tetranychus cinnabarinus SDH, which was about twofold superior compared to the active metabolites of cyenopyrafen (IC50 = 4.72 µM). Molecular docking study showed that the active metabolites 2 and 3 and their corresponding silicon counterparts form H-bonds and cation-π interaction with the residues of Trp165, Tyr433, and Arg279.

Determination of a novel pesticide cyetpyrafen and its two main metabolites in crops, soils and water.

Novel insecticide cyetpyrafen is frequently used in various crops, however, knowledge of its fate in crops and environments is largely unexplored. In this study, an effective method was firstly established for simultaneous determination of cyetpyrafen and its metabolites (M-309 and M-391) in 13 matrices (e.g., plants and soils) to explore their fate. Mean recoveries of the three compounds ranged from 73.1 % to 118.7 % with the relative standard deviations (RSDs) less than 17.9 %. Further, after 28 days of exposure in a field soil-strawberry system, cyetpyrafen and M-309 exhibited great accumulations in strawberry leaves by foliar spray while both compounds were predominately accumulated in roots by root irrigation, where cyetpyrafen was poorly translocated within plant. An equal amount of M-309 was measured in both strawberry plants and soils indicates the extensive transformation of cyetpyrafen in soil-strawberry system. Therefore, metabolism of cyetpyrafen in foods need to be considered for its better risk assessment.