Resistance of Panonychus citri (McGregor) (Acari: Tetranychidae) to pyridaben in China: monitoring and fitness costs

Identification and functional characterization of UDP-glycosyltransferase genes involved in cyetpyrafen resistance in Panonychus citri (McGregor)

BACKGROUND

Cyetpyrafen is a newly developed acaricide. The citrus red mite, Panonychus citri (McGregor), is an important citrus pest that has developed resistance to cyetpyrafen. Uridine diphosphate-glycosyltransferases (UGTs) have been widely reported to be associated with resistance to multiple acaricides. However, it has been rarely documented that UGT genes participate in cyetpyrafen resistance in P. citri.

RESULTS

In this study, a significantly upregulated UGT gene, PcUGT201E1, was identified in P. citri using transcriptome analysis. Expression of PcUGT201E1 was significantly upregulated at all stages in the cyetpyrafen-resistant strain and silencing PcUGT201E1 significantly increased the susceptibility of P. citri to cyetpyrafen. Molecular docking of PcUGT201E1 with uridine diphosphate glucose (UDPG) and cyetpyrafen indicated that UDPG and cyetpyrafen can interact with PcUGT202E1 via hydrogen bonds. Heterologous expression and in vitro functional assays revealed that enzyme activity could be inhibited by cyetpyrafen and that recombinant PcUGT201E1 can deplete cyetpyrafen.

CONCLUSION

These results indicated that PcUGT201E1 participates in cyetpyrafen resistance in P. citri by sequestration, and provided a molecular foundation for understanding cyetpyrafen resistance in P. citri. © 2025 Society of Chemical Industry.

Risk assessment of broflanilide resistance in Panonychus citri (McGregor): Cross-resistance, inheritance and relative fitness

Panonychus citri (McGregor) is an important economic pest in the orange orchard of the world, which has developed varying degrees of resistance to many acaricides. Broflanilide is a novel γ-aminobutyric acid (GABA) receptor allosteric modulator with high insecticidal activity against a broad spectrum of insects. However, the risk of resistance to broflanilide in P. citri has not been studied. In this study, the BR strain selected from susceptible strain of P. citri with broflanilide for 44 generations, developed 32.5-fold resistance to broflanilide, and did not exhibit cross-resistance to fipronil, fluxametamide, abamectin, pyridaben, and cyflumetofen. Broflanilide resistance in the BR strain of P. citri was autosomal, incomplete dominant and polygenic. The duration of larval and deutonymph, total life span and the number of eggs were significantly increased in the BR strain compared to the SS strain. The higher relative fitness (Rf) value (1.289) indicated that there was a fitness advantage in the BR strain. Glutathione S-transferase and esterase activities in the BR strain were significantly increased compared with the SS strain. These findings provide valuable information for developing resistance management strategies to delay broflanilide resistance and maintain sustainable control of P. citri.

Suitability of Rosaceae fruit tree species for Panonychus citri (McGregor) (Acari: Tetranychidae)

The citrus red mite (CRM), Panonychus citri (McGregor) (Acari: Tetranychidae), a worldwide pest chiefly infesting Citrus plants, has spread from Southern China to Northern China. Little information is known about the population performance of CRM on the plants except for citrus trees and pear trees. In order to evaluate the extent of damage might caused by CRM to the fruit trees cultivated in Northern China, the performance of CRM on four Rosaceae species, including three main fruit tree species (pear-Pyrus pyrifolia Nakai cv. Shannongsu, apple-Malus pumila Mill. cv. Fuji, peach-Prunus persica (L.) Batsch cv. Zhongyou 4) cultivated in Shandong Province, Northern China, and one rootstock for grafting apples (crabapple-Malus micromalus Makino) was determined using the age-stage, two-sex life table at laboratory conditions (25 ± 1 °C, 75 ± 5% RH and L16: D8 h photoperiod). The results showed that CRM could complete the whole life cycle on all the four plant species. The development time of larva, protonymph and deutonymph and the survival of immature stage of CRM did not vary among the four plant species. Differences on the egg incubation period explained the total duration of the immature stage among the four plants. The total duration of the immature stage was shorter on pear and peach than on crabapple and apple, but no difference was observed between pear and peach. The mites reared on pear and peach exhibited a higher fecundity, net reproductive rate (R0), intrinsic growth rate (r) and finite rate of increase (λ) and longer longevity of the adult females than on crabapple and apple, but no significant differences between pear and peach, crabapple and apple. The mean generation time (T) of CRM reared on crabapple was the longest, which did not differ significantly on pear, peach and apple. In summary, the cultivars of pear, peach, apple and crabapple used in this study, especially that of peach and pear were suitable for the development and reproduction of CRM. CRM might be a serious risk for the main Rosaceae fruit species in Northern China.

Transcriptome reanalysis and gene expression of 13 detoxification genes for avermectin and pyridaben resistance in Panonychus citri

Citrus red mites (P. citri) are key pests affecting citrus production worldwide due to pesticide resistance. The resistance mechanisms of ten pesticides are known, but a comprehensive study using transcriptome data is missing. This study employed deeptools, cuffdiff, rmats, bcftools and other software to examine gene expression variation, alternative splicing (AS), and mutations in mite resistance. The research highlighted that pesticides can regulate gene transcription, and red mites with resistance increase cytochrome P450, glutathione S-transferases, carboxylesterase, and acetylcholinesterase expression. Pyridaben also induces new AS events. Fluazinam-induced mites show mRNA splicing peaking earlier than transcription, both peaking at one day and returning to baseline after two days. AS profiles are similar in different mite populations with overlapping pesticide resistances. Lastly, specific mitochondrial SNPs in mites might mediate resistance against select pesticides.

Cross-resistance, inheritance and biochemical mechanism of abamectin resistance in a field-derived strain of the citrus red mite, Panonychus citri (Acari: Tetranychidae)

BACKGROUND

The citrus red mite, Panonychus citri (McGregor), a global pest of citrus, has developed different levels of resistance to various acaricides in the field. Abamectin is one of the most important insecticides/acaricides worldwide, targetting a wide number of insect and mite pests. The evolution of abamectin resistance in P. citri is threatening the sustainable use of abamectin for mite control.

RESULTS

The abamectin resistant strain (NN-Aba), derived from a field strain NN by consistent selection with abamectin, showed 4279-fold resistance to abamectin compared to a relatively susceptible strain (SS) of P. citri. Cross-resistance of NN-Aba was observed between abamectin and emamectin benzoate, pyridaben, fenpropathrin and cyflumetofen. Inheritance analyses indicated that abamectin resistance in the NN-Aba strain was autosomal, incompletely recessive and polygenic. The synergy experiment showed that abamectin toxicity was synergized by piperonyl butoxide (PBO), diethyl maleate (DEM) and tributyl phosphorotrithiotate (TPP) in the NN-Aba strain, and synergy ratios were 2.72-, 2.48- and 2.13-fold, respectively. The glutathione-S-transferases activity in the NN-Aba strain were significantly increased by 2.08-fold compared with the SS strain.

CONCLUSION

The abamectin resistance was autosomal, incompletely recessive and polygenic in P. citri. The NN-Aba strain showed cross-resistance to various acaricides with different modes of action. Metabolic detoxification mechanism participated in abamectin resistance in NN-Aba strain. These findings provide useful information for resistance management of P. citri in the field. © 2023 Society of Chemical Industry.

CYP4CL2 Confers Metabolic Resistance to Pyridaben in the Citrus Pest Mite Panonychus citri

The citrus red mite Panonychus citri has developed strong resistance to acaricides. Cytochrome P450 monooxygenases (P450s) can detoxify pesticides and are involved in pesticide resistance in many insects. Here, a pyridaben-resistant P. citri strain showed cross-resistance to cyenopyrafen, bifenazate, fenpyroximate, and tolfenpyrad. Piperonyl butoxide, a P450 inhibitor, significantly increased the toxicity of pyridaben to resistant (Pyr_Rs) and susceptible (Pyr_Control) P. citri strains. P450 activity was significantly higher in Pyr_Rs than in Pyr_Control. Analyses of RNA-Seq data identified a P450 gene (CYP4CL2) that is potentially involved in pyridaben resistance. Consistently, it was up-regulated in two field-derived resistant populations (CQ_WZ and CQ_TN). RNA interference-mediated knockdown of CYP4CL2 significantly decreased the pyridaben resistance in P. citri. Transgenic Drosophila melanogaster expressing CYP4CL2 showed increased pyridaben resistance. Molecular docking analysis showed that pyridaben could bind to several amino acids at substrate recognition sites in CYP4CL2. These findings shed light on P450-mediated pyridaben resistance in pest mites.