Synthesis and evaluation of acaricidal activity of zinc oxide nanoparticles against phytophagous and predatory mites in bell pepper cultivation

Abstract

Bell Pepper plants are widely grown and utilized all over the world. A number of phytophagous mites are associated with this plant and the control over these pests has been a challenge to growers due to its development of resistance to synthetic chemicals and short reproduction cycle. The agriculture sector is currently embracing nanotechnology as a target-specific, relatively safe, and effective alternative to traditional pest management tools. The main goal of undertaking the current study was to evaluate the effectiveness of different doses (200, 400, 600, 1000, 1250 and 1500 ppm) of zinc oxide nanoparticles (ZnONPs) at all growth stages of the mites; Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae) and the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Simultaneous impacts on predatory mites, Neoseiulus cucumeris (Oudemans) and Euseius scutalis (Athias-Henriot) (Acari: Phytoseiidae) was also observed. All trails were carried out under field and laboratory conditions. The obtained results have shown that an increase in zinc oxide nanoparticle concentrations was related to a higher mortality rate of both phytophagous mites. While negligible impact on N. cucumeris and E. scutalis was observed. zinc oxide nanoparticles demonstrated great efficacy in eliminating P. latus and T. urticae. The percentages of deaths were 25.59, 42.36, 56.43, 72.02, 85.47 and 97.07% for P. latus and 22.61, 39.79, 52.66, 69.35, 82.22 and 95.24% for T. urticae, while the mortality percentage was 1.78, 3.60, 4.44, 15.30, 16.67 and 19.59% for N. cucumeris and 3.68, 5.33, 7.21, 17.92 and 20.26% for E. scutalis three days after exposure to 200, 400, 600, 1000, 1250 and 1500 ppm of zinc oxide nanoparticles, respectively. Additionally, the findings showed that the use of zinc oxide nanoparticles reduced the percentage of egg hatching. The percentages of eggs that hatch into larvae were 79.33, 69.51, 62.66, 46.54, 43.62 and 39.08% for P. latus and 83.17, 71.60, 67.26, 48.94, 46.95 and 38.26 for T. urticae three days after exposure to 200, 400, 600, 1000, 1250 and 1500 ppm of zinc oxide nanoparticles respectively, compared with the control (well water). Lethal concentration; LC50 (µg/ml) at confidence level 95 (CL95) was found to be 556.4 and 611.8 for P. latus and T. urticae and 2304.6 and 2259.7 for N. cucumeris and E. scutalis. Similarly, LC95 (µg/ml) was found to be 1325.9 and 1404.9 for P. latus and T. urticae and 33671.2 and 3773.8 for N. cucumeris and E. scutalis. The investigation proved that zinc oxide nanoparticles are a useful tool for controlling P. latus and T. urticae.