Effect of Ultraviolet UV-A Irradiation on the Efficacy of Three Acaricides for Mortality and Egg Hatching of Spider Mite: Tetranychus Urticae in the Laboratory

This study examined the influence of three acaricides, Bifenazate, Clofentezine, and Spirodiclofen, exposed to artificially ionizing UV-A irradiation for four duration times: 30, 60, 90, and 120 minutes on mortality of the herbivorous mite Tetranychus urticae in the laboratory. Guava leaves were used as a test fruit substrate to assess the lethality effect of acaricides on mites. The study demonstrated that UV-A irradiation reduced the action of active ingredients of tested acaricides and produced less toxic products, decreasing mite individuals' mortality. Lethality in T. urticae was reduced to 77.5% compared to the control (P < 0.05), after spraying with 30 minutes of UV-A irradiated Bifenazate, while it was 40% in Clofentezine and 27% in Spirodiclofen. After a 120-minute exposure period, Bifenazate demonstrated 62.5% lethality. In the same time interval, the lethality of mites was significantly decreased, as recorded at 22.5% in Clofentezine and 12.5 % in Spirodiclofen (P < 0.05). These results suggest that the effectiveness of acaricides in killing adult mites decreases with prolonged exposure to UV-A irradiation [Pearson's correlation coefficient (R= 0.84, P < 0.05)]. Regarding egg viability, control treatments without UV-A exposure showed a percentage viability of 5-19%, while the treated groups exhibited a viability range of 38-53% during the 30-minute irradiation. Two hours of irradiated acaricides caused highly surviving mite individuals and extremely viable eggs compared to the control. In conclusion, the random application of acaricides in some regions during sunny periods is ineffective for optimal pest control.