The Effect of Light Cycles on the Predation Characteristics of Phytoseiulus persimilis (Acari: Phytoseiidae) Feeding on Tetranychus urticae (Acari: Tetranychidae)

Environmental factors, such as the duration of daylight, can significantly influence the predation ability of arthropod predators. This study aimed to examine the influence of photoperiods of 8:16 h, 12:12 h, and 16:8 h (L:D) on the predation rate of <i>Phytoseiulus persimilis</i> preying on <i>Tetranychus urticae</i> eggs under constant temperature. The daily predation rate (<i>D_j</i>) and the total number of prey eggs consumed (<i>P_j</i>) per predator increased with longer photophases, reaching their peak in the 16L:8D photoperiod. The highest net predation rate (<i>C</i>₀) was observed under 16L:8D conditions (173.22 prey eggs/predator), while it was 170.28 and 89.77 prey eggs/predator under the 12L:12D and 8L:16D photoperiods, respectively. The finite predation rate (ω) also increased with longer photophases. The transformation rate (<i>Q_p</i>) was highest under the 16L:8D photoperiod. Significant differences were noted in the stable predation rate (ψ), with the highest value being 5.84 prey eggs/predator under 16L:8D conditions. The number of <i>T. urticae</i> eggs predated by <i>P. persimilis</i> was higher under longer photoperiods, and the 16L:8D photoperiod can thus be recommended as optimal for the biocontrol of spider mites in controlled environments. We suggest that future research explores other effects of the light cycle on plant-herbivore-predator interactions to optimize the lighting conditions for effective spider mite control.