Predation efficiency of <i>Amblyseius swirskii</i> Athias-Henriot (Acari: Phytoseiidae) against <i>Saissetia oleae</i> (Oliver) (Hemiptera: Coccidae) for sustainable biological control in olive cultivation

<i>Saissetia oleae</i> (Oliver) (Hemiptera: Coccidae) is a major pest of olive trees that requires effective biological control methods. This study evaluated the predatory mite <i>Amblyseius swirskii</i> Athias-Henriot (Acari: Phytoseiidae) for its predation efficiency against <i>S. oleae</i> eggs and nymphs under laboratory (25 ± 1 °C, 60 ± 10% RH) and screenhouse (25 ± 4 °C) conditions. Two laboratory trials were conducted over 6 days: Trial 1 assessed predation on <i>S. oleae</i> eggs, and Trial 2 on nymphs. Additionally, screenhouse trials tested four predator-prey ratios (T1: 1:2, T2: 1:4, T3: 1:8, T4: 1:10, adult <i>A. swirskii</i> to <i>S. oleae</i> eggs), with weekly observations over 10 weeks. Under laboratory conditions, <i>A. swirskii</i> caused significantly higher mortality in eggs (17.9 eggs consumed) than in nymphs (10.2 nymphs killed) by day 6, while mortality in control groups remained low (1.5 eggs, 2.0 nymphs). In screenhouse trials, <i>A. swirskii</i> significantly reduced <i>S. oleae</i> populations at all predator-prey ratios, with the 1:2 ratio achieving the greatest suppression, reducing densities to 0 eggs and 6 nymphs per plant by week 10, compared to 30 eggs and 110 nymphs in untreated controls. Predator populations increased in a density-dependent manner (T1 > T2 > T3 > T4). Treated plants maintained a high visual quality score (≥9.5 at week 10), whereas untreated plants showed a severe decline (0.9 at week 10). These results demonstrate that <i>A. swirskii</i> effectively suppresses <i>S. oleae</i> and holds promise as a sustainable biological control agent in integrated pest management for olives.