Citrus leaf essential oils as sustainable alternatives for the control of Tetranychus urticae with enhanced selectivity toward Neoseiulus californicus

The effect of essential oils from the leaves of four Citrus species on the agricultural pest Tetranychus urticae was investigated on the laboratory and greenhouse scales, with the inclusion of selectivity tests involving the predator Neoseiulus californicus. GC-MS analysis revealed distinct chemical profiles, with a predominance of methyl-n-anthranilate (33.2%) in the C. reticulata oil, linalool in the C. sinensis × C. reticulata (29.5%) and Citrus aurantium (24.7%) oils, and terpinolene (13.2%) in the Citrus sinensis oil. Laboratory tests demonstrated that the residual contact method was superior to fumigation for all oils investigated. The best toxicity results for fumigation (LC50 = 0.01 µL L−1), residual contact (LC50 = 9.70 µL mL−1), and ovicidal activity (LC50 = 0.002 µL mL−1) were found with the C. reticulata oil. All oils were selective for N. californicus (mortality < 30%), surpassing the positive control azadirachtin in selective compatibility. The best repellent activity was recorded for the C. sinensis × C. reticulata oil (RC50 = 0.002 µL mL−1). This oil was also more active in the greenhouse (96–100% mortality), reaching the same toxicity level as the synthetic insecticide and surpassing that of the botanical insecticide after 48 h.