Continuously exhausting air (hypobaric treatment) to selectively control spider mites Tetranychus urticae and T. kanzawai (Acari: Tetranychidae) and its impact on their natural enemy Neoseiulus californicus (Acari: Phytoseiidae)

Abstract: Environmental and human health issues restrict the use of traditional chemical treatment of agricultural pests. Hypobaric treatment disinfests goods by adjusting atmospheric pressure to be unfavorable to pests. In the present study, we assessed the effectiveness of hypobaric treatment against eggs and adults of two most injurious plant pest mites, Tetranychus urticae and T. kanzawai, and its impact on a biological control agent, the predatory mite Neoseiulus californicus. Experiments were performed at 20, 25 and 30 °C, and the hypobaric exposure durations were 0 (control), 6, 12 and 24 h. Egg hatchability of N. californicus reduced just slightly even after treatment for 24 h at 30 °C, at which no spider mites survived. However, the effect on adult female mites was the reverse: spider mites were more tolerant than the predatory mite, and there were still a few surviving spider mites even after treatment for 24 h at 30 °C. If water was available to the mites, survival of all species exceeded 90% after the same treatment. These results suggest that (1) the lethal factor in hypobaric treatment is dehydration, and (2) hypobaric treatment can selectively control only the eggs of spider mites.