Toxicity Activity of Five Plant Extracts against Tetranychus truncatus (Acari: Tetranychidae) and Its Predatory Mite Amblyseius longispinosus (Acari: Phytoseiidae)

Tetranychus truncatus Ehara (Acari: Tetranychidae) is one of the major economically important mite pests of numerous plant species. The predatory mite Amblyseius longispinosus (Evans) (Acari: Phytoseiidae) has been successfully used in biological control programs. This study evaluated the contact toxicity activities of ethanol extracts from 5 plants—Cymbopogon nardus (L.) Rendle, Ocimum basilicum L., Ocimum sanctum L., Andrographis paniculata (Burm.f.) Nees, and Stemona tuberosa Lour.—against T. truncatus and A. longispinosus. The ethanol plant extracts revealed different toxicity activity against T. truncatus and A. longispinosus. At concentrations of 7–9% (w/v), Cy. nardus and S. tuberosa extracts showed significant direct contact toxicity against T. truncatus adults, resulting in mortality rates of 64.00–70.67 and 51.33–55.00%, respectively, at 3 d after treatment. Application of 3–9% concentrations of Cy. nardus, 5–9% concentrations of O. basilicum and O. sanctum, and 9% concentrations of A. paniculata to T. truncatus eggs reduced egg viability, with >50% unhatched eggs 4 d following treatment. Concentrations of 5–9% of Cy. nardus and O. sanctum extracts were moderately toxic to A. longispinosus in residual contact toxicity, with mortality ranging from 22.67–34.67 and 22.67–29.33%, respectively, at 3 d after exposure. Based on our findings, extracts of Cy. nardus and T. tuberosa show promise as botanical acaricides for controlling T. truncatus adults, whereas extracts of Cy. nardus, O. basilicum, O. sanctum, and A. paniculata may be effective for the control of T. truncatus eggs. Furthermore, Cy. nardus and O. sanctum extracts negatively affected A. longispinosus.