Contact and fumigant toxicity of Foeniculum vulgare and Citrus limon essential oils against Tetranychus turkestani and its predator Orius albidipennis

Tetranychus turkestani is one of the most important pests of greenhouse plants in the southern provinces of Iran. Several benefits of using essential oils over chemical pesticides make them appropriate for IPM programs. Contact and fumigant toxicity of the essential oils of Foeniculum vulgare and Citrus limon against the spider mite and its predator, Orius albidipennis were investigated under laboratory conditions. Contact toxicity experiments were conducted at six concentrations, (۰, ۵۰, ۱۰۰, ۳۰۰, ۸۰۰ and ۲۰۰۰ ppm) of each essential oil on the mature and immature life stages of the pest, and mortalities were recorded ۷۲ h after exposure. In fumigant toxicity trials, LC۵۰ values of the essential oils were determined on different developmental stages of T. turkestani and O. albidipennis. At ۸۰۰ and ۲۰۰۰ ppm, both essential oils had high contact toxicity on the eggs, ۲nd instar nymphs and adults of T. turkestani, while the same concentrations caused less mortality on O. albidipennis. No significant phytotoxicity of the essential oils was observed. The mortality rates of T. turkestani and O. albidipennis increased as concentration was increased. Also, the ۲nd instar nymph of T. turkestani was more sensitive to contact application of the essential oils than other developmental stages. In the fumigant toxicity bioassay, LC۵۰ values of the essential oil derived from F. vulgare on the egg, ۲nd instar nymph and adult of T. turkestani were ۱۶.۰۸, ۷.۹۸ and ۱۴.۰۶, and the values for C. limon essential oil were ۱۱.۶, ۹.۸۶ and ۱۱.۵۲ µl × l-۱air, respectively. The highest fumigant toxicity was observed against the ۲nd instar nymphs of the mite. Fumigant toxicity of the essential oils was lower against O. albidipennis than against T. turkestani. This data suggests that the essential oils of these plants have the potential of being employed in the IPM programs of T. turkestani in greenhouse crops, especially cucumber.

Keywords:

Essential oils , contact toxicity , fumigant toxicity , Phytotoxicity