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

Abstract

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, (0, 50, 100, 300, 800 and 2000 ppm) of each essential oil on the mature and immature life stages of the pest, and mortalities were recorded 72 h after exposure. In fumigant toxicity trials, LC50 values of the essential oils were determined on different developmental stages of T. turkestani and O. albidipennis. At 800 and 2000 ppm, both essential oils had high contact toxicity on the eggs, 2nd 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 2nd instar nymph of T. turkestani was more sensitive to contact application of the essential oils than other developmental stages. In the fumigant toxicity bioassay, LC50 values of the essential oil derived from F. vulgare on the egg, 2nd instar nymph and adult of T. turkestani were 16.08, 7.98 and 14.06, and the values for C. limon essential oil were 11.6, 9.86 and 11.52 μl × l-1air, respectively. The highest fumigant toxicity was observed against the 2nd 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.