Relative Toxicity of Fenazaquin Against Two-Spotted Spider Mite on Okra

Abstract

Continuous use of previous generation acaricides in okra [Abelmoschus esculentus (L.) Moench] has increased resistance to pesticides and pest resurgence. The project was undertaken to evaluate a new acaricide, fenazaquin 10 EC, for effective control of two-spotted spider mites [Tetranychus urticae Koch (Acari: Tetranychidae)] in pot culture and under field conditions. Fenazaquin was used at 75, 100, 125, or 150 g·ha−1 a.i. and compared with the standard acaricide dicofol 18.5 EC at 250 g·ha−1 a.i. and an untreated control. The adulticide bioassay, ovicidal action to T. urticae and safety of Dwarf honey bees (Apis florea Fabricius), was performed under laboratory conditions. Pot culture and two field trials were conducted to evaluate efficacy. Impact on okra yield and phytotoxicity were determined. The LC50 was 1.440 mg·L−1 and LT50 at 1.50 mg·L−1 was ˜8 hours. Fenazaquin produced more than 70% egg mortality in all doses for T. urticae. Fenazaquin at 125 and 150 g·ha−1 a.i. caused the highest reduction in numbers of mites in pot culture and field experiments. Fruit yields (9.89 Mt·ha−1, 10.59 Mt·ha−1) and cost–benefit ratio (1:3.25, 1:3.48) were higher in fenazaquin-treated plants at 150 g·ha−1 a.i in field experiments. No test doses were phytotoxic and all doses were relatively safe to Dwarf honey bees.