Resistance to acaricides in Tetranychus truncatus ehara on vegetables
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A study was undertaken at the College of Horticulture, Vellanikkara, KAU to investigate the status of acaricide resistance in Tetranychus truncates Ehara (Prostigmata: Tetranychidae), the predominant species of spider mite infesting vegetable crops of Thrissur district, Kerala. Susceptibility of three field strains of T. truncatus collected from okra (VkOk1), amaranthus (VkAm3) and pumpkin (VkPm3) to three commonly used acaricides, viz., spiromesifen 240 SC, fenazaquin 10EC and diafenthiuron 50WP was evaluated in the laboratory following leaf dip bioassay in comparison with a laboratory maintained susceptible strain (SS). Bioassay study revealed that the level of resistance varied among the strains for the acaricides evaluated. The strain VkOk1 recorded highest LC50 value and has developed 8 (1794.293 ppm), 13 (852.394 ppm) and 10 (1968.496 ppm) fold resistance to spiromesifen, fenazaquin and diafenthiuron, while VkAm3 recorded 7.0 (1571.021 ppm), and 5.53 (362.789 ppm) resistance to spiromesifen and fenazaquin, respectively. The strain VkPm3 showed susceptibility on par with the SS to all the acaricides evaluated. The study reports acaricide resistance in T. truncatus for the first time in India.
Tetranychus truncatus, okra, amaranthus, pumpkin, acaricides, resistance, spiromesifen, fenazaquin, diafenthiuron, LC50, leaf dip bioassay.