The population dynamics and stage composition of T. tabaci, and predacious natural enemies in lambda-cyhalothrin and methomyl treated and untreated onion plants were determined during the spring season using the whole-plant sampling method. In addition, sticky blue and white plastic cup traps and CC traps were used for trapping thrips. Result from this study indicated that the whole-plants sampling with absolute numbers of T. tabaci on onion plants was the most accurate method, but it was also most time consuming. Sampling thrips adults could provide a relatively good estimation of the total thrips population on onion plants with 70-75% precision. Of the developmental stages of T. tabaci on onion plants, 76-85% were nymphs, <0.1% were pupae, and 15-24% were adults. Although thrips densities were significantly reduced by applications of the insecticides compared with those on untreated plants, thrips densities were still far exceed the economic threshold. Several species of predators were found on onion plants. Orius insidiosus (Say) was the most dominant species of predators, with 41.0 and 74.5% of total predators collected from insecticide-treated and untreated onion plants, respectively. However, it appears that they were not the major factor regulating thrips population. Numbers of predators were significantly reduced on insecticide-treated plants compared with those on untreated plants. Of the traps, the blue plastic cup traps caught the most thrips (19-23 thrips per trap per day), followed by the white cup traps (10-12 thrips per trap per day), and the CC traps only caught a few (<1 thrips per trap per day).
Species 1: Thysanoptera Thripidae Thrips tabaci (onion thrips)
Keywords: onion thrips management
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