Abstract: 【Aim】 As a new pest on American ginseng, Panax quinquefolium L.，the root mite Schwiebea similis Manson bores into and feeds on tissues inside roots of the plant, causing remarkable losses. The study aims to determine its feeding amount of roots and to estimate its economic threshold in the future. 【Methods】 Female mites were inoculated onto powders of the ginseng root dusted on wet fine sands in plastic rings within plastic dishes in the experiment, which was conducted under the conditions of seven levels of initial females inoculated (N₀) (1, 2, 3, 4, 5, 6 and 7 ♀ per ring) and five gradients of rearing temperatures (T) (15.6, 18.5, 21.2, 24.5 and 27.2℃). Five variables including duration of mites living stably on the food (D), number of mites counted on the peak day (Np), per capita reproduction of females (PCR), adult equivalent adjusted from Np (AE), and feeding amount of fresh ginseng tissues by a filial mite from egg to adult (FA) were recorded and analyzed. 【Results】 Variable D decreased rapidly against T, and slowly against  N₀. N_p increased significantly with N₀, and the equation was N_p =21.8+17.2 N₀. PCR decreased significantly against N₀, the equation was PCR=63.4-28.1 N₀+6.2 N₀ ²-0.4N₀³, and its track was reverse with that of N_p. A crowding effect was found among mites. AE increased significantly with N₀ , and the equation was AE=16.2+12.7N₀. FA=0.25±0.13 mg/adult. 【Conclusion】 The five variables reflect the range of feeding amount and the reproductive potential of the laboratory populations of S. similis; not only does each of them show specialty, but also relates to others. As important bionomics, the values estimated in the experiment would be essential in the calculation of its economic threshold, and the methods used would also be beneficial in similar studies.

Key words: Schwiebea similis, Panax quinquefolium, adult equivalent, feeding amount, reproductive potential