The two-spotted spider (Tetranychus urticae) is an important pest of many agricultural crops. Laboratory bioassayswere conducted to determine the toxicity of Pyflubumide and Cyenopyrafen against three populations of T. urticae collectedfrom apple orchards. The adults and eggs of three populations all showed susceptibility to Pyflubumide and Cyenopyrafen,as the 50% lethal concentration (LC50) values were all lower than each of the recommended concentrations. There wereconsiderable differences in susceptibility of the acaricides between eggs and adults in different populations. Pyflubumideshowed highest toxicity to adults of Yeongju population (LC50 = 1.40 mg/l) and eggs of Andong population (LC50 =0.54 mg/l). Cyenopyrafen showed lowest toxicity to adults of Andong population (LC50 = 20.29 mg/l) while displayedhighest toxicity to their eggs (LC50 = 2.64 mg/l). These results suggested that T. urticae had not developed resistancein these three regions, Pyflubumide and Cyenopyrafen can serve as alternative chemical candidate for integrated mite managementin apple orchards.

• Shubao Geng(Department of Bioresource Sciences, Graduate School, Andong National University)
• Chuleui Jung(Department of Bioresource Sciences, Graduate School, Andong National University)