This study was conducted to compare the effectiveness of single and combination use of N. californicus and N. womersleyi for control of Tetranychus urticae. The experiment was conducted with 5 replications in kidney bean leaf disc (2.5cm diameter) at 25℃, 60-70% RH, a photoperiod of 16:8 (L:D) h. The inoculation ratio was 5:1 for T. urticae:pytoseiidae mite and treatments are: a, N. californicus:T. urticae (4 adult female:20 adult female) b, N. womersleyi:T. urticae (4:20) c, (N. californicus+N. womersleyi):T. urticae ((2+2):20) d, Only T. ulticae (20). T. urticae population became significantly lower in the treatment plots than in the control plot but the higher egg number of T. urticae was observed in the treatment "b" plot than in "a" and "c" plots. In the "c" plot, lower number of N. womersleyi was observed than N. californicus. The result indicates that single use of N. californicus and combination use of N. californicus and N. womersleyi were more effective than single use of N. womersleyi but, there was no significantly difference between single use of N. californicus and combination use of N. californicus and N. womersleyi for control of T. urticae. Also, N. californicus appears to interfere or outcompete N. womersleyi.

• TaeGyun Kim(Entomology Program, Department of Agricultural Biotechnology, Seoul National University)
• Jeongjoon Ahn(Entomology Program, Department of Agricultural Biotechnology, Seoul National University)
• YongJun Kwon(Entomology Program, Department of Agricultural Biotechnology, Seoul National University)
• Joon-Ho Lee(Entomology Program, Department of Agricultural Biotechnology, Seoul National University)