Phytoseiulus persimilis Athias-Henriot (Acari: Phytoseidae) is well known as an effective natural enemy of two-spotted spider mite, Tetrnychus urticae Koch (Acari: Tetranychidae). However, successful biological control usually requires adequate management of temperature. While P. persimilis did suppress T. urticae at moderate condition (20~25oC) in a week or so, the density of P. persimilis was barely increased at cold condition (5~10oC) in three weeks or so. The problem is that winter temperature is too cold for the development and reproduction of P. persimilis in greenhouse for forcing strawberry. Night temperatures in greenhouse were even mostly lower than 6oC. So, winter application of P. persimilis against T. urticae is useless. To avoid damage from T. urticae in early spring season, it was better that the release amount of P. persimilis was double at middle- and late-October, instead of early-November to next early-February. If necessary, the double releasing of P. persimilis might be good for control of T. urticae at middle- and late-February.

• Yong-Heon Kim(Applied Entomology Division, Department of Agricultural Biology, National Institute of Agriculture Science and Technology, Rural Development Administration)
• Hwang-Yong Kim(Applied Entomology Division, Department of Agricultural Biology, National Institute of Agriculture Science and Technology, Rural Development Administration)
• Jeong-Hwan Kim(Applied Entomology Division, Department of Agricultural Biology, National Institute of Agriculture Science and Technology, Rural Development Administration)
• Dae-Hong Lee(Department of Applied Biology, College of Agriculture and Life Sciences, Chungnam National University)
• Young-Nam Youn(Department of Applied Biology, College of Agriculture and Life Sciences, Chungnam National University)