Abstract
Neoseiulus womersleyi is a potentially important biological agent for controlling Tetranychus urticae in apple orchards. However, overwintering sites of N. womersleyi in apple orchards have not been identified; therefore, the population dynamics of N. womersleyi and T. urticae on apple trees were investigated in Akita Prefecture, northern Japan, from April 2007 to March 2008. The population of T. urticae peaked on the leaves in mid-September. In contrast, the population of N. womersleyi rapidly increased and peaked in early October, and many adults were present until early November. Eggs of the predacious mite were not observed at all in early November. Adult females of N. womersleyi were found under rough bark in early December. N. womersleyi was significantly more abundant under rough bark containing many diapausing T. urticae females than under bark where the prey were few; however, the mean number of N. womersleyi early in March 2008 was significantly lower than in early December. Both N. womersleyi and T. urticae were collected using Phyto traps attached to apple twigs. Neither was captured between April and September, but the numbers of both increased rapidly in October.
