Abstract
The seasonal occurrence of Neoseiulus womersleyi and Tetranychus urticae in apple orchards that received pyrethroid applications was investigated from 2006 to 2007 in Akita Prefecture, northern Japan. The density of N. womersleyi increased continuously during the summer in response to the density of T. urticae, even in pyrethroidtreated plots. The susceptibility of six strains of N. womersleyi was examined against nine pyrethroid insecticides. The mortality of females of the six strains of N. womersleyi was less than 30% in most insecticides tested. These results suggested that pesticide-resistant N. womersleyi occurred in commercial apple orchards, which is promising for the control of T. urticae in the apple IPM program.
