Pesticide Susceptibility of Two Dominant Phytoseiid Mites, Neoseiulus californicus and N. womersleyi, in Conventional Japanese Fruit Orchards (Gamasina: Phytoseiidae)

Abstract

Pesticide (six insecticides and 16 acaricides) susceptibility of populations of N. californicus (4 populations) and N. womersleyi (5 populations) was investigated to test the hypothesis that the recent species replacement between these two species was due to a change in pesticides used in orchards combined with a differential susceptibility of the two species to one or more of the new pesticides. Although the present results cannot provide a clear conclusion regarding factors responsible for the change in dominant phytoseiid, it was suggested, at this point, that none of the pesticides examined here seemed to have a decisive influence on the replacement of N. womersleyi by N. californicus.