Biological Control of Pink Citrus Rust Mite, Aculops pelekassi（Acari: Eriophyidae）, by Euseius sojaensis（Acari: Phytoseiidae）in Commercial Citrus Orchards

Euseius sojaensis(Ehara)(Acari: Phytoseiidae)is an effective indigenous natural enemy of Aculops pelekassi(Keifer)(Acari: Eriophyidae). However, dithiocarbamates, which are seriously harmful to E. sojaensis, are usually applied in commercial citrus orchards in June when the density of this phytoseiid mite peaks. In this study, we examined the suppressive effect of the E. sojaensis release on A. pelekassi in conservation control by using selective pesticides until late June. In the E. sojaensis release plot, phytoseiid populations were larger, A. pelekassi populations were smaller, and the rate of fruit injury was lower than those in the no-release plot; these differences were significant in some years. Many phytoseiid mites were observed in conservation-control orchards, with E. sojaensis being the dominant species; however, only a few phytoseiids occurred in conventional-control orchards. These results suggest that E. sojaensis was conserved by using selective pesticides and the initial density of A. pelekassi was reduced by this phytoseiid mite. However, it is difficult to control fruit injury only by conserving E. sojaensis, because it generally disappears after July. Therefore, we should study the possibilities for enhancement of E. sojaensis populations from summer onwards for sustainable biological control of A. pelekassi.