Biological Control of Frankliniella occidentalis(Thysanoptera: Thripidae) on Cucumber, using Amblyseius swirskii(Acari: Phytoseiidae)

By releasing predatory mite, Amblyseius swirskii Athias-Henriot, with 25 individuals per cucumber plant in a commercial greenhouse (1,600 ), the population of western flower thrips, Frankliniella occidentalis (Pergande), was kept under the economic threshold level. The initial thrips population of 18.3 individuals per leaf decreased to 2.1 individuals per leaf after four weeks, while the number of A. swirskii reached to 16.6 individuals per leaf. It was also observed that at a point where the thrips occurred in high density of about 34.3 individuals per leaf, A. swirskii population built up on the lower part of cucumber plant first, but as time passed the predatory mites moved upward to the top of the plant and aggregated.