Influence of Greenhouse Microclimate on Neoseiulus (Ambyseius) Cucumeris (Acari: Phytoseiidae) Predation on Frankliniella Occidentalis (Thysanoptera: Thripdae) and Oviposition on Greenhouse Cucumber

Abstract

The influence of leaf boundary layer vapor pressure deficit (VPD) and leaf temperature on the predation rate by Neoseiulus (Amblyseius) cucumeris (Oudemans) (Acari: Phytoseiidae) on Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) and on the oviposition rate by N. cucumeris on cucumber leaves were determined for greenhouse cucumber grown under semi-commercial production conditions. Vapor pressure deficit did not affect either the predation or oviposition rates by N. cucumeris. Examination of ambient and boundary layer VPDs revealed that it was difficult to produce substantial changes in boundary layer VPD in high-gutter greenhouses. Therefore, the relatively steady state of humid conditions at the leaf boundary layer resulted in no significant differences in predation and oviposition rates despite changes in ambient VPD. However, leaf temperature did influence the predation and oviposition rates by N. cucumeris: both rates increased at the higher temperature. This suggests that establishing seasonal release rates should result in increased efficiency of this predator during the cooler periods of the year.