Computerized climate control systems provide precise and flexible control of climate for greenhouse crops. Temperature and vapour pressure deficit (VPD), are two factors that can have a major impact on the biology and dispersal of pests, and on the efficacy of biological control programs. Previous studies of greenhouse climate concentrated on the ambient conditions. However, the boundary layer of air around a leaf, where pests and their biological control agents spend most of their time, can have microclimatic conditions that can be very different from ambient conditions. Infrared sensors and humidity probes make it possible to calculate the microclimate within 0.5 mm from the leaf surface. Manipulation of microclimate may improve control efficacy of greenhouse pests, such as F. occidentalis. Controlled environmental chamber trials revealed that the predation rate of A. cucumeris on F. occidentalis increased with increased temperature and decreased with increased VPD. The objective of this study was to determine the influence of ambient and leaf surface temperature and VPD on the predation rate by A. cucumeris on F. occidentalis in greenhouse cucumbers. Predation trials involved confining a single A. cucumeris with 15 first instar F. occidentalis to the underside of a cucumber leaf using a small clip cage. Cages were set up at two levels within the crop (1.5 and 2.2m). Trials were preformed at two ambient air temperatures (22°C [20°C] , 27°C [22°C] (day [night]) and at three VPD ranges (0.25-0.45, 0.50-0.60, 0.70-1.10 kPa) for each temperature regime. Predation trials were examined 24 hours later for the number of dead thrips. Preliminary analysis found that A. cucumeris fed twice as much on F. occidentalis at the higher temperature but showed no significant differences among the predation rates at the three VPD ranges.
Species 1: Thysanoptera Thripidae Frankliniella occidentalis (western flower thrips, thrips)
Species 2: Acari Phytoseiidae Amblyseius cucumeris (predatory mite)
Keywords: predation, greenhouse microclimate
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