Can trichome density explain the differences in behaviour and performanceof Amblyseius swirskii on greenhouse ornamentals?

Abstract: Biological control in ornamental crops is challenging due to the wide diversity ofcrops and cultivars. In this study, we tested the hypothesis that trichome density on different hostplants influences the behaviour (walking speed and prey finding) and performance (predation andoviposition capacity) of the predatory mite Amblyseius swirskii Athias-Henriot (Acari:Phytoseiidae). Tests were done on leaf disks of ornamental plant species differing in trichomedensity (rose, chrysanthemum and gerbera) and compared to a smooth surface (plastic). Thrips(Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) were used as prey. Behaviourand performance of A. swirskii were influenced by plant species. Up to a certain density oftrichomes, trichome number had a negative effect. Walking speed was highest on plastic,followed by rose. No differences were found between chrysanthemum and gerbera. Proportion oftime spent walking was the same on leaf disks of all plant species. Predation of thrips was higheston gerbera and least on rose. Predation rates on chrysanthemum and plastic were intermediate. Incontrast, no differences in oviposition rate were found among plant species. According to theseresults, release rates of A. swirskii may need to be adjusted depending on the crop in which it isused.