Comparison of Transeius montdorensis (Acari: Phytoseiidae) to Other Phytoseiid Mites for the Short-Season Suppression of Western Flower Thrips, Frankliniella occidentalis (Thysanoptera: Thripidae).

Under winter and early spring greenhouse growing conditions, suppression of thrips by predatory mites can vary considerably on a species basis. For certain mite species, shorter photoperiods, cooler temperatures, and lower vapor pressures translate to reductions in predation, oviposition, and survival. Therefore, predator species need to be assessed simultaneously to identify those most suitable for use under short-season conditions. In this study, laboratory trials were first conducted to compare rates of Frankliniella occidentalis (Pergande) thrips predation, and oviposition by the phytoseiid predator Transeius montdorensis (Schicha) under simulated summer and winter conditions. Transeius montdorensis consumed similar numbers of first instar thrips, and laid a similar number of eggs under both conditions. In short-season greenhouse cage trials, crop establishment and predatory capacity of T. montdorensis were compared to those for three other predatory mites: Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae), Amblydromalus limonicus (Garman & McGregor) (Acari: Phytoseiidae) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae). Over 4-5-wk trials performed in early spring in 2014 and 2016, the number of T. montdorensis mites on pepper plants was either equal or greater to levels in other treatments. In T. montdorensis cages, high levels of thrips suppression were observed, equal to those achieved by A. swirskii or A. limonicus treatments in the 2016 trial, and superior to those by N. cucumeris in both trial years. These findings show that T. montdorensis is a good thrips predator, and provides rationale for the development of this species as a new agent for greenhouse pest management in an expanded temperate area of the world.