Efficacy of natural enemies against the tobacco thrips Thrips parvispinus (Karny) in laboratory and greenhouse studies

BACKGROUND: The tobacco thrips, Thrips parvispinus, is threatening greenhouse horticulture crops worldwide. RESULTS: In a laboratory trial, gravid females of Amblyseius swirskii, Amblydromalus limonicus, Neoseiulus cucumeris and Transeius montdorensis consumed between 2 and 3.5 first instars of the thrips daily. The predation rates of the phytoseiids tested were lower than those reported when the western flower thrips Frankliniella occidentalis was provided as prey. This predation pattern was confirmed for A. swirskii in a separate trial. In a greenhouse cage trial with sweet pepper plants infested with tobacco thrips, A. swirskii, A. limonicus and N. cucumeris significantly reduced the pest numbers. However, in a commercial Ficus elastica Robusta crop, where A. swirskii and N. cucumeris were introduced weekly, no single predator proved to be sufficiently effective. Larger generalist predators, such as the lacewing Chrysoperla carnea, the predatory thrips Franklinothrips vespiformis, and the predatory bugs Orius laevigatus and Macrolophus pygmaeus were also tested. They reduced populations of tobacco thrips in a cage experiment on sweet pepper. Chrysoperla carnea and F. vespiformis were tested in a commercial Ficus greenhouse and reduced the pest population but were unable to eradicate it. CONCLUSION: Our results show that the tested mite and insect predators have potential to control tobacco thrips. More research on strategies involving preventative and curative releases of natural enemies, the combination of predatory mites with insect predators or with biopesticides, and the use of supplemental food sources will be needed to curb the spread and damage of T. parvispinus.