Side effect on thrips of the spider mite predator Neoseiulus californicus

Abstract

The phytoseiid mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) is an effective biological control agent of spider mites. Due to its generalist nature, it is also able to survive on alternative food sources such as different types of pollen, broad mites and several astigmatid mite species. At Koppert Biological Systems, a possible sideeffect of this predator on western flower thrips Frankliniella occidentalis (Pergande) (Thripidae: Thysanoptera) was investigated. In semi-field trials, originally set-up to test the N. californicus effectivity against spider mites, a significant reduction in thrips density was found after four weeks. There are two possible explanations: (1) direct predation by N. californicus on F. occidentalis and (2) an indirect effect: thrips, known to be an intraguild predator of spider mite eggs, is competing for food with N. californicus. In laboratory experiments it was found that N. californicus is able to feed on first instar thrips larvae and produce eggs. This predatory mite species combined with a generalist that is effectively able to control both whiteflies and thrips, such as Amblyseius swirskii, would favour relatively simple biocontrol systems capable of controlling the three main greenhouse pests: thrips, spider mites and whiteflies.