Thrips egg predation by phytoseiids: an overlooked pest control mechanism

Abstract: Western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) remains one of the most challenging problems in protected crops worldwide. Although a variety of natural enemies can be introduced to control this pest, phytoseiid predatory mites remain a cornerstone in IPM programs. It is well-established that phytoseiids mainly prey on the first and to a lesser extent the second instars of F. occidentalis. However, it is less known that some phytoseiid predators are also able to consume thrips eggs. In the present study, we tested a range of commercially available predatory mites with regard to their egg killing capacity. We observed marked differences between the predatory mite species in their ability to feed on thrips eggs, as well as regarding their tendency to engage in egg feeding when thrips larvae are present. For example, the generalist phytoseiid Euseius gallicus Tixier & Kreiter showed a strong preference for eggs over larvae in a choice test, whereas Amblyseius swirskii (Athias-Henriot) preferentially killed thrips larvae. Predation rate on thrips larvae is often used as the only criterion to evaluate the potential of new predatory mites. On the basis of the present study, we advise to incorporate egg predation in the evaluation procedure.