Food supplements for Amblyseius swirskii: supporting predator or prey populations?
Abstract: In order to reduce the cost of repeated introductions of natural enemies in protected crops, food supplements can be provided when target prey levels are low. However, selecting such foods should be done with extreme care, as some omnivorous pests may also benefit from those resources. Western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae) is such an omnivorous herbivore feeding on both plant and animal materials. In the present laboratory study, we tested three supplemental foods used in protected cultivation to support populations of the phytoseiid predators: pollen of narrow-leaved cattail Typha angustifolia L. (NutrimiteTM), dry decapsulated Artemia franciscana Kellogg (Branchiopoda: Artemiidae) cysts of high quality, and a commercial product consisting of decapsulated cysts of Artemia sp. (Artefeed). The value of these supplemental foods for sustaining population growth of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) and its prey F. occidentalis was investigated. Furthermore, we assessed the impact of the presence of the supplemental foods on the predation efficacy of A. swirskii on first instars of F. occidentalis. Results showed that the foods differentially affected population growth of both pest and predator. Thrips performed better on pollen than on Artemia cysts when provided on bean leaves (Phaseolus vulgaris L.). Similarly, when fed on T. angustifolia pollen, the population growth rate of A. swirskii was higher than on both types of Artemia cysts.