Does the analysis of molecular gut contents reveal efficacy of phytoseiid mites in fields?

Abstract: We developed species-specific primers for molecular identification of the thrips
species Frankliniella occidentalis and Frankliniella intonsa and the predatory mite, the
phytoseiid Amblyseius swirskii. In laboratory experiments, the detection rates, 24 h after feeding on thrips, were 33 % for F. occidentalis and 20 % for F. intonsa, respectively. So, it was thought that this technique could reveal predator-prey relationships. Ninety-nine predatory mites collected from the field were tested; however, thrips-specific polymerase chain reaction products were not detected. This means either of (1) condition of filed samples are decreased in comparison with laboratory samples, or (2) they actually did not feed on thrips. We considered the former possibility is low. In this case, the mites might have survived with feeding on plant pollen. To elucidate it, we need to develop pollen markers.