Gut-content analysis of predatory phytoseiid mites using fluorescent-labeled polymerase chain reaction: age of spider-mite eggs influences detection rates

As spider mites become increasing resistant to chemical acaricides, interest in establishing biological control programs using natural enemies has also risen, requiring verification of spidermite predators. Although some phytoseiid mites are considered effective predators in agroecosystems, their small size makes it difficult to confirm predation through field observation. Polymerase chain reaction (PCR) can be an effective detection technique and has been used commonly in studies on microfaunal predator-prey interactions. However, preliminary data revealed that ordinary agarose gel electrophoresis cannot detect PCR products from phytoseiid mites that consumed spider-mite eggs. In this study, I used fluorescent-labeled primers and genetic analyzers to successfully amplify the gut contents of phytoseiid mites and confirmed they were derived from spider-mite eggs based on fragment analysis. The results indicated that spidermite eggs can be detected ≥24 h post-oviposition, but not within 3 h. Thus, fluorescent PCR is an effective tool for elucidating predator-prey interactions among microfaunal food chains.