Targeted RT-PCR Based Gut Content Analysis for Potato Psyllid Predation in Laboratory Assays

RT-PCR was used to test whether DNA from potato psyllid (Bactericera cockerelli (Šulc)) could be detected in generalist predators that had been allowed to feed on psyllids in laboratory feeding trials. The assay used primers that had been developed in Europe to amplify a region of the ITS2 gene in psyllids for use in identifying psyllid specimens intercepted at border inspection stations or discovered in regions currently free of the pest. We conducted feeding trials with arthropod generalist predators in diverse taxonomic groups (Araneae, Acari, and two orders of Insecta). RT-PCR readily detected potato psyllid DNA in predators that had recently fed upon the insect. DNA from a closely related psyllid, Bactericera dorsalis (Crawford), was not detected, suggesting that our approach is unlikely to lead to false positives. RT-PCR was found to be more sensitive than conventional PCR at detecting very dilute quantities of potato psyllid DNA. Predator taxa differed in how long after a feeding event prey DNA could be detected. Signal retention was longer in spiders and a predatory mite (Anystis) than in predatory true bugs (Hemiptera). We believe this new molecular tool will be of value in identifying potentially important sources of psyllid biological control under field conditions.