Development of a PCR-based method for the screening of potential predators of the African citrus psyllid Trioza erytreae (Del Guercio)

Trioza erytreae is one of the vectors of Huanglongbing (HLB), the main global citrus groves threat. Since its recent detection in the north-western Iberian Peninsula (Spain and Portugal), its contention and eradication have been a priority to prevent its spread. For the biological control of T. erytreae, it is important to understand the role that each potential natural enemy could have. With the aim to determine which predators have incorporated T. erytreae into their diet, a PCR-based method has been developed for the specific detection of T. erytreae in their gut contents. For this, a pair of specific primers was designed from the mitochondrial cytochrome c oxidase subunit I (COI) region. Specificity of this pair of primers was studied and feeding trials with two predator species were conducted to determine the decay rates of T. erytreae within their gut. None of the non-target species was amplified, showing the high specificity of these T. erytreae primers. Feeding trials showed 4.8h and 4.5h half-life time detections of T. erytreae ingested by Chrysoperla carnea and Cryptolaemus montrouzieri, respectively. Finally, field-collected generalist predators of T. erytreae-infested citrus trees from the Canary Islands and Galicia (Spain), were analysed by conventional PCR for the presence of T. erytreae in their guts. Results showed that a wide range of predator taxa ingested the target prey, like the families Coccinellidae, Anthocoridae, Chrysopidae, Hemerobiidae, Forficulidae, Miridae, Syrphidae, Formicidae, Erythraeidae and the order Araneae, with detection percentages ranging from 20 to 100%. These results confirm that most of the analysed generalist predators found in citrus trees could be potential candidates for the biological control of T. erytreae in future biological control programs of this HLB vector.