A single-step multiplex PCR assay for the detection of European Peristenus spp., parasitoids of Lygus spp.

Lygus Hahn ( Hemiptera: Miridae) are serious pests of agricultural and greenhouse crops throughout North America. In Europe, bivoltine Peristenus Forster ( Hymenoptera: Braconidae) species have a significant impact on Lygus populations. Release and establishment of European P. digoneutis Loan in Lygus lineolaris ( Palisot de Beauvois) populations in northeastern USA has renewed interest in the intended liberation of European parasitoids for Lygus control in Canada. Accurate identification of natural enemies is the cornerstone of biological control but conventional methods for identifying Peristenus species and estimating parasitism rates rely on tedious and time- consuming dissection and rearing methods. The present study describes species- specific PCR primers for three species of Peristenus, and the use of a multiplex PCR assay to detect P. digoneutis and P. stygicus Loan eggs and larvae from Lygus rugulipennis Poppius nymphs. Results indicate that the primers amplify uniquely sized, species- specific PCR products for the three species and are capable of detecting single eggs in parasitized nymphs within 3 days post- parasitism. Using a multiplex PCR assay, the primers maintain specificity and sensitivity, and allow detection of each of the three species in a single reaction. Although molecular diagnostics have previously been used in the identification of parasitoids and estimation of parasitism rates, this is the first time a single- step multiplex PCR protocol has been described.