Determining Parasitoid Species Composition in a Host Population: A Molecular Approach

Larvae of closely related parasitoid taxa often lack morphological differences that can be used for species level identification. Determining the parasitoid species present in a host population may require rearing, often a time-consuming process. To monitor field parasitism rates by several species of Peristenus wasps (Hymenoptera: Braconidae) that are natural enemies of Lygus (Heteroptera: Miridae), we have developed a two-step molecular approach. Polymerase chain reaction (PCR) of the COI gene with wasp-targeting primers is performed on DNA extracted from a Lygus nymph and the parasitoid larva (if any) therein. A positive reaction indicates parasitoid presence. A restriction digest of the PCR product then indicates which parasitoid species is present among known alternatives, and a diagnosis is achieved in days rather than weeks or months.