Does fundamental host range match ecological host range? A retrospective case study of a Lygus plant bug parasitoid

Using the retrospective case study of Peristenus digoneutis (Hymenoptera: Braconidae) introduced in the United States for biological control of native Lygus plant bugs (Hemiptera: Miridae), laboratory and field studies were conducted in the area of origin to evaluate whether the fundamental host range of P. digoneutis matches its ecological host range. Furthermore, it was determined whether these approaches would have been indicative of the post-introduction host range of P. digoneutis in North America [Day, W.H., 1999. Host preference of introduced and native parasites (Hymenoptera: Braconidae) of phytophagous plant bugs (Hemiptera: Miridae) in alfalfagrass fields in the north-eastern USA, BioControl 44, 249–261.]. Seven non-target mirid species were selected to define the fundamental host range of P. digoneutis in the area of origin in Europe. Laboratory choice and no-choice tests demonstrated that all selected non-target species were attacked by P. digoneutis and were largely suitable for parasitoid development. To confirm the validity of the fundamental host range, the ecological host range of P. digoneutis in the area of origin was investigated. Peristenus digoneutis was reared from 10 hosts, including three Lygus species and seven non-target hosts from the subfamily Mirinae. Despite the fact that laboratory tests demonstrated a high parasitism level in non-targets, ecological assessments in both North America (Day, 1999) and Europe suggest a much lower impact of P. digoneutis on non-target mirids, with low levels of parasitism (below 1% in Europe). Therefore, ecological host range studies in the area of origin provide useful supplementary data for interpreting pre-release laboratory host range testing.