ControllingLygusplant bugs (Heteroptera: Miridae) with EuropeanPeristenus relictus(Hymenoptera: Braconidae) in Canada – risky or not?

The EuropeanPeristenus relictusLoan (syn.P. stygicus) has been considered for biological control ofLygusplant bugs native to Canada. Laboratory and field studies were conducted in the area of origin to evaluate the host specificity ofP. relictus. Laboratory choice and no-choice tests demonstrated thatP. relictusattacked all non-target species offered (fundamental host range). However, closely related non-target mirids (tribe Mirini) were generally well accepted byP. relictus, while hosts from the tribe Stenodemini were less frequently attacked and less suitable for parasitoid development. To validate the laboratory results, a thorough examination of the parasitoid complex of common mirids in Europe was conducted to determine which non-target species may serve as alternative hosts forP. relictusin a natural situation (ecological host range). When comparing both approaches, the fundamental host range ofP. relictusmatched its ecological host range. In addition to threeLygusspecies, the ecological host range ofP. relictusin the area of Schleswig-Holstein, northern Germany, contains at least 16 non-target species, including hosts belonging to the subfamilies Mirinae, Phylinae and Bryocorinae. A broad ecological and fundamental host range suggests thatP. relictusis a generalist; however,P. relictuswas not the primary contributor to parasitism of most non-target hosts studied. AlthoughP. relictusis assumed to be of minor importance for regulating non-target populations in the area of investigation, the results of the present study indicate thatP. relictushas the potential to use non-target host populations for reproduction.