Interspecific competition between exotic and native Peristenus (Hymenoptera: Braconidae) parasitoids of Lygus bugs (Hemiptera: Miridae) of western Canada: a

Abstract

Four species of Lygus bugs (Hemiptera: Miridae), Lygus lineolaris , L. keltoni , L. elisus, and L. borealis , are native pests of many crops throughout North America. In eastern Canada, a European parasitoid, Peristenus digoneutis (Hymenoptera: Braconidae), occurs adventively from intentional releases made in the 1980s in the northeastern region of the United States of America. In the Canadian prairies, P. mellipes and P. howardi are common native parasitoids that attack the first and second generations of Lygus , respectively, albeit at low levels. Therefore, relocation of P. digoneutis has been considered to enhance biological control in western Canada. We investigated the potential for competition between the native and exotic Peristenus spp. in laboratory settings. Our results showed that no statistically significant effects of simultaneous or sequential competition occurred on the success of parasitism by the native species, particularly for P. howardi . Minor reductions in parasitism by P. mellipes were observed only when the exotic species was added one day before the native species. From these findings, we conclude that the risk for competitive displacement of native Peristenus spp. by P. digoneutis is low. The potential benefits of having a parasitoid with two generations and the likely additive mortality effects on Lygus bug pests should outweigh the low environmental risks of introducing P. digoneutis .