Review of the Nearctic species of Leiophron and Peristenus (Hymenoptera: Braconidae: Euphorinae) parasitizing Lygus (Hemiptera: Miridae: Mirini)

Abstract

Plant bugs belonging to the genus Lygus Hahn (Hemiptera: Miridae) are important pests of a wide variety of North American crops. Efforts to use biological control as one strategy in an integrated pest management approach have been impeded by a poor understanding of the endoparasitoids, particularly species of the genera Leiophron Nees and Peristenus Foerster (Hymenoptera: Braconidae) many of which parasitize the nymphal stages of Lygus, among other Miridae. The taxonomy of Leiophron and Peristenus species associated with agricultural habitats is reviewed based on reared material contributed by numerous researchers. Sixteen species of the two genera were found parasitizing Lygus nymphs, including the following eight species described as new, Leiophron australis Goulet, L. simoni Goulet, Peristenus braunae Goulet, P. broadbenti Goulet, P. carcamoi Goulet, P. dayi Goulet, P. gillespiei Goulet and P. otaniae Goulet. The species are differentiated in a key, described and illustrated. Two names are newly placed in synonymy, L. trigonotylidis Loan, 1974 under Leiophron lygivorus (Loan 1970) and Brachistes nocturnus Viereck, 1905 under P. mellipes (Cresson 1872). Euphorus mellipes Cresson is removed from synonymy with P. pallipes (Curtis). Most of the endoparasitoid species are known to be associated only with Lygus spp. and appear to be distinct in their distribution and their biology. Analysis of the endoparasitoid complex in southern Quebec shows that of the six species that occur in alfalfa and hay fields, four species use Lygus lineolaris (Palisot) as the main host. The introduced Peristenus digoneutis Loan has recently established in southern Quebec and although its numbers have increased substantially it has not yet had an evident impact on reducing L. lineolaris population levels.

Detection of EuropeanPeristenus digoneutisloan in mirid populations in southern Ontario

“…18, No. 6, 2008, 583Á590 Sears, Goulet and Mason 2006). Two species, P. mellipes Cresson and P. pseudopallipes Loan, are univoltine and attack Lygus nymphs in the spring and summer, respectively (Lim and Stewart 1976;Goulet and Mason 2006).…”

“…6, 2008, 583Á590 Sears, Goulet and Mason 2006). Two species, P. mellipes Cresson and P. pseudopallipes Loan, are univoltine and attack Lygus nymphs in the spring and summer, respectively (Lim and Stewart 1976;Goulet and Mason 2006). These species are North American members of the Peristenus pallipes complex, a complex of difficult to distinguish species of Holarctic distribution and are members of the Peristenus mellipies subgroup described in the taxonomic revisions of Goulet and Mason (2006).…”

A large-scale rearing method forPeristenus digoneutis(Hymenoptera: Braconidae), a biological control agent ofLygus lineolaris(Hemiptera: Miridae)

“…Several native parasitoid species in the genus Peristenus Fö rster and Leiophron Nees (Hymenoptera: Braconidae) attack nymphs of Lygus spp. populations in Canada (Goulet and Mason 2006). However, these are ineffective because overall parasitism is insufficient to significantly suppress the pest Lygus spp.…”

“…Since its first release in New Jersey (USA) P. digoneutis has dispersed naturally into Canada, where it is now present in plant bug populations in southern Quebec, southern Ontario and Nova Scotia (Goulet and Mason 2006), more than 15 years after the initial release. However, the tarnished plant bug, L. lineolaris, is still considered the most important pest of strawberries Fragaria x ananassa Duchesne (Rosaceae) in Ontario and until now intensive use of insecticides has been the only means of control (Broadbent et al 2009).…”

Impact of the introduced parasitoidPeristenus digoneutis(Hymenoptera: Braconidae) on tarnished plant bug (Hemiptera: Miridae) infesting strawberries in northwestern New Jersey, USA

“…Parasitism mortality was determined each week, but is presented only when TPB nymphs reached peak levels, when maximum feeding and damage occurs. Reared adults of the introduced parasitoid (P. digoneutis) were easily distinguished from native Peristenus species using the key of Goulet and Mason (2006).…”