Detection of EuropeanPeristenus digoneutisloan in mirid populations in southern Ontario

Abstract

Lygus spp. Hahn (Hemiptera: Miridae) are serious pests of a wide variety of economically important crops in North America. A European parasitoid, Peristenus digoneutis Loan (Hymenoptera: Braconidae), released in the northeastern USA for the biological control of Lygus, has successfully established in nine states and in eastern Canada, including southeastern Ontario, southern Quebec and Nova Scotia. To determine the extent to which P. digoneutis has dispersed and established in mirid populations in Ontario, a single-step multiplex PCR assay, designed to differentiate European species P. digoneutis and P. relictus from native North American Peristenus species, was used to identify parasitoid larvae dissected from field-collected Miridae. A total of 222 parasitoid larvae were analysed with the multiplex assay. Most (172) were identified as members of the P. pallipes Curtis complex; however, three from the Niagara region were identified as P. digoneutis. Specimens that did not amplify using the Peristenus multiplex PCR assay were screened with a PCR primer set designed to detect Leiophron (Hymenoptera: Braconidae) species, and most were confirmed to be Leiophron larvae. This study confirms the presence of P. digoneutis species in southern Ontario, and is another example of the utility of molecular methods for the detection of newly introduced or dispersed parasitoids. The presence of exotic P. digoneutis in southern Ontario may expedite future releases to augment already-established populations. Following such releases, the Peristenus multiplex PCR assay will be a useful component of post-release studies to evaluate the success of the biological control programme for Lygus plant bugs in Canada.

Bioclimatic analyses of distributions of a parasitoid Peristenus digoneutis and its host species Lygus spp. in Europe and North America

“…The phenology of P. digoneutis in North America predicted by our model is very similar to the observed phenology in south‐western Ontario, where P. digoneutis is now well established (Goulet & Mason, 2006; Gariepy et al , 2008). Nymphs parasitized by P. digoneutis were first found in the first and second week of June and then again from the third week of July to the end of August of two subsequent years (2007, 2008) (Mason et al , 2009).…”

“…However, laboratory studies showing that P. digoneutis does not have a pre‐oviposition period (Haye et al , 2005) bring this assumption into question. Surveys conducted in 2007 and 2008 in south‐western Ontario, where P. digoneutis is now well established (Gariepy et al , 2008), showed that P. digoneutis adults were found in the field as early as 30 May, when Lygus nymphs were already present (Mason et al , 2009). However, parasitism of nymphs was not recorded before 13 June, suggesting that, under field conditions, P. digoneutis may not start to parasitize immediately after emergence.…”

“…Peristenus digoneutis is now present in all of the northeastern states, is moving westward along the southern edge of Lake Erie (Day & Hoelmer, 2008) and became established in eastern Canada, beginning in Quebec (1999), Ontario (2002) and then Nova Scotia in 2006 (Broadbent et al , 1999; Goulet & Mason, 2006; Gariepy et al , 2008). Although genetic selection may eventually allow this parasite to move further south, biological control of Lygus will probably be limited to northern U.S.A. and southern Canada (Day, 1996; Day et al , 1998).…”

“…The final model was then used to project the potential distribution of P. digoneutis across North America. In the final development phase, the model was validated by comparing the known distribution and abundance of P. digoneutis in eastern North America (135 records from Canada and U.S.A.) (Day et al , 1990, 1998, 2000; Broadbent et al , 1999; Day, 2005; Goulet & Mason, 2006; Day & Hoelmer, 2008; Gariepy et al , 2008) with the predictions of the model. The P. digoneutis model was constrained by the minimum degree days above limiting low temperature (DV0) required for this species to complete two generations.…”

Landscape context shifts the balance of costs and benefits from wildflower borders on multiple ecosystem services

“…DNA from nymphs was extracted using an abbreviated chloroform: isoamyl alcohol protocol developed by Tilmon & Hoffmann [39]. DNA extractions along with negative controls were amplified using Peristenus species-specific primers as in [40]. Using this method, species-specific forward primers are combined with a genus-specific reverse primer to amplify a region including ITS1 and ITS2.…”