Introductions of a European parasitoid, Peristenus relictus (=P. stygicus), against tarnished plant bug in the mid-Atlantic states
1Beneficial Insect Introduction Research Unit, USDA-ARS, Newark, DE, USA
2European Biological Control Laboratory, USDA-ARS, Montferrier-sur-Lez, France
3P. Alampi Beneficial Insect Laboratory, New Jersey Dept. Agriculture, Trenton, NJ, USA
4Dept. Agriculture & Natural Resources, Delaware State University, Dover, DE, USA
Populations of tarnished plant bug, Lygus lineolaris, in alfalfa have declined by 65% in New Jersey since the establishment in 1984 of Peristenus digoneutis, a European nymphal parasitoid of Lygus species. Although it has expanded its distribution substantially to the NE and NW, P. digoneutis has not become widely established south of its original release site in northern NJ. The recent establishment in California of Peristenus from hot-summer regions of Europe suggests that if P. relictus (=P. stygicus of older literature), the predominant nymphal parasitoid of Lygus distributed throughout southern Europe, could be established in the mid-Atlantic states, similar reductions in Lygus populations might be obtained. After permission for field release of P. stygicus was received, individuals from field collections in eastern and central France (Aveyron & Drome departments) were increased by mass-rearing on a laboratory colony of L. lineolaris at the New Jersey Dept. Agriculture Beneficial Insect laboratory. Field releases in New Jersey commenced in 2001. In 2003, the rearing colony was replaced with new stock collected in southern Spain (Andalucia) and central Italy (Umbria), and the host Lygus colony was switched to rearing on artificial diet, significantly increasing parasitoid production for field release from 3,200 in 2004 to more than 17,000 in 2005. Beginning in 2006, field releases were made in managed alfalfa fields at 8 sites in New Jersey and Delaware at weekly intervals throughout the summer, totaling ca. 30,000 released. At each site half of the releases were of laboratory-parasitized late-instar nymphs and half were adult parasitoids placed within field cages over alfalfa for one day before cage removal. Releases will be continued in this manner for several years and recovery samples taken to monitor for signs of establishment. Within-season recoveries of progeny were made at two sites in Delaware during 2006. One overwintering female P. relictus was also recovered in 2006 from a 2004 release site in New Jersey planted with a wildflower mixture.
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