Regional spread of the colonized Lygus parasitoid, Peristenus relictus along the Central Coast of California

Peristenus relictus (Braconidae) was imported into California and released into the Monterey Bay region beginning summer 2002 for control of Lygus spp., a key pest of strawberries. They were last released in 2006. Beginning in 2009, we sampled for this parasitoid at increasing distances from original release sites to determine how far they have spread since first released. Lygus nymphs were collected from six locations on an expanding sampling radius, intermediate (ca. 30 km) and far (ca. 60 km) from the original release area, at three points on the compass, northwest, northeast, and southeast (the original release sites were within 10 km of the ocean, precluding sample sites to the west). Dissected larvae were identified to species using a novel multiplex PCR analysis of their DNA since a native Peristenus sp. has been found, though rarely, attacking Lygus spp. Peristenus relictus was found at the most distant locations, north and east of original release sites, and at the intermediate distance, 30 km to the southeast. Sampling will continue in 2010 to determine the limit of spread by P. relictus.