Long term post-release impacts of the introduced parasitoid Peristenus relictus (Hymenoptera: Braconidae) on Lygus spp. (Hemiptera: Miridae) populations in California

Publication date: Available online 21 July 2017 Source:Biological Control Author(s): Charles H. Pickett, Diego J. Nieto, Janet A. Bryer, Sean L. Swezey, Marypat Stadtherr The European Lygus spp. parasitoid Peristenus relictus (Ruthe) was released into California between 1998 and 2004. Four release sites, including one in the Central Valley and three along the Monterey Bay, were monitored from 1999 to 2015. Lygus spp. and P. relictus populations were monitored in alfalfa, weedy non-crop vegetation, and commercial strawberries. An experimental field cage study was also conducted to measure the contribution of both P. relictus and resident predators to Lygus spp. mortality. Results from both caging and longitudinal studies demonstrated that P. relictus had a negative impact on Lygus spp. nymphal densities. Annual percent parasitism peaks ranged from 45-71% in alfalfa or non-crop vegetation, which were either correlated with host densities or demonstrated a delayed density dependent response. Lygus spp. population reductions of over 90% were recorded at five of six sampling locations by 2011-2012. An increase in Lygus spp. densities was observed at two release sites during the last two years of monitoring in the Monterey Bay region and may be related to climate. In-season nymphal densities were correlated with winter temperatures, as warmer than average winters may have affected diapause and accelerated population growth rates. We consider this study, which corroborates th...
Source: Biological Control - Category: Biology Source Type: research