Seasonality and species composition of Peristenus (Hymenoptera: Braconidae) species, and Lygus (Hemiptera: Miridae) species parasitism in southern Alberta, Canada

We report a long-term survey summarising the seasonal variation in species composition of Peristenus species, and their levels of parasitism in an assemblage of Lygus spp., over more than 10 years in southern Alberta in western Canada. Plants sampled include alfalfa (Medicago sativa L.), canola (Brassica napus L.), and stands of different weed and grass species commonly found on crop field edges. Three native Peristenus species (Peristenus dayi, Peristenus mellipes, and Peristenus howardi) were recorded in 2003-2011 and 2013-2015. In laboratory trials, P. mellipes emerged 13 days earlier than P.howardi. Degree-days for field-collected individuals suggested a sequential occurrence during the growing season: P. dayi appears early in the season, followed by P.mellipes, and later on by P.howardi. Studies of species composition and phenology of native parasitoids of insect pests provide valuable baseline information when considering introduction of exotic agents, and contribute to the management and improvement of conservation biological control by endemic natural enemies in agricultural systems.