Characterizing spring emergence of adult Halyomorpha halys using experimental overwintering shelters and commercial pheromone traps
To improve our understanding of adult Halyomorpha halys (Stal) (Hemiptera: Pentatomidae) overwintering biology and to better inform models of its population dynamics, its temporal pattern of spring emergence was investigated using experimental overwintering shelters in screened cages within protective structures. In 2012, plastic shelters containing 100 adults were deployed in unheated, unlighted buildings, and adjacent woodlots in Virginia, USA. In 2013 and 2014, wooden shelters containing 300 paint-marked adults were deployed in pairs in six woodlots across Virginia, West Virginia, and Maryland, USA; one in a closed cage and one in a cage with the top removed, enabling emerged adults to be counted or to disperse, respectively. In 2013 and 2014, pheromone-baited and non-baited pyramid traps encircled the shelters at each site. Regular counts of adults that emerged into the closed cage and of marked and wild' (unmarked) adults captured in traps were conducted from February or March through early July. In 2012, emergence patterns from shelters in buildings and woodlots were very similar and matched those recorded from woodlots in 2013 and 2014. In all years, a small peak of emergence occurred in about mid-April, a larger and more prolonged peak was observed between mid-May and early June, and emergence ended by early July. Of the 449 H.halys adults captured in traps between 2013 and 2014, only three were marked individuals from shelters in the open cage, suggesting that adults emerging from overwintering sites may require a dispersal flight before responding to pheromone-baited traps. In 2013 and 2014, respectively, 98 and 93% of captures were in pheromone-baited traps, but there was no correlation between the weekly number of adults that emerged from shelters in the closed cages and captures in traps.