A funnel trap for the detection of hemlock woolly adelgid (Hemiptera: Adelgidae) and a method of extracting crawlers from trap samples

Eastern hemlock, Tsuga canadensis (L.) Carr., in eastern Canada is under threat from the invasive hemlock woolly adelgid, Adelges tsugae Annand (Hemiptera: Adelgidae). Early detection is a key feature to the management of A. tsugae because the impacts of this pest accrue quickly due to its bivoltine life cycle, and treatments can take a year or more to become effective. We tested a novel funnel trap design to collect the mobile first instar nymphs (crawlers) as a tool for early detection of adelgid infestations prior to host symptoms. The funnel traps performed better at detecting A. tsugae crawlers at very low abundance in a stand compared to vertically oriented sticky traps or to canopy branch tip sampling. Satisfactory detection rates for operational surveys were achieved using one or two funnel traps per site deployed for 2 wk during each of the two generations of A. tsugae and moving traps to new locations in the stand-between generations. We also optimized a protocol for extracting crawlers from trap samples, using stacked sieves (425 and 100 µm) to remove debris and retain crawlers, respectively, with the probability of detecting at least one crawler unaffected by the presence of debris. The improved trapping and extraction technique is aimed at stand-level early detection of this destructive pest and could be adapted to other similar, cryptic insect pests.