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The wool of the invasive, non-native hemlock woolly adelgid, Adelges tsugaeAnnand (Hemiptera: Adelgidae), occurs mostly on hemlock (Tsugasp.) twigs, but can be dislodged from the canopy and end up on the forest floor and tree stem underneath the canopy. Herein, we developed and tested the efficacy of two novel sampling techniques, which are based on a visual examination of the forest floor and the hemlock stem for A. tsugaewool. Subsequently, we compared these two techniques to a visual examination of foliage and ball sampling which are two methods currently used operationally. We sampled 11 hemlock stands, with low to moderate incidence A. tsugaepopulations, near Ithaca, New York in 2016 and assessed the probability of detecting wool on a tree and in a stand, as well as the relative variation and relative net precision for each of the four techniques. We found that sampling the tree stem outperformed foliage and ground sampling, likely because of its higher detection rate and lower relative variation, but not ball sampling. Our findings suggest that combining stem, ball and ground sampling was the most effective combination of techniques and gave a high probability of detecting an infested tree or an infested stand. All techniques were an improvement over foliage sampling, even after increasing the foliage sampling effort fivefold.

We developed an approach using sticky trap arrays as an early detection tool for populations of first-instar nymphs of the hemlock woolly adelgid (Adelges tsugaeAnnand), a pest of hemlocks (Tsugaspp. [Pinaceae]) in North America. We considered the detection rate of at least one nymph from trapping arrays consisting of one to six sticky panels, where we varied both the surface area of each trap that we assessed and the length of the trapping duration. We also estimated the time needed to set up, service, and assess groups of traps and attempted to relate capture of nymphs on traps to incidence and abundance of A. tsugaein the canopy above the traps. Arrays consisting of two traps provided a detection rate of 75% when 87.5% of the surface area of each trap was assessed, a process that required 38 min per array. The probability of detecting nymphs on traps left in the field for 5–6 d was similar to that for traps left for 12 d. The number of nymphs trapped in an array predicted the probability of finding A. tsugaein the canopy but only when all six traps were fully assessed. To reliably detect incipient A. tsugaeinfestations, we recommend placing arrays of traps at 1 km intervals along the perimeter of a stand during peak activity of first-instar sistentes nymphs and servicing these arrays every 5–7 d.