Abstract
The hemlock woolly adelgid (Adelges tsugae Annand) is an invasive forest pest in eastern North America that has caused significant decline and mortality in populations of eastern hemlock (Tsuga canadensis (L.) Carr.) and Carolina hemlock (T. caroliniana Engelm.). The breeding of adelgid-resistant genotypes for reforestation activities is still in the early development phases, and most resistance screening programs have depended on labor-intensive direct artificial infestation techniques for introducing adelgids to target seedlings. We investigated the timing and effectiveness of a potentially less labor-intense suspended branch infestation technique compared to two levels of a direct infestation method. Results indicated that peak crawler emergence from adelgid infested hemlock branches occurred within a 10 to 14 day period and that crawler emergence was higher from non-hydrated compared to hydrated branches. Greater infestation pressure was achieved when using progrediens crawlers compared to sistens crawlers. In 2013, when the infestation attempts were most successful, the suspended branch technique induced the same or higher adelgid densities on target seedlings as the direct infestation techniques. Assuming an initial investment in infrastructure, the suspended branch approach could be a more time and cost effective method for inducing adelgid infestations for resistance screening of large numbers of candidate trees.
Highlights
The hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera: Adelgidae) is an invasive forest insect pest in eastern North America that was likely transported from Asia on southern Japanese hemlock (Tsuga sieboldii Carr.) nursery stock
Crawler dispersal from non-hydrated twigs continued a steady decline through the final day of the experiment, while dispersal from hydrated twigs declined from days 5 to 8 before increasing on days 9 and 10
Total crawler dispersal was significantly higher from non-hydrated compared to hydrated hemlock twigs (t = 3.47, df = 9, p = 0.0070) (Figure 2), a non-significant trend that was apparent in the 10 day means for hydrated (135.7 ± 32.5) and non-hydrated (145.1 ± 33.3) twigs in the daily dispersal experiment
Summary
The hemlock woolly adelgid (Adelges tsugae Annand) (Hemiptera: Adelgidae) is an invasive forest insect pest in eastern North America that was likely transported from Asia on southern Japanese hemlock (Tsuga sieboldii Carr.) nursery stock. The adelgid feeds on eastern (Tsuga canadensis (L.) Carr.) and Carolina (T. caroliniana Engelm.) hemlock in eastern North America and has caused significant decline and mortality in populations of both species. These ecologically important trees provide food and shelter for wildlife and play key roles in the regulation of stand structure, nutrient cycling, and water relationships in the ecosystems they inhabit [3,4]. The sistens generation is present from June to March and gives rise to eggs of the progrediens generation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
