Forests 2015, 6(6), 2066-2081; https://doi.org/10.3390/f6062066
Comparison of Suspended Branch and Direct Infestation Techniques for Artificially Infesting Hemlock Seedlings with the Hemlock Woolly Adelgid for Resistance Screening
1
Camcore, Department of Forestry and Environmental Resources, North Carolina State University, 2720 Faucette Drive, Raleigh, NC 27695, USA
2
USDA Forest Service, Southern Research Station, 200 W.T. Weaver Boulevard, Asheville, NC 28804, USA
3
Christmas Tree Genetics Program, Department of Forestry and Environmental Resources, North Carolina State University, 2720 Faucette Drive, Raleigh, NC 27695, USA
*
Author to whom correspondence should be addressed.
Academic Editors: Fei-Hai Yu and Eric J. Jokela
Received: 14 April 2015 / Revised: 1 June 2015 / Accepted: 3 June 2015 / Published: 8 June 2015
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. View Full-TextKeywords:
adelges tsugae; tsuga canadensis; tsuga caroliniana; tsuga heterophylla; artificial infestation
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Powers, Z.L.; Mayfield, A.E., III; Frampton, J.; Jetton, R.M. Comparison of Suspended Branch and Direct Infestation Techniques for Artificially Infesting Hemlock Seedlings with the Hemlock Woolly Adelgid for Resistance Screening. Forests 2015, 6, 2066-2081.