Hemlocks are significant components of temperate forests of Asia and North America, and in eastern North America, they are threatened by an exotic herbivore, the hemlock woolly adelgid, Adelges tsugae. The adelgid is native to Asia and northwestern North America, but is highly invasive in eastern North America where natural enemies are unable to regulate populations and eastern hemlock, Tsuga canadensis, is highly susceptible. In order to gain a better understanding of the metabolic effects of A. tsugae on eastern hemlock, we evaluated its effects on photosynthesis and also evaluated photosynthesis on Tsuga species from various geographic origins. We measured light-saturated photosynthesis (A sat) and dark respiration of T. canadensis that were infested with adelgid and found a significant decrease in A sat and a small but significant increase in dark respiration, suggesting that A. tsugae triggers a physiological response in eastern hemlock by decreasing metabolic activity. In a separate experiment, we also measured A sat of five different hemlock species, including eastern hemlock, the Pacific Northwestern T. heterophylla and T. mertensiana, and the Asian T. diversifolia and T. chinensis. Only weakly significant differences in A sat were found, with the highest rate in the eastern North American T. canadensis and the lowest in the Pacific Northwestern T. mertensiana. The relatively high photosynthetic rate of T. canadensis could possibly play a role in its susceptibility to A. tsugae. A better understanding of this metabolic response could help develop effective management strategies for combating the highly invasive A. tsugae.
|Number of pages||7|
|State||Published - Feb 2014|
Bibliographical noteFunding Information:
Acknowledgments The authors thank Joshua Adkins, Luke Dodd, Ignazio Graziosi, Abe Levin-Nielsen and Melanie Sprinkle for assistance in the field, and Millie Hamilton who provided assistance with the LICOR 6400 portable photosynthesis system. Dan Potter and John Obrycki reviewed earlier versions of this manuscript. This work was supported by USDA Forest Service FHP EM and MacIntire Stennis funds from the Kentucky Agricultural Experiment Station and is published as Experiment Station #12-08-114.
- Adelges tsugae
- Eastern hemlock
- Hemlock woolly adelgid
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Agronomy and Crop Science
- Insect Science