Monitoring hemlock vitality using ground-based digital imaging

Abstract

The vitality of hemlock (Tsuga spp.) trees needs to be assessed in order to evaluate the effectiveness of treatments that combat hemlock woolly adelgid (HWA), Adelges tsugae Annand 1 (Homoptera: Adelgidae). Ground-based photomonitoring can be used to assess canopy dynamics, which serves as a visual indicator of tree vitality. Here we propose a sampling strategy using a digital camera with a telephoto lens to examine change in needle count over time. The magnification provided by the lens optics reduces some of the complicating effects inherent in other forms of below-canopy photographic methods and enables direct measurement of the objects of interest, the needles.

Citation

Clark, Neil A.; Lee, Sang-Mook. 2005. Monitoring hemlock vitality using ground-based digital imaging. In: Onken, B.; Reardon, R. eds. 3^rd symposium on hemlock wooly adelgid in the eastern United States, 1-3 Februrary 2005. Monitoring hemlock vitality using ground-based digital imaging Asheville, NC: U.S. Department of Agriculture, Forest Service, Forest Health Technology Enterprise Team