Silvicultural Treatments May Reduce Impact of Hemlock Woolly Adelgid

Abstract

Eastern hemlock (Tsuga canadensis) is a foundational species in forests across the eastern United States. Hemlock trees provide critical ecosystem services, such as shading for streams, regulation of water temperature, and wildlife habitat for many species. Hemlocks are also economically important for the forest products industry, especially for paper and pulpwood. The invasive insect, hemlock woolly adelgid (HWA, Adelges tsugae Annand), has killed millions of hemlocks across the eastern United States and altered forest dynamics since it was first discovered in 1950. In response, forest managers have sought proactive silvicultural strategies to strengthen hemlock resilience before infestation occurs. Researchers at the U.S. Department of Agriculture, Forest Service, published a new study on improving hemlock resilience. Mary Ann Fajvan (Northern Research Station) and Andrea Hille (Allegheny National Forest) studied how thinning hemlock stands might be used as a proactive strategy against HWA establishment and spread by improving tree vigor and increasing light availability.

Citation

USDA Forest Service, Northern Research Station. 2025. Silvicultural Treatments May Reduce Impact of Hemlock Woolly Adelgid. Rooted in Research Issue 49, May 2025. Madison, WI: U.S. Department of Agriculture, Forest Service, Northern Research Station. 2 p.