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Goal: Sustain Our Nation’s Forests and Grasslands More Sunlight: A Friend in the Fight Against an Invasive Tree-Killing Insect

Dr. Robert Jetton examines a hemlock seedling

Dr. Robert Jetton of North Carolina State University experimentally infests potted hemlocks with hemlock woolly adelgids to examine the effects of shade on both the seedlings and the insects. Photo by Albert E. Mayfield III, USDA Forest Service.

Introduction

Eastern hemlock, a species with key ecological roles in eastern forests, is being killed throughout its range by an invasive insect, the hemlock woolly adelgid. Using artificial shade treatments on potted hemlocks, Forest Service scientists and their partners showed that elevated sunlight levels improved seedling growth and carbon status and dramatically reduced numbers of HWA on the branches. The findings suggest that forest management practices, such as thinning or creating small canopy gaps, that increase sunlight exposure on hemlocks could be valuable tools in the effort to manage and conserve eastern hemlock.

Summary

Eastern hemlock, a species with key ecological roles in eastern forests, is being killed throughout its range by an invasive insect, the hemlock woolly adelgid (HWA). Recently, Forest Service scientists and their partners conducted a study in which they subjected potted hemlock seedlings to different levels of artificial shade and infested them with HWA. The results, published in the journal Forest Ecology and Management, showed that elevated sunlight levels improved hemlock growth and carbon status and dramatically reduced numbers of HWA on the branches. The findings suggest that forest management practices, such as thinning or creating small canopy gaps, that increase sunlight exposure on hemlocks could be valuable tools in the effort to manage and conserve eastern hemlock. Additional research to test the effect of such practices on the health of hemlocks growing naturally in the forest is ongoing. The research is ongoing, and aims to provide forest managers with additional strategies for protecting hemlock trees.

Principal Investigators
Steven T. Brantley, Joseph W. Jones Ecological Research Center
Albert E. Mayfield III, Research Entomologist
Robert M. Jetton, North Carolina State University
Chelcy F. Miniat, Project Leader
RWUs
4552 - Insects, Diseases, and Invasive Plants
4353 - Center for Forest Watershed Research
Strategic Program Area
Invasive Species
Publication
Elevated light levels reduce hemlock woolly adelgid infestation and improve carbon balance of infested eastern hemlock seedlings
CompassLive Story
Sunlight vs. Hemlock Woolly Adelgids
Research Partner
USDA Forest Service, State and Private Forestry, Forest Health Protection, Region 8
External Partner
North Carolina State University, Camcore, Dep. Forestry and Environmental Resources