A Tree-ring Reconstruction of Balsam Woolly Adelgid Infestations in the Highlands of West Virginia

Authors: Morgan Leef*, West Virginia University, Amy Hessl, Department of Geology and Geography, West Virginia University, Andrew Liebhold, US Forest Service Northern Research Station, Jonathan Hall, Department of Geology and Geography, West Virginia University
Topics: Biogeography
Keywords: balsam woolly adelgid, balsam fir, red spruce, infestation, growth rings
Session Type: Poster
Day: 4/5/2019
Start / End Time: 3:05 PM / 4:45 PM
Room: Lincoln 2, Marriott, Exhibition Level
Presentation File: No File Uploaded


Balsam woolly adelgid (BWA), Adelges piceae(Ratzeburg), is a sap-sucking, exotic invasive insect that arrived in North America from central Europe around 1900. Since then, it has expanded its range from New Brunswick, Canada to the mountains of North Carolina. It is a threat to all North American true-fir species, but populations can be controlled by cold continental winters. Feeding leaves noticeable traces on the wood tissue and increases the size of annual growth rings temporarily. Using practices rooted in Dendrochronology, we used these traces on the wood tissue to determine initial infestation dates and measured the differences in radial growth for 14 balsam fir stands (Abies balsamea), located across the highlands of West Virginia, and compared them to that of nearby red spruce (Picea rubens) trees. We also compared infestation dates with local climate records, to ascertain the relationships between infestations and air temperature. BWA was originally thought to have invaded balsam fir stands in Canaan Valley, West Virginia around 1992, but based on samples we have collected, the infestations date as early as 1965. Infestations are also noticeable on mean chronologies, as periods of rapid growth, followed by a period of reduced growth. Using a host vs non-host model, we determined that changes in growth caused by infestations are also evident when the growth indices of the non-host red spruce were subtracted from the growth indices of the host balsam fir.

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