@article{hollingsworth_hain_1994, title={BALSAM WOOLLY ADELGID (HOMOPTERA, ADELGIDAE) - EFFECTS ON GROWTH AND ABNORMAL WOOD PRODUCTION IN FRASER FIR SEEDLINGS AS INFLUENCED BY SEEDLING GENETICS, INSECT SOURCE, AND SOIL SOURCE}, volume={24}, ISSN={["0045-5067"]}, DOI={10.1139/x94-293}, abstractNote={ Fraser fir, Abiesfraseri (Pursh) Poir., seedlings were grown in the greenhouse and at four field sites in the southern Appalachian Mountains to study the effects of infestation by the balsam woolly adelgid (BWA), Adelgespiceae (Ratz.). Swelling in the main stem was used as an indicator of abnormal wood (i.e., "rotholz") production induced by infestation. At three of the four field sites, the main stems of infested seedlings were significantly more swollen than those of uninfested seedlings. The amount of swelling caused by BWA generally was not affected by seed source (half-sib family), soil source (soil from higher or lower elevations), or interactions of these variables. At two of four field sites, infestation was associated with a significant increase in root:shoot ratio. Variability in root:shoot ratios and total dry weights of seedlings was influenced by interactions of infestation, soil source, and seed source. This result demonstrates that both tree genetics and environment play a significant role in the growth responses of infested Fraser fir seedlings. Results from the greenhouse study indicated that BWA might be represented by two or more biotypes in the southern Appalachians. Shoot weights and diameter increases were relatively large for Mount Mitchell seedlings infested by BWA from Mount Rogers, and relatively small when infested by BWA from Mount Mitchell. For seedlings from Mount Rogers, the converse was true. Overall, these results suggest that environment is probably more important than tree or insect genetics in explaining why so many infested trees have died in the Black Mountains of North Carolina. }, number={11}, journal={CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE}, author={HOLLINGSWORTH, RG and HAIN, FP}, year={1994}, month={Nov}, pages={2284–2294} }
 @article{hollingsworth_hain_1994, title={EFFECT OF DROUGHT STRESS AND INFESTATION BY THE BALSAM WOOLLY ADELGID (HOMOPTERA, ADELGIDAE) ON ABNORMAL WOOD PRODUCTION IN FRASER FIR}, volume={24}, ISSN={["0045-5067"]}, DOI={10.1139/x94-294}, abstractNote={ Fraser fir (Abiesfraseri (Pursh) Poir.) seedlings were artificially infested with balsam woolly adelgid, Adelgespiceae (Ratz.), then subjected to drought-stress treatments. Infestation caused a distinct swelling in the main stem, caused by the accumulation of abnormal wood (i.e., "rotholz"). As expected, drought stress reduced diameter growth in the main stem. However, the reduction in wood increment caused by drought stress was relatively small for infested seedlings as compared with uninfested seedlings, owing to the production of rotholz. This implies that infested trees expend considerable energy and nutrients for the production of poorly functioning wood even during periods of stress. The implications of this research for interpreting patterns of tree mortality in the southern Appalachian Mountains are discussed. }, number={11}, journal={CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE}, author={HOLLINGSWORTH, RG and HAIN, FP}, year={1994}, month={Nov}, pages={2295–2297} }
 @article{hollingsworth_hain_1992, title={BALSAM WOOLLY ADELGID (HOMOPTERA, ADELGIDAE) EFFECTS ON WOOD AND BARK STRUCTURE OF FRASER FIR AND SILVER FIR}, volume={21}, ISSN={["0046-225X"]}, DOI={10.1093/ee/21.5.1103}, abstractNote={Response of Fraser fir, Abies fraseri (Pursh) Poiret, to the balsam woolly adelgid, Adelges piceae (Ratzeburg), was evaluated by studying wood cores and bark samples taken from six sites near Mount Rogers, VA, and five sites in the Black Mountains of North Carolina surrounding Mount Mitchell. For comparison, samples were also collected from silver fir, Abies alba Miller, at four sites in the Black Forest of Germany. Average A. piceae densities were higher on trees at Mount Rogers than on Mount Mitchell trees. Proportions of trees producing abnormal wood in response to low or moderate A. piceae densities was greater for Mount Mitchell trees than for trees at Mount Rogers. Results from Mount Rogers support observations made for other fir species that A. piceae infestation induces outer bark formation, leading to tree recovery. Outer bark formation in trees from the Black Mountains and the Black Forest of Germany was not correlated with A. piceae density. There was indirect evidence that the outer bark measured in Mount Mitchell trees was incompletely formed, with an indistinct boundary layer between living and nonliving bark layers.}, number={5}, journal={ENVIRONMENTAL ENTOMOLOGY}, author={HOLLINGSWORTH, RG and HAIN, FP}, year={1992}, month={Oct}, pages={1103–1109} }
 @article{hollingsworth_hain_1991, title={BALSAM WOOLLY ADELGID (HOMOPTERA, ADELGIDAE) AND SPRUCE-FIR DECLINE IN THE SOUTHERN APPALACHIANS - ASSESSING PEST RELEVANCE IN A DAMAGED ECOSYSTEM}, volume={74}, ISSN={["0015-4040"]}, DOI={10.2307/3495294}, abstractNote={Research on tree decline has shown that the proportion of sapwood area to heartwood area is an important measure of tree health. Infestation by the balsam woolly adelgid (BWA), Adelges piceae (Ratz.), causes the formation of abnormal wood, which is thought to conduct sap poorly. BWA infestation is also associated with lower (more negative) xylem pressure potentials and increased areas of heartwood. We hypothesize that lower pressure potentials (a consequence of abnormal wood production) increase the rate of cavitation (gas-filling) of sapwood tracheids, thereby accelerating heartwood formation. If this hypothesis is correct, adelgid attack causes loss of functional sapwood both directly and indirectly. There is evidence that the balsam woolly adelgid is an important factor causing the decline of Fraser fir, Abies fraseri (Pursh) Poiret, in the southern Appalachians. However adelgid damage is probably interacting with many other environmental factors to cause reductions in per cent sapwood area. Determining the relevance of this pest to tree decline can be accomplished by examing the relationship that exists between adelgid infestation, increment growth, and per cent sapwood area.}, number={2}, journal={FLORIDA ENTOMOLOGIST}, author={HOLLINGSWORTH, RG and HAIN, FP}, year={1991}, month={Jun}, pages={179–187} }
 @article{hollingsworth_blum_hain_1991, title={The effect of adelgid-altered wood on sapwood conductance of Fraser fir Christmas trees}, volume={12}, number={3}, journal={IAWA Journal}, author={Hollingsworth, R. G. and Blum, U. and Hain, F. P.}, year={1991}, pages={235} }